# Modeling internal flow with normal velocities on walls- permeable walls

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 April 27, 2014, 07:07 Modeling internal flow with normal velocities on walls- permeable walls #1 New Member   Ali Madayen Join Date: Apr 2014 Posts: 22 Rep Power: 12 Hi everyone. I'm trying to simulate blood flow in a vessel, where the boundary condition on wall for u is no slip, but for v is a constant definite value. In other words, wall is permeable in y direction. How can I apply this kind of boundary to my problem in CFX? Tnx for your help

 April 27, 2014, 18:27 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,746 Rep Power: 143 I presume you mean u is in the tangential direction and v is in the normal direction. The easiest way of doing this would seem to be a normal no-slip wall with a mass source/sink applied to the wall which gobbles up fluid at your prescribed rate. dengdeng likes this.

 April 27, 2014, 18:35 #3 New Member   Ali Madayen Join Date: Apr 2014 Posts: 22 Rep Power: 12 Tnx for your reply your assumption is correct. But now the question is what is the relation between source/sink intensity and the normal velocity? Question is posed regarding that the problem specifies the normal velocity on the wall, and nothing more.

 April 27, 2014, 18:55 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,746 Rep Power: 143 Make the magnitude of the mass sink a function of the wall shear stress. I would not make it a function of normal velocity as it will then be mesh dependent. AliMadayen likes this.

 April 27, 2014, 19:05 #5 New Member   Ali Madayen Join Date: Apr 2014 Posts: 22 Rep Power: 12 Real Smart. I will try it for sure

 April 27, 2014, 19:06 #6 New Member   Ali Madayen Join Date: Apr 2014 Posts: 22 Rep Power: 12 Real smart, I will try it for sure Thanks a lot, friend.

 Tags normal velocity, permeable wall