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Showing results 1 to 13 of 13 Search took 0.00 seconds. Search: Posts Made By: alberto

Forum: OpenFOAM June 20, 2010, 15:10

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Are there zones of the system where you can... Are there zones of the system where you can observe some unphysical behaviour (velocity too high, for example? Additionally, what under-relaxation factors are you using? Did you try to reduce them...

Forum: OpenFOAM June 16, 2010, 10:48

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto How did you set a "second order upwind" scheme in... How did you set a "second order upwind" scheme in OpenFOAM? You might want to try For gradients: cellLimited Gauss linear 1; For divergence: Gauss linearUpwind cellLimited Gauss linear 1;...

Forum: OpenFOAM June 15, 2010, 16:10

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Hi, we do not have enough details to answer.... Hi, we do not have enough details to answer. P.S. Please, when you have a question, open a new thread. Thanks! :-)

Forum: OpenFOAM May 28, 2010, 16:02

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto OK. If you used snappyHexMesh, it is probably... OK. If you used snappyHexMesh, it is probably easier to fix than in tet meshes. Check in particular around surfaces, because sometime snappy adds some very thin cell there :) Best,

Forum: OpenFOAM May 27, 2010, 23:10

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Let me guess: is the mesh tetrahedral (maybe... Let me guess: is the mesh tetrahedral (maybe generated with Salomé)? Please run checkMesh, and if you have very skewed cells and/or a high degree of non-orthogonality, yes, the mesh can be the...

Forum: OpenFOAM May 27, 2010, 17:11

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto You clearly have a problem in the setup of your... You clearly have a problem in the setup of your case if some variable tends to explode. Limiters to impose arbitrary ranges won't be of much help if you do not understand the reason why this is...

Forum: OpenFOAM May 26, 2010, 22:54

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Are their values actually limited between the... Are their values actually limited between the bounds you specify? Meaning, is your model including that limitation? If yes, it is correct to use a limiter on the scheme to keep the quantity bounded...

Forum: OpenFOAM May 26, 2010, 16:14

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto The gradient scheme is used only with some of the... The gradient scheme is used only with some of the schemes, and OpenFOAM will return an error if the syntax is not appropriate for the scheme you are using. The upwind schemes does not require...

Forum: OpenFOAM May 26, 2010, 09:59

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto It's bit technical to explain in detail, so... It's bit technical to explain in detail, so please refer to the literature. In short, the terms dissipation error/diffusion are used with to indicate the same thing, meaning the numerical...

Forum: OpenFOAM May 26, 2010, 00:11

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Correct. However also upwinded schemes (QUICK,... Correct. However also upwinded schemes (QUICK, for instance) are diffusive by nature ;-) To compare with CDS you don't have to run a huge practical case. Just compare in a realistic but small test...

Forum: OpenFOAM May 25, 2010, 11:38

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Interesting, because QUICK is known to have some... Interesting, because QUICK is known to have some trouble due to the possibility of having coefficients that change sign. Did you try to estimate the influence of the numerical diffusion (QUICK is...

Forum: OpenFOAM May 25, 2010, 02:55

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Do you notice significant improvements compared... Do you notice significant improvements compared to limitedLinear or linearUpwind with these schemes? In my experience, QUICK doesn't offer any particular advantage (it's either second or first...

Forum: OpenFOAM May 25, 2010, 02:51

Replies: 42 Explanation bounding k and bounding epsilon Views: 37,510 Posted By alberto Hello, just a quick clarification. The... Hello, just a quick clarification. The limitedLinear scheme is the linear scheme with a limiter (if I remember correctly, it uses Sweby's limiter). It's not a blended version of the "linear"...

Showing results 1 to 13 of 13

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