Transient sinusoidal velocity inlet

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 September 27, 2010, 11:07 Transient sinusoidal velocity inlet #1 Member   Join Date: Jun 2009 Posts: 31 Rep Power: 17 I'm trying to impose a sinusoidal velocity boundary condition in a cylinder, but instead of having the velocity magnitude changing in time (according to the sinusoidal eq), I only get my inlet profile to change into a sine wave. I tried using different equations for defining my transient boundary condition, but the result is always the same: a sine profile at the entrance. The UDF I'm using is below. Is this the correct way to impose a transient boundary condition? does anyone have any suggestions? Thanks! #include "udf.h" DEFINE_PROFILE(unsteady_velocity, thread, position) { face_t f; real t = CURRENT_TIME; real vel; vel= 0.2+0.1*sin(t); begin_f_loop(f, thread) { F_PROFILE(f, thread, position) = vel; } end_f_loop(f, thread) }

 September 27, 2010, 11:17 #2 Member   Neil Join Date: Jun 2009 Location: The Moon Posts: 42 Rep Power: 17 An easy way around this would be to get hold of the de laval nozzle 2D tutorial which has a UDF that imposes a transient sinusoidal velocity profile at the inlet. Then modify it for your problem or see how the code is structured then modify your UDF. Neil

 September 27, 2010, 12:03 #3 Member   Join Date: Jun 2009 Posts: 31 Rep Power: 17 Hi Trev, I actually have the same structure, but the only thing that I changed is that instead of using pressure I'm imposing velocity. To do this I'm just reading the UDF into the velocity inlet BC... but it doesn't work.

 Tags porfile, transient bc, udf, velocity