From: Brian T. <mr...@in...> - 2010-06-23 02:57:40
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Hi- First, thank you guys for the amazing work with the libraries! I'm new to using libmesh and reasonably new to FEA. My background is mainly in controls (with a little bit of spectral methods). So I apologize in advance for what may be a simple question. I am trying to get example 18 to "work." It is outputting without error to exodusII now that I downloaded the latest files from the repository. However, as far as I can tell all of the outputted files are approximately the same. I've tried messing with the Reynolds number (by default it is set to 0) as well changing the time step (including to large values trying to get instability in order see something evolve). I'm going to keep playing with it. However, the webpage mentions the example uses experimental routines so I thought I'd ask if the example works and/or if there are better parameters than the default ones. Many thanks in advance! Brian ____________________________________________________________ Publish your photos in seconds for FREE TRY IM TOOLPACK at http://www.imtoolpack.com/default.aspx?rc=if4 |
From: Roy S. <roy...@ic...> - 2010-06-23 16:03:25
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On Tue, 22 Jun 2010, Brian Templeton wrote: > I am trying to get example 18 to "work." It is outputting without > error to exodusII now that I downloaded the latest files from the > repository. However, as far as I can tell all of the outputted files > are approximately the same. I've tried messing with the Reynolds > number (by default it is set to 0) as well changing the time step > (including to large values trying to get instability in order see > something evolve). Large time steps just approach the steady-state problem, which for the default EulerSolver (backward Euler) has a fixed stable solution for low Re. > I'm going to keep playing with it. However, the webpage mentions the > example uses experimental routines Mostly that experimental warning is there because the API may still be in flux; we had to refactor it in a non-backwards-compatible way early last year and might have to do so again. > so I thought I'd ask if the example works But partly that experimental warning is there because we're working on some new features under the hood, and even the API-compatible changes might break things from time to time. The FEMSystem stuff is working fine on my own examples, but you're right, it's as if it's just solving the steady problem on ex18. I'll check it out. Thanks, --- Roy |
From: Roy S. <roy...@ic...> - 2010-06-23 19:02:39
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On Wed, 23 Jun 2010, Roy Stogner wrote: > it's as if it's just solving the steady problem on ex18. It was just solving the steady problem on ex18. Our nondimensionalization there was picked to demonstrate overriding mass_residual rather than to demonstrate good sense, and our time transformation goes singular at Re=0. I'm setting navier.in back to using Re=1, for which at least for me we get sensible-looking transient behavior. Let me know if the new default options still don't look right for you. Thanks again, --- Roy |