Hi all, 

I am trying to do Biglobal floquet stability analysis of flow over a cylinder. My base flow has converged and I am getting the Strouhal numbers correctly for different Reynolds numbers. Then I tried to do the stability analysis, but I am not getting the desired results for floquet multipliers. I think there are some wrong settings in my input file that I am not able to figure out.

Can anyone look at my input files and help me figuring out the possible source of error?  Please check the attached files.

Here are the steps I am following:
1. Solve for the 2D base flow using UnsteadyNavierStokes equations. (Input file Cylinder.xml)
2. Get the base flow (.bse files) by taking 32 time slices over one period. (Input file Cylinder-base.xml)
3. Use the base flow to set up stability simulation for a specified LZ (Input fie Cylinder-Stability.xml)

The output .evl file is also attached.

General data: Re=220, LZ=2.4166, Expected floquet multiplier=0.45.

I am new to the solver. Any help will be greatly appreciated.

Regards,
Arfan Uddin



On Saturday, September 19, 2015 2:59 PM, Hongfu Zhang <hongfu2233@gmail.com> wrote:


Dear Gianmarco,
I have tried  to copy the filename_eig_0 to filename_eig_0.fld and processed this field with FieldConvert. A file named filename.vtu is created and then visualized with paraview. But, nothing was shown in paraview. I then looked into the filename.vtu and found that all variables such as u ,v w, p existed, but the  cell number is zero. I am sure the solution was converged, and I have tried many times, but all failed  (I have tried version 4.01 and 4.10 )
Then, I am going to try to use the branch fix/INSCoupledStabilitySolver. I don't know if it is a right operation: 
step 1, I downloaded the last code with Git (git clone http://gitlab.nektar.info/clone/nektar/nektar.git nektar++) and compile it in order to use the branch fix/INSCoupledStabilitySolver.
step 2, I have used the BiGlobal Floquet analysis to acquire filename_eig_0 file and used FieldConvert to create .vtu file.
But it doesn't works ( same  problems as above)
 So I am confused. Please help me. Thanks very much for your help!
Best Regards!
Hongfu 

2015-09-12 19:06 GMT+08:00 Mengaldo, Gianmarco <g.mengaldo11@imperial.ac.uk>:
Dear Hongfu,

you can just try to use the following command:
    FieldConvert filename.xml filename_eig_0.fld filename_eig_0.vtu 

in order to get a vtu file which can be then loaded into Paraview.

Please, note that I have explicitly added the extension .fld to your original filename_eig_0 - this is to allow the postprocessing routine to avoid the error you may have encountered trying to convert it.

Let me know if this works.

Best regards,
Gianmarco

Gianmarco Mengaldo
Department of Aeronautics and Mathematics
Room 730/731, Huxley Building
Imperial College London
South Kensington Campus
London SW7 2AZ 
M: +447462029290 

On 10 Sep 2015, at 13:52, Hongfu Zhang <hongfu2233@gmail.com> wrote:

Hi All, 
            I want to computethe eigenmode of a period field using BiGlobal Floquet analysis. I have gotten the "filename_eig_0" like file, how to do post-processing with this kind of file?
Thanks very much for any help!
Best Regards!
Hongfu
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