[tgvosk]

I am trying to solve a problem which has a nonlinear source term. For simplicity in this example I am not linearizing it. I have defined a function to calculate the explicit source term as

tmp<volScalarField> fSu(volScalarField& y)
{
    return y + y*y + y*y*y;
}

and I perform inner iterations (within the time loop) as

while( yRes > resmin )
{
    volScalarField Su = fSu(y);

    fvScalarMatrix yEqn
    (
        fvm::ddt(y) == fvm::laplacian(y) + Su
    );

    Info<<"Before solve: " << average(y) << endl;

    yEqn.relax();
    lduMatrix::solverPerformance sp = yEqn.solve();

    Info<<"After solve: " << average(y) << endl;

    yRes = sp.initialResidual();
}

The problem I am having is that the value of y does not seem to update as this iterates. The output of this solve (shown below) seems to use the same value of y to calculate Su each time, rather than using an updated value

Before solve: average(y) [0 0 0 0 0 0 0] 0.0445286
GAMG:  Solving for y, Initial residual = 0.433038, Final residual = 0.0109313, No Iterations 3
After solve: average(y) [0 0 0 0 0 0 0] 0.0444641

Before solve: average(y) [0 0 0 0 0 0 0] 0.0445286
GAMG:  Solving for y, Initial residual = 0.433038, Final residual = 0.0109313, No Iterations 3
After solve: average(y) [0 0 0 0 0 0 0] 0.0444641

(... dozens more times ...)

Before solve: average(y) [0 0 0 0 0 0 0] 0.0445286
GAMG:  Solving for y, Initial residual = 0.433038, Final residual = 0.0109313, No Iterations 3
After solve: average(y) [0 0 0 0 0 0 0] 0.0444641

How can I make the value of the source term be recalculated with the updated values of y? Is there a problem with the way I have defined the source term function?