(Help)udf for inlet boundary condition

Cfdbug · June 9, 2016, 04:41

Hello，i want specify Instant velocity,u,v,w,for the inlet condition.The three velocities are related because the continue equation, they can be only produced on one run.
I used random function in define profile. So if i use three define profile functions for the three velocities,they can't fit the continuity.
How to manage it?
Thank you in advance

Cfdbug · June 9, 2016, 04:43

Maybe i can use external variables?

pakk · June 9, 2016, 06:17

Quote:

Originally Posted by Cfdbug

The three velocities are related because the continue equation,

No. Check the equations: the continuity equation relates the derivatives of the velocity. Since you prescribe them on a surface, there is one derivative that you don't prescribe, and that one will follow from the continuity equation automatically.

June 9, 2016, 04:41	(Help)udf for inlet boundary condition	#1
Cfdbug New Member Join Date: Dec 2015 Posts: 10 Rep Power: 10	Hello，i want specify Instant velocity,u,v,w,for the inlet condition.The three velocities are related because the continue equation, they can be only produced on one run. I used random function in define profile. So if i use three define profile functions for the three velocities,they can't fit the continuity. How to manage it? Thank you in advance

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June 9, 2016, 04:43		#2
Cfdbug New Member Join Date: Dec 2015 Posts: 10 Rep Power: 10	Maybe i can use external variables?