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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 Dynamics A 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-Dimensions Compressible / incompressible Mechanical / thermal shocks Viscous / non-viscous Laminar / turbulent Multi-species Multi-phase Solution of Navier-Stokes Equations Fluid Solver

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Non-Newtonian Flows : Bingham law Power law Chemical – combustion reactions Arrhenius model Eddy-break-up model Eddy dissipation model Deflagration & fire BLEVE Pool fire Detonation JWL model Two phase flows droplets, bubbles, particles Euler-Lagrange Monte-Carlo, Free surface flow ( VOF method + CSF method) Fluid Solver

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Algebraic Models Baldwin- Lomax Mixing Length : Van Driest damping Abbott & Bushnell Cebeci- Smith Sub grid scale model SGS Two equations transport (k - ) & RNG Reynolds stress model (anisotropic turbulence) Turbulence Models Fluid Solver

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Perfect gas Ideal gas JWL (Jones - Wilkins - Lee) for explosions Linear - polynomial User defined Equations of State Temperature functions User defined Viscosity & Prandtl number Fluid Solver

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Spatial discretization schemes Explicit: Van Leer Flux Vector Splitting Roe Flux Difference Splitting 3 rd order Advection Upwind Splitting, HLLC Semi- implicit : Weighted Upwind Scheme QSOU 2 nd order Implicit : Central Difference Scheme 3 rd order Flux Limiter Scheme (Van Leer, SMART, etc.) Fluid Solver

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Explicit : Time step global minimum for transient simulations local for steady state simulations convergence acceleration Temporal Integration 6 step 2 nd order Runge Kutta. Implicit: Gauss-Seidel or Jacobi iterative methods steady state calculation & low velocities. Temporal discretization scheme Fluid Solver

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3 available models Arrhenius Model coefficients 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 & EDC adapted to high velocity turbulent flows Monitoring combustion gases (CO, CO2, NOX...) & smoke, dispersion Combustion Modelling

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Finite Volumes computation in the fluid Radiation Models Transparent Media Automatic calculation of 3D view factors Shadow effect of intermediate obstacles Opaque Media Six-Flux model Discrete ordinate model Collaboration with research laboratories (EM2C laboratory of Ecole Centrale, Paris) et industries (CIAT) for heat transfer modelling Radiation Modelling

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Convection finite volumes computation in the fluid automatic computation of heat transfer coefficient in fluid - structure high order spatial solution schemes (3 rd order) Conduction finite elements computation in the structure (beams, shells, tetrahedrals, etc.) computation with an adapted local time step Strong coupling with automatic exchange of boundary conditions between fluid & structures Convection / conduction modelling

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Finite Elements beams shells tetrahedral, hexahedral bricks, springs, etc. Material characteristics Linear elasto-plastic, orthotropic Piecewise linear Non linear plastic Structured solver

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Small deformations & large displacements Finite Elements method Large deformations Finite Elements method Finite Elements solvers Explicit / implicit Rayleigh damping

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Boundary Conditions Transient or constant Outside : at nodes : temperature, forces, displacements at faces: pressure, volume forces Imposed automatically in fluids & structures Modelling displacement of fluid mesh with Updated Lagrangian method Structured Solver

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Computation Procedure - 4 steps FLUID-STRUCTURE REMESHING Iterations until convergence Fluid solver Fluid temperature Heat transfer coefficient Distribution of boundary pressures Thermal solver Transient heat transfer Solid temperature Structured solver Thermal load Mechanical load (pressure) stress & deformations

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Multi-block structured Un-structured Delaunay method 2D & 3D meshes Hybrid, tetrahedral or hexahedral mesh Adaptative mesh Shocks, turbulent boundary layers,.. Refined mesh & automatic interpolation of the solution. Interactive, simple & automatic Complex geometries Mesh Pre - 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 Animations Post - processor

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Examples of studies conducted with fluidyn - MP Modelling of Fluid Structure Heat Transfers Fire in a train Fire in a train compartment Exchanger slab (CIAT) Exchanger slab (CIAT) Refrigerator Afterburner Riser Waste incinerator Waste incinerator Cooling metal Cooling metal Pipe with 2 fluids (high pressure) Pipe with 2 fluids (high pressure)

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CASE 1 Fire in a train compartment

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Two phases : ÙSimulation of code calibration in the case of fire modelling in an enclosure experimental results : sample compartment consisting of a 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 as radiative & convective energy mesh Simulation done for the whole car (complex geometry, Multiple boundary conditions) Study Framework

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Phase 1 : geometry Compartment meshBoundaries conditions VENTILATION AND FIRE INSIDE A COMPARTMENT

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Phase 1 : Model setting Trace points positionCalibration with experience VENTILATION AND FIRE INSIDE A COMPARTMENT

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Phase 2 : geometry VENTILATION AND FIRE INSIDE A WHOLE CARRIAGE Geometry and boundaries conditions

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Phase 2 : mesh

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Phase 2 : Results VENTILATION & FIRE IN A WHOLE CAR Velocities field on a cross section

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Phase 2 : Results Temperature (°C) 900 seconds after the beginning of fire

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Phase 2 : Results VENTILATION & FIRE IN A WHOLE CAR Evolution of temperature

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Phase 2 : Results VENTILATION & FIRE IN THE COMPLETE CAR Temperature evolution in a compartment

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Phase 2 : Results Temperature at t=900s Roof

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CASE 2 Heat exchanges in a exchanger slab

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Study framework Description 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 = 25°C. External temperature (air) = 10°C. Inlet air velocity = 2 m/s Simulation until temperature stabilisation in the structure Description 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 = 25°C. External temperature (air) = 10°C. Inlet air velocity = 2 m/s Simulation until temperature stabilisation in the structure

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Geometry Tube with refrigerant outflow fluid radiating plate fluid air inlet

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Mesh MP Structure mesh : Finite Elements / Fuid mesh : Finite Volumes

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Results MP pressure field

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Results MP velocities field

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Results MP temperature in the fluid

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Results MP temperature field

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Results MP temperature in the structure

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CASE 3 Heat Exchanges in a refrigerator

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Study framework Description The refrigerator has 4 compartments separated by 3 slabs cooled by a cooler (- 90°C). Dimensions of the refrigerator = × 55 × 74 cm The 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 rest The external temperature is 20°C. 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) Description The refrigerator has 4 compartments separated by 3 slabs cooled by a cooler (- 90°C). Dimensions of the refrigerator = × 55 × 74 cm The 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 rest The external temperature is 20°C. 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 = kg/ m 3 = kg/ m 3 µ = 1.23e-5 Pa.s k = W/mK Cp = J/kgK Cp = 400 J/kgK Pr = = Air Polyurethane = kg/ m 3 = kg/ m 3 µ = 1.23e-5 Pa.s k = W/mK Cp = J/kgK Cp = 400 J/kgK Pr = =

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Geometry

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Mesh Transverse View Top view

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Results Temperature Contours in the insulator x = 0.45 m

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Results Temperature Contours in the insulator y = 0.4 m

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Results Temperature Contours in the insulator z = 0.75 m

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Results Natural convection : velocity field x = 0.24 m

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Results Natural convection : velocity field y = 0.53 m

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Results Temperature contours in the compartments along X axis

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Results Temperature contours in the compartments along Y axis

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Results Temperature contours in the compartments along Z axis

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CASE 4 Heat 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, CO 2, H 2 0) Parameters : hot & cold air mixture, fuel vapor-gas mixture, stabilisation of the flame 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, CO 2, H 2 0) Parameters : hot & cold air mixture, fuel vapor-gas mixture, stabilisation of the flame Study framework

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Geometry

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Mesh

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Numerical Methods Description 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 – combustion model EDC fuel spray : discrete particle model, Monte Carlo size distribution Description 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 – combustion model EDC fuel spray : discrete particle model, Monte Carlo size distribution

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Results Velocity contours in the median plane

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Results Temperature Contours in the median plane

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Results Heat flux on the jacket of the cold air passage

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Results Post combustion efficiency

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Results Deformation of the after-burner flame holder Initial state Final state

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Results Results of the displacements at the injector levels

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Results Deformation at injectors level Initial State Final State

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CASE 5 Heat transfers in a riser in maritime environment

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Study framework Description 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 45°C Vertical Pipe = steel Insulator = gel, foam & polypropylene Temperature of sea water = 4°C Stabilised temperatures during simulation = 7 h Objective : establish a temperature map in the pipe & in the reactor Description 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 45°C Vertical Pipe = steel Insulator = gel, foam & polypropylene Temperature of sea water = 4°C 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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Results Temperature contours in the fluid domain

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Results Temperature contours in the structure

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CASE 6 Heat exchanges in a refractory of a domestic waste incinerator

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Wall protected by the refractories HEAT EXCHANGER IN A DOMESTIC WASTE INCINERATOR

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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). DESCRIPTION : The water / vapour pipes are inside the incinerator wall. The pipes are thermally protected by a refractory material (7 different insulators). Tube water/vapour Heat Transfers insulator refractory 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 7 Cooling in a piece of metal

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METAL RETRACTION Temperature contours in the metal

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Mesh deformation Dynamic adaptative mesh which follows the retraction

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CASE 8 Nuclear 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/m 3 = Pa.s Structure : Density = 7800 kg/m 3 Conductivity = 63W/m-K Specific Heat = 420 Inlet : Pressure = 157 bar Velocity = 1 m/s cold fluid : Temperature = 423K heat fluid :Temperature = 523K Outlet : Pressure = 157 bar HEAT TRANSFERS IN A PIPE

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Geometry

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Boundary Conditions Accidental scenario in with 2 fluids present

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Turbulent incompressible flow fluid = water model k- for turbulence Multiblock Modelling Pipe = steel Linear elastic model Finite elements = hexahedral FLUID STRUCTURE

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Results Temperature Contours in the fluid near the wall

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Results Temperature contours in the wall

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Results Stress on the walls

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Results Final state Initial state Pipe deformations under heat stress

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Results Velocity field in the plane of the pipe diameter

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CONCLUSION The 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 generation study of different temperatures adjustable & optimisable parameters (material choice, thickness…)

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INDIA Bangalore, New Delhi UK Sutton Coldfield USA Lafayette, CA FRANCE Lyon CHINA Beijing JAPAN Tokyo FRANCE 7, bd de la Libération Saint-Denis Tel: 33 (0) Fax: 33 (0) S.KOREA Séoul

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