How to implement production term due to buoyancy for k-omega equations? Note that this is automatically taken into account for k-epsilon models and RSM.
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These terms will be automatically taken into account in the future release.
For versions Fluent12.1 (and previous releases), use the following UDF: It works for incompressible ideal gas option and can be easily adapted to boussinesq approximation. /* A source term to the k equation could be invoked through a */ /* DEFINE_SOURCE UDF to include this effect in k-omega model */ #include "udf.h" #include "sg.h" #include "models.h" /* UDF to compute buoyancy production in TKE equation */ DEFINE_ADJUST(store_tg,domain) { Alloc_Storage_Vars(domain, SV_T_RG, SV_T_G, SV_NULL); T_derivatives(domain); Free_Storage_Vars(domain, SV_T_RG, SV_NULL); } DEFINE_SOURCE(tke_gb, c0, t0, dS, eqn) { real beta, mu_t, temp; real prod1=0.,source; real pr_t = M_keprt; /* Compute Buoyancy Production */ mu_t = C_MU_T(c0,t0); temp = C_T(c0,t0); /* This assumes ideal gas behavior. More general */ /* implementation would query beta from the solver */ beta = 1./temp; if(NNULLP(T_STORAGE_R_NV(t0, SV_T_G))) { prod1 = beta*mu_t/pr_t*NV_DOT(M_gravity,C_T_G(c0,t0)); } else if (c0==0) Message0("Error, temperature gradient not storedn"); source = prod1; return source; } /* option full buoyancy directional */ DEFINE_SOURCE(omega_gb_directional, c0, t0, dS, eqn) { real beta, mu_t, temp; real prod1=0.,source; real pr_t = M_keprt; real C_epsilon3=1.; /* Compute Buoyancy Production */ mu_t = C_MU_T(c0,t0); temp = C_T(c0,t0); /* This assumes ideal gas behavior. More general */ /* implementation would query beta from the solver */ beta = 1./temp; if(NNULLP(T_STORAGE_R_NV(t0, SV_T_G))) { prod1 = beta*mu_t/pr_t*NV_DOT(M_gravity,C_T_G(c0,t0)); } else if (c0==0) Message0("Error, temperature gradient not storedn"); C_epsilon3=compute_keC3(C_U(c0,t0),C_V(c0,t0),C_W(c0,t0)); source=C_epsilon3*M_keC1*MAX(0,prod1)*0.09*C_O(c0,t0); return source; } |
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