[petsc-dev] I have a question about PETSc example.

Barry Smith bsmith at mcs.anl.gov
Thu May 28 19:31:10 CDT 2015

   I am forwarding this to the other PETSc developers since they know more about these types of problems then I do.

> On May 28, 2015, at 6:58 PM, Jung, Ki Won <KiWon.Jung at pnnl.gov> wrote:
> Dear Dr. Barry Smith,
> My name is KiWon Jung working as a postdoctoral research associate at Pacific Northwest National Laboratory located in Richland, WA.
> My specialty is physical acoustics and I earned my Ph.D. in Acoustics at Pennsylvania State University.
> I have used several finite element modeling softwares for years, but I started building a code that will propagate sound wave in ocean using 3D Helmholtz equation approach based on the use of PETSc. (specifically we are trying to use PETSc 3.2p6 which is readily available on our computers for now.)

   Please DO NOT DO THIS. It is straightforward to install the latest version of PETSc; it will just lead to headaches to use an older version that we do not support and then have to change your code to work with a newer version. Just get the latest release and install it.

> Because I am new to PETSc, I am trying to learn how to formulate my problem using different preconditioners, parallel computing, or multigrid scheme by reading and running examples available in tutorial directory. Luckily, I was able to find some relevant examples such as 2D Helmholtz problem, but I hope that I could get some example of 3D Helmholtz problem. I have been looking for an example using Google, but I was unable to find one.
> My colleague suggests that I should contact you and that is why I am sending you this e-mail.
> If you have some examples of 3D Helmholtz using PETSc or know someone who has done the same thing using PETSc, I would very much appreciate if you kindly let me know.

  If you provide additional information it will help us to provide guidance. By Helmholtz do you mean 

-delta u - sigma1*u + i*sigma2*u = f,

and what range of values of sigma1 and sigma2 matter for your "propagate sound wave in ocean"?

What geometry do you need to handle? The ocean bottom? the shore line? objects in the ocean such as ships? the ocean surface? Do you have any "far field boundary conditions? 

Ideally you could use a higher order (spectral?) method and not just a second order method like in our examples. 

Depending on the problem Helmholtz can be notoriously difficult for multigrid and is, I would say, a research area.

  Once we have more information about the details above we can make suggestions as to particular publications to look at initially.


> Thank you for your time.
> Sincerely,
> KiWon Jung

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