2008 Int ANSYS Conf Strongly Coupled Fsi Sim

7/24/2019 2008 Int ANSYS Conf Strongly Coupled Fsi Sim

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2008 International

ANSYS Conference

Strongly Coupled FSI SimulationMoving Compressible Pressure Pulse through a Tube

Daniel L. Cler,

US Army RDECOM/ ARDEC/WSEC/ Benet Labs


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Overview

Background

Problem Description

Objectives and Assumptions

Workflow

Results

Future Work

Conclusion


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A Collage of Real Life Multiphysics

Applications

Examples of multiphysicsare plentiful

Realistic FSI analysis is

needed to address design

and performance issues. Wing flutter, engine noise,

VIV, oil exploration, offshore

structures, air crafts and

components, defense

equipment, pumps, valves,arteries, bones, ...

Courtesy of Pluere

Total deformation contours

on a pump impeller in a

coupled structural and flowanalysis

Coupled FSI of bio-med valve

Typical torsional

blade modes:

impact of gas on

swept surfaces

ANSYS Adv.v1,n3,2007,

FSI of distributor headerCourtesy: CADFEM


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Background

Multiphysics Solutions: State-of-the-Art

Much has been achieved In-depth single discipline solutions

Ability to make these solutions communicate

Efforts to facilitate communication at data level MPCCI, dedicated solvers, and communicators

Multi-disciplinary applications need real world collaborationof discipline specialists

Analysis tools need framework to share multiple data fields thatrepresent the true physics

Technology maturity is providing new opportunities Need for improvement stays ahead of the progresses made

Hardware and software capabilities entice practitionerswith increased demand of complex real life analysistowards Simulation Driven Product Development


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Current RealityIntegrated Process in Workbench

Geometry Model

CHT Solid Mesh

CFD with CHT

Thermal Stress Setup

Thermal Loads from CFX

Thermal Stress

Solution

Base level coupling


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A Sample Engineering Case

Consider a problem with flow physics involving

High speed compressible flow in a tube From pavement / concrete digger to oil well drills

From BB guns to more serious defense equipment

From musical instruments to pneumatic control equipment...

Very high cyclic pressure and thermal loads over long time

Simple principle Use potential energy of compressed fluid through systematic release

in kinetic form

Focus on optimized delivery of an object or a force on a target

The release segment of these cycles involve a reaction force

Engineering challenge Minimize the reaction impact without any degradation on the forward

motion, direction and force fields

Important to analyze the response of the tube material Accuracy of the target motion, direction and force fields

Long term fatigue behavior of the equipment (tube)

Time

P/

TS

pike

s


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Engineering Solution

Consider a lightweight structure attached at theend of the tube to reduce the recoil action

Loads on the new attachment device Pressure pulse from inlet end of the tube

Thermal loads from the source of the pressure

pulse Design objective

Maximize braking by smart design tominimize forces and moments (torques) onthe tube Smartness defined by minimum space and

material use without loss of strength or life


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Engineering Solution

The case studied here is a muzzle block

The attachment geometry is for exemplificationonly and is not for any real equipment or anydesign

The total engineering of such system require

analysis of multiple fields of physics Propulsion system, material science, aero-acoustics,turbulence, fatigue life estimation, stress-concentrationand micro-cracks, solidification, heat treatment,machining, surface finish, etc.

This study focuses only on analysis of coupled FSI

problem to demonstrate maturity of the analysis tool


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Objectives

Explore the state of th e artin simulation for two-way fluid structureinteraction to predict the pressure, thermal loads, on the fluid side and

deformations of the structures

Multiple loading cycles in a single analysis

Objective is NOTto do all the detailed simulation of 1 cycle

Requirements: Two way coupled, unsteady, FEA & CFD analysis

Robust, easy to use, flexible

Automated with minimal user intervention

Optimization tools

Develop the initial Proof-of-Concept ! Feasibility study

Focus on correctness of physics by establishing proper coupling


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Assumptions

Fluid simulation

Blow down simulation

No moving solid-load in the tube

Typical chamber pressure is compensated

Half geometry, vertical symmetry

Fluid material properties

NASATM 4647 ; NASA/TP-2002-211556

FEA simulation

Flexible multi body dynamics Tube inlet is fixed in space

Solid material properties

Alloy Steel

http://www.efunda.com/materials/alloys/alloy_home/steels_properties.cfm


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Workflow and Data Transfer

Pre-processing

ANSYS Simulation: Solid mesh, mechanical simulation setup

ICEM CFD: Fluid mesh

ANSYS CFX-Pre: CFD, FSI simulation setup

Solver and Execution ANSYS Multiphysics: A single integrated, fully coupled environment

FEA Solver: ANSYS Simulation CFD solver: CFX-Solver

Data Transfer CFD to FEA: Wall heat flux and total force

FEA to CFD: Wall temperature and displacement

Data transfer between ANSYS and CFX solvers is fully automated

Post-processing ANSYS CFX Post

Solid and Fluid field variables can be post processed together


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Fluid Domain and Mesh

Mesh Generated using ICEM CFD

Blocking concept, hexahedral mesh

Initial proof of concept mesh

Number of Nodes 49322

Outer domain:External flow

Chamber:High pressure, hightemperature

Barrel

Ground

Muzzle block

FLUID Domain


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Solid Domain and Mesh

Mesh Generated using ANSYS Simulation

Easy to use, highly automated and fast!

Hex mesh in the barrel

Tet mesh in the muzzle block

PulseSource


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Workflow SnapshotsMechanical Simulation Setup

Boundary Conditions : Solid

Material: Steel Alloy

Analysis Type : Flexible Dynamics

Coupled Field Element Solve for thermal and structural stresses


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Workflow SnapshotsCFD Simulation Setup

Material properties

Density: Ideal Gas mixture

Temperature dependentproperties

NASATM 4647;

NASA/TP-2002-211556

Physical Models SST K- turbulence model

Natural convection

Initial condition 1atm and 300K, zero velocity

Source term approach forinitial high P and T Mass and energy sources

corresponding to 820 atm and1120 K at pulse source

Applied at the first time step of

each cycle

Adaptive Time stepping Time step size ramp up from

7e-6 s (min) to 0.25 s (max)

B.C. types Green : Opening

Red : FSI interface

Cyan : Ground

Open face: Symmetry


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Workflow SnapshotsFSI simulation set-up in ANSYS CFX Pre

FSI Simulation Setup

External coupling

Interface load transfer

CFD solver control


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CFX Solver input ANSYS Solver input

Workflow SnapshotsFSI simulation start-up using ANSYS CFX-Solver


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MFX Multi-Field Solver

Supports Simulation betweenMultiple Executables

FEA CFD

Third Party Coupling Scheme NotRequired

Uses Client/Server architecture

TCP/IP

Heterogeneous Networks(LAN/WAN/Internet)

Supports Large Models

Solution on Two Machines

CFX Solution can use ParallelProcessing

Supports Nonconformal Meshes

Transfers Surface Loads

Automatically Morphs CFD Mesh

ANSYS Multi-Field Solver

Sequential load transfer coupling

MFSCoupling within a

single executable

MFXCoupling between

multiple executables

ANSYS/CFXFSI

Other combinations infuture releases!

Coupling of structural,

thermal, electric and

electromagnetic fields

in ANSYS Multiphysics.


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ResultsSolvers output CFX & ANSYS

Cooling period

b/w the pressure

pulses ~10sec

CFX Output

ANSYS Output

Total force (N) Fx, Fy, Fz

on FSI interface

Maximum mesh

displacement (m) in the

Fluid Domain


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Workflow SnapshotsPost Processing

Coupled simulation post-processing in ANSYS CFX Post

Common Graphical User Interface

Can analyze intermediate time step data

Easy to create/save animations

Geometry definition

Post surfacesAnimation controls


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Results CFD

Mach no. @ Symmetry Plane Temperature @ Symmetry Plane

16 - Cycles


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Results CFD

Temperature iso-surface, 500K Pressure iso-surface, 0.1 atm(g)

5 - cycles


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Results Mechanical

Temperature on FSI interface Temperature on the Muzzle block

7- cycles


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Results Mechanical

Structural deformation x25000

5 - cycles


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Future Work

Appropriately finer mesh

Inclusion of additional physics Radiation model

Real gas effects

Including moving solid loads

Moving solid considered rigidApproximated by a moving

interior plane in layering

Fully coupled 1-DOF solids motion

Significant time saving

Source terms to model energyimpulse of the cartridge detonation

Improve run time performance Effects of tightness of the convergence criteria on solution accuracy

Ensure parallel performance


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Conclusion

Two way coupled FEA & CFD Demonstrate seamless two way fluid/thermal and structural coupling

for high speed compressible flow simulation

Easy to Use

Single, intuitive environment for the entire FSI simulation setup

Robust Minimal user intervention for the FSI run

Robust FEA and CFD solvers, even with larger time step size

Automation with minimal user intervention

Full automation through scripts possible

Flexible Ability to add advanced models to include more physics

Optimization Design Explorer in Workbench


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Questions and Answers


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Multi-field Solver Field Interface

Loads Transferred Across Field Interface

Physics Fields SEND RECEIVE

Structural Displacement Force, Temperature

ThermalTemperature, Heat

Generation, Heat Flux

Displacement, Heat

Generation

Electric Field Force, Heat Generation Displacement, Temperature

Magnetic Force, Heat Generation Displacement, Temperature

FluidSurface Force, Surface

Temperature

Displacement, Surface

Temperature

HF Electromagnetic Heat Generation Temperature

Please refer to ANSYS coup led field analysis gu ide for tho roug h detai ls.


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MFX Multi-field Solver

ANSYS Master CFX Slave

Time Loop

End Time

Loop

Stagger Loop

End Stagger

Loop

Time Loop

End Time

Loop

Stagger Controls (ANSYS to CFX)

Load Transfers

Stagger Controls (Bidirectional)

Stagger Loop

End Stagger

Loop

CFX

SolverANSYS

Solver

Time Controls

Time Controls

Do Mapping

Documents

2008 Int ANSYS Conf Strongly Coupled Fsi Sim