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noSlip boundary condition and Turbulent flow

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Old   July 11, 2019, 11:54
Default noSlip boundary condition and Turbulent flow
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Raza Javed
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Hello Everyone,


I have a question that, If I have Turbulent fluid flow from a pipe, Can I use noSlip boundary condition for velocity(U) at the walls of the pipe?


I shall be very thankful for your helpful response.


Thank you
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Old   July 12, 2019, 03:23
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I am currently building a case where I initially used noSlip boundary condition on the side walls. It gave me a considerable and grid-dependent pressure drop through my system. Now I changed to nutkWallFunction and then to nutkRoughWallFunction. Both gave me more reasonable pressure drop. I assume, for noSlip boundary condition you have to resolve the boundary layer with your grid... and possibly be careful with the selection of the turbulence model.
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Old   July 12, 2019, 03:57
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Quote:
Originally Posted by ingraban View Post
I am currently building a case where I initially used noSlip boundary condition on the side walls. It gave me a considerable and grid-dependent pressure drop through my system. Now I changed to nutkWallFunction and then to nutkRoughWallFunction. Both gave me more reasonable pressure drop. I assume, for noSlip boundary condition you have to resolve the boundary layer with your grid... and possibly be careful with the selection of the turbulence model.

Thank you so much for your reply.


Can we use nutkwallfunction or other wallFunctions for velocity boundary conditions as well?



I thought we can only use them for 'k' in turbulence modelling.
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Old   July 12, 2019, 04:01
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I see, you're right. I use noSlip for 'U', nutkRoughWallFunction for 'nut' and kqRWallFunction for 'k'. Not sure if this is right. At least, the pressure drop in my system appears reasonable.

There are so many tutorials on meshing and application selection - I wish there'd be more on boundary conditions.
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