[elmo555]

Hello Foamers,

is there a way to calculate the gradient (or any other OF tensor operation) for only a subset of cells that fulfill a given condition? In my case, I need a concentration gradient Xv only near the phase interphase, that is where eps < alpha1 < 1-eps.

Since most of the cells in the domain are not close to the interface, calculating the gradient in them is a waste of computational time.

I can easily limit normal calculations to the required cells using:

forAll(alpha1, celli) {
    if(alpha1[celli] > eps && alpha1[celli] < 1-eps) {
        // ... calculation ...
    }
}

Is there a similar way for the gradient (without manually computing it - I would like to stick with the OF-implementation fvc::grad)?