Flow boiling implementation with OpenFoam

Transcription

1 Flow boiling implementation with OpenFoam Qingming Liu KTH,Department of Energy

2 contents Introduction Background Physical and mathmatic models Implementation on OpenFoam Transport model Solvers Boundary conditions

3 Introduction Set up the bubbly flow case in OpenFOAM. Implementing myinterfoamdiabatic based on interfoam which using VOF method for simulation of two phase isothermal flow by adding energy equation as well as implementing an heat flux boundary condition. To study the flow pattern and temperature of elongated bubble flow in micro-channels(with diameter 1.7mm). Future plan:adding source terms to the U,T equations.

4 Background MEMS(micro electronic and mechanic systems) fuel cells cooling of micro-electronic chips compact heat exchangers

5 Macro scale Flow boiling in a uniformly heated circular tube ( Collier & Thome, 1994, p.170)

6 Bubbly flow slug flow(elongated bubble) Transition skewed flow liquid ring flow frothy annular flow Transition annular flow rivulet flow

7 α t+u α=0 ; Mathmatical models

8 Discription of problem

9 Openfoam OpenFOAM interfoam InterFoam +Energy equation +Cp,K, Libraries TransportModels myinterfoamdiabatic Utilities Swak4Foam mytransportmodels myinterfoamdiabatic

10 transportmodels/incompressibletwophaseproperti es/twophasemixture.h const dimensionedscalar& Pr1() const return Pr1_; } Add specific heat capacity,prandlt number,thermal conductivities for each phase dimensionedscalar cp1_; dimensionedscalar cp2_; dimensionedscalar Pr1_; dimensionedscalar Pr2_; Const tmp<surfacescalarfield> kappaf() const dimensionedscalar& Pr2() const return Pr2_; }; const dimensionedscalar& cp1() const return cp1_; } const dimensionedscalar& cp2() const return cp2_; };

11 twophasemixture.c cp1_(numodel1_- >viscosityproperties().lookup("cp" )), cp2_(numodel2_- >viscosityproperties().lookup("cp" )), Pr1_(nuModel1_- >viscosityproperties().lookup("pr" )), Pr2_(nuModel2_- >viscosityproperties().lookup("pr" )), tmp<surfacescalarfield> twophasemixture::kappaf() const surfacescalarfield alpha1f = min(max(fvc::interpolate(alpha 1_), scalar(0)), scalar(1)); return tmp<surfacescalarfield> ( new surfacescalarfield ( "kappaf", alpha1f*rho1_*cp1_*(1/pr1_)*fv c::interpolate(numodel1_- >nu()) + (scalar(1) - alpha1f)*rho2_*cp2_*(1/pr2_)*f vc::interpolate(numodel2_- >nu()) ) ); }

12 Read function twophasemixture.c bool twophasemixture::read() if (transportmodel::read()) if ( numodel1_().read(subdict(phase1name_)) && numodel2_().read(subdict(phase2name_)) ) numodel1_- >viscosityproperties().lookup("rho") >> rho1_; numodel2_- >viscosityproperties().lookup("rho") >> rho2_; numodel1_- >viscosityproperties().lookup("cp") >> cp1_; numodel2_- >viscosityproperties().lookup("cp") >> cp2_; numodel1_- >viscosityproperties().lookup("pr") >> Pr1_; numodel2_- >viscosityproperties().lookup("pr") >> Pr2_; complied the lib to $FOAM_USER_LIBBIN modifying the Make/files: LIB = $ (FOAM_USER_LIBBIN)/ libmyincompressiblet ransportmodels

13 Solver: myinterfoamdiabatic alphaeqnsubcycle.h Add specific heat capacity,prandlt number,thermal conductivities for each phase CreateFields.H: const dimensionedscalar& cp1 = twophaseproperties.cp1(); const dimensionedscalar& cp2 = twophaseproperties.cp2(); Info<< "Reading / calculating rho*cp\n" << endl; volscalarfield rhocp ( IOobject ( "rho*cp", runtime.timename(), mesh, IOobject::NO_READ, IOobject::NO_WRITE ), alpha*rho1*cp1 + (scalar(1) - alpha)*rho2*cp2, alpha.boundaryfield().types() ); rhocp.oldtime(); Info<< "Reading / calculating rho*phi*cp\n" << endl; surfacescalarfield rhophicpf ( IOobject ( "rho*phi*cpf", runtime.timename(), mesh, IOobject::NO_READ, IOobject::NO_WRITE ), rhophi*cp1

14 create TEqn.H solver surfacescalarfield kappaf = twophaseproperties.kappaf(); fvscalarmatrix TEqn ( fvm::ddt(rhocp, T) + fvm::div(rhophicpf, T) - fvm::laplacian(kappaf, T) ); Teqn.solve(); InterFoam.C Add: #include "Teqn.H" Modifying Make/files EXE = $ (FOAM_USER_APPBIN)/myinterFo amdiabatic

15 Make Modifying Make/options EXE_INC = \ -I$(LIB_SRC)/transportModels \ -I$ (WM_PROJECT_USER_DIR)/src/transpor tmodels/incompressible/lninclude \ -I$ (LIB_SRC)/transportModels/interfaceProp erties/lninclude \ -I$ (LIB_SRC)/turbulenceModels/incompressi ble/turbulencemodel \ -I$(LIB_SRC)/finiteVolume/lnInclude EXE_LIBS = \ -L$(FOAM_USER_LIBBIN) \ -linterfaceproperties \ -lmyincompressibletransportmodels \ -lincompressibleturbulencemodel \ -lincompressiblerasmodels \ -lincompressiblelesmodels \ -lfinitevolume

16 Utilities Swak4Foam svn checkout

17 Set up Case Mesh fluent3dmeshtofoam

18 Set up the case:add Cp and Prandlt number constant/transportproperties add Cp and Prandlt number phase1 phase2 transportmodel Newtonian; transportmodel Newtonian; nu nu [ ] 0.75e-06; rho rho [ ] ; Pr Pr [ ] 0.9; cp cp [ ] ; nu nu [ ] 3.57e-06; rho rho [ ] ; Pr Pr [ ] 0.87; cp cp [ ] ;

19 system/controdict, fvschemes add new finite divergence schemes for Temperature divschemes application myinterfoamdiabatic; to use the new libraries libs("libmyincompressible TransportModels.so"); } div(rho*phi,u) Gauss limitedlinearv 1; div(phi,alpha) Gauss vanleer; div(rhophicpf, T) Gauss upwind; div(phirb,alpha) Gauss interfacecompression; add new finite volume solution methods for Temperature T solver BICCG; preconditioner DILU; tolerance 1e-7; reltol 0;}

20 Temperature boundary conditions vi 0/T dimensions [ ]; internalfield uniform 300; boundaryfield inlet type fixedvalue; value uniform 300; outlet type pressureinletoutlettemperature; } phi value phi; $internalfield; } wall type fixedvalue; value uniform 300;

21 Set up the constant heat flux wall set boundary condtions constant heat flux wall gradient(t)=q/k =15000/81.626=183, outlet type } zerogradient; vi 0/T wall type fixedgradient; value uniform ; } set the gravity in the constant/g dimensions [ ]; value ( ); constant/turbulenceproperties

22 Initialize the phase (bubble) funkysetfields (swak4foam) funkysetfields -field alphagas -expression 1 -time 0 -keeppatches -condition "pow(pos().x,2) + pow(pos().y,2) < pow(0.0075,2) && pos().z>0.12"

23 Run in parallel decomposate DecomposePar numberofsubdomains 4; method simplecoeffs simple; n ( ); delta 0.001;

24 Run case System/ControDict application interfoam; startfrom latesttime; starttime 0; stopat endtime; endtime 0.02; deltat 2e-4; writecontrol adjustableruntime; writeinterval 0.001; purgewrite 0; writeformat writeprecision 6; writecompression uncompressed; timeformat timeprecision 6; runtimemodifiable adjusttimestep maxco 0.5; ascii; general; yes; on; maxalphaco 0.5; maxdeltat 1;

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