Computational Fluid Dynamics Simulations for Risk ...

School of Civil and Industrial Engineering Department of Structural and Geotechnical Engineering

“Computational Fluid Dynamics Simulations for Risk Analysis of Fires in Road Tunnels” Candidate: Tiziano Baroncelli A.Y. 2013/2014

Rome, 21 May 2014

Advisor: Prof. Eng. Franco Bontempi Co-advisor: Eng. Alessandra Lo Cane

TUNNEL FIRE SAFETY

1) Problem

CONCEPTUAL MAP

2) General framework

3) Specific aspects

4) Results

COMPREHENSION OF FIRE DYNAMICS

CASE HISTORY

SPECIFIC EVENT (FREJUS FIRE)

140 EVENTS STATISTICS

FLOW CHART OF THE EVENT

NORMATIVE ASPECTS

EUROPEAN NORMS: Directive 2004/54/EC

“Computational Fluid Dynamics Simulations for Risk Analysis of Fires in Road Tunnels”

NUMERICAL ASPECTS

ITALIAN NORMS: D.Lgs 264/2006, ANAS 2009

TUNNEL CFD MODELS

EXPLICIT HGV FIRE

Candidate: Tiziano Baroncelli

BENCHMARK OF THE CODE

quantitative RISK ANALYSIS

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1

2A) FIRE DYNAMICS

COMPREHENSION OF FIRE DYNAMICS

UNDERSTANDING FIRE DYNAMICS

CLASSIFICATION OF THE CASE HISTORY

SPECIFIC EVENT: FREJUS FIRE – 06/04

a1) Typology of tunnel a2) Length of the tunnel a3) Cause of ignition a4) Number of victims a5) Number of wounded persons a6) Relevant structural damages 4) 2) 3) 5) S TRUCTURAL FATALITIES WOUNDED LENGHT D.

N°

0) EVENT

1) TYPOLOGY

6) CAUS E

7) COUNTRY

1

S. M artino 10/09/2007

R

2

137

YES

A 4.8 km

HF Collision

ITA

2

Burnley 23/03/2007

R

3

3

NO

A 3.5 km

HF Collision

AUS

3

Eidsvoll 26/10/2006

R

1

1

NO

B 1.2 km

HF Collision

NOR

4

Viamala 16/09/2006

R

9

9

NO

C 0.7 km

HF Collision

SWI

5

M auernried 25/12/2005

R

5

5

NO

D 0.3 km

HF Collision

GER



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NORMATIVE ASPECTS

NORMATIVE ASPECTS

Directive 2004/54/EC

CASE HISTORY OF MAJOR TUNNEL FIRES

2B) NORMS

«on Minimun Requirements for all the Tunnel of the Trans-European Road Network (TERN)»

executive

D. Lgs. 264/2006

1) DIRECTIVE 2004/54/EC about ‘minimum requirements for all the tunnels of the Trans-European Road

Network’ : gives a whole new approach in the tunnel fire safety, for as regards both new and existing tunnels. -

Definition of MINIMUM REQUIREMENTS FOR ROAD TUNNELS LONGER THAN 500 m;

-

Introduction of the RISK ANALYSIS as an instrument for RISK ASSESSEMENT and DECISION MAKING; RISK ANALYSIS is explicitly required in tunnel projecting;

-

Definition of the SAFETY PARAMETERS of road tunnels that SHALL BE TAKEN INTO COUNT EXPLICITLY IN THE RISK ANALYSIS (length of the tunnels, cross section, lanes, traffic etc).

2) D. Lgs. 264/2006: EXECUTIVE NORM for Italy of the previous Directive 2004/54. “Computational Fluid Dynamics Simulations for Risk Analysis of Fires in Road Tunnels”


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BENCHMARK OF THE CALCULATION CODE

2C) NUMERICAL ASPECTS

NUMERICAL ADVANCED METHODS for the assessment of the consequence of road tunnel fires

ISO 13887 (‘Assessment and verification of Mathematical Fire Models’) REFERENCES

NUREG 1824 (‘Validation of Fire Models for nuclear power plant applications

BENCHMARK OF THE CODE: Fire Dynamics Simulator (FDS), vers. 6.0

PHYSICAL ACCURACY (representativeness of the phenomenon)

CRITERIA

MATHEMATICAL ACCURACY (absence of large numerical errors)

PHYSICAL ACCURACY

𝓧

ANALYTICAL TESTS (submodels) SENSITIVITY TO PHISICAL PARAMETERS

𝓧 𝓧

CODE CHECKING MATHEMATICAL ACCURACY

NUMERICAL TESTS (DNS simulations) INFLUENCE OF THE MESH (‘sensitivity analysis’) “Computational Fluid Dynamics Simulations for Risk Analysis of Fires in Road Tunnels”


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BENCHMARK OF THE CALCULATION CODE

BENCHMARK OF THE CODE: Fire Dynamics Simulator (FDS), vers. 6.0 1) MODEL # 1

2C) NUMERICAL ASPECTS IGNITION

a) GLOBAL LEVEL b) INTERMEDIATE LEVEL c) LOCAL LEVEL

3) MODEL # 2* Mesh transformations

2) MODEL # 2

4) MODEL # 3

5) MODEL # 4

MAIN ASPECTS OF THE BENCHMARK: 1) A fine grid (namely about 25 cm) should be used to represent adequately the fire source; 2) The use of a fine grid increases significantly calculation times;

3) Possibility to represent the following phenomena: IGNITION (surface, object)

FLASHOVER

PROPAGATION


INFLUENCE OF OXYGEN


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ADVANCED NUMERICAL METHODS: Application to a REAL TUNNEL

2C) REAL TUNNEL ST. DEMETRIO

Eng. Luigi Carrarini ANAS

ST. DEMETRIO ROAD TUNNEL (SICILY)

Risk Analysis

Quantitative Risk Analysis (QRA)

GEOGRAPHY

GEOMETRY

SAFETY EQUIPMENTS

Cross section

Qualitative Risk Analysis (Risk Matrix)


Mechanical ventilation Safety infrastructures Illumination

Parameters

CATANIA - SYRACUSE

TUNNEL MODELLING

Tunnel schedule

Safety/control systems


Systems for users’ information

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Eng. Luigi Carrarini ANAS

2C) REAL TUNNEL ST. DEMETRIO

TUNNEL MODELLING

Tunnel schedule


Risk Analysis



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2C) REAL TUNNEL HGV MODEL


LARGE SCALE TESTS

CREATING A SCENARIO

VEHICLE MODEL

SCENARIO VENTILATION

CONE CALORIMETER VALIDATED MODELS

LARGE SCALE FIRE TESTS – RUNEHAMAR TESTS (2003)

5.5 ton 81% wood 19% plastic



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TUNNEL MODELLING



LARGE SCALE TESTS

VEHICLE MODEL VENTILATION


VALIDATED MODELS FOR VEHICLES – BUILDING A SIMPLE MODEL To model the real geometry of the pallets, a mesh of about 1 cm or less would be required: this is pratically impossible

SIMPLIFIED APPROACH: materials are organized in layers



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TUNNEL MODELLING



LARGE SCALE TESTS

VEHICLE MODEL VENTILATION


VALIDATED MODELS FOR VEHICLES – BUILDING A SIMPLE MODEL To model the real geometry of the pallets, a mesh of about 1 cm or less would be required: this is pratically impossible

SIMPLIFIED APPROACH: materials are organized in layers



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TUNNEL MODELLING


LARGE SCALE TESTS

VEHICLE MODEL


VENTILATION

OTHER MATERIALS



IGNITION SOURCE


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TUNNEL MODELLING


LARGE SCALE TESTS

VEHICLE MODEL


VENTILATION

OTHER MATERIALS



IGNITION SOURCE


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2C) REAL TUNNEL VENTILATION

TUNNEL MODELLING



VEHICLE MODEL NATURAL VENTILATION

VENTILATION MECHANICAL VENTILATION

NATURAL VENTILATION

ONLY FOR TUNNELS NO LOGER THAN 500 m

TRANSVERSE: often in BIDIRECTIONAL TUNNELS (ONE TUBE) MECHANICAL VENTILATION

LONGITUDINAL: in MONODIRECTIONAL TUNNELS (TWO TUBES) – «JET FANS SYSTEMS»



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2C) REAL TUNNEL VENTILATION

TUNNEL MODELLING



VEHICLE MODEL NATURAL VENTILATION

VENTILATION MECHANICAL VENTILATION

NATURAL VENTILATION

ONLY FOR TUNNELS NO LOGER THAN 500 m

TRANSVERSE: often in BIDIRECTIONAL TUNNELS (ONE TUBE)

𝓧

MECHANICAL VENTILATION

LONGITUDINAL: in MONODIRECTIONAL TUNNELS (TWO TUBES) – «JET FANS SYSTEMS»



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RESULTS OF THE ANALYSIS


HGV SIMULATIONS

RISK ANALYSIS

Scenario

Fire source

Distance from the portal

Ventilation

Jet fans

Scenario

Fire source

Distance from the portal

Ventilation

Jet fans

1

HGV

200 m

No

No

1

2 CARS

200 m

Yes (~ 3 m/s)

Yes

2

HGV

200 m

Yes (1 m/s)

No

2

BUS

200 m

Yes (~ 3 m/s)

Yes

3

HGV

200 m

Yes (2 m/s)

No

4

HGV

200 m

Yes (3 m/s)

No

5

HGV

200 m

Yes (~ 2 m/s)

Yes

The vehicles are not modelled explicitly, but using a specific ramp (forced combustion at a specific rate).

RESULTS Global level: SMOKE and FLAME DEVELOPMENT (qualitative); FIELDS OF TEMPERATURES Intermediate level: HRR and BURNING RATE Local level: THERMOCOUPLES

RESULTS Global level: SMOKE DEVELOPMENT (qualitative); FIELDS OF TEMPERATURES Local level: TEMPERATURES, CO, SOOT and OXYGEN CONCENTRATIONS, VISIBILITY, FED



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v = 2 m / s (uniform)

EXIT PORTAL (Syracuse)

+z

BY-PASS

300 m

ENTRANCE PORTAL (Catania)

BY-PASS


9.5 Φ

27.3 Φ

36.8 Φ

HGV

TRAFFIC FLOW

195 m

2695 m

2595 m

2295 m +z

105 m

9.5 Φ

45.9 Φ

2895 m 17.7 Φ

BACKLAYERING after 95 s

GLOBAL LEVEL RESULTS: 1) SMOKE DEVELOPMENT

+y

+Φ 66.7 Φ

TUNNEL FULFILLMENT after 239 s

t = 1 min

t = 2 min

t = 3 min

t = 4 min

t = 5 min

REACHED BY SMOKE after 208 s




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HGV / #3 v = 2 m / s (uniform)



+z

BY-PASS

BY-PASS

300 m

105 m

9.5 Φ

36.8 Φ

27.3 Φ

HGV

195 m

TRAFFIC FLOW

2695 m

2595 m

2295 m

2190 m +z


9.5 Φ

45.9 Φ

+y

2895 m 17.7 Φ

+Φ 66.7 Φ

LOCAL LEVEL RESULTS: 1) THERMOCOUPLES PERFORMANCE FIRE BASED DESIGN

PRESCRIPTIVE FIRE BASED DESIGN

FIRE SOURCE

Front

Mid1

Mid2

Back

NO DECAY



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INTERMEDIATE LEVEL RESULTS: 1) SMOKE DEVELOPMENT «FUEL – CONTROLLED» FIRES UNLESS SEVERAL VEHICLES ARE INVOLVED IN THE FIRE, THE QUANTITY OF AIR IS MUCH ENOUGH TO ALLOW THE COMPLETE COMBUSTION OF THE MATERIAL: THE VEHICLE

COMPARISON

BURNS AS IN OUTDOOR FIRES, WHERE THE VENTILATION DOESN’T INFLUENCE THE HEAT

RELEASE.

Scenario #2 – v = 1 m/s Scenario #3 – v = 2 m/s Scenario #1 – v = 0 m/s CFD comparison test*


TIME SHIFT FOR THE HRR CURVE


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INTERMEDIATE LEVEL RESULTS: 1) SMOKE DEVELOPMENT

+z «FUEL – CONTROLLED» FIRES THE TIME SHIFT IS ASSOCIATED TO

-y -x

THE DIFFERENT ORIENTATION OF

COMPARISON

THE IGNITION SOURCE IN THE

≠

COMPARED SIMULATIONS. Scenario #1 – v = 0 m/s

CFD comparison test*

Scenario #2 – v = 1 m/s Scenario #3 – v = 2 m/s Scenario #1 – v = 0 m/s CFD comparison test*


TIME SHIFT FOR THE HRR CURVE


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TUNNEL MODELLING

SIMPLIFIED APPROACH FOR QUANTITATIVE RISK ASSESSMENT

CRITERIA FOR QUANTITATIVE RISK ASSESSMENT

BURNING SURFACES ON THE BASIS OF THE EUREKA TESTS

WHICH ASPECTS OF THE FIRE THREAT TO USER’S LIFE?

2C) REAL TUNNEL VENTILATION HEAT SMOKE RADIATION

2 CARS FIRE

SIMPLIFIED APPROACHES: based on simple criteria about the mentioned aspects

BUS FIRE

COMPLETE APPROCHES: based on toxicity criteria with all the concentrations of toxic gases and oxygen.



Carbon dioxide

Carbon monoxide

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Oxygen

18

v,emergency ~ 3 m / s (jet fans)



+z

BY-PASS

JET FAN

2190 m

2295 m

2375 m

+z

9.5 Φ

300 m

JET FAN 2525 m

28.6 Φ

BY-PASS 2595 m

38.1 Φ

JET FAN

100 m

BUS


TRAFFIC FLOW

200 m

2675 m 2695 m 9.5 Φ

47.6 Φ

2825 m 19 Φ

+y

2895 m

+Φ 66.7 Φ

GLOBAL LEVEL RESULTS: 1) SMOKE DEVELOPMENT – 2 CARS FIRE t = 4 min

t = 6 min

t = 8 min

t = 10 min

t = 12 min

Controlled Backlayering

t = 14 min


𝑉𝑚,2 = 1.92 m/s

REACHED BY SMOKE after 49 s 𝑉𝑚,1 = 2.04 m/s



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v,emergency ~ 3 m / s (jet fans)



+z

BY-PASS

JET FAN

2190 m

2295 m

2375 m

+z

9.5 Φ

300 m

JET FAN 2525 m

28.6 Φ

BY-PASS 2595 m

38.1 Φ

JET FAN

100 m


BUS

TRAFFIC FLOW

200 m

2675 m 2695 m 9.5 Φ

47.6 Φ

2825 m 19 Φ

+y

2895 m

+Φ 66.7 Φ

GLOBAL LEVEL RESULTS: 1) SMOKE DEVELOPMENT – BUS FIRE t = 2 min

t = 4 min

t = 6 min

t = 8 min

t = 10 min

Loss of stratification


𝑉𝑚,2 = 2.59 m/s

REACHED BY SMOKE after 66 s 𝑉𝑚,1 = 1.51 m/s



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CONCLUSIONS:

- Numerical advanced methods are assuming a crucial role in the Fire Safety Engineering, with an increasing level of detailing and a fine reprodution of the

phenomenon; the main advantages are the deterministic description of the CONCLUSIONI

consequences of a fire and the diffusion of validated models for vehicles, extremely useful both in the Fire Structural Engineering and in the Risk Analysis, and the

possibility to assess different failure scenarios. - The explicit model of a vehicle can catch very precise (local) aspects that can’t be reproduced with a different approach; - Some aspects are well catched by the model of the St. Demetrio Road tunnel (growing phase, peak of HRR, first phase of decay), while others would need a finer model, both for the grid and the vehicle; - The criteria for the assessment of the risk give a very precise description of the safety conditions inside a tunnel for escaping users. “Computational Fluid Dynamics Simulations for Risk Analysis of Fires in Road Tunnels”


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THE END Fig. 6.6 – Summary of the local results (thermocouple temperatures).

Fig. 6.7 – Temperatures above the fire source.

The local analysis of the temperatures (fig. 6.6 and 6.7) show that the temperature above the fire source is good represented (unless the second phase of the decay mentioned



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TURBULENCE MODELLING



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