Mailman 3 July 2013 - SfePy

Re: Torque
by Robert Cimrman 09 Mar '18

09 Mar '18

In examples/large_deformation/hyperelastic.py a rotation by displacements is applied. By using a similar function the vectors defining the force couples could be defined for dw_surface_ltr (IMHO). Does it make sense? r. ----- Reply message ----- From: "Andre Smit" <freev...(a)gmail.com> To: <sfepy...(a)googlegroups.com> Subject: Torque Date: Sat, Dec 18, 2010 05:10 What is the best way to apply a torque load to a model? -- Andre -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...(a)googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...(a)googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en.

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1D line elements in SfePy
by Nimish 22 Jan '16

22 Jan '16

I am currrently looking for FEM packages to help me solve a system of beams and columns, basically a collection of 1D bernoulli/timoshenko line elements. I started reading SfePy docs and i am getting the idea that doing the above is not really possible here, am i right? Are only 2D area elements permitted in SfePy? Or is there any direct support for solving 1D line elements too.. Cheers Nimish

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Python 3 compatibility
by Robert Cimrman 11 Aug '14

11 Aug '14

FYI: As SciPy 0.12.0 is out and one of the release highlights is "Support for Python 2 and Python 3 from the same code base (no more 2to3)", we can think seriously about updating SfePy in this respect as well, cf. [1]. r. [1] https://github.com/sfepy/sfepy/issues/164

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Evaluate a solution in the arbitrary point in the domain
by Alec Kalinin 03 Apr '14

03 Apr '14

Dear SfePy users, Is it possible to evaluate a solution not only in the FEM mesh node, but in any arbitrary point in the domain with the given (x, y, z) coordinates? For example, consider Dirichlet problem for Poisson equation. We apply essential boundary conditions on the surface nodes and after the problem has been solved we have the solution vector, i.e. vector of values in the FEM mesh nodes. But I want to know the solution in point v(x, y, z) that is not FEM mesh node. What is the best way to obtain solution in this point v? Sincerely, Alec Kalinin

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elliptical hole under isotropic stress
by David N. Mashburn 13 Jan '14

13 Jan '14

Hello sfepy developers and users! I am modelling a simple linear elastic sheet under isotropic stress with an elliptical hole in the center (and I have it working under sfepy, great little platform!). It is obvious the model should initially yield more easily in the direction of the short axis of the ellipse. What is not so obvious to me is what should happen in the limit as stress goes to infinity. Part of me wants to believe that the hole should eventually become a circular, but the results of the simulation show that the ellipse eventually switches its aspect ratio with what was the the short axis becoming the long axis and vice-versa. My question is whether: A: The finite element result is the product of a small-displacement/non-moving mesh artifact (and if so, if there is a way to get the correct behavior using sfepy...) OR B: My intuition about the physical behavior of this ideal system is incorrect and the ellipse really wouldn't round out into a circle under increasingly large stress (aka, the FE model is still physical/correct with large displacements). This might be obvious to people who have done more finite element modeling than I have, but thanks anyway! I'm attaching a picture to make it easier to see at a glance (quarter-ellipse with x and y symmetry boundary conditions and equal tractions applied at the top and right boundaries). Thanks! -David Mashburn

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GSoC Phase 1
by Ankit Mahato 30 Jul '13

30 Jul '13

Hi R, I was very sick for the past few days. Just got up from bed yesterday. Earlier I went through the docs, samples, guide as you had instructed. Also I got the weak form of the equations. Kindly look at the attached PDF and suggest me the path I should take. >From today onwards I will remain online all day and will ping you whenever I get struck. Regards Ankit

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Re: [sfepy-devel] Re: 2d NS terms
by Robert Cimrman 26 Jul '13

26 Jul '13

On 07/04/2013 03:02 PM, Ankit Mahato wrote: > Hi R, > > For our Navier-Stokes currently we use the Newton method with backtracking > line-search. Yes, in sfepy we use that. > in OpenFoam and most of the CFD code the linearization > approach is based on Patankar's SIMPLE algorithm.[1][2] > I talked to my professor who told me that SIMPLE is used in commercial > softwares like FLUENT too. Do you think you could then try implementing SIMPLE in the FE context? > I found few papers which tells us some other approaches. Do have a look at > them and lend your views: > > - > http://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ve… > - http://numerik.iwr.uni-heidelberg.de/Oberwolfach-Seminar/CFD-Course.pdf > - > http://dspace.uta.edu/bitstream/handle/10106/5144/JIAJAN_uta_2502M_10764.pdf > - http://www.reaction-eng.com/downloads/nksolver_pernice.pdf > - http://aero-comlab.stanford.edu/Papers/birkenjamesonproceedings09.pdf > - https://cs.uwaterloo.ca/research/tr/1993/02/CS-93-02.pdf > - http://www.cs.sandia.gov/~rstumin/backtrack.pdf > - http://repository.cmu.edu/cgi/viewcontent.cgi?article=1032&context=math > - http://www8.cs.umu.se/kurser/5DA001/HT07/lectures/newton-handouts.pdf > > > [1]: > http://www.cfd-online.com/Forums/openfoam-solving/60167-how-nonlinear-discr… > [2]: http://web.cecs.pdx.edu/~gerry/class/ME448/notes/pdf/SIMPLEslides.pdf Nice list. I will try to look at it, but doubt that I will be of much help in deciding what path to pursue. We need something that could be implemented in a reasonable time. IMHO that rules out the multigrid-based solvers, unless a prepared solution like pyamg could be used directly. > PS: For the python 3 fix which I had forgotten earlier :( . While going > through the codes I came across that we use output() in base.py to print. > You have already called > if sys.version[0] < '3': > basestr = basestring > else: > basestr = str > So basically we know the python version and call the print function > according to the python version. If I am correct it is quite easy to fix > then, am I? In the sfepy codebase, there should be no print statements - output() should be used everywhere (if it is not, it's a bug), so yes, updating that for python 3 should be pretty easy. r.

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Help regarding pressure gradient
by Ankit Mahato 24 Jul '13

24 Jul '13

Hi Guys, I had formulated the problem combining Navier Stokes with Energy Equation. For that I wanted to try out Couette flow with pressure gradient (*plane Poiseuille flow*) with Thermal boundary conditions. For simple Couette Flow ( pressure gradient =0 ) the code is working fine and giving us the proper velocity profile but how to do it with user defined pressure gradient. See Link - http://www2.mech.kth.se/~luca/Smak/rec5.pdf which will give us velocity profile for this flow. I tried imposing pressure boundary condition but it is not working out. I have attached the problem file. Regards, Ankit

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NS: algorithms to try
by Robert Cimrman 11 Jul '13

11 Jul '13

Hi Ankit, I have contacted a friend who suggested some algorithms to try out for solving the linear system: 1. algebraic brute force (does not address the nonlinearity, reported to work on moderately sized problems): gmres with ILU(0) preconditioning. 2. If ILU(0) does not work: We are solving K*x = b where K has a block structure: K = | A B | | B^T -C | (C can be positive semi-definite or zero - our case) Instead, an "augmented Lagrangian" technique would lead to Q*x = b with Q = | A + alpha*B*B^t B | | B^T -C | alpha>=0, small Either the augmented system can be solved, or Q could be used in ILU(0) preconditioner. 3. Ultimately you want to solve a time-dependent problem, so try also the Chorin-Temam projection method [1]. This could be used even for the stationary case by solving in time until a steady state is (hopefully) obtained. r. [1] http://en.wikipedia.org/wiki/Projection_method_%28fluid_dynamics%29

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2d NS terms
by Robert Cimrman 10 Jul '13

10 Jul '13

Hi, I have removed the "3d only" restriction from the Navier Stokes and related terms. There is also a new example: examples/navier_stokes/navier_stokes2d.py. r.

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