# How to define PDE BC with UDF?

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 April 6, 2004, 00:10 How to define PDE BC with UDF? #1 KKLAU Guest   Posts: n/a To all Fluent experts all over the world, I am facing problem for defining BC involved PDE with UDF. Can somebody give me a hand? My PDE BC is div(v)/div(y) = v + constant where v = velocity in y direction Thanks alot... KKLAU

 April 6, 2004, 02:28 Re: How to define PDE BC with UDF? #2 FJ Guest   Posts: n/a Hi, We can define it via UDF. div(v)/div(y) is defined as C_DVDY(c, t) in UDF macro and this macro is for cell values . So when we use this macro at a specified face via DEFINE_PROFILE , we have to define C0 and THREAD_T0 in the macro. Thank you FJ

 April 6, 2004, 08:35 Re: How to define PDE BC with UDF? #3 thomas Guest   Posts: n/a Hello, Before asking all those question you should read the fluent documentation in order to knwo what are the BC you can use, and then how to modify them using a UDF. To answer your first message about how to fix the BC div(v)/div(y) = v + constant. What I am proposing to you is to use a Velocity inlet. From there you can descretize your equation div(v)/div(y) = v + constant and easily calculate via UDF your velocity v. Then using a Velcoity Inlet you are gonna attached this velocity to your BC. Thomas

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