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-   -   UNIVERSITY OF WARMIA AND MAZURY IN OLSZTYN (http://www.cfd-online.com/Forums/fluent/49406-university-warmia-mazury-olsztyn.html)

wojciech October 2, 2008 07:53

UNIVERSITY OF WARMIA AND MAZURY IN OLSZTYN
 
Hello,

I calculate in Fluent 6.3.26 a typical flow in porous medium with Forchheimer model (equation 7.19-2 in Fluent doc.). I have permeability and Forchheimer coefficient from own experiment. When I use the original Fluent model, the results are very good (error <3% in all cases). Now I try calculate the same sample with a UDF. Unfortunately, the pressure fall is smaller (about 0.3 the good value). What can bee the reason? There is my UDF:

-------------------------------------------- #include "udf.h" DEFINE_SOURCE(forchheimer_z,cell,thread,dS,eqn) { real k; real 2_beta; real Uz; real linear; real nonlinear; real source;

k = 4.90987500E+08; 2_beta = 36430.72; Uz = C_W(cell,thread); linear = C_MU_L(cell,thread)/k; nonlinear = 2_beta * 0.5 * C_R(cell,thread); source = -(linear * Uz + nonlinear * fabs(Uz) * Uz); dS[eqn] = -(linear + 2.0 * nonlinear * fabs(Uz));

return source; }

--------------------------------------------

Thanks for all answers...


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