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Re: [ff3d-users] Stationary Navier-Stokes equations / Flow past cylinder
From: |
Stephane Del Pino |
Subject: |
Re: [ff3d-users] Stationary Navier-Stokes equations / Flow past cylinder problem |
Date: |
Mon, 21 May 2007 23:50:03 +0200 |
User-agent: |
KMail/1.9.6 |
Hi Dominique.
Le lundi 21 mai 2007, Dominique Deloison a écrit :
> Hi Stéphane,
>
> Thank you for your quick answer. I have however still some problems.
>
> To answer your question, I found the out-of-date" navier-stokes"
> example here: http://www.freefem.org/ff3d/examples.html
Ooops. These are really obsolete. The same applies for the online
documentation...
I have just updated the files.
> Concerning the files you sent me, I have the following comments:
> 1) - during the resolution, the following warning appears:
> "implementation not finished! use of dofposition required". Is is a
> problem?
This is not important. It is just a reminder for fictitious domain
development...
> 2) - the size of each element (0.1) is the same than the
> radius of the cylinder, so it is very difficult to recognize anything and
> to be able to decide whether the solution looks reasonable or not. I guess
> I have to increase the number of elements.
Yes. This is just an example of use, it might not be anyway physical...
By the ways I don't know why the cylinder size changed...
I just have been looking to it and it seems to me that it is not a good
example. So I slightly changed the example. You can download it from the web
site...
> 3) - the syntax of the "convect" operator is different than the
> one used in the documentation.
> According to the documentation, the syntax is:
> "convect(phi,ux,uy,uz)".
> In the file there is: "convect([u0,v0,w0],dt,u0)" which is
> identical to the freefem++ syntax.
Yes. The online manual was also obsolete. I just put a newer version, sorry
for the confusion...
> 4) - I have difficulties to figure out the mathematical description
> of the problem described in the example file. For me it looks like a
> transient problem. I would be interested in a stationnary solution as
> described by the equations I wrote in my previous mail. Is there a non
> time dependent version of the convect operator ?
Yes. This is a transient resolution...
There is no stationary convect operator, but, you can write a fix point
algorithm. I join you an example.
> 5) I tried to postprocess the streamlines with medit (I wrote an .iso
> file to describe the seeding points). I was unsuccessful (segmentation
> fault). have you ever tried this with this example?
The reason is that medit is not very good for hexahedra.
In the joined file I use a tetrahedrization of the mesh and an alternative VTK
output.
I hope that helps. Thanks for your reports.
Best regards,
Stéphane.
stationary-ns.ff
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