stream function boundary condition for cylinder with slots on it

sara2115 · May 13, 2011, 09:47

Hi.
I have written a code for flow field around a square cylinder.
The base of my code is written in vorticity stream function approach.
For calculation of stream function on the cylinder I have used "single pressure magnitude" for multi-connected domains. now it works properly. but after I decided to insert two slot on the top and down edge of square it dose not work any more. the down slot sucks the fluid and the upper slot blow the fluid by constant velocity. I was wondering is there any one who know how i can determine the right magnitude of stream function on the cylinder?
thanks

Jonas Holdeman · May 18, 2011, 10:50

See if I understand your problem. You have a 2D box with two symmetrically placed slots in the downstream face. The velocity is high enough that the box is shedding vortices. If shedding vortices, you would expect pressure near the slots to oscillate, the two slots more or less out of phase. Similarly, you would expect out-of-phase flow in and out of the slots.

If this is correct, then you would expect the value of the stream function on the surface between the slots to oscillate. This value would not be fixed by a static boundary condition, but rather would have to be determined as a part of the calculation.

May 13, 2011, 09:47	stream function boundary condition for cylinder with slots on it	#1
sara2115 New Member sara Join Date: Mar 2011 Posts: 7 Rep Power: 0	Hi. I have written a code for flow field around a square cylinder. The base of my code is written in vorticity stream function approach. For calculation of stream function on the cylinder I have used "single pressure magnitude" for multi-connected domains. now it works properly. but after I decided to insert two slot on the top and down edge of square it dose not work any more. the down slot sucks the fluid and the upper slot blow the fluid by constant velocity. I was wondering is there any one who know how i can determine the right magnitude of stream function on the cylinder? thanks Last edited by sara2115; May 13, 2011 at 10:51.

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May 18, 2011, 10:50		#2
Jonas Holdeman Senior Member Jonas T. Holdeman, Jr. Join Date: Mar 2009 Location: Knoxville, Tennessee Posts: 128 Rep Power: 18	See if I understand your problem. You have a 2D box with two symmetrically placed slots in the downstream face. The velocity is high enough that the box is shedding vortices. If shedding vortices, you would expect pressure near the slots to oscillate, the two slots more or less out of phase. Similarly, you would expect out-of-phase flow in and out of the slots. If this is correct, then you would expect the value of the stream function on the surface between the slots to oscillate. This value would not be fixed by a static boundary condition, but rather would have to be determined as a part of the calculation.