UDF for upper wall velocity lid-driven cavity

piri · March 28, 2018, 15:24

Hello,
I am trying to give a position depended velocity to lid-driven cavity, top wall. My coordinate system is x-y and top wall is located at y=top.

I know all the procedure about loading the udf etc. but for some reason my udf is not working.

#include "udf.h"
DEFINE_PROFILE(top_x_velocity, thread, position)
{
real x[ND_ND];
real y;
face_t f;
begin_f_loop(f,thread)
{ F_CENTROID(x-coord, f, thread);
y = x-coord[1];
F_PROFILE(f, thread, position) = y*3+5;
}
end_f_loop(f, thread)
}

+5 part is working but not the y*3. My idea is to have the cavity from -1 to 1 and have a top wall velocity (x^2-1)^2 so on the corners there won't be any singularity.

AlexanderZ · March 28, 2018, 20:59

you have define x variable ( real x[ND_ND] ), but use x-coord later. Why? This is mistake
Read console output after compiling your code to avoid such mistakes

Best regards

piri · March 29, 2018, 11:15

Yes, you are right. I was doing exactly what you mentioned because initially, I used only x there. But in Fluent it was reported y-coord x-coord. I thought that was the mistake but it is not. For some reason I get 5 from F_PROFILE(f, thread, position) = y*3+5; not the y*3 which should be x position*3 @ the top wall. As I mentioned in the main post I want to avoid the singularity at the corners for scientific reasons. I

March 28, 2018, 15:24	UDF for upper wall velocity lid-driven cavity	#1
piri New Member Erdem Join Date: Aug 2014 Posts: 3 Rep Power: 12	Hello, I am trying to give a position depended velocity to lid-driven cavity, top wall. My coordinate system is x-y and top wall is located at y=top. I know all the procedure about loading the udf etc. but for some reason my udf is not working. #include "udf.h" DEFINE_PROFILE(top_x_velocity, thread, position) { real x[ND_ND]; real y; face_t f; begin_f_loop(f,thread) { F_CENTROID(x-coord, f, thread); y = x-coord[1]; F_PROFILE(f, thread, position) = y3+5; } end_f_loop(f, thread) } +5 part is working but not the y3. My idea is to have the cavity from -1 to 1 and have a top wall velocity (x^2-1)^2 so on the corners there won't be any singularity.

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March 28, 2018, 20:59		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	you have define x variable ( real x[ND_ND] ), but use x-coord later. Why? This is mistake Read console output after compiling your code to avoid such mistakes Best regards

March 29, 2018, 11:15		#3
piri New Member Erdem Join Date: Aug 2014 Posts: 3 Rep Power: 12	Yes, you are right. I was doing exactly what you mentioned because initially, I used only x there. But in Fluent it was reported y-coord x-coord. I thought that was the mistake but it is not. For some reason I get 5 from F_PROFILE(f, thread, position) = y3+5; not the y3 which should be x position*3 @ the top wall. As I mentioned in the main post I want to avoid the singularity at the corners for scientific reasons. I