The fluid solver when the volume fraction is advected is only first order accurate.
There are two problems:
The advection diffusion solver only iterates one time, and we're using a forward Euler scheme. This means that it can only be first order accurate. We need to make sure the solver can use something like trapezoidal rule.
The fluid solver only does a single step of trapezoidal rule with an initial approximation of the volume fraction at time $t_{n+1}$. I think this is also resulting in first order accuracy.
I have made some progress in fixing these issues. I can obtain second order accuracy in time, but it requires solving for the velocity twice. We may need to do a multi-step scheme for the advection solver. I will try to push code for this tomorrow.
The fluid solver when the volume fraction is advected is only first order accurate.
There are two problems:
I have made some progress in fixing these issues. I can obtain second order accuracy in time, but it requires solving for the velocity twice. We may need to do a multi-step scheme for the advection solver. I will try to push code for this tomorrow.