[aspect-devel] Flow through free surface

[Wolfgang Bangerth]

On 01/16/2018 01:53 PM, Lev Karatun wrote:
> 
> I was wondering if you could give me an idea of how hard it would be to 
> allow material flow through the free surface? Right now I'm just able to 
> dampen the elevation change by applying the diffusion equation, but is 
> it possible to actually take material out of the system? Would the 
> hardest part be figuring out if a point is inside a curved domain? Or is 
> there an inherent limitation in Aspect that makes it not feasible in 
> principle?
> To rephrase what I mean: is it possible to let the material move at the 
> surface with Stokes velocity, and then draw the new top boundary on top 
> of it, getting rid of material that  was eroded away (falls outside of 
> the new model boundaries), and filling in the now less deep trenches 
> with crustal material?

Mathematically, the free boundary is of course determined just so that 
no flux goes across it.

I think what you want is essentially a two-step process:
* You want the boundary to be free and move according to whatever flow 
you get below
* Then you want to erode away or deposit material on top of it.

The easiest way to implement may be exactly to do this: do one; then do 
the other. For any more complicated procedure, it would be useful to 
first define exactly what equations you want to solve, and then (and 
*only* then) think about how you want to solve them.

Best
  W.

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