# why does slip velocity take no changes?

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 April 25, 2007, 06:39 why does slip velocity take no changes? #1 Wang Guest   Posts: n/a Sponsored Links Hi,In my case slip velocity: u_wall=B*du_wall/dy. B is the slip length. shear stress : t_wall=A*du_wall/dy. I have to contain B in my UDF program. I use the equation t_wall=(A/B)*u_wall instead of t_wall=A*du_wall/dy.So when I changed the slip coefficient B,the flow should also change But the result seem not so.Flow rate is always the same when B changes.I don't know how mistakes accure, could you please help me? I wrote a UDF to simulate slip boundary condition.and hooked it at the specified shear. My UDF is below: ---------------------- DEFINE_PROFILE(slip_wall,thread,index) { ... begin_f_loop(f,thread) { if(time<0.001) F_PROFILE(f,thread,index)=0; else { c=F_C0(f,thread); cell_thread=THREAD_T0(thread); F_PROFILE(f,thread,index)=coef*C_U(c,cell_thread); } } end_f_loop(f,thread) } ------------------------------- best regards! Wang
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 June 26, 2010, 09:23 hi wang,slip velocity ,help! #2 New Member   王国斌 Join Date: Jun 2010 Location: beij,chongqing,Chengdu Posts: 22 Rep Power: 9 hello, wang, i am studying at beijing, where are you now? if you see my message,please add my QQ 568179641, i have some slip problem to chat with you faithlly.

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