HowTo Adding a new transport equation
Suppose you want to solve and additional scalar transport equation for the scalar ψ by adding it to an existing solver. The equation has the form
where ρ and Γ are defined as dimensionedScalar and are retrieved from a dictionary using the lookup member function. Sφ is the source term.
To implement the equation, just add the line:
to the createFields.H file of the solver,
Then, solve the equation by adding the following lines in the point of the solver where you want the equation to be solved.
solve ( fvm::ddt(rho, psi) + fvm::div(phi, psi) - fvm::laplacian(gamma, psi) == S_psi );
In this example, the source term is treated explicitly. To manage it implicitly, OpenFOAM provides the Sp and the SuSp functions. Suppose we can write it as Sk = Κψ. The code lines to solve the same equation with an implicit treatment of the source term are:
solve ( fvm::ddt(rho, psi) + fvm::div(phi, psi) - fvm::laplacian(gamma, psi) == fvm::Sp(kappa, psi) );
SuSp(kappa, psi) can be used to discretise the source term implicitly or explicitly according to the sign of kappa.