# How to add coupled euqations with coupled exponential term in a solver

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 November 4, 2019, 11:09 How to add coupled euqations with coupled exponential term in a solver #1 New Member   Xun Lan Join Date: Oct 2019 Posts: 21 Rep Power: 3 Hi, everyone. I am new to OpenFoam and I feel so addicted when exploring. The problem I need to solve is an equation system with the frame as below: fvm::laplacian(a , X) = c*exp(X-Y) fvm::laplacian(b , Y) = -c*exp(X-Y) where a, b and c are constant coefficients. X and Y are two passive scalar fields to be solved. I have no idea how to implement it in a solver (can be laplacianFoam). My questions are: 1. How to deal with this coupled exponential equation? Should I treat it like what pisoFoam dose? 2. How to deal with the exponential source term. Should I use fvOptions? Since the second equation has the same source as equation but with negative sign. Any suggestions and answers are welcome. Thanks in advance! Last edited by Lann; November 14, 2019 at 10:29.

 November 5, 2019, 11:13 #2 New Member   Xun Lan Join Date: Oct 2019 Posts: 21 Rep Power: 3 I don't know if I should use fvOption or just coupled loop to solve this equation. Any idea is super welcomed. Thanks again

 November 14, 2019, 10:24 #3 New Member   Xun Lan Join Date: Oct 2019 Posts: 21 Rep Power: 3 Now I am more clear about the linearization of the exponential terms. But still stumped on the coupling equations.

 Tags coupled, coupled equations, exponential, fvoptions, solver