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local thermal non equilibrium model in porous media |
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November 1, 2014, 16:00 |
local thermal non equilibrium model in porous media
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hi guys,im simulating a 2D transient problem,i have 9 different faces,i need to simulate 3 of these faces as a porous media using thermal non equilibrium model,and im using fluent6.3.26 and ansys fluent 15.0,fluent15 support the ltne model but its so heavy and slow,but fluent 6.3 is 2 times faster than fluent 15,my problem will take 17 days to reach the periodic state with fluent 6.3 (so 34 days with fluent 15.0),so i want to use fluent6.3 in order to reduce the time,going to the details of my problem i have to say that my porous solids are copper and steel and my working fluid is helium,and my solid walls are also copper and steel in non-porous zones,i have written some udf's and uds's to model the ltne in porous zones,but i dont know how to implement my codes,(specially the solid source term and solid diffusivity),i wonder if someone would help me,here is my code:
/********************************************/ /* user defined functions(UDFs) for LTNE MODEL */ #include "udf.h" /******************************************/ /* Global definitions ***/ /************************************************** ***/ /****************** constants********************/ /* particle diameter (m)*/ #define dp 27.9e-6 /* porosity */ #define porosity 0.696 /* hydraulic diameter(m)*/ #define dh (porosity*dp)/(1.0-porosity) /* c5,c6 copper thermal conductivity constants*/ #define c5 638.3495 /**********************************************/ #define c6 -0.0815 /* c7,c8 steel thermal conductivity constants*/ #define c7 1871.0374 /**********************************************/ #define c8 -0.5522 /****************** porous media:constants/functions for solid diffusivity******************/ #define COPPER_SOLID_DENSITY(T) 8933.0 #define COPPER_SOLID_THERMAL_COND(T) c5*pow(T,c6) #define COPPER_SOLID_CP(T) 385.0 #define STEEL_SOLID_DENSITY(T) 7870.0 #define STEEL_SOLID_THERMAL_COND(T) c7*pow(T,c8) # define STEEL_SOLID_CP(T) 447.0 /************************************************** *****************************/ /* Definition of user defined scalars (UDS) */ /************************************************** *********************/ enum { /*0*/ SOLID_TEMP, /*UDS for solid temperature*/ }; /************************************************** **********/ /** Diffusivity for UDS(SOLID_TEMP)*****************/ DEFINE_DIFFUSIVITY(UDS_diff_copper,cell,thread,i) { real source_copper,Ts,k_copper,rho_copper,cp_copper; if(i==SOLID_TEMP) { Ts=C_UDSI(cell,thread,SOLID_TEMP); k_copper=COPPER_SOLID_THERMAL_COND(Ts)*(1.0-porosity); rho_copper=COPPER_SOLID_DENSITY(Ts)*(1.0-porosity); cp_copper=COPPER_SOLID_CP(Ts); source_copper=(k_copper)/(rho_copper*cp_copper); } else source_copper=0; return source_copper; } DEFINE_DIFFUSIVITY(UDS_diff_steel,cell,thread,i) { real source_steel,Ts,k_steel,rho_steel,cp_steel; if(i==SOLID_TEMP) { Ts=C_UDSI(cell,thread,SOLID_TEMP); k_steel=STEEL_SOLID_THERMAL_COND(Ts)*(1.0-porosity); rho_steel=STEEL_SOLID_DENSITY(Ts)*(1.0-porosity); cp_steel=STEEL_SOLID_CP(Ts); source_steel=(k_steel)/(rho_steel*cp_steel); } else source_steel=0; return source_steel; } /************************************************** ***/ /* Helium properties ***/ /************************************************** ******/ /** Dynamic viscosity************************/ DEFINE_PROPERTY(helium_viscosity,cell,thread) { real mu,c1,c2,T; c1=3.9928e-7; c2=0.6853; T=C_T(cell,thread); mu=c1*pow(T,c2); return mu; } /**Thermal conductivity of helium******************/ DEFINE_PROPERTY(helium_thermal_conductivity,cell,t hread) { real kh,c3,c4,T; c3=2.3715e-3; c4=0.7294; T=C_T(cell,thread); kh=c3*pow(T,c4); return kh; } /************************************************** ******************/ /* Heat Transfer */ /************************************************** *****************/ /** Heat transfer coefficient between Solid and Gas *******************/ real HTC_solid_gas(cell_t cell,Thread*thread) { real Nu,Re,Pe,Pr,Us,hsf,asf,hv; /* calculate superficial velocity*/ Us=sqrt(pow(C_U(cell,thread),2.0)+pow(C_V(cell,thr ead),2.0)); /* calculate Reynolds number*/ Re=Us*dh*C_R(cell,thread)/helium_viscosity(cell,thread); /* calculate Prandtl number*/ Pr=C_CP(cell,thread)*helium_viscosity(cell,thread)/helium_thermal_conductivity(cell,thread); /* calculate peclet number*/ Pe=Re*Pr; /*calculate nusslet number*/ Nu=(1.0+((0.99)*(pow(Pe,0.66))))*pow(porosity,1.79 ); /* calculate HTC*/ asf=(4.0*porosity)/dh; hsf=(Nu*C_K_L(cell,thread))/dh; hv=hsf*asf; return hv; } /** Heat source fluid **************************/ DEFINE_SOURCE(SRCE_fluid_heat,cell,thread,dS,eqn) { real hv,Ts,T,source; hv=HTC_solid_gas(cell,thread); Ts=C_UDSI(cell,thread,SOLID_TEMP); T=C_T(cell,thread); source=hv*(Ts-T); dS[eqn]=-hv; return source; } /** Heat source solid****************/ DEFINE_SOURCE(SRCE_solid_heat,cell,thread,dS,eqn) { real hv,Ts,T,source; hv=HTC_solid_gas(cell,thread); Ts=C_UDSI(cell,thread,SOLID_TEMP); T=C_T(cell,thread); source=-hv*(Ts-T); dS[eqn]=-hv; return source; } |
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