# k-e equation in in cartesian coords

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 January 15, 2003, 19:46 k-e equation in in cartesian coords #1 carlslack Guest   Posts: n/a Hi, I'm trying to expand the k-epsilon equations from cartesian tensor notation to cartesian coordinates to form a system of equations for finite element analysis. Both the k- and e-equations contain a term with the Reynolds stresses expressed as follows: ( @Ui/@Xj + @Uj/@Xi ) ( @Ui/@Xj) Does this represent a scalar quantity (ie the scalar product of the two tensors), or a 3x3 matrix product in 3D? Thanks in advance, -CS

 January 15, 2003, 22:45 Re: k-e equation in in cartesian coords #2 Linfeng BI Guest   Posts: n/a Any term in k and e equations is scalar because k and e themselves are scalars.

 January 20, 2003, 09:45 Re: k-e equation in in cartesian coords #3 Bredberg Guest   Posts: n/a What you are looking at is part of the production term in k and eps-equation, which are - yes a scalar. However in order to compute the production term you need to cycle through i and j indices from 1 to 3, hence the expression becomes something like: P_k=\nu_t((dU/dy+dV/dx)dU/dy+(dU/dz+dW/dx)dU/dz+.... /Jonas

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