I have problem with volume loss in FLIP simulation.
Unfortunately it's necessary to obey the CFL condition when using explicit integration methods (RK2 in my case) to advance particle positions using the Fluid Implicit Particle method, otherwise fluid volume gets lost over time (simulation becomes unstable).
It turns out that in my case its very expensive to take several sub-iterations per frame and obey the CFL condition.
I thought the problem with volume loss could be solved by using an implicit integration method, that'd make the fluid unconditionally stable and would allow me to take larger time steps without obeying the CFL condition and performing the costly sub-iterations.
Does such implicit formulation of FLIP exist? If not, is there another way how to alleviate (or completely remove) volume loss in FLIP (other than CFL)?