# can you help? Its great for me.

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 January 25, 2006, 22:45 can you help? Its great for me. #1 Tajul Guest   Posts: n/a Sponsored Links HI I am Tajul. I am a little bit despair about Fluent User Forum. I posted messages two times about my same problem but no one answered. This is the 3rd time I am sending the same problem. I do not think that no one does not know the answer. I am working with microchannel flow with slip wall boundary condition. The slip wall boundary condition is uw=Kn.(delu/deln)where uw is the fluid velocity at the wall, n is the normal coordinate pointing inward from the channel wall. Kn is the Knudsen number where kn=1/H.(viscosity*sqrt(pi)/sqrt(2*density*pressure)). H is the height of the channel. I wrote a UDF like this but giving floating point error and invalid number. I do not not how to set boundary conditions and hook this UDF. If any one help me I will be grateful to him and apreciate his kindness. #include #include #define PI 3.141592 DEFINE_PROFILE(wall_vel, t, i) { face_t f; cell_t c0; Thread *t0; double lamda, viscosity, density, Kn, R, Temperature, pressure, H, val, sigma_m, g_u, g_v, g_mag; H = 0.0000012; sigma_m = 1.0; begin_f_loop(f,t) { c0=F_C0(f,t); t0=t->t0; viscosity = C_MU_L(c0,t0); density = C_R(c0,t0); R=C_RGAS(c0,t0); pressure=C_P(c0,t0); Temperature=C_T(c0,t0); pressure = density*R*Temperature; lamda = viscosity * sqrt(PI) / (sqrt(2.*density*pressure)); Kn = lamda / H; g_u = C_U_G(c0,t0)[1]; g_v = C_U_G(c0,t0)[2]; g_mag=.5*(g_u+g_v); val = ((2. - sigma_m)/sigma_m)*Kn*g_u; F_PROFILE(f,t,i)=val; } end_f_loop(f,t) } Thanking Tajul

 January 26, 2006, 04:33 Re: can you help? Its great for me. #2 HVN Guest   Posts: n/a In your include you have forgetton the "udf.h"

 January 26, 2006, 04:50 Re: can you help? Its great for me. #3 Tajul Guest   Posts: n/a Hi HVN, I have written that in my original UDF. It was left at the time of copying. If you have any other suggestions I'll apreciate. Thanks Tajul #include #include

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