Hello,
I have a rather general question on how previous timelevels are filled if one has more than one refinement level. So, assuming I have GF called RHO which has 3 timelevels and I have a mesh which consists of a coarse and a refined part, so 2 levels. On the coarse mesh I will have the timestep DT while on the fine mesh I will have dt = DT/2. The zeroth timelevel of RHO is the solution at time t on all levels.
My first question is whether RHO_p on the refined grid lives on t - dt or on t - DT ( t - 2*dt or t -2*DT for RHO_p_p ) before timelevel rotation takes place?
In the case that RHO_p lives on t - dt in the refined region, I would have another question:
Imagine I have the same setup as before, evolve for one coarse step such that the whole solution is at t + DT now, no timelevel rotation yet. If I now decide to regrid and coarsen the refined region such that I only have one refinement level in the whole domain, which values will be given in RHO_p and RHO_p_p in the region which was previously refined and is now coarse?
Do we have to extrapolate to get RHO_p_p at t - DT, because after the evolution has provided RHO on t + DT in the fine domain but before coarsening we will have RHO_p at t+dt and RHO_p_p at t if my understanding is correct. This means we would have to copy RHO_p_p to RHO_p and extrapolate RHO_p_p to t - DT. Otherwise, the three timelevels of RHO in this specific region wouldn't be equidistant anymore after the next evolution step of size DT ( RHO at t+ 2*DT, RHO_p at t + DT and RHO_p_p at t + dt).
Thanks,
Michail Chabanov