# Div(F)

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 July 26, 2010, 13:01 Div(F) #1 Senior Member   Nima Sam Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,123 Blog Entries: 1 Rep Power: 14 hi friend i get some how confused about the function of fvc::div in openFoam how does it work? i had a scalar variable with dimension set [1 -2 -1 0 0 0 0] after div ,i had a variable with dimension set [1 -5 -1 0 0 0 0] , how is it possible ?

 July 31, 2010, 09:40 #2 Senior Member   Claus Meister Join Date: Aug 2009 Location: Wiesbaden, Germany Posts: 241 Rep Power: 8 Basically, div(U):=u_x + v_y + w_z for any tridimensional vector U=[u v w] and div(f):=f_x+f_y+f_z for any scalar field f. Derivation of any quantity includes a change in dimension, for instance, let U be a velocity vector, i.e. [m/s], then U_x has the dimension [1/s]. Better is you would look into book of contiuums mechanics. Futhermore, in OpenFOAM the evalutaion is numerically, meaning central differencing is used when in fvSchemes div(U) Gauss linear; is specified. The rest will ya proberly find in some numerical textbooks.

 July 31, 2010, 10:59 #3 Senior Member   Nima Sam Join Date: Sep 2009 Location: Tehran, Iran Posts: 1,123 Blog Entries: 1 Rep Power: 14 then what was the reason? i know the meaning of div(F) i can't understand why initial dimensionSet [1 -2 1 0 ...] after "div" change into [1 -5 1 0 ....] instead of [1 -3 1 0 ...] ?

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