what is wrong with my UDF for slip boudary

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 May 23, 2005, 14:13 Re: what is wrong with my UDF for slip boudary #3 lichun Dong Guest   Posts: n/a Hi, Zhao: Could you tell me how you decide the slip coef? thanks a lot

 May 23, 2005, 16:28 Re: what is wrong with my UDF for slip boudary #4 Alec Eiffel Guest   Posts: n/a Hi Zhao Im not sure how cxzhao calculated his slip coefficient but fluent 6 has a slip boundary condtion for low pressure rarefied gas flow. Its based on a Maxwell boundary conditon. Its in section 14.2.2 of Fluent 6.2 help files and shows how its calculated. http://www.fluentusers.com/fluent/do...ug/node547.htm

 May 23, 2005, 21:18 Re: what is wrong with my UDF for slip boudary #5 cxzhao Guest   Posts: n/a Yes, as mentioned by Alec Eiffel, i using Maxwell boundary condition that there is a relation between wall slip velocity and Kn number. and it can be write as : u=(2-F/F)*du/dy or dx. where du/dy is the wll mormal veloctiy gradient. F is always set 1. and Kn number can be writen as : Kn=l/D, where l is the mean freee path of the fluid and D is the length scale of th e physical system. or another form: kn=squr(pi*alfer)*Ma/Re.

 September 1, 2011, 15:37 #6 New Member   hadi ramin Join Date: Aug 2011 Posts: 3 Rep Power: 5 hi dear Alec Eiffel Iam trying to implement maxwell slip velocity too, I have a udf that have been written for maxwell slip velocity but when I use it in (specified shear condition on fluent), fluent could not accept it and has an error(Error: FLUENT received fatal signal (ACCESS_VIOLATION) 1. Note exact events leading to error. 2. Save case/data under new name. 3. Exit program and restart to continue. 4. Report error to your distributor. Error Object: ), I would be please if you help me, thanks in advance

 September 27, 2011, 00:46 #7 New Member   Georgy Join Date: Apr 2011 Location: Russia Posts: 19 Rep Power: 6 I'm also trying to implement velocity slip and temperature jump boundary conditions. It is necessary for me to use density based solver, but not pressure one. hadiramin, did you resolve your problem? If not it would be better to show your UDF code and maybe somebody can help you. cxzhao, why did you try to use U-velocity? I think, it depends on geometry. In theory, there should be tangential and normal velocity to a wall. All the best, Gera

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