Use of face centered differences in gradient computation

henningh · August 25, 2011, 05:56

Hi,

According to the recent work of Richrds and Norris (J. Wind Eng Ind.Aerodyn 99 (2011) 257-266), the near ground spike in turbulent kinetic enery in the k-epsilon
model originates from an inconsistency in the discretization. This error can be removed by computing all gradients in terms of face centered differences.

Can this shift be achieved by any of the options in the fvSchemes file?

Best regards,
Henning Heiberg-Andersen

stevenvanharen · August 25, 2011, 09:34

Are you sure this is not already being done?

I think discritization (53) from the paper you refer to is not possible in an unstructered code.

Furthermore, in kEpsilon.C:

Code:

volScalarField G("RASModel::G", nut_*2*magSqr(symm(fvc::grad(U_))));

where fvc::grad(U_) are the gradients at the face.

Is this what you were referring to?

praveen · August 25, 2011, 11:41

I have asked this question before

http://www.cfd-online.com/Forums/ope...ume-field.html

and I think there is no such scheme available. Please correct me if I am wrong.

August 25, 2011, 05:56	Use of face centered differences in gradient computation	#1
henningh New Member Henning Heiberg-Andersen Join Date: Aug 2011 Location: Bergen, Norway Posts: 2 Rep Power: 0	Hi, According to the recent work of Richrds and Norris (J. Wind Eng Ind.Aerodyn 99 (2011) 257-266), the near ground spike in turbulent kinetic enery in the k-epsilon model originates from an inconsistency in the discretization. This error can be removed by computing all gradients in terms of face centered differences. Can this shift be achieved by any of the options in the fvSchemes file? Best regards, Henning Heiberg-Andersen

August 25, 2011, 09:34		#2
stevenvanharen Senior Member Steven van Haren Join Date: Aug 2010 Location: The Netherlands Posts: 149 Rep Power: 15	Are you sure this is not already being done? I think discritization (53) from the paper you refer to is not possible in an unstructered code. Furthermore, in kEpsilon.C: Code: volScalarField G("RASModel::G", nut_2magSqr(symm(fvc::grad(U_)))); where fvc::grad(U_) are the gradients at the face. Is this what you were referring to?

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August 25, 2011, 11:41		#3
praveen Super Moderator Praveen. C Join Date: Mar 2009 Location: Bangalore Posts: 342 Blog Entries: 6 Rep Power: 18	I have asked this question before http://www.cfd-online.com/Forums/ope...ume-field.html and I think there is no such scheme available. Please correct me if I am wrong.