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Smearing of Mass Transfer(condensation)using UDS over interface. 

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May 23, 2016, 11:19 
Smearing of Mass Transfer(condensation)using UDS over interface.

#1 
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Rajukiran Antham
Join Date: Dec 2012
Location: Sweden
Posts: 39
Rep Power: 5 
Hej,
I am working on phase change problem (condensation). I wrote UDF's for calculation of source terms. I want to smear mass transfer near the interface using a Diffusion equation and then pass the smeared values as source terms to the equations. I am solving the diffusion equation using UDS and passing mass transfer as source term to UDS. Below is the diffusion equation which I am solving, D*del2(phi)= S here, D is diffusion coefficient, phi is scalar variable and S is source term, I am passing source term using Define_source UDF, DEFINE_SOURCE(UDS_src,c,t,dS,eqn) /*smearing source udf*/ { real UDS_source; UDS_source = 0.0; UDS_source = C_UDMI(c,t,1)C_UDSI_M1(c,t,0) ; dS[eqn] = 0.0; return (UDS_source); } In the above UDF C_UDMI(c,t,1) is the mass transfer term which is calculated in a different UDF. Diffusion coefficient D is passed using below UDF. #include "udf.h" DEFINE_DIFFUSIVITY(mean_age_diff,c,t,i) { return 0.0000001; } What I was expecting was a smeared mass transfer over few cells close to the interface , since mass transfer is calculated only at the interface. but I am not getting the expected result. I am not sure where I am going wrong. I would really appreciate if someone can point out where I am going wrong. regards, Rajukiran. PS: I am also attaching pic of scalar value of phi and interface where source terms are added. 

May 24, 2016, 08:19 

#2 
Member
Rajukiran Antham
Join Date: Dec 2012
Location: Sweden
Posts: 39
Rep Power: 5 
Hej,
I tried a simple case, where I tried solving a steady diffusion equation using UDS. I switched off inlet Diffusion, Flux and unsteady function in the UDS. I used Neumann boundary conditions over the domain. I gave a constant source term through UDF only at the interface. I was expecting that the given source term to smear over the interface. But I got something similar to previous case. I would really appreciate if someone can answer this. Thanks in advance Regards, Rajkiran 

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