[CIG-CS] Particle problems and Semi-Lagrangian Schemes for Gamr

[Wolfgang Bangerth]

> > > and eliminate particles, making the code much simpler, especially in
> > > parallel.
> > 
> > How would you do P-T traces with SL?
> 
> I am probably exposing my own ignorance, but I assume you mean
> Pressure-Temperature,
> or phase diagram traces so we can determine what phase is active. You
> interpolate all the
> fields to the point you want evaluated.

I'm with Matt for pretty much all cases, but I think there are cases where 
tracers are probably hard to avoid. Think for example if you wanted to keep 
apart a dozen different kinds of rock, i.e. the quantity in question is 
integral. Yes, we can have a field that starts with these integral values, but 
an interface between rock type 1 and 3 will smear out and produce rocks of 
kind 2 -- not what you probably wanted. This can only work if you have N-1 
fields for N different phases, which might make it expensive if N is larger 
than 3 or 4.

But I agree that for most everything else, in particular history values, I 
find field-based descriptions easier and more efficient as well. In 
particular, it is simpler to match the accuracy (or polynomial degree) of the 
field to that  of the velocity field, or the field from which the history is 
computed.

W.

-------------------------------------------------------------------------
Wolfgang Bangerth                email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/