Re: [Libmesh-users] Starting out with libmesh

[Jorge L. <jor...@gm...>]

Thank you for the reply,

2018-03-26 23:07 GMT+01:00 Roy Stogner <roy...@ic...>:

>
> On Thu, 22 Mar 2018, Jorge Lopes wrote:
>
> 1) Understanding the structure of the documentation: It is highly
>> non-trivial to browse through that.
>>
>
> It is; it's a half-decent reference but not a tutorial.
>
> The closest thing we have to a tutorial is the examples, and even
> there you have to skim descriptions and skip over the ones
> focused on features you don't care about.
>
> I'm going to describe my problem and ask you to direct me to several
>> relevant structures for me to get familiar with.
>>
>> 2) The problem I want to tackle is a combination of the Poisson equation
>> and the Heat Equation.
>> For a given time step we solve
>> \nabla V = Source
>>
>
\nabla V = Source(\phi)
The source depends on the function \phi.


> and use this to evolve to evolve the Heat-like equation
>> i \partial \phi / \partial t = f(\phi, \phi', \phi'') + V \phi
>> where \phi is a complex function, naturally.
>
>
>> 3) I noted that libmesh has the 2 problems solved separately in
>> examples/introduction/introduction_ex4 and somewhere in fem_systems. If
>> this is useful, I'd have my problem half solved.
>>
>> All I'm looking for is some guidelines on how to start tackling the
>> problem
>> with my moderate knowledge of C++ and enormous difficulty in browsing
>> through the documentation.
>>
>
> Two questions about your problem:
>
> Do you want to solve it decoupled (e.g. if Source is independent of
> phi, so you can get an exact value of V at each time step before
> solving for phi) or (weakly or fully?) coupled?
>
\nabla V = Source(\phi)
The source depends on the function \phi.
Sorry for not being explicit about this.

>
> Do you want to integrate with implicit time stepping, explicit, or
> both?
>
I'd say we start with explicit to see if it runs and simulates smoothly and
then, if there are numerical problems we can switch to implicit.
We have some freedom here, at this point either is fine.

> ---
> Roy
>

Thank you ,
Hellium0