[Users] Timelevels on refined meshes

[Michail Chabanov]

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