[petsc-users] calculating eigenvalues for the Stokes equations in 3D

[Matthew Knepley]

On Tue, Oct 29, 2019 at 5:06 AM Dave May via petsc-users <
petsc-users at mcs.anl.gov> wrote:

>
>
> On Tue, 29 Oct 2019 at 08:59, <av-baron at yandex.ru> wrote:
>
>> Hi, Dave! Thank you for your assistance. The problem is that I don't have
>> the matrix representation for my problem.
>>
>
> You will have to explain in more detail if you want further help.
> Explain what "I don't have the matrix representation for my problem" means.
> If you don't have a matrix representation, how do you solve the forward
> problem??
>
> Maybe you mean you use a matrix-free (MF) method. That is still a matrix
> representation of your problem, however the MF representation does not
> explicitly store the matrix a_{ij} entries in a CSR (or other) format.
>

You could start by using SNES ex62. It is a 3D Stokes problem with
Dirichlet conditions. Adding SLEPc is easy
(I have done it myself but not yet contributed back to SLEPc). After
everything works, you can substitute in your
own problem.

  Thanks,

    Matt


>  I've searched on the internet for a solution, but found only some
>> examples of solving 2D eigenvalue problems for the Stokes equations. Maybe
>> you could help me with the matrix representation for the 3D Stokes
>> eigenvalue problem?
>> Thank you in advance,
>> Alex
>>
>> 29.10.2019, 11:16, "Dave May" <dave.mayhem23 at gmail.com>:
>>
>>
>>
>> On Tue 29. Oct 2019 at 08:13, alex via petsc-users <
>> petsc-users at mcs.anl.gov> wrote:
>>
>> Hello!
>> In my project I have to calculate eigenvalues for the three dimensional
>> Stokes equations with Dirichlet boundary conditions. I would like to use
>> SLEPc iterative solver for this purpose, but I'm not quite sure how I
>> should set up the matrices for the solver. I would be grateful if anyone
>> could share a source code for solving this eigenvalue problem.
>>
>>
>> I presume your forward model uses petsc. What matrix representation do
>> you use in that code? Why cannot they be used directly with slepc?
>>
>> Thanks
>> Dave
>>
>>
>>
>>
>> Thank you very much!
>> Alex
>>
>>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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