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COMPUTER MODELING OF FLUID STRUCTURE HEAT TRANSFER
SOFTWARE fluidyn - MP
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PRESENTATION OF fluidyn - MP
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General : role & utility of Computational Fluid DynamicsA reliable numerical representation of a real processus with the help of well adapted physical models
Easy to use & adapted to optimisation studies in industrial processes
Economic with a security advantage
Ideal complementary tool for experimental measurements
Access to physical variables (velocities, pressure, temperature, etc.) at each point in the domain
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Software fluidyn - MP, CHT Model Strong coupling & conjugate heat transfer between fluid & structures integrated in a single software platform
Robust physical models & various well adapted solvers
Finite Volume Method for fluids and Finte elements method for structures
Automatic exchange of boundary conditions between fluids & structures - Adaptative Fluid Mesh
Local time step used to reduce CPU time
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3-DimensionsCompressible / incompressibleMechanical / thermal shocks Viscous / non-viscousLaminar / turbulentMulti-speciesMulti-phaseSolution of Navier-Stokes EquationsFluid Solver
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Non-Newtonian Flows : Bingham lawPower law
Chemical combustion reactions Arrhenius modelEddy-break-up modelEddy dissipation model
Deflagration & fireBLEVEPool fire
DetonationJWL model
Two phase flows droplets, bubbles, particlesEuler-Lagrange Monte-Carlo, Free surface flow ( VOF method + CSF method)
Fluid Solver
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Algebraic ModelsBaldwin- LomaxMixing Length :Van Driest dampingAbbott & BushnellCebeci- SmithSub grid scale model SGS Two equations transport (k - e) & RNGReynolds stress model (anisotropic turbulence) Turbulence ModelsFluid Solver
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Perfect gasIdeal gasJWL (Jones - Wilkins - Lee) for explosionsLinear - polynomialUser definedEquations of StateTemperature functionsUser definedViscosity & Prandtl numberFluid Solver
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Spatial discretization schemesExplicit: Van Leer Flux Vector Splitting Roe Flux Difference Splitting 3rd order Advection Upwind Splitting, HLLCSemi- implicit : Weighted Upwind Scheme QSOU 2nd order Implicit : Central Difference Scheme 3rd order Flux Limiter Scheme (Van Leer, SMART, etc.)
Fluid Solver
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Explicit :Time stepglobal minimum for transient simulations local for steady state simulationsconvergence accelerationTemporal Integration 6 step 2nd order Runge Kutta.
Implicit:Gauss-Seidel or Jacobi iterative methodssteady state calculation & low velocities.Temporal discretization schemeFluid Solver
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3 available models
Arrhenius Modelcoefficients of chemical reactions linked to Arrhenius parameters & activation temperatures
EDC Model (Eddy Dissipation Concept)Magnussen formula used to link the intermittent turbulent flame to the turbulent dissipation rate
Minimum of the Arrhenius model & EDCadapted to high velocity turbulent flows
Monitoring combustion gases (CO, CO2, NOX...) & smoke, dispersionCombustion Modelling
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Finite Volumes computation in the fluid
Radiation ModelsTransparent MediaAutomatic calculation of 3D view factorsShadow effect of intermediate obstaclesOpaque Media Six-Flux modelDiscrete ordinate model
Collaboration with research laboratories (EM2C laboratory of Ecole Centrale, Paris) et industries (CIAT) for heat transfer modellingRadiation Modelling
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Convectionfinite volumes computation in the fluidautomatic computation of heat transfer coefficient in fluid - structurehigh order spatial solution schemes (3rd order)
Conductionfinite elements computation in the structure (beams, shells, tetrahedrals, etc.)computation with an adapted local time step
Strong coupling with automatic exchange of boundaryconditions between fluid & structuresConvection / conduction modelling
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Finite Elements beams shellstetrahedral, hexahedralbricks, springs, etc.
Material characteristics
Linear elasto-plastic, orthotropic Piecewise linear Non linear plasticStructured solver
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Structured solver Small deformations & large displacements Finite Elements method
Large deformationsFinite Elements method
Finite Elements solversExplicit / implicit
Rayleigh damping
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Boundary Conditions
Transient or constant
Outside :at nodes : temperature, forces, displacementsat faces: pressure, volume forces
Imposed automatically in fluids & structures
Modelling displacement of fluid mesh with Updated Lagrangian methodStructured Solver
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Computation Procedure - 4 steps
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Multi-block structured
Un-structuredDelaunay method2D & 3D meshesHybrid, tetrahedral or hexahedral mesh
Adaptative meshShocks, turbulent boundary layers, ..Refined mesh & automatic interpolation of the solution.
Interactive, simple & automatic
Complex geometries
MeshPre - processor
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Geometry & computation parameters visualisation during simulation.
3D colour visualisation.
Multi-viewport facility : upto 30 viewports
Comparison of results obtained from different computations
Vectors, iso-contours, iso-surfaces & 3D current lines
Translations, rotations, multi projections
XY plots: residual & other parameters
AnimationsPost - processor
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Examples of studies conducted with fluidyn - MPModelling of Fluid Structure Heat Transfers Fire in a traincompartmentExchanger slab (CIAT)RefrigeratorAfterburnerRiserWaste incineratorCooling metalPipe with 2 fluids (high pressure)
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CASE 1Fire in a train compartment
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Study FrameworkTwo phases :Simulation of code calibration in the case of fire modelling in an enclosure
experimental results : sample compartment consisting ofa seat & a ventilation system reproduction of heat phenomenon(convection + radiation) optimisation of principal parameters : smoke rates coefficient of smoke absorption distribution of chemical energy of the burned seat asradiative & convective energy mesh Simulation done for the whole car (complex geometry,Multiple boundary conditions)
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Phase 1 : geometry
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Phase 1 : Model setting
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Phase 2 : geometry
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Phase 2 : mesh
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Phase 2 : Results
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Phase 2 : Results
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Phase 2 : Results
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Phase 2 : ResultsVENTILATION & FIRE IN THE COMPLETE CARTemperature evolution in a compartment
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Phase 2 : ResultsRoof
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CASE 2Heat exchanges in a exchanger slab
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Study frameworkDescription
Cooling in one of the fin tubes of an exchanger by air flow
Dimensions of the fin tube = 100 45 0.5 mm
Fin tube material = aluminium
Cooling fluid circulating in the tubes, T = 25C.
External temperature (air) = 10C.
Inlet air velocity = 2 m/s
Simulation until temperature stabilisation in the structure
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Geometry
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Mesh
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ResultsMPpressure field
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ResultsMPMPvelocities field
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ResultsMPMP
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ResultsMPtemperature field
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ResultsMPtemperature in the structure
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CASE 3Heat Exchanges in a refrigerator
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Study frameworkDescription
The refrigerator has 4 compartments separated by 3 slabs cooled by a cooler (- 90C).Dimensions of the refrigerator = 128.5 55 74 cmThe compartments are interconnected behind the refrigerator.The refrigerator is insulated by a polyurethane layer.Insulator thickness : 8 mm cm on the panel in front, 12 cm in the restThe external temperature is 20C.The heat transfer across the insulation involves the natural convection currents in the compartments.Simulation time= 100 min (temperatures stabilised in the insulator & in the refrigerator)Air Polyurethane
= 1.972 kg/ m3 = 48.053 kg/ m3 = 1.23e-5 Pa.s k = 0.025 W/mK Cp = 1007.4 J/kgK Cp = 400 J/kgK Pr = 0.744 = 0.0055
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Geometry
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MeshTransverse View Top view
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ResultsTemperature Contours in the insulator x = 0.45 m
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ResultsTemperature Contours in the insulator y = 0.4 m
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ResultsTemperature Contours in the insulator z = 0.75 m
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ResultsNatural convection : velocity field x = 0.24 m
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ResultsNatural convection : velocity field y = 0.53 m
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ResultsTemperature contours in the compartments along X axis
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ResultsTemperature contours in the compartments along Y axis
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ResultsTemperature contours in the compartments along Z axis
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CASE 4Heat exchanges in an afterburner
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Description
Expansion of hot gases in the main body of an afterburner
Injection of cold air in the bypass duct which mixes with the hot air through the wall with holes.
Stabilisation of the turbulent flame by an arris gutter.
Liquid fuel injected across 4 surfaces.
Chracteristics : hot flows (combustion), heat transfers, structural deformations
Objectives : measurement of combustion efficiency (CO, CO2, H20)
Parameters : hot & cold air mixture, fuel vapor-gas mixture, stabilisation of the flameStudy framework
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Geometry
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Mesh
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Numerical MethodsDescription
Twophase compressible flow, turbulent with kinetic reactions, jet, radiation
Unstructured mesh
High order schemes for solution of heat transfers
Steady implicit solver for the fluid & transient explicit solver for the structure
turbulence model RNG k e
combustion model EDC
fuel spray : discrete particle model, Monte Carlo size distribution
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ResultsVelocity contours in the median plane
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ResultsTemperature Contours in the median plane
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ResultsHeat flux on the jacket of the cold air passage
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ResultsPost combustion efficiency
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ResultsDeformation of the after-burner flame holderInitial stateFinal state
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ResultsResults of the displacements at the injector levels
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ResultsDeformation at injectors levelInitial StateFinal State
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CASE 5Heat transfers in a riser in maritime environment
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Study frameworkDescription
The riser is a system composed of a vertical pipe consisting of a circulating fluid which is imbricated in an insulated matrix (chemical reactor). It is submerged in sea water.
Fluid = water circulating at an initial temperature of 45C
Vertical Pipe = steel
Insulator = gel, foam & polypropylene
Temperature of sea water = 4C
Stabilised temperatures during simulation = 7 h
Objective : establish a temperature map in the pipe & in the reactor
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Geometry
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ResultsTemperature contours in the fluid domain
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ResultsTemperature contours in the structure
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CASE 6Heat exchanges in a refractory of a domestic waste incinerator
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Wall protected by the refractoriesHEAT EXCHANGER IN A DOMESTIC WASTE INCINERATOR
INCORPORER AutoCAD-r13
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DESCRIPTION :The water / vapour pipes are inside the incinerator wall.The pipes are thermally protected by a refractory material (7 different insulators).insulatorrefractory Study framework
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Mesh
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TEMPERATURE CONTOURS T = 0 ms
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TEMPERATURE CONTOURS T = 500 s
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TEMPERATURE CONTOURS T = 1000 s
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TEMPERATURE CONTOURS T = 2000 s
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CASE 7Cooling in a piece of metal
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METAL RETRACTIONTemperature contours in the metal
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Mesh deformation Dynamic adaptative mesh which follows the retraction
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CASE 8Nuclear applications : heat exchanges in a pipe under high pressure
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Flow in a bend with heat transfer in the fluid & the pipe walls
Fluid : Incompressible = 870 kg/m3 = 0.001 Pa.s
Structure : Density = 7800 kg/m3Conductivity = 63W/m-K Specific Heat = 420
Inlet : Pressure = 157 bar Velocity = 1 m/s
cold fluid : Temperature = 423Kheat fluid :Temperature = 523K
Outlet : Pressure = 157 bar
HEAT TRANSFERS IN A PIPE
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Geometry
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Boundary ConditionsAccidental scenario in with 2 fluids present
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Turbulent incompressible flowfluid = watermodel k- for turbulenceMultiblockModellingPipe = steelLinear elastic modelFinite elements = hexahedral
FLUIDSTRUCTURE
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ResultsTemperature Contours in the fluid near the wall
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ResultsTemperature contours in the wall
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ResultsStress on the walls
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ResultsPipe deformations under heat stress
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ResultsVelocity field in the plane of the pipe diameter
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CONCLUSIONThe software fluidyn - MP is well adapted to the modelling of strong heat coupling between the fluid & structure
The software fluidyn - MP is well adapted to the modelling of deformations (mechanical & heat in the structure)
Possibility to develop a software dedicated to the study of heat transfers between the bridge (structure) & the lacquer (fluide)automatic mesh generationstudy of different temperaturesadjustable & optimisable parameters(material choice, thickness)
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UKSutton ColdfieldFRANCELyonCHINABeijingJAPANTokyo