The Horizontal Mooring: A Two-Dimensional Array, Description of the ...

WHOI-99-14

Woods Hole Oceanographic Institution

Technical Report

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September 1999

1930

The Horizontal Mooring: A Two-Dimensional Array,

Description of the Array, Components, Instrumentation, Deployment and Recovery Operations by

Richard P. Trask Steven P. Anderson Bryan S. Way

Willam M. Ostrom Walter Paul

Mark A. Grosenbaugh Jason I. Gobat Robert A. Weller September 1999

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Upper Ocean Processes Group Woods Hole Oceanographic Institution

Woods Hole, Massachusetts 02543 UOP Technical Report 99-02

WHOI-99-14 UOP-99-02

The Horizontal Mooring: A Two-Dimensional Array,

Description of the Array, Components, Instrumentation, Deployment and Recovery Operations by

Richard P. Trask

Steven P. Anderson Bryan S. Way Wiliam M. Ostrom Walter Paul

Mark A. Grosenbaugh

Jason i. Gobat Robert A. Weller

Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543 September 1999

Technical Report Funding was provided by the Offce of Naval Research under Grant No. N00014-97-1-0158.

Reproduction in whole or in part is permitted for any purpose of the United States Government. This report should be cited as Woods Hole Oceanog. Inst. Tech. Rept., WHOI-99-14.

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Approved for public release; distrbution unlimited.

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Terrence . J yce, Chair

Department of Physical Oceanography

Abstract A moored two-dimensional array with instrumentation distributed both horizontally and verticaly was deployed for 27 days in August 1998 at an 85 meter deep site in Massachusetts Bay near Stellwagon basin. The horizontal mooring consisted of a 160meter long horizontal element positioned at a depth of 20 meters between two subsudace

moorings. Suspended below the horizontal member were five 25-meter long vertical strings. The vertical strings had a horiontal separation of30 meters and each had instruments at depths of20, 25, 30, 35, 40 and 45 meters. Instrumentation deployed on the

two-dimensional array included acoustic current meters, temperature sensors, conductivity measuring instruments, pressure sensors and motion monitoring packages. the two-dimensional aray, the an-

This report includes a detailed description of

choring system and the instrumentation that were deployed. Also included is a description of the deployment and recovery technques that were employed as well as an assessment of

the pedormance of

the array.

2

Table of Contents ABS TRA CT .............................................................................................. ........... .............. ..................... 2

LIST 0 F FI G URS..................................................................................... ........................................... 4

LIS T OF TABLES ............................. ..................................... .................. ........................ ..................... 5 SECTION 1: INTRO D U CTI ON.................................................................... ........... ...... ......... .............. 6

SECTION 2: DESCRITION OF THE ARY .................................................................................. 7 A. MooRIG DESCRIPTION.................................................................................................................. 7 1. End Buoys (Steel Spheres).......................................................................................................... 7

2. End Buoy Mooring Details....................................................................................................... 11 3. Horizontal Mooring Member......................... ......................................... ... ...................... ......... 12 4. Instrmentation Attachment to Horizontal Member................................................................... 12 B. SUPPLEMENTAL BUOyANCy............. ............... ........ .................. ...................................................... 21 C. ANCHORIG SySTEM.......................................... .......... ................................................................. 22

1. Anchoring Tests....................................................................................................................... 22 2. Test Results.............................................................................................................................. 26 3. The Selected Anchor .......................... ......... ............................. ............................. ................... 26

SECTION 3: INSTRUMENT A TIO N .................................................................................................. 27

A. FSI 3D-ACM................................................................................................................................ 27 B. SEA-BIRD SBE-39......................................................................................................................... 27 C. SEA-BIRD MIcRoCAT SBE-37 1M.................... ...................... ... ................................ ........ ........... 27 D. BRACKERRESEARCH, LTD. XL-200 ........................................................................................... 28 E. MOTION PACKAGE .... .......... .................... ......... .... ............. ............ ... .............. ............................... 28

F. Ax ACKS.. .............................................................................................................................. ....... 28

SECTION 4: DEPLOYMNT AND RECOVERY OPERATIONS......................................... 29 A. DEPLOyMENT............................................................................................................................... 29 B. RECOVERY OPERATION ......... ........... ................ ............................. .................. ..................... ......... 31

SECTION 5: ARY PERFORMCE ........................................................................................... 33 A CKN 0 WLED G MENTS .................................................................................................................... 40

REFEREN CES ..................................................................................................................................... 40

APPENDIX 1: INSTRUMNT LOCATIONS WITHI THE HORIONTAL ARy............. 41

APPENDIX 2: TI MA ON TEMPERATUR SENSING INSTRUMNTS....................... 49 APPENDIX 3: PRESSURE TELEMETRY SySTEM............................................................ 51

3

List of Figures Figure 1: (a) Side view of the horizonta moorig................."................"..".............................,,8

Figure 1: (b) Schematic of the horizonta moorig ground line ..."......."...................................... 9 Figure 2: Horizonta moorig sphere modifications. ...................................................................10 Figure 3: (a) Schematics of the horizonta moorig wire rope. .....................................................13 Figure 3: (b) Schematics of the horionta moorig wire rope elements......."...............................i 4 Figure 4: Photograph of the modified cage used with the FSI 3D-ACM.......................................15 Figure 5: Photograph of the clamp used to attch the vertcal strigs ........................................ ..16 Figure 6: (a) Horizonta moorig wire clamp plates. ......................"............"........................... ..18 Figure 6: (b) Horiontal moorig wire clamp backig plates..... .......... .......... ........... ............ ........19 the clamp attchig the temperature recorder to the vertcal Figure 7: Photograph of instruent strg. ....................................................................................................... .20 Figure 8: Schematic of temperature recorder wire clamps. ..........................................................2 I Panther Plast floats. ............".......... ............................ ....23 Figure 9: Photograph of attchment of Figure 10: Clamp used to attch 17-inch glass bals to wire rope for supplementa buoyancy.......23 Figure 11: Anchors testd for the horizonta moorig................................................................ ..24 Figure 12: Photo of

thee DorMor(ß anchors. ................................... ...................................... ....24

Figure 13: A schematic of the confguration of the anchor holdig tests...........................:......... ..24

Figure 14: Pressure telemetry tether.......................................................................................... .32 Figure 15: Anchor locations for intruented platforms at moorig site. .....................................34 Figure 16: Rage, mean and quarle of the currents................................................................ ....36

Figure 17: (a) Location of FSI instrents. .............................................................................. ..37 Figure 17: (b) Sensor locations at bottom of intruent strig................................ ................... ..38 Figure 18: (a) Moorig tilt durig flood. ......................................."......................................... ...38 Figure 18: (b) Moorig tit durig ebb.............. ........................................................................ ..38 Figure 19: Maxum moorig tit.......................................:..................................................... .39 Figure 20: Horionta moorig data at 25 meters. .......................................................................39 Figure AI-I: Vertical strig numbers. ..... ...................................................................................42 Figure Al -2: x, Z, coordite system. ..........................................................".................... .........46 Figure A3- 1: Tattle IV drawig. ............................................................................................... ..53

Figure A3-2: Moorig schematic. .............................................................................................. .54

4

List of Tables Table 1: Sphere buoyancy test results........................................................................................ 11

Table 2: Anchor holdig test results. ........................................................................................ ..25

Table Al -1: Instruent tye and serial number. ....................................................................... ..43

Table Al-2: Coordiates of deployed instrentation using x, z coordite systern......................47

Table A3-l: Program used to query MicroCA T. ...... ............................................................. ......52

5

Section 1: Introduction In 1997 prelimiai work began toward developing a thee-dimensional moored aray

for studyig the upper ocean from the very near sUDace down though the permanent thermoclie in shallow and deep water. As a first step in its development, a two-dimensional aray with the capability of makg measurements in the vertcal along one horizontal axs was designed and tested. The design of such an aray poses the same engieerig challenges as the more complex thee-dimensional aray, and is, therefore, a necessai first step. lbs report

documents the work completed to date (mid-1999) on the two-dimensional moored aray project, with emphasis on the 1998 effort.

A numerical model of a subsUDace horizontal moorig was developed in 1997 to aid in the evaluation of horizonta moorig designs. The numerical simulation and study of the

performance of the horiontal moorig were performed using a general purose numerical code, developed at WHOI, for calculatig statistics and dynamc response of moored and towed oceanographic systems (Gobat et a/., 1997). The simulation is built around a mathematical model of cable dynamcs that includes the effects of geometrc nonlearties, material nonlinearties, material bendig stiffess, and material torsion. lbs permts accurate theedimensional modelig of systems in which the cable goes slack. The nonlear, one-sided

boundai condition at the seabed is modeled as an elastic foundation for systems with cable lyig on the bottom. The numerical implementation includes an adaptive time-stepping algorith to speed the solution of problems with high nonlinearty.

The simulation was used to model the behavior of the subsUDace horizontal moorig under sea-state and curent forcing up to the worst hurcane scenaro. Line tensions, tension fluctuations, motion of the comer buoys and component accelerations were so established. The

results allow the detal moorig design to be with acceptable safe workig load levels of all components. On 19 August 1997, the fist horizontal aray was deployed off chusetts, in 100 meters of

Provicetown, Massa-

water. An intrented horionta element, 100 meters long, was

tensioned between two subsUDace moorigs at 20 meters depth. Thee curent meters and five temperatue/pressure recorders were deployed along the horionta element recordig data

every one and two miutes respectively. In addition to these intrents, a motion-measurg package was deployed in one of the two subsUDace moorig spheres. Thee sUDace buoy

guard moorigs were deployed around the aray to protect it from any damage due to fishig activities. One of the thee surace buoys was deployed with an internally recordig wid speed and direction sensor to monitor the surace forcing. A signficant storm passed though the area two days afer deployment, testig the holdig power of the anchors and the integrity

the system under rough weather conditions. The aray was successfuly recovered on 27 August 1997. All instrentation deployed along the horizontal element collected data for the of

entire deployment.

Experience gaied from the first deployment led to the design of a new, modified, two-

dimensional aray, which had sensors distrbuted both horizontally and vertcally. To evaluate ths two-dimensional aray, ajoint engieerig and scientific deploythe unque capability of ment was planed. The scientific focus was to explore the coherence at short horizontal and

6

temporal scales of the internal waves on the contiental shelf, specifically targetig the effect of internal solitons on sediment tranport. Workig in conjunction with the United States Geological Surey (USGS), a site was selected in Massachusetts Bay near Stellwagon basin in 85 meters of water.

A two-dimensional moorig was deployed on 6 August 1998 from the RN Argo Maine. The horizontal moorig consisted of a 160-meter long horizontal element positioned at a depth of 20 meters between two subsurace moorigs. Suspended below the horiontal member were five, 25-meter long vertcal strgs. The vertcal strgs had a horionta separa-

20, 25, 30,35,40 and 45 meters. The

tion of30 meters and each had intrents at depth of

central vertcal strg was intrented with an acoustic curent meter, five temperatue- and

conductivity-measurg intrents, and one acceleration-sensing package. The other four

vertcal strgs were each intrented with six temperatue recorders. The instrents at the bottom of

the vertcal strgs also measured pressure. Two additional acoustic curent meters

were deployed along the horizonta member. Pressure sensors and motion monitorig packages were deployed at the ends of the horiontal member. The two-diensional aray was successfuly recovered on 1 September 1998 afer 27 days on station.

the two,.diensional moored aray, the

Ths report will include a detailed description of

intrentation that was deployed, the technque used to deploy and recover the aray, as well

as an assessment of its pedormance.

the Array

Section 2: Description of

A. Moorig Description The two-diensional aray consisted of two subsurace moorigs with a taut horiontal member stretched between them (Figure 1a). Figure 1b shows the details of

the ground line

that was deployed as a means of properly tensionig the aray. A description of the subsurace

moorigs will be followed by a detaled description of the horizonta member with its associated vertcal strgs.

1. End Buoys (Steel Spheres) Each of

the two subsurace moorigs had a 48-inch diameter steel sphere as their pri-

mar buoyancy. The spheres were modified with new bales to accommodate the two points of

attchment requied for the aray (Figue 2). These same spheres had been used durg the first the pressure data collected from that

horizontal moorig deployment in 1997. Analysis of

moorig revealed that there was a persistent slope along the aray with one side approximately six meters deeper than the other. Both spheres were assumed to be identical, and the manufactuer's buoyancy specifications were used in the design process. The numerical model suggested that one way for the observed slope to persist thoughout all the varable tidal curent forcing was to have one of

the subsurace spheres with 20% less buoyancy than the other.

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10

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The buoyancy of the two spheres was determed experimentally at the WHOI dock.

An anchor of known weight in water was attached below each sphere, and the spheres were lowered into the water with a crane until the. spheres were completely submerged. The weight measured using a load cell. The results of the in water of the sphere-anchor assembly was buoyancy tests appear in Table 1.

Table 1: Sphere buoyancy test results Test

March

date: 17

1998

Anchor Wet Weight: 2050 pounds SDhere #

Weight in water with anchor

1480 pounds

570 pounds 880 pounds

17 8

Net buoyancy

1170 pounds

Although the spheres appeared identical, there was considerable difference in their available buoyancy. These buoyancy differences were taen into consideration in the design of the two-diensional aray deployed in 1998.

2. End Buoy Moorig Details A two-meter shot of 1/2-inch trawler chai was attched diectly below the sphere for

ease in handlg durg deployment and recovery. Below the two-meter shot of chai was 3/8-

inch diameter 3x19 jacketed wire rope. The lengt of each wie rope was adapted to lead to a horizontal

long-lie positionig despite the differences in buoyancy of the two comer buoys.

back-up recovery. Above and below the acoustic release were two lengts of 1/2-inch trawler chai. The longer lengt (15 meters) above the release was intended as an adjustable shot had there been a discrepancy between the design water depth and the actual depth. Since there was no One of

the two subsurace moorigs had an acoustic release as a mean of

acoustic release on the other subsurace moorig, a single 15-meter lengt of 1/2-inch trawler chai was deployed below the 3/8-inch diameter wire rope with a 5-ton swivel between the

two. Below the 1/2-inch chai on each moorig was a lengt of 1.25-inch steamer chai. The steamer chai weighed, on average, 46 pounds (21kg) per meter. It was included in the

design to reduce the angle between the bottom and the diection of the force exerted on the anchor. A pai ofDorMor(I inverted pyramd-shaped moorig anchors were used to secure each subsurace moorig leg. Accordig to the manufactuer, the DorMor(I style anchor has the greatest holdig capacity when used in conjunction with large scope moorigs. The steamer chai was used to replicate the low angle of pull characteristic of a large (3: 1) scope moorig. The horiontal moorig anchor system consisted of a 2000-pound and a 1000-pound Dor-

Mor(I anchor connected by a 10-meter lengt of3/4-inch chai. The priar anchor was the

11

larger of the two. The smaller anchor was added due to uncertaities about the holdig capacity of the DorMor(Ê anchors in the expected bottom conditions and in ths parcular application. The DorMor(Ê anchor was chosen afer testig several anchor tyes. The results of those tests are described in Section 2C.

The DorMor(Ê anchors were modified with additional bales so that two anchors could be used in series as shown in Figure 1, as well as tensioned durg the deployment operations as described in Section 4 of ths report.

3. Horizontal Moorig Member

sistig of

Stretched between the two 48-inch diameter spheres was a horizontal member conthe wire four lengts of3/8-inch diameter 3x19 jacketed wire rope. The details of

shots are shown in Figure 3(a) and (b). Instrentation was either clamped to the horizontal

wire or placed in line with the wire. Thee Falmouth Scientific, Inc. (FSI), 3D acoustic curent meters (3D-ACM) were deployed in line with the horiontal wire. The FSI 3D-ACM cages

were modified with additional bales so that the curent meter could be deployed in-lie with the horiontal wire and still maitai the vertcal orientation required for proper operation of the

compass (Figue 4).

Every effort was made to reduce the loadig along the horintal member. Typical wire rope termations consist of a closed swage socket and a strai relief boot. To connect intrentation in-lie, the normal complement of moorig hardware consists of a shackle-lin-

shackle combination. To reduce the localized loadig, the horizontal moorig wire shots were termated with an open swage socket. The open socket was placed over an instrent bale

and connected by mean of a single bolt. The open swage sockets used in ths application were Crosby S-501 sockets for 71l6-inch or 1/2-inch diameter wire rope.

TIs confguration reduced the loadig; however, because lins were not used, there was no readily avaiable place where the moorig could be stopped off either durg deployment or recovery. A light-weightsolution to ths problem was the addition ofY ale grips~to

the wire at selected locations. The Yale grp(Ê works on the same priciple as a Chiese figer. It has an eye with four long tals ofKevlar flat braid that are spirally wrapped around the wire. The Yale griP(Ê provides an eye at which the moorig can be stopped off As tension is

applied to the eye the spiraled Kevlar material tightens around the wie. The ends of the wire shots that were connected to the two 48-inch diameter spheres had conventional closed swage boots. The common hardware complement of shackle-lin-shackle sockets and strai relief was used.

4. Instrumentation Attachment to Horiontal Member Intrentation that was not placed in line with the horizontal member was clamped to the wire. Four of

the five vertcal strgs shown in Figure 1 were clamped to the horizontal

member by means of a pair ofPVC plates. Figure 5 is a photograph of the upper par of a

12

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Figure 3': (a) Schematics of the horiontal mooring wire rope.

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Figure 3: (b) Schematics of

the horizontal moorig wire rope elements.

14

Figure 4: Photograph of the modifed cage used with the FSI 3D-ACM. 15

Figure 5: Photograph of the clamp used to attch the vertical strings to the horizontal wire. 16

vertical string showig the PVC clamping plates and a temperature recorder. Figure 6 (a) and (b) are schematics of the PVC clamping plates used to attach a vertical string to the horizontal member. A short (5-inch) piece of 1/2-inch tygon tubing slit lengthwise was

placed over the horizontal wire at the desired clamping location. The horizontal wire was then laid in the machined groove and four 1/4x20 bolts compressed the plates, clamping the PVC blocks to the wire. The use offour 1/4x20 bolts with associated flat and lock washers and nut that had to be assembled on deck did not present a problem during the August 1998 deployment due to the calm seas; however, it would have been a challenge had the sea state been higher. This clamping assembly provided mid-wire attachment

points. It was from these sites that the vertical strings were hung. The vertcal strgs were made of3/16-inch diameter 3x19jacketed wire rope. They

were mated to the PVC clamp in advance by passing the wire though a hole in the clamp plate

and formg an eye by nicopressing the wire back onto itself No thble was used in the eye. Chafe protection to the wie was provided around the eye by a lengt of tygon tubing that had been theaded onto the wire prior to formg the eye. Each vertcal strg had five Sea-Bird SBE-39 temperatue recordig instrents and one Brancker Research, Ltd., pressure and temperatue instrent. The instrents were

clamped to the vertcal wire using the assembly shown in Figure 7. Figure 8 is a schematic of one hal of machied end of

the clamp used with the temperatue recorders. As before, two PVC plates were with

a groove and clamped around the wire using four 1/4x20 bolts. One vertcal

the PVC blocks was radiused to accept the cylidrcal shaped intrents. The instr-

ments were secured to the PVC blocks with two hose clamps that passed around the instr-

ment and though two machied slots in the blocks. At the bottom of each vertcal strg was a

cast iron sash weight that, on average, weighed 78 pounds (dr). The weight was used to

mize the horiontal excursion of the bottom of the vertcal strg. The central vertical string was diferent from the other four described above. Un-

the FSI 3D ACM located in

like the others, it was shackled directly to the bottom bale of

the center ofthe horiontal member. Not only was it attached diferently but it also had a diferent complement of instruments, which had their own clamping mechansm. The

central vertical strig was made from 3/16-inch diameter 3x19 jacketed wire rope. The instrumentation deployed on this vertical string included five Sea-Bird MicroCATs (model SBE-37IM. The MicroCATs were clamped to the wie using the clamping mechansm supplied by the manufacturer provided with instruments with inductive modems. Although the data from these instruments was not transmitted inductively up the wie, the

clamping mechansm was utilized. A 61-pound (dry) cast iron sash weight was shackled into an eye at the bottom of

the vertical string.

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,

-T

J !I

IT

¡-T-i

, , , ,

1.0'

4

-l t( l--

R.S" 687S"t bole

.78" -i1

1.0" I.. ..i

I I 0.

-r 2.5' -I ~ 01.0"_

~ --.0" ~ i

~ 5.0"--

WOOids ~Holie Üc:eaCOgnpmC lmistimltiOl!

1Jppe: O~:e P:lJ~St: 'Tit.i: By:

IHorionta nori wie cl plates W. Ostrm

Materal:

I

Du?; 6/16/98

ha

SC8.i: I

1 " th. PC plate

V~tliD : i

DtWing e: I

I

Oi=et

5 plates re

Figure 6: (a) Horiontal mooring wire clamp plates.

18

1.0' --

0.50. 1

°

4-

I 1

4.8'1 4.4" 1i

3.3"

-=j ø2J2"

i cae r'..i:=-~

Å I

2.4"

, , , ,-i

0," 0.25"

1.40"

1.0"

~ -j. I Pl

th boles 4

Ii.. ~ 4.0' I 5.0"~--

W'ooci ¡HOlte ;Qc:tognibc li~1Ôtuit.oii Up~e: :~:eu IF-C:t:;~ 'Title:

Ei:

IHoZaita moru wie cla J: plate W. Ostrm

Maial:

I

Date: 6/16/98

I

ha

Scae:

1 . thle PC plate

Drawig i:

Y.!:OZl : i I

I

Q.,i:d

23 plates re

Figure 6: (b) Horiontal mooring wire clamp backing plate.

19

Figure 7: Photograph of the clamp attaching the temperature recorder to the vertical instrument string. 20

--

r- 1.0" -1 r- .946D 1 R1.19D

7 ¡01l11

1

2.94"

.625 x .50

l

thru hole 2 places

-El~_-f---t-i

2.12D

1.94"

t .37"

0.26" thru hole 4 places

-EB.50"

.93"

2.19"

~

3.25D

3.75"

Figure 8: Schematic of temperature recorder wire clamps.

B. Supplemental Buoyancy

Supplemental buoyancy was provided at each element deployed along the horizontal member to offset their weight. The two FSI curent meters at either end of the horiontal aray each had two plastic Panther Plast floats (product number 629) which were 9 inches in diamenylon line was passed though buoyancy each. A short lengt of ter and provided 8.8 pounds of

21

the molded lugs in the floats as shown in Figure 9 and shackled to the top bale of

the curent

meter cage.

the horizontal member required a pai of l7-inch diameter glass balls for supplemental buoyancy. The glass balls were attached to a two meter-long shot of wire that was shackled into the top bale of the curent meter cage. The wire was termated with a nicopressed eye with thble. The clamp used with the glass balls is shown in Figure 10. It consists of two backig plates from the clamps used to attach the The FSI 3D-ACM deployed in the center of

vertcal strgs to the horizonta member as shown in Figure 6. The two matig PVC plates were bolted to the plastic hard hat of the glass ball using a single 3/8-inch diameter bolt and large washers on one side of a wire groove in the PVc. Two 1/4x 20 bolts were used on the other side of the wire groove to compress the plates agaist the wire. One clamp was used per glass balL. The other four vertcal strgs also had two 17-inch diameter glass balls that were

clamped to a short lengt of wire (2 meters). The wire was termated with a nicopressed eye ard shackled into the top of

the PVC clamp on the horizontal wire.

C. Anchòring System

Maitaig the position of the horiontal moorig anchors afer deployment is a critical requirement. Draggig anchors would shorten the distace between the two anchors and position the horiontal aray at less water depth or brig it to the sea surace. The exposure to surface waves would most likely damage the instrentation and compromise the recorded data.

1. Anchorig Tests

Several field tests were conducted in 1997 to determe the holdig capability of thee tyes of anchors prior to the horiontal moorig deployment. A cast iron Dome-topped cylidrcal anchor was tested along with a Mace anchor (deadweight cast iron cylinder with steel skiffs on the bottom) (Figure 11). A new anchor tye from DorMoriI, Inc., was the thd design tested. Ths is a pyramd-shaped cast iron wrt with a holdig stem (Figure 12). The anchors were towed along the bottom with the towline puling at 45 degrees and at 30 degrees relative to the sandy floor of

Vineyard Sound (Figure 13). The anchors responded with a tyi-

cal slip-stick response to applied anchor lie loads. At the higher slip force the anchor break out of the sand and is dragged towards the towig vessel, unti the anchor line load is low enough so that the anchor bures itself agai and is holdig. Once the line load has increased to the slip tension, the anchor break out of

the sandy ground agai in a self-repeatig process.

The holdig tensions did not change when the angle between the anchor line and the seafoor was decreased from 45 to 20 degrees. The line tensions were monitored with a load cell. Table 2 shows the results from the anchor pull tests.

22

Figure 9: Photograph of attachment of Panther Plast floats.

......:.:.:.:.:-:.:-:.:.:.:.:.:.: ...................... n........................

111~fl¡I.i¡¡¡:iil¡li¡.::!i¡iii¡i¡¡::III¡ll:lil!!!:li¡!11.lililllliilll¡I.I.I:I:::::::::/::::"" .......................................... .......................................... .:.:.:.:.:.:.:-:-;.:....:.:.;.:.:.:.;.:.:.;.:.:.:.:.:.:.:.:.:.:.:.:.;.:.;.:.:.:.... ...................................,.... .:.:.:.:.:.:.:-:.:.:.:.;.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.;.:.:.:.:...:.:."

-¡'!'¡~'!'~.!¡I¡l:.:.:::::::::::r:::::" .h................ ..................

..................

;~:~:~~~:~;:~:::;~:.:;

Figure 10: Clamp used to attach 17-inch glass balls to wire rope for supplemental buoyancy.

23

--

:;:::;:;:::;:::::;:::::;:::::::;:::::;:::::::;:;:::::;:;::. ::::::::::::~:::::::::::::::::: :.;-:.:.:.:.:.:.:.;.:.:.:.:.:.:.:.:.:.:.:-:.:.:-:.:.:.:.:':';'"':':':':':':':':':';':':':':':'. : ~: ~: ~ :~: ~:~:~:~:~:¡:!:~:~:~: ~:~:r:¡:~: ¡: ~;:~:r=~:~:~:;: ~:~ . t~: ~: ~:? ~: ~: ~: ~:;:;: r ~: ~:~:~:~:~:~~r~:~:~:::;~:~:~:~:~:~:~:~:~:~:~:¡:~:;:¡:~:~;~:':r:rr~:~;~:~:~:~:~:~;~::

'::~::::::::::':'~:?~:~~frff\rrf\ rtrfittt:;" .:-:':':'-':-:0:':':':':'"' Ili¡¡li¡llill¡I¡I¡¡¡¡li¡IIIIIIIIIII!III¡¡IIIII.II¡I~I~1¡¡.I11¡i¡::.:;1Ii¡1'1¡1'.¡.¡illllr

three DorMor( anchors.

Figure 11: Anchors tested for the horionta moori. Figure 12: Photo of

~ ./

",////'"

//./

~'5 .//

~ ./ ",./ ./'"

./",\/.//

52' \ -",.//./

./ //\ 30.0°

", 45°

v./././ Medium Hard Sand

Figure 13: A schematic showing the configuration of the anchor holding tests.

24

",

VI

N

3,000

2,000

103

52

1,890

2,200

or.

.. Anchor lesls were perlormed al two slles in Vineyard Sound near Menemsha, Martha's Vineyard, MA, The bottom consisled 01 medium hard sand allhe 52 II deep sile, 01 soller sand allhe 100 II deep sile-,

langling.

Mace = nal cylinder wllh bottom skiffs 10 Increase resislance 10 horizontal pull. Dome = nal cylinder wilh rounded lop to reduce

* Anchors lesled (all casllron dead weight): 0-1000, 0-2000 = quadratlc base Inverted pyramid wilh shank, produced by DorM

15:50

Anchor surfaced clean

WOODS 1i00E, MA 02~43

1930

\~ )

I i. If

¡O...-'

3,000-3,500

2,000

142

100

1,890

2,200

0-2000

0-9

looser sind al daeper sile 15:00

2,000

1,000

142

100

900

1,050

0-1000

0-8

Resulls unchanged alter settling

1,200

1,000

156

52

900

1,050

0-1000

0-7

slips at 1,600 Ibs.

1,600

1,200

73

52

2,010

2,360

OOME

OOME.l

slips al 2,000 Ibs.

2,000

52

2,270

2,640

MACE

M-2

1,800

73

52

2,270

2,640

MACE

M-l 103

slips al2,OOO Ibs.

2 : 1 scope, slarts slipping at 3,000 Ibs,

2,000 13:30

13:25

-40 min,

1,500

0-2000

0-6

0-4 aller 5 min, settlemenl

13:00

4,000

2,000

73

52

1,890

2,200

0-2000

0-5

Dragging al 3,500 Ibs.

3,500

2,000

73

52

1,890

2,200

0-2000

0-4

73

52

900

1,050

0-1000

0-3

12:40

2,000

1,000

Slip-stick between 1,000 and 2,000 Ibs, Repeal ollesl 0-2 allowing anchor to dig In for

11:40

52

900

1,050

0-1000

52

1,890

0-2

2,000

Anchor covered wlsand on one side

Notes

1,000

lib.'

73

'lb.'

10:45

1111

Time of Te&t

4,000

¡II

Peak

Holdln l Power

Static

4,000

IIb.1

lib..

Cable Paid Out

Waler Depth.. 73

In SeaWater

Anchor Welaht In Air

2,200

Type.

Anchor

0-2000

0-1

TEST 10

ANCHOR HOLDING TESTS, MN DIANE G IN VINEYARD SOUND ON 7/21/97

= .i-.

"' ~ ~

.. ~ ~ ..

o=is lJS'

n o="'

~ =

N ..

-

~

= cr ~

2. Test Results

The anchor holdig power expressed as a fraction of the anchor weight was determed as the mimum anchor arrestig force ( stick force) measured. The DorMorOO holdig power

was equal to its submerged weight, the Mace anchor holdig tension was 66 to 79 percent of its submerged weight. The higher slip its weight, and the Dome anchor was 59 percent of forces were 1.58 to 2.2 ties the weight of

the DorMorOO, equa to its weight for the Mace an-

chor and 80 percent of its weight for the Dome anchor. The DorMorOO anchor was selected to secure the horiontal moorig. The proper sizg of anchors was most important in order not

to lose the horiontal arays in severe seas. An additional drag test with a DorMorOO anchor was pedormed in March 1998 at a site

with a soft muddy sea floor. The slip-stick response of the anchor was not observed. The anchor could be dragged smoothy at a tension equal to its weight without any jerkig and sudden lockig into the sea floor. Ths test trggered a search for optimied anchorig of a horizontal

moorig with its signficant vertcal tension component in the anchor rope. The offshore oil exploration industr is facing a simar theat in parcular with anchorig the new deep water floatig platform and taer-based Floatig Producton, Storage,

and Off-loadig (FSO) unts. These platform moorigs are no longer relyig on traditional drag embedment anchors with catenar moorigs (Huang and Lee, 1998) (Chisso et a/., 1998) (Wanvik et al., 1998), but use a taut moorig with a anchor rope angle of

35° to 45°

with the sea floor intead (similar to the horiontal moorig). The catenar moorigs are much

longer and, therefore, more costly. The signcant vertcal component of the anchor lie tension requires a new anchorig method. The industr is now using suction pile anchors and

Vertcal Loaded Anchors (VAs). VLAs are manufactued by Bruce in England and Vryhoff in The Netherlands and have very high holdig power afer being dragged for often 10 to 20 meters vertcaly into soft mud and clay. Large diameter polyester ropes with chai segments near the anchor and at the platform are used to provide the needed strengt and compliance. Extensive geotechncal tests are pedormed to determe the undraied shear strengt of the ocean floor at a futue anchor site whch is needed to design the size of sucton pile anchors or VLAs. The VLAs requie embedment drag loads of 40 to 50 percent of their ultiate holdig power. The signcant exta cost to secure anchors at a given location assure that the platform stay on station under all weather and sea-state conditions. 3. The Sclected Anchor The DorMorOO anchor is a compromise candidate. Due to its concentrated steel mass, it may dig signcantly into soft mud with time, thereby increasing its resistance to vertcal

li.

The local sea floor firmess at shallow-water, open-ocean sites needs to be tested under the effects of large sUDace waves. Large ripples can form in sandy sea bottoms due to wave action, which dislodge the upper sea floor layer, thereby destabilizg the anchor embedment.

Ths effect should be somewhat limited at 100-meter water depth (Traykovski et a/., submitted). The anchor holdig force is critically dependent on the sea floor in which it is placed. Some of the procedures developed by the oil industr may need to be considered for long-term reliable station keeping of

horiontal moorigs.

26

Section 3: Instrumentation There were a total of38 instrents deployed on the horionta moorig. They included thee curent meters, one sphere-mounted motion sensing package, two acceleration

recordig intrents, eight instrents for measurg conductivity and temperatue (thee of

whch also measured pres-

which also measured pressure), 24 temperatue recorders (four of

sure) and one acoustic release. Appendi 1 lists al of the intrents that were deployed on the horiontal moorig.

With a parcular intrent tye, the intrents are sorted by serial number, vertcal strg,

and depth (relative to the horionta member) in Table AI-I. Table Al-2 also has the nomial x and z coordiates assigned to each instrent.

With the exception of the curent meters, all the temperatue sensing intrents were submerged in a cold bath at a known tie before their deployment and afer recovery in order to place a time mark in the data fie. Appendi 2 lists the intrents and the times that they

were placed in and removed from the cold bath prior to the deployment and followig the recovery.

A. FSI 3D-ACM Thee FSI acoustic curent meters (3D-ACM, sIn 1467, 1468, and 1469) were deployed along the horionta member at a nomial depth of 20 meters. See Appendi 1 for grd location of the FSI curent meters. The FSI curent meters "measure velocity along four acoustic path, thee ortogonal magnetic vectors and two ortogonal gravity vectors (tit) from

which it calculates velocity relative to the ear", (pSI 3D-ACM Operatig Intrctions). The velocity, vector-averaged east

FSI curent meters sampled vector-averaged nort component of component of

velocity, vector-averaged up velocity component, vector-averaged tilt, intrent

headig, instantaeous x and y tilt, intantaeous temperatue and instataneous pressure. The averagg interval was set for 90 seconds.. No pressure data was obtaed from sIn 1468 since the pressure sensor was inadvertently disconnected.

B. Sea-Bird SBE-39 The Sea-Bird SBE-39 temperatue logger is a high-accuracy temperatue recorder with internal battery and memory. The SBE-39s used on the horionta moorig had sheathed ther-

mistors, which, accordig to the manufacter, have a tie constat of approxiately 0.7 seconds. The instrents were powered by a lithum 9-volt battery, and they recorded intataeous temperatue data every 15 seconds. See Appendix 1 for the grd locations of

the SBE-39

temperatue loggers. c. Sea-Bird MicroCA T SBE-37 1M

The SBE-37-IM MicroCAT is a high-accuracy, self-contaied conductvity and tem-

peratue sensor (pressure optional) with an integral inductive modem for communcation. The the horizontal moorig had four MicroCATs measurg conductivity central vertcal strg of

27

and temperatue; a fi intrent measured conductivity, temperatue and pressure at the bottom of the vertcal strg. The pressure sensor had a range of 0 to 100 psi. Instrents de-

ployed on the central strg did not utilize the inductive modem capability. However, the in-

ductive modem clamping mechansm was used to secure the MicroCATs to the vertcal wire. The MicroCATs recorded data every 15 seconds.

A MicroCA T measurg temperatue, conductivity and pressure was mounted on each the 48-inch diameter steel spheres to monitor sphere depth. A 30-meter long shot of3/16inch diameter jacketed wie rope connected the MicroCAT to a surace float and was used to transmit data and receive commands. The float housed a Sea-Bird Electronics Inductive Modem Controller (!e); an Onset Computer Corporation, Tattetae N data controller / logger; and a Free Wave Technologies, Inc., wireless data tranceiver along with the necessar battery power. The Tattetale N would send a command to request a data sample from the MicroCAT though the !MC. Havig received the pressure data from the MicroCAT, it was then sent to of

the wieless data tranceiver for transmission in real time to a shipboard mounted transceiver.

The depth of the spheres was monitored in real time as the ship tensioned the moorig. Details of the pressure telemetI system can be found in Appendi 3. See Appendix 1 for the grd locations of

the SBE-37 instrents.

D. Brancker Research Ltd XL-200 Brancker Research, Ltd., temperatue and pressure loggers (model XL-200) were dethe four outermost vertcal strgs. The temperatue range was -200 C to 500 C and the pressure range was 0 to 100 psi. The sample interval of the Brancker XL-

ployed at the bottom of

200s was 4 miutes.

E. Motion Package

The end buoy contaed a Tattetae Model 6 controlled motion package consistig of thee Systron Donner GyoChips, and a Columbia Triaxal accelerometer, model SA-307. The

sensors were sampled for twenty miutes at the top of every hour. The sample rate was 12.5 Hz. Data was wrtten to an 800-:M hard disk at the conclusion of each samplig period. Ths intrent ran without problems durg the 1998 Horizonta Moorig deployment.

F. AxPacks The Axacks, which were deployed near the opposite comer, at the bottom of

the cen-

tral strg, and on one of the guard buoys, were small (approximately 8 inches long and 3

inches in diameter), light (air weight 1 kg, near neutral in water), self-contaied acceleration

measurg instrents. The controller is an Onset Tattetae Model 8 mated to a Peripheral Issues Persistor CF8 compact flash device. The sensor is a Sumt Intrents traxal accel34103A). The advantages of the 34103A accelerometers are its power superometer (Model ply requirements: a single +5V supply, drawig approximately 30 mA onboard anti-alasing fiters and ouput amplifiers, and a direct 0-5V output signal, all in a cube smaller than one inch 8 and the Persistor CF8 allows large the Tattletae Model on a side. The combination of amounts of storage capacity (24-:M in the case of the Axacks), low power consumption

28

(-750 uA in hybemation mode, -30 mA whie sampling), small form factor (2" x3" x I"), and eas data retreval via the compact flash cards.

The Axacks used the same samplig scheme as the larger motion packages, 20 miutes at the top of each hour. The Axack samplig rate is 10Hz. Al thee Axacks experienced prematue faiures durg the deployment. Unit 1 ran for 91 hours, unt 2 for 33 hours,

and unt 3 for 15 hours. These failures have since been traced to a problem with the hybemation routies in the Tattetae operatig system. In laboratory testig, the faiures were repro-

ducable. Afer an upgrade to the operatig system (which fied unpecified hybemation bugs) the Axacks successfuy ran though a 24-day deployment cycle.

Section 4: Deployment and Recovery Operations A. Deployment

In preparation for the deployment, the 44-meter shot of 3/8-inch wie rope was pre-

wound onto the deployment wich dr. The fist leg of the horizonta moorig to be deployed was that whch contaed the acoustic release. The 1000-pound DorMorOO anchor was

the fist component to enter the water followed by the 3/4" chai and the 2000-pound DorMorOO anchor. The steamer chai 1/2-inch trawler chai, the acoustic release and the 15-meter

shot of 1/2-inch trawler chai above it were lowered to the bottom using the 44-meter shot of the 3/8-inch wie rope was damaged jacket of 3/8-inch wire rope. Durg the lowerig the

whie on the wich dr when the heavy anchor load caused the wie to bur into the dr tearg the plastic jacket.

Once the anchors had been lowered to the bottom the four 3/8-inch diameter wie rope shots that made up the horinta element were pre-wound onto the wich dr. The fist 48-

inch diameter steel sphere was attached to the moorig leg that had just been deployed and to the horiontal member. The wich was used to lower the sphere into the fist wire shot (B) of the water.

Just prior to deployig the sphere the surlyn pressure telemetr float was placed in the water and alowed to dr af. The float housed the pressure telemetr electronics and was

connected to the sphere by means ofa 30-meter long shot of3/16-inch diameter wire rope that passed though the inductive modem of a MicroCA T mounted to the top of the sphere. The ship slowly began to steam forward (ship speed approxiately 1 knot) as the horiontal ele-

ment was paid out. Each of the vertcal strgs were pre-assembled with al intrentation clamped to the

wire and ready for deployment. At the fist pre-marked vertcal strg location the PVC clamp was secured to the horionta wire. The supplemental buoyancy provided by the two 17-inch diameter glass balls were attached to the top of

the PVC clamp. The vertcal strg was dethe strg made it

ployed by hand, bottom end first. The 77-pound weight at the bottom of

29

diffcult to get a firm hand grasp of the small diameter wire without it slipping. The best holding points were the intrent attachments. The deployment procedure that eventualy devel-

oped involved stretchig the vertcal strg out on deck and protectig each instrent by hav-

ing someone car it to the stem where it was passed over the side. Each person shared the load of the vertcal strg as they walked the intrents af. With the first vertcal strg in the water, payout of the horizontal member contiued. An FSI curent meter was placed in line with the horiontal element between shots B and C. The moorig was stopped off uSing the Yale grp at the end of shot B while the curent meter was attached in lie. The curent meter and supplemental buoyancy (two Panther Plast floats) were eased over the side and payout of shot C contiued. The second vertcal strg was de-

ployed in much the same maner as the fist. The second curent meter located in the center of the horizontal member had a vertcal strg attched to the bottom bale of the curent meter

cage. The curent meter was placed in line between shots C and D. (The central vertcal strg

had five MicroCAT intrents that measured temperatue and conductivity, with the deepest intrent also measurg pressure. An acceleration sensing instrent (Ax Pack) was

clamped to the deepest MicroCAT.) The vertcal strg was lowered into the water by hand using the technque described above. The curent meter and supplementa buoyancy, consisting of

two 17-inch diameter glass balls, were eased over the side and payout of

wie shot D

resumed. The remaig two vertcal strgs and curent meter were deployed in the same

maner as the others. The surlyn foam float housing the second pressure data tranmitter was lowered into the water from the starboard side just prior to deployig the second 48-inch diameter steel sphere. Once the steel sphere was deployed the surlyn float was cast off The second sphere housed a motion package, which caused the sphere to be top heavy. In response to the weight of the motion package the sphere rolled so that the motion package and MicroCA T mounted to the top of the sphere ended up pointig downward whie the sphere was on the surace. Ths created a potential problem involvig the wire tether to the pressure data transmitter in the surlyn float. Durg the deployment, if the sphere had made a complete rotation, the wire

the sphere. Fortately, as the moorig

tether would have become fouled on the underside of

was tensioned, the sphere rotated back so that the wie did not become entagled. In the futue some supplementa buoyancy may be needed on the sphere to keep it in the preferred orientait is deployed without the motion package, the weight of tion. Even if the MicroCAT may be enough to cause the sphere to tu upside down if it is not outftted with some supplementa buoyancy. Followig the deployment of the steel sphere the chai and wie rope of the second leg were deployed up to and includig the 2000-pound DorMortI anchor. Before proceedig, a 120-meter long 3/8-inch diameter wie rope ground line was wound onto the wich dr along wire were used to lower the pair ofDorMortI with a second 120-meter shot. These shots of anchors to the bottom and would be used to tension the moorig. When the wire took the load of the two DorMortI anchors, the same problem that was experienced earlier with the wire burg into the dr occured agai. The wich also had diffculty holdig the load even

when the brake was applied. Once a lay of wire became bured the wich experienced snap

loads each time the wie became freed, causing the wich to lurch on its mountigs. The plasthe wich but due to the high tensions the tic jacket on the wire was damaged as it came off

30

payout contiued without stopping until the anchors were on the bottom. A 500-pound depressor weight was placed between the two 120-meter shots and lowered to the bottom with the second wire shot.

With all the moorig components in the water, the moorig had to be tensioned in order to pull both spheres underwater to the appropriate depth. The tensionig was accomplished by havig the ship pul on the ground lie while monitorig the pressure data that was transmitted to the ship from the pressure telemetr floats. Pressure data from sphere number 17 could not be received due to a problem with the MIcroCA T. The pressure data from sphere number 8

was, therefore, used to tension the moorig. Whle monitorig the pressure data the ship the MIcroCAT, the slowly steamed ahead. Due to the relatively slow sampling scheme of pressure data was only updated eveiy 15 seconds. The relatively slow output from the pressure intrent coupled with the momentu of the ship, which made it nearly impossible to quickly stop pulling on the moorig, resulted in overshootig the taget depth of 20 meters. The pressure obtaied at the conclusion of

tensionig the moorig was 24.87 dbars. Satisfied

with both the orientation of the aray and the depth of the horionta member as indicated by

the pressure data from sphere number 8, a marker can buoy was attched to the end of the tensionig wire shot and cast off

The ship then recovered the pressure telemetr floats tethered to both spheres. The the 3/16-inch wire tether was recovered before cut-

float was hauled on board and as much of

tig the wie. Each tether (Figue 14) had an attached float located 12-meters from the MIcro-

CAT in order to prevent the tether from fouling with the other intrentation on the moorig

followig removal of the pressure telemetr floats.

The origial plan was to recover the aray backwards by haulg back on the wire rope used to tension the moorig. Ths would permt the recoveiy of the entire moorig includig the DorMorOO anchors. The acoustic release deployed on the fist leg of the aray was intended as a backup recoveiy aid should the sUDace expression of the tensionig line be lost. A conse-

quence of fig the acoustic release is that the anchors from that leg of the moorig would be left behid on the bottom.

B. Recovery Operation

Followig the deployment cruse, alternatives were explored for using the same wich for recoveiy as had been used durg the deployment. It was felt that the ship's wich would not be able to recover the anchors as had been origialy planed, based on its performance durg the deployment cruse. For a varety of reasons, includig the availability of an alternate

wich and the lack of adequate tie down on the ship, a decision was made to use the ship's existig wich but to alter the recoveiy plan in order to utilize the wich's capabilties.

The recoveiy began by fig the acoustic release, which permtted both steel spheres to come to the sUDace. The ship then steamed to the sphere that was still connected to the anchors on the bottom and the sphere was recovered. The wie rope leadig to the anchors was cut, freeing the horizontal moorig from the bottom. The ship could then maneuver in whatthe moorig could be recovered easily. ever diection was necessai, and the remaider of

31

Open swage socket

modified for inductive telemetr. To be provided.

Tygon tubing for chafe protection

9" diameter Panther Plast Float Hose Clamped to the wire.

30m

Strp Jacket from lower

12m

2" of wire rope for exposure to sea water

3 Assemblies Required Woods Hole Oceaogrphic Intitution

Upper Ocea Processs Group Title: Tether for pressure telemetry

Dwg. by: Trask

Dwg. No.

Figure 14: Pressure telemetry tether.

32

The recovery of the horizontal member began from the sphere number 8 end and was the reverse operation of the deployment. The vertcal strgs were hauled out of the water by hand. Lops (approximately 12 inches in diameter) of dacron line (that was tied off on itself

with a square knot) were looped around the vertcal strg intrent clamps. These provided a firm hold of

the vertcal strgs that were a bit slimy afer the month deployment. Each per-

son had a loop and would wrap it around a clamp and wal the intrent forward. When the next instrent suraced another person would loop their lie around its clamp and walk it forward until all the intrents and depressor weight were out of the water. It may sound like

stone-age oceanography but the loads were small, there were plenty of people to assist, and it worked well.

Of the two pairs of anchors that were left behid, one set stil had the tensionig cable and marker can buoy attched. Ths left open the option of recovery at a later date should a

ship be available with adequate hauling capabilty. The other set of anchors that were left on the bottom afer fig the acoustic release would have to be recovered with a draggig opera-

tion, which is more time consumg and a more diffcult tak. The cost of recovery must be weighed with the replacement cost of the anchors. Recovery only becomes attactve when a

ship is in the area for another project and there is time in the schedule to conduct the operation without adversely impactig the other project.

Section 5: Array Penormance In ths section we present some preliar results on the pedormance of the horionta submerged aray.

The aray specifications caled for the aray to be aligned so that it was perpendicular to the crests of the solitons that tranit across Stellwagen Basin from Stellwagen Ban. The the specifcation was for the moorig to lie along a 60°-240° line, tre. Thus, from leg 2 of moorig, leg 1 would lie 60° east of

nort. Figue 15 shows the anchor locations for the var-

ous intrented platform at the moorig site. The leg 1 anchor location was determed us-

ing GPS, A GPS position was obtaed when the anchor was lowered to the bottom. The leg

2 position indicated is the ship's position as tension was released from the ground lie followig tensionig the moored aray. Ths would not be the actual anchor location, but should be inine with the aray at that

time. The alignent with leg 1 determed from these positions is

the telemetr floats remaig on the surace and from the ship's compass to with approximately 10°. We con60.8°east of

nort. Ths algnent was confrmed by visual inpection of

servatively conclude that the aray was aligned with j: 10° of the desired location. A more accurate surey could have been done if we had recorded the GPS location and algnent of

each telemetr float individually prior to its removal from the aray. The 1.5 scope of the telemetr float tether would, however, still have introduced a degree of uncertaity. The design goal was to have the intrents displaced by no more than j:2 meters

from their design taget depth. The design maxum curent for ths specification was

33

cso oio. . ,. ,. C\

. \. \ .. \\0 .

'

. . . . - . - - . . . ".' . . . . . . . . . . . . . . " - . . . . . . . . . . .............\... ,\

,\

\ surface C:

\\

,..\ \".. 0........,..... \ s~bsurf

\ eg1

, . .. '

'ß'92Range 197.8~; align 60.8° :

.,.':..\,.,.-....,... ....,...........,.... \\ \

\

qnPO\ ... \.. .:." ...,.... .

\

Gnomonic Projecton

Figure 15: Aichor locations for instrumented platforms at mooring site.

34

42°N 17.40'

100 cm/s. The surval curent was specified as 300 cm/s. Figure 16 shows the statistics of the observed curents durg the deployment. The data are from the United States Gelogical Surey (USGS) ADCP located on a trpod positioned approxiately 200 meters south of aray. The ADCP provided a vertcal profile of

the

the horizonta curents every 2 miutes. Figure

16 shows the range, mean, and the quarles (in gray boxes) of the curent for each depth bin. the time, the curents were located with the gray box indi-

The quarles indicate that 50% of

cated. The maxum observed curents were located in the depth range of the submerged ar-

ray but did not exceed 100 cm/s. The east component of the curent was larger and had more varabilty than the nortern component. Ths is because the tidal curents were located mostly east-west.

The sensor locations were determed using the pressure measurements from the Brancker, SBE-39 and FSI instruments. The pressure record from a Sea-Bird tide gauge located on the anchor at a depth of 84-meters of a nearby subsudace moorig, monitored the local tidal elevation. This was subtracted from the sensor pressures as was an atmospheric bias determed from the tie series just prior to the deployment of the intrents.

Ths processing yielded a sensor position referenced to the bottom. Figue 17 shows the mean, range and quares for the sensor locations. The top figue (Figure 17a) shows the FSI intr-

ments SIN 1467 and SIN 1469 located on the horionta member and the Sea-Bird MicroCAT SBE-37 instrent, SIN 670, on sphere number 8. The bottom figure (Figue 17b) shows the sensor locations at the bottom of each intrent strg relative to the bottom.

The target depth for the top of

the aray was 20 meters (or 64 meters above the bot-

tom.) The bottom of each strg should be located 39 meters above the bottom. There appears

to be a slight tilt or sag in the aray with the eastern end approximately one meter deeper than the western side. The bottoms of the strgs did not var by much more than one meter from

their mean locations. A larger range and varance is observed in the shalower pressure records. Ths is likely not due to moorig motion, but rather from alasing of the pressure signal of sUDace gravity waves, whch canot be diectly accounted for in ths analysis. Ths signal

decays exponentialy and wi have a much smaller afect on the lower sensors. Figues 18a and 18b show the locations of the bottom of the strgs durg the flood

and ebb tides relative to their average positions. The flood tide was located nearly diecty along the aray whie the ebb tide had some cross aray component. The domiant motion appears to be that the motion of the ends of the aray are incoherent. The depth of the upstream side of

the aray increases whie the downtream side shoals. However, the range of

motion

associated with the tides does not appear to account for most of the varance in depth observed

in Figure 17. Figure 19 shows the locations of the bottom of the strgs, relative to their average lo-

cation, durg a single soliton event on August 22. Ths single event lasted less than 15 miutes. However, the instrents were displaced by more than a meter from their nomialloca-

tions. The lengt of the aray is well matched to the horionta wavelengt of the solitons we observed. The curents observed with these solitons were nearly 50 cm/s and would reverse in

direction over its wavelengt. Ths can be seen in Figue 20, which shows the temperatue and velocity records from the top of the aray durg the passage of several solitons. One leg of the aray is encounterig curents and drags that are incoherent from the other. Ths is resultig in 35

ADCP Current Statistics ,

IE

II i: rn CD

~ i~ i~~ -lil~ iimI ~ iii~ i~ lf-i-

' .

1m

rm rm

ff m

20

~ fi ~

., .- 40

'-6 -S

c. o

o

60

80

-100

rn

20

a;--

~ li I£ ~ r: ~ ~ ~

I ~~ ~ ~ ~ ~ ~ i ii~ i~I! i ~ ~ 1 -50 0 50

.- 40

'-6

.... c. o o

(I

il il

rn

60

80

-100

100

-50 0 50 Nort,Current (em s.l)

East Current (em s.l)

Figure 16: Range, mean and quartile of

36

the currents.

100

Boxplots of Pressure Sensor I?ìstance from Botton

--a a

68

B 66 0

-

l

CQ

a e c: 64

~

.l I1

~ u i: =

-;

Õ

62

60 o

50 100

150

Dištace frm Sphere #8 (m)

Figure 17: (a) Location of FSI instruments.

Figure 17: (b) Sensor locations at bottom of instrument strigs.

37

Moorig Tilt Durig Flood 42

iE .

Along Moorig Currnt Component

Ê ..

"

41

E

~

MCl Floo Cunnt

t

.. ~i7

~

rF ~

t

#08 :~ -

.2

Õ 40

"

i:

f

E

..o uu 39

t

c

t

c:

êi

is

~

38

Averae Position Flood Position

37 1

o

fr

50 -100 Distace frm Sphere #8 (m)

Figure 18: (a) Moorig tit durig flood.

Figure 18: (b) Mooring tilt during ebb.

38

t t

150

Maximum Mooring Tilt Durg Soliton on 22 August 42

ê--

a,

41

""..

E

9 40 Õ

~

r-

ee E

~

.:0 uc. 39

t

rr

cCD

E

';

Õ

~

38

t-

Average Position

r c L

r r

Soliton Position 37

150

100

50

0

.Distace from Sphere #8 (m)

Figure 19: Maxum moorig tilt.

Horizontal Mooring Data at 25m Below the Surfce 30

G 2S

~

f 20

x-120m

"; ..u

15

x=9 x=6

10

x-30m

=

i: e ~

x=O 5

120

~ 100

.. u ..

;- 80

x=115m

i: 60

-~ 40

C'

x=6

.. ..

8 20

x=5m

o

o

10

20

30 40 Time (minutes)

50

Figure 20: Horizontal mooring data at 25 meters.

39

60

70

a dynamcal moorig motion we had not encountered in our modeling studies that assumed that the curents were horiontally homogeneous across the aray. In conclusion, the submerged aray was successfuly deployed in the specified orientation and depth. There was an across-aray tilt of approximately one meter over 120 meters.

The tidal curents did not lead to signficant moorig motion; however, fuer modeling is required to understand the motion of the aray in response to solitons.

Acknowledgments The captain and crew of the R/ Argo Maine deserve special mention for their assistance with the deployment and recovery of this unique mooring system. We also wish to than Brad Butman, Jon Borden, Mark Baumgartner, Kent Bradshaw, Lar Costello

and Jim MacConnell for their help at sea during the deployment and recovery operations.

The guard moorigs which surrounded and protected the horiontal moorig during its 27-day deployment were designed by George Tupper. Special thans are extended to

Dave Simoneau and the WHOI Moorig and Riggig Shop for their careful preparation of the complicated elements of the horiontal mooring. We sincerely thank Penny Foster for all her help in preparng this report. This work was supported by the Offce Naval Reof search Grant No. N00014-97-1-0158.

References Chimisso, G., H. Tagher, N. C. Bliss, and 0. Stan, 1998. Deepwater FPSO for Aquila Field Development in the Adratic, OTC 1998 Proceedigs, VoL. 2, OTC #8808,

Houston, Texas, May 1998, pp 259-267. Falmouth Scientific, Inc., no date. Operatig Instrctions. 3-D Acoustic Curent Meter, 3DACM, Version 6.0, Firmware Version 2.18. Falmouth Scientific, Inc., Cataumet, Massachusetts 02534, 126 pp.

Gobat,1. I., M. A. Grosenbaugh, and M. S. Triantafllou, 1997. WHOI Cable: Time Domai Numerical Simulation of Moored and Towed Oceanographic Systems, Woods Hole Oceanographic Institution Technical Report No. WHOI-97-15, 103 pp. Deepwater Moorig Systems

Huang, K., and M-Y Lee, 1998. Experiences in Classifcation of

for Floatig Strctues", OTC 1998 Proceedigs, VoL 2, OTC #8772, Houston, Texas,

May 1998, pp 227-236. Traykovski, P., 1. D.lrsh, and 1. F. Lynch, Geometr, Migration, and Evolution of Orbital Ripples at LEO-IS, Journal of

Wave

Geophysical Research, submitted.

Wanvik, L., L. Poldervaa, and H. Mong, 1998. FPSO with Turet Based Drilling System (FPDSO): An Approach to a Cost-Effective Deepwater Field Development, OTC 1998 Proceedigs, VoL. 2, OTC #8811, Houston, Texas, May 1998, pp 289-

303.

40

Appendix 1: Instrument Locations within the Horizontal Array the instrentation de-

Two technques have been employed to describe the location of

ployed on the horiontal moorig. The fist references the vertcal strg number and depth with respect to the horionta member. Figure A1-1 identies the vertcal strg numbers and, for each instrent tye and serial number, Table A1-1 identifies the vertcal strg on which it

was deployed. Ths technque, though convenient, did not adequately describe the location of instrents that were not par of a vertcal strg.

The second technque utiizes a coordiate system whereby the reference for the hori-

zontal axs (x axs) is sphere number 17 and the reference for the vertcal axs (z) is the sea sUDace. Intrents are located by their vertcal and horiontal distances (in meters) from

those reference points. Using ths convention the coordiates of sphere number 8 are (160.9,20). Ths indicates that sphere number 8 is nomialy 160.9 meters from sphere number 17 and 20 meters below the sea surace. Figure Al-2 shows the coordiate system and Table Al-2 lists the coordiates of all intrents deployed on the two dimensional aray.

41

~

~

-i r'

!~

(J

::. = = =

!. i: ..

n

:: ..

~

I

..~

~ ~

~

~. i-

84 meters

-SpHere 1/17

SBD9 005

SBD9 ool5'

Aii r.tk 2

Xl100 io

20m _ _ _ _./ _ _ _ _ _. SBD~OO48 25m _ _ --_ _ _ _ _ _ _ ~B~"Õ044

15m' - - --

10m

5m

Om

..

Southwest

Iiislriiiient Legend

xLiooiiim - ~. ;.':1 .peA'F6ß - - - -

.pCA'F6ß - - - -

SÕD' 00i9 - - - -

ŠBË3,0046 - - - - ìieA'F6ß - - -, ŠBEl'oo'fO - - - -

siiÈiiOOl- - - -

* Acceleration Pack

1. XL-200 Temperature and Pressure . MicroCat Conductivity and Temperature . MicroCat Cond., Temp, and Pressure . FSI Current Velocity and Temperature

Dwg. by:

Title:

iizõå iõ -

SiiD9 õioi -

SiEI õiol -

SiEÏ9 0047 -

siïii 0038- -

SBD9001

Sphere 1/ 8 wI

R. Trask

14 Sept

98

1"=30m

ate: ~cale

Horizontal Mooring Instrument Array Venical String Reference

Woods Hole Oceanographic Institution Woods Hole MA 025'43 Upper Ocean Processes Group

xLzooeõ9l- - - -

siib,oiÕl- - - -

SBD9OO51

SOD9OO49

ŠBË3,oo54 - - - - .IICAT61l - - - -

lD.ACM 1469

-------

SOD9OO40

lD.ACM 14i1

ŠBË3,oo - - - - peÃ'riIi - - - -

. SBE-39 Temperature

lD.ACM 1467

pCAT670

.. -- -- -- __ ~ -- -- -- ~ ~

Vertical String Number I 2 3 4 5

Northeast

Table AI-I: Instrment type and serial number

Horizontal Mooring, August 1998 Instrumentation

SSE.39 Sorted by String Number

Sorted by Serial Number

DepthU

String

Instr

No.

No.

7

35 38 39 40 41

44 45 46 47 48 49 50 51

2

5

1

0.2

5

5

4

4

15 0.2 0.2 20 10 15 10 15 0.2

2

20

4 1

2 5 1 1

2 5 1

String

No.

No.

35 52 45 48 44 40

DepthU

1 1 1 1 1

2

7

2 2

54 46 50 49

2 2

51

4 4

53'"

4

5

39

5

101 41

4 4

52 53' 54

4

101

4

102 103

5

20 20

5

15

2

Instr

10 10

5 5 5

38 47 103 102

Sorted by Depth

0.2 5

10 15 20 0.2 5

10 15

20 0.2 5

10 15 20 0.2 5

5

10 15

5

20

, = did not log data

''"Depth Shown is nominal depth relative to horizontal element Horizontal Element at approximately 20 meters depth

43

Instr

String

No.

No.

DepthU

35 40 49

2

41

5

52

1

4 1

0.2 0.2 0.2 0.2 5 5

7 51

2

38 45 54

5

53'"

4

10

47 48 46 39 103 44 50

5

101

4

10 15 15 15 15 20 20 20

102

5

20

4 1

2

1

2

4 5 1

2

5 5

10 10

Table AI-I: Intrent tye and serial number (contiued)

Horizontal Mooring, August 1998 Instrumentation (continued)

MicroCat SBE-37 Sorted by Serial Number

Instr

String

No.

No.

Depth'"

Sorted by String Number

Sorted by Depth

lnstr

String

Instr

String

No.

No.

No.

No.

669

3

20

670t

669t

Sphere 8

0

683 684 685 686

671 t* Sphere 17

683

684t 685 686

3 3 3

3

0 5

25 15 10

3 3

20

3

25

3 3

15 10

671 t* Sphere 17

670t

Depth**

Sphere 8

5

0 0

Brancker Temperature Loggers XL 200 Instr String Depth**

No. No. 8093 8094

2

8091

4

8090

5

1

25 25 25 25

t= With pressure

* = did not collect data **Depth Shown is nominal depth relative to horizontal element Horizontal Element at approximately 20 meters depth

44

683 686 685 669 684

3 3 3 3

3

671 t* Sphere 17

670

Sphere 8

Depth""

5

-10 15 20 25 0 0

Table AI-I: Intrent tye and serial number (contiued)

.

Horizontal Mooring, August 1998 Instrumentation (continued)

FSI 3D ACM Instr Location Depth**

No. (m)

1467t

Horiz

1468

String 3

1469t

Horiz

20 20 20

Motion Package Instr

Location Depth**

No.

001

(m) Sphere 8

20

Ax Pack

Instr

Location Depth**

No.

(m)

1

String 3

25

2

Horiz

0

t= With pressure

* = did not collect data **Depth Shown is nominal depth relative to horizontal element Horizontal Element at approximately 20 meters depth

45

.t 0\

F3

tD

~

II II ~

tD

Q.

..= a

"'

Q

nQ

t'

~

N ..

,

tD

~ .. ~"' ~ ~

Cl

fl

-S

g

~

Northeast

Insirument Legend

I

I

I

I

I

I

I

I

I

i

i

i

SBEJ90040

5°.l8 I

i

SBEJ9OO49

110.66

ii

i 140.94

135.85

XUOO 8094 A. P.ck 1

. MicroCat Conductivity and Temperature . MicroCat Cond., Temp, and Pressure . FSI Current Velocity and Temperature

A XL-200 Temperature and Pressure

* Acceleration Pack

!;:~: = = = =l:~:~;:= = =:=

I

i

Moiion r.chll 001

Sphere # 8 wI

160.94

Southwest

R. Trask

t4 Sept

x, z coordinate system ale: 98

Horizontal Mooring Instrument Array

Woods Hole Oceanographic Institution Woods Hole MA 02543 Upper Ocean Processes Group

Dwg. by:

Title:

I I I I

1I

I I I I

I I

II II II

- - - - - - - - - -1.~e-Af"6Ii I XUOO 8091 I I

ŠBËJ90050 - - - - -~e-Af"6I - - - - SBEJ'ioThI- - -1-

šBËJf'oO - - - -

ŠBËJ900S4 - - - -

ŠBËJ9 oo - - - -

r-----l------1______ -~e-A"-6ß SBEJ9OO39 I r-----l------- -------.l

ii

2p 25.09

. SBE-39 Temperature

i I

o 2

Distance (m) from Sphere No. i 7

Table Al-2:Coordinates of deployed instrumentation using x, z coordinate system

Horizontal Mooring, August 1998 Instrumentation

sse 39

Sorted by X position

Sorted by Z position

Instr X Z

Instr X Z

Instr X Z

No. Coord Coord

No. Coord Coord

No. Coord Coord

35 52 45 48 44 40

35 40 49

Sorted by Serial No.

7

35 38 39 40 41

44 45 46 47 48 49 50 51

52 53*

54 101

102 103

50.28 25 20 20.2 140.9 25 110.7 35 50.28 20.2 140.9 20.2 40 20 20 30 50.28 35 140.9 30 20 35 110.7 20.2 50.28 40 110.7 25 20 25 110.7 30 50.28 30 110.7 40 140.9 40 140.9 35

7

54 46 50 49 51

5339 101 41

38 47 103 102

20 20 20 20 20 50.28 50.28 50.28 50.28 50.28 110.7 110.7 110.7 110.7 110.7 140.9 140.9 140.9 140.9 140.9

X and Z coordinates are nominal locations

* = did not log data

47

20.2 25 30 35 40 20.2 25 30

.35 40 20.2 25 30 35 40 20.2 25 30 35 40

20 50.28 110.7 41 140.9 52 20 7 50.28 51 110.7 38 140.9 45 20 54 50.28 53* 110.7 47 140.9 48 20 46 50.28 39 110.7 103 140.9 44 20 50 50.28 101 110.7 102 140.9

20.2 20.2 20.2 20.2 25 25 25 25 30 30 30 30 35 35 35 35 40 40 40 40

Table Al-2: Coordiates of deployed intrentation using x, z coordiate system (contiued)

Horizontal Mooring, August 1998 Instrumentation (continued)

MicroCat SBE-37 Sorted by Senal Number

Sorted by X Position

Sorted by Z Position

Instr

X

Z

Instr

X

Z

Instr

X

Z

No.

Coord

Coord

No.

Coord

Coord

No.

Coord

Coord

(m)

(m)

669

40 19.4 19.4 25 45 35 30

670t

80.47 160.9

671 t*

0

683

80.47 80.47 80.47 80.47

684t 685 686

671 t*

(m)

(m)

0

19.4 25 30 35 40 45 19.4

683 686 685 669

80.47 80.47 80.47 80.47 684t 80.47 670t 160.9

Brancker Temperature Loggers

XL 200 Instr

X

Z

Instr

X

No.

Coord

Coord

No.

Coord

Z Coord

(m)

(m)

(m)

(m)

140.9 110.7 20 50.28

45 45 45 45

8090 8091

8093 8094

8093 20 8094 50.28 8091 110.7 8090 140.9

t= With pressure

" = did not collect data

48

45 45 45 45

671 t*

(m)

(m)

0

19.4 19.4 25 30 35

670t 160.9 683 686 685 669

80.47 80.47 80.47 80.47 684t 80.47

.40 45

Appendix 2: Time Marks on Temperature Sensing Instruments " Horionta Mooring

Pre-deployment cold bat times. Date: 4 August 98

Instrment

Time In

Time Out

(UTC)

(UTC)

2238:31 2239:17 2239:31 2242:10 2242:15 2242:10

2240: 19

2245 .

2248: 18

2245 2245 2245 2250:15

2248:18 2248:18 2248:18

2250: 15

2255:13

2250: 15 2250: 15

2255:13

2250: 15 2250: 15

2255: 13

101 102 103

2257:18 2257:08

2258:05 2258:05 2258:05

Strng 1 Strng 2 Strng 4

2300:20 2302:20

Strng 4 (repeat)

2315:37 2320:50

2303:23 2308:09 2316:37 2321:50

2257:08 2307:07

2258:05 2308:09

Strng 3

2325: 10

2326: 10

461(USGS) 465(USGS)

2309:24 2309:25

2313:30 2313:30

Seacats 143A 994 (spare) 928 993 991 929

2241:30 2241:14 2244:10 2244: 10 2244: 10

Brancker's (XX 1 05)

4483 4494 3699 4491 4487 3662

(spare)

XL200 8092 (spare) 8089 (spare)

2255: 13

2255: 13..

Wada 274 062

(spare)

2255:13

SBE 39

Strng 5

2257 :08

2307 :07

2301: 19

MicroCats 671

670

49

Honzonta Mooring

Post-deployment cold bath times Dat: 3 September 98

Intrment

Time In

Time Out

(UC)

(UC)

Seacat 143A 928 993 991 929

1702:30

1718:30

164:15

1701: 15

1645:15 1702:30 1646:15

1701:15 1718:45 1701:20

1559:20 1602:15 1559:20

1604:30 1604:30 1604:30 1606:30 1604:30

1542:30 1542:50

1548:20 1546:35

1543:20 1543:35 1543:25 1543: 15

1546:45 1546:20 1546:15 1546:25

1542:40

1548: 15

1643:15

1701:35

062

1706:30

1719:30

Strg 1 Strg 2 Strg 4

1533: 15 1532: 15

1535: 15

Brackers 4483 4494 3699 4491 3662

1559: 15 1559: 15

MicroCa 671

670 Strg 3

683 686 685 669 684

Seagauge 046

Wad

Strng 5

SBE 39 SBE 39 , SBE 39 SBE 39 SBE 39 XL200

1536:15 1537:15 1540:15

1531:15 1538:15 Strng 1

Smng 2

String 4

Smng 5

035 052 045 048

040 007 054 046 050 8094

049 051 053 039

041 038 047

04

8093

50

101

103 102

8091

8090

Appendix 3: Pressure Telemetry System A system was developed to tranmit real-time pressure data to the deployment vessel using a Sea-Bird Electronics, Inc., MicroCAT (SBE 371 conductivity, temperatue, and

pressure data logger. A Sea-Bird Electronics Inductive Modem Controller (!C) was required for communcations with the MicroCAT. The!MC is supplied with DC power in the range of 7 to 25 volts and an operatig curent of about 60 millamps when the modem is active. The mai computer or buoy controller can be interfaced via an RS232 serial port to the !MC; the standard interface protocol between the computer 1 controller and the !MC is 9600 baud, 8 bits, no party, RS-232C; with echoing of characters. The!MC (a modem is a modulator 1 demodulator") impresses ("modulates") the moorig cable with a Differential-Phase-Shi-Keyed (DPSK) signal that is encoded with the commands received from the computer/controller. These encoded signals are "demodulated" by the MicroCATs coupled to the moorig cable. Replies from MicroCATs are simlarly coupled to the moorig cable and "demodulated" by the !Me. The DPSK communcation lin between the !MC and MicroCAT is half duplex, meaning that talkig and listenig is sequential only. Even though the data li between the !MC and the computer Icontroller is established at 9600 baud, the DSPK modem communcation between the!MC and MicroCAT operate at 1200 baud. The MicroCAT was set to sample every 15 seconds, with ths data being stored interthe MicroCAT telemetr data was controlled separately by an Onset Comnally. Samplig of puter Corporation, Tattetale IV data controller/logger. The Tattletale IV, which was programed in IT Basic would send a command to request a data sample from the MicroCAT, though the IMC (Table A3-1), every 15 seconds. 1bs data would then be sent to a FreeWave Technologies, Inc., wieless data transceiver for tranmission in real time to a shipboard

mounted transceiver. The !MC, Tattletale IV, and wireless tranceiver were mounted on a smal surace float that was tethered to the sphere-mounted MicroCAT with a 30 meter long shot of 3/16" diameter plastic jacketed wie rope. The surace float system was powered by thee internal batteries, which operated at +10.5 volts DC. The shipboard transceiver was

powered by Ae.

The Free Wave tranceiver requied an input in the range of +9.5 to +14 volts DC with an average curent consumption of 180 millamps. FreeWave allows the user to tue several parameters to optimize its performance for a parcular application. Al adjustments are done though the FreeWave setup program, a user interface which eliates the need for setup

diskettes, DIP switches settgs, or custom softare. The setup program is invoked by con-

nectig the Free Wave to any termal program, settg the baud rate for that termal to i 9200 baud, and using a smal pointed object to press the Setup buttom on the front panel of

the

the shipboard transceiver. The transceiver used in the surace float system ( OEM module) model DGRO-115, is invoked by groundig pin 2 on the mai connector of that board. The output rate of the tranmitted pressure data was set to

tranceiver. 1bs procedure alowed setup of

9600 baud. The tranceivers were setup to ru in Point to Multipoint Master mode, which al-

lows one master (shipboard system) to simultaneously be in communcation with numerous slaves (surace float systems). Both of

the horizonta moorig subsurace spheres had a Mi-

croCAT and associated pressure telemetr system.

51

CAT.

Table A3-I: Program used to query Micro

MicroCAT Tattletale iv / Inductive Modem Controller Program - MicroCAT I.D. #01

200 RE ***** SEND W #01TSw TO MICROCAT ***** 220 FOR X=1T0100 :

NEXT X

222 RE USEND 9600,WW,\10;:FOR X=1T030:NET X 224 RE USEND 9600, WW, \13; : FOR X=1T030 :

NEXT 235 USEND 9600, WW, \13; : FOR X=1T030 : NEXT 240 US END 9600, WW, \10; : FOR X=1T030 : NEXT 247 USEND 9600, WW, \13; : FOR X=1T030 : NEXT 250 USEND 9600, w#w; : FOR X=1T030 : NEXT X 260 USEN 9600, wOw; : FOR X=1T030:NEXT X 230 USEN 9600, WW, \10; : FOR X=1T030 :

NEXT X X X X X

270 USEND 9600,w1w;:FOR X=1T030:NET X 280 US END 9600, wTw; : FOR X=1T030 : NET X 290 USEND 9600,wsw;:FOR X=1T030:NET X NEXT X

292 USEND 9600, WW, \13; : FOR X=1T030 :

300 SLEEP 1500 310 GOTO 220

The 3/16-inch diameter wire rope that connected the sphere-mounted MIcroCAT to the telemetr surace float, which housed the !MC package, was used to tranmit data and receive

commands. The pressure data received from the MIcroCATs in real time was monitored as the

ship tensioned the moorig. Tensionig was halted when the sphere reached the design depths. The IT Basic programs used in the Tattetale N controller, interconnecton drawig (Figure A3-1) and moorig schematic (Figure A3-2) are provided.

52

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RELEASE

ACOUS T IC

r L riA T SCH, D'WG

BRYAN 'WAY 05 JAN 1999

H(IRIZONTAL MOORING SCHEMATIC

MICRO-CAT

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Service Documentation - Publications

Working Collection Texas A&M University Dept. of Oceanography College Station, TX 77843

BP 70 29280 PLOUZANE FRANCE

50272-101

REPORT DOCUMENTATION 11. REPORT NO. WHOI-99-14

2.

UOP-99-02

3. Recipient's Accession No.

PAGE

The Horizontal Mooring: A Two-Dimensional Array, Description of the Array,

5. Report Date September 1999

Components, Instrumentation, Deployment and Recovery Operations

6.

Author(s) Richard P. Trask, Steven P. Anderson, Bryan S. Way, Willam M. Ostrom Walter Paul, Mark A. Grosenbaugh, Jason i. Gobat, Robert A. Weller

8. Performing Organization Rept. No.

4. Title and Subtitle

7.

9. Performing Organization Name and Address

WHOI-99-l4 10. ProjectlaskIork Unit No.

Woods Hole Oceanographic Institution Woods Hole, Massachusetts 02543

11. Contract(C) or Grant(G) No.

(C) NOOO14-97-l-0l58 (G)

13. Type of Report & Period Covered

12. Sponsoring Organization Name and Address

Office of Naval Research

Technical Report 14.

15. Supplementary Notes

Ths report should be cited as: Woods Hole Oceanog. Inst. Tech. Rept., WHOI-99-14.

16. Abstract (Limit: 200 words)

A moored two-dimensional aray with instrmentation distrbuted both horizontally and vertcally was deployed for 27 days in August 1998 at an 85-meter deep site in Massachusetts Bay near Stellwagon basin. The horizontal mooring consisted of a

160-meter long horizontal element positioned at a depth of 20 meters between two subsurface moorings. Suspended below the horizontal member were five 25-meter long vertcal strngs. The vertcal strngs had a horizontal separation of 30 meters and each had instrments at depths of 20, 25, 30, 35, 40 and 45 meters. Instrumentation deployed on the two-dimensional aray

included acoustic curent meters, temperature sensors, conductivity measurng instrments, pressure sensors and motion monitoring packages.

Ths report includes a detailed description of the two-dimensional aray, the anchoring system and the instrmentation that were deployed. Also included is a description of the deployment and recovery techniques that were employed, as well as an assessment of the performance of the aray.

17. Document Analysis a. Descriptors

horizontal mooring anchor systems

two-dimensional moored aray b. IdentifiersOpen-Ended Terms

c. COSATI Field/Group

19. Security Class (This Report)

18. Availability Statement

Approved for public release; distrbution unlimited.

(See ANSI-Z39.18)

21. No. of Pages

UNCLASSIFIED 20. Security Class (This Page)

See Instructions on Reverse

58 22. Price OPTIONAL FORM 272 (4-77) (Formerly NTIS-35)

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