This is big for me. Both PDEsolve and numol are too restrictive. PDEsolve needs to handle vector variables (subscripted variables). Numol, which can handle vectors, can't have mixed boundary condtions at either end of the problem. These problems have been noted in the discussion groups, several years ago. I couldn't find this problem mentioned in this group. If PDEsolve can be made to accept vector variables, that would be preferred because (1) it handles mixed boundary condition types and (2) it looks better (more like math notation). Because of these restrictions, I've created a dynamic, 2D (space dimensions) pde solve program using a semi-implicit numerical approach. Works great, but it has to be hidden in a report. An Update I've thought of one way of changing the PDEsolve that would handle most problems. I understand that the subscripts are needed to show what independent variables are to be used for the differential. This currently prevents the use of a vector dependent variable. But suppose you make two changes. First, have Prime designate all vector and matrix variables with bold names. Second, have PDEsolve recognize when a scalar variable or a vector/matrix variable is involved. It then knows that it needs to solve the equation for all elements of the dependent variable. This should work for most problems. If the entire equation can be written in vector/matrix form, then it should work. If the equations have to indicate individual elements in a vector or matrix, it won't work. The boundary conditions can be written in vector form also. Message was edited by: Harvey Hensley
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