# problem with gradient as source term in coupled equations

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 August 16, 2010, 13:12 problem with gradient as source term in coupled equations #1 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 245 Rep Power: 10 Hi! I am trying to implement the following equations in OpenFOAM. There are nspecies resolution of these coupled equations according to the number of species in the system. http://img148.imageshack.us/img148/6...reenshot1v.png I have a problem with the implementation of the A-species evaporation rate. There is an error when compiling the code because of the gradient terms in the calculation of Sevap[i]. Code: ```// Species transport calculation for (int i=0; i<= nspecies; i++) { volScalarField& Y_beta_i = Y_beta[i]; volScalarField& Y_gamma_i = Y_gamma[i]; Sevap[i] = U_gamma_beta[i] & fvc::grad(Y_gamma_i) -U_beta_gamma[i] & fvc::grad(Y_beta_i) - alpha[i]*(H[i]*Y_gamma_i-Y_beta_i); mass_evap += Sevap[i]; solve ( fvm::ddt(eps_beta*rho_beta, Y_beta_i) + fvm::div(phi_beta, Y_beta_i) == fvm::laplacian(eps_beta*rho_beta*D_beta_beta[i] , Y_beta_i) + fvm::laplacian(eps_beta*rho_beta*D_beta_gamma[i], Y_gamma_i) + Sevap[i] ); solve ( fvm::ddt(eps_gamma*rho_gamma, Y_gamma_i) + fvm::div(phi_gamma, Y_gamma_i) == fvm::laplacian(eps_gamma*rho_gamma*D_gamma_gamma[i], Y_gamma_i) + fvm::laplacian(eps_gamma*rho_gamma*D_gamma_beta[i] , Y_beta_i) - Sevap[i] ); }``` Here the velocity-like coefficients U_beta_gamma and U_gamma_beta are declared as Code: ``` PtrList U_gamma_beta(nspecies); PtrList U_beta_gamma(nspecies);``` Do you have any suggestion ?? Moreover, I saw that there is a FvCoupledScalarMatrix class existing. Do you think it is useful in my case or the sequential method can be sufficient enough ? Regards, Cyp Last edited by wyldckat; September 3, 2015 at 17:53. Reason: disabled embedded images