# laplacian discretisation: interpolation of the diffusion coefficient

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 October 27, 2019, 07:22 laplacian discretisation: interpolation of the diffusion coefficient #1 New Member   javad haqqani Join Date: Dec 2017 Posts: 16 Rep Power: 8 Hi. I need some extra info on how laplacian function works in openfoam. According to https://www.openfoam.com/documentati...n-details.html, "the laplacian is given by the sum over all faces of the dot product of the face normal with the gradient value at the face. To transform the quantity from the cell centre to the face centre, an interpolation scheme is required". First, how is the gradient at the face calculated? is it the cell values interpolated to the face? If so, with what scheme is it interpolated? Or it is calculated directly by differentiating cell values? Second, what if the quantity? what if we input an interpolated quantity?

 October 30, 2019, 04:19 #2 Senior Member   Michael Alletto Join Date: Jun 2018 Location: Bremen Posts: 616 Rep Power: 16 Hello, all this questions are answered in the programmer guide. http://foam.sourceforge.net/docs/Gui...mmersGuide.pdf a very good book about the numerics in OF is https://www.springer.com/de/book/9783319168739. I found this book very useful and it is written very well and in a very comprehensive way. Best Michael