[aspect-devel] Flow through free surface

[Lev Karatun]

If someone could give me an idea of whether what I'm thinking of is
realistic or not, I'd appreciate it!

Best regards,
Lev Karatun.

2018-01-17 20:50 GMT-05:00 Lev Karatun <lev.karatun at gmail.com>:

> Hi Wolfgang,
>
> * You want the boundary to be free and move according to whatever flow you
>> get below
>>
> My understanding is that this is the current implementation of free
> surface?
>
> 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.
>>
> What I was thinking of doing is either something as simple as eroding all
> material that is above a specified elevation (in which case I don't even
> need to solve a system of equations -- correct me if I'm wrong please), or
> solving a diffusion equation (which (I think) I know how to solve).
>
> Essentially, right now I know how to adjust the velocity of the surface
> vertices according to the solution of the diffusion equation. But I don't
> know how to superimpose the new boundary on top of the advected material.
> Is it a realistic thing to do? How would I go about it?
>
> Best regards,
> Lev Karatun.
>
> 2018-01-17 16:03 GMT-05:00 Wolfgang Bangerth <bangerth at colostate.edu>:
>
>> 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.
>>
>> --
>> ------------------------------------------------------------------------
>> Wolfgang Bangerth          email:                 bangerth at colostate.edu
>>                            www: http://www.math.colostate.edu/~bangerth/
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>
>
>
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