A New Unstructured Grid Based Framework For Large

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Fig. 1: Top left: Civil aircraft design & development; Top right: Turbulence Studies (Credit: Album of Fluid Motion);. Bottom left: Landing Gear Noise Studies ...
A New Unstructured Grid Based Framework For Large Scale Computing of Fluid Flows V. K. Suman & V. Y. Mudkavi Computational & Theoretical Fluid Dynamics Division, CSIR-NAL

Motivation

Achievements

Develop code base to

• Employed meshes as large as 427 million elements • Employed 17,280 cores (99.26 % of full capacity) of CSIR-4PI’s 360 TF Anantha supercomputer

• Tackle complex problems pertaining to aerospace industry (high AoA aerodynamics, stall, CAA) accurately and efficiently

• Significant speed-up of Partitioning & sub-domain assembly

• Enable research on prototypical problems to gain insight

• Tremendous speed-up & super-linear scaling of a simple solver

Results E:/Work-K/CFD/ICEM/NCA/NCA_69/WBDE

Z

X

Y

ICEM CFD 14.0; NCAD@Vishal-PC

Fig. 1: Top left: Civil aircraft design & development; Top right: Turbulence Studies (Credit: Album of Fluid Motion); Bottom left: Landing Gear Noise Studies (Credit: Onera Lab); Bottom right: High AoA aerodynamics (Credit: Russ Tedrake, MIT Computer Science and Artificial Intelligence Laboratory)

Responsibilities Task Solve real problems

Responsibilities/Difficulties

Handle complex geometries ⇒ Unstructured grids/Chimera Methodology 9 O(Re 4 ) points required 6 Develop accurate computational methodologies for DNS ⇒ Massively parallel computing & high scalability O(10 processors) 6 15 Typical analysis of transport aircraft configuration (Re ∼ 20 × 10 ) requires quadrillion (10 ) points Transitional, Turbulent flows LES Grid sizes of billion, trillion elements ⇒ Highly scalable I/O for managing data.

Common Framework- Purpose & Scope

Figure 2: Schematic of a transport aircraft configuration. Partitions created for full Parallel aircraft mesh configuration ( 96Elapsed millionTimes hex elements) Elapsed Times for 96 million mesh example: Algorithm with serial for 96 million mesh example: Parallel Algorithm with Parallel I/O I/O using HDF5 API 180 cores 240 cores 300 cores I/O 1465.0338 1534.025 1393.8819 Partitioning 4.68135 3.92714 4.00486 Local Mesh Assembly 122.0348 62.5623 41.7881

360 cores 1469.6725 4.53537 30.3730

180 cores 240 cores 300 cores 360 cores HDF5 based parallel I/O 2.6462 1.6641 3.4510 2.9646 Partitioning 4.68135 3.92714 4.00486 4.53537 Local Mesh Assembly 122.0348 62.5623 41.7881 30.3730

Mesh Details for Missile Configuration. Aircraft

Store

design

separation

No. of Vertices No. of Faces No. of Cells Cell Type

RANS

FVM

Transition

170,857 1,808,793 884,142 Tetrahedron

Elapsed Time Per Iteration for Simulation of Flow Past 3D Missile.

Transition

Turbulence

Turbulence

Common

DNS

UDNS

Framework

Instabilities

Instabilities

DG

FD

Receptivity

Receptivity

LES

FSI

Transition

CAA

No. of Nodes(cores) Elapsed Time (s) Speedup (Obtained/Ideal) 2(32) 0.12532 10(160) 0.02443 5.129/5 20(320) 0.01171 10.702/10 50(800) 0.00427 29.349/25 100(1600) 0.00225 59.698/50

Turbulence

Future Developments Common Framework- Features

• Support for meshless solver development • Robust RANS solver for design & analysis

• Developed for writing CFD codes for generic unstructured grids

• High fidelity solvers (DNS/LES)

• Designed using OOP concepts & written in C++ • Highly scalable algorithms for massively parallel computing • Hierarchical neighbor construction for high-order FV

References

Common Framework Parallel Computing Environment

MPI

OpenMP

• G. Karypis and V. Kumar, A fast and highly quality multilevel scheme for partitioning irregular graphs, SIAM J. Sci. Comp. 20, 359 (1999).

+

MPI+OpenMP

Parallel I/O (HDF5 API)

• The HDF Group, Hierarchical data format version 5 (2000–2010). • V.K. Suman. An Improved Parallel Domain Decomposition Methodology Based on Parallel I/O for Unstructured Grid Based Petascale CFD Computations, Project Document, NAL-PD/CTFD/2013/1009, 2013.

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