calculating Sigma anb*Unb
Do you guys know how can I calculate Sigma(anb*Unb) for each cell, where nb is the neighbouring coefficients?

Are Unb velocities at cell centers of neighboring cells?
What is anb? Best regards, Fumiya 
Hi Fumiya
Sorry for my late respond. Yes, nb is the neighboring cell, and anb is the diagonal coefficient corresponding to the neighboring cell. 
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