# Computation of kinetic energy of the flow

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 November 9, 2011, 21:15 Computation of kinetic energy of the flow #1 Member   Yuri Feldman Join Date: Mar 2011 Posts: 30 Rep Power: 8 Sponsored Links Hi foamers, I am really puzzled about how tocompute the overall kinetic energy of the flow, i mean I(1/2*U^2)dV, where I is an integral over the given volume. I understand that I have to sum over all subvolumes but I do not even know how to start . Please help me

 November 10, 2011, 08:16 #2 Senior Member   Nima Samkhaniani Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,215 Blog Entries: 1 Rep Power: 17 volScalarField ke=0.5*(U&U); dimensionedScalar ketotal = sum(ke*mesh.V());

 November 10, 2011, 16:15 #3 Member   Yuri Feldman Join Date: Mar 2011 Posts: 30 Rep Power: 8 Dear nimasam, Thank you very much for your answer it was very useful. Just a small comment, It is better just to compute the Ek just by dimensionedScalar ketotal = sum(0.5*(U&U)*mesh.V()); In this way you do not need to construct an additional volScalar field which can save alot of memory Yuri

 November 10, 2011, 16:43 #4 Member   Yuri Feldman Join Date: Mar 2011 Posts: 30 Rep Power: 8 Thinking about the issue once agin, the last change does not reduce the memory consumption since U&U opration still consumpts the same amount of memory as if volScalarfield is defined explicitly. I would recommend another way , which is longer but allows you to save the memory: forAll (mesh.C().internalField(), patchI) { Ekin_= Ekin_+0.5* (sqr(U.internalField()[patchI].component(vector::X))+ sqr(U.internalField()[patchI].component(vector::Y))+ sqr(U.internalField()[patchI].component(vector::Z))) *mesh.V()[patchI]; } This is of course right for non-slip boundary conditions. Yuri

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