# This result reasonable help me

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 August 15, 2005, 23:55 I compute the motion of threee #1 Member   zoujianfeng Join Date: Mar 2009 Location: Hangzhou, China Posts: 30 Rep Power: 10 I compute the motion of threee bubbles with interFoam. The cGamma is 1.5 for 3D case. From the following jpg figure, we can find some dirty fragments. These fragments may be introduced by the algorithm embedded in interFoam? I have not got idea to solve this problem. Can anyone give me any advie? time=0.1s and time=.35s: Thanks.

 August 16, 2005, 00:05 The result for the single mode #2 Member   zoujianfeng Join Date: Mar 2009 Location: Hangzhou, China Posts: 30 Rep Power: 10 The result for the single mode RT instability is as follows: The interface is beautiful, yet.

 August 16, 2005, 04:22 It is not clear that those fra #3 Senior Member   Join Date: Mar 2009 Posts: 854 Rep Power: 15 It is not clear that those fragments are incorrect, they may be a natural consequence of a break-up process caused by the up-draft in the wake of the middle bubble but they may also be numerical as you suggest. What schemes are you using for the terms of the U an gamma equations?

 August 16, 2005, 04:36 The scheme list: ddtSchemes #4 Member   zoujianfeng Join Date: Mar 2009 Location: Hangzhou, China Posts: 30 Rep Power: 10 The scheme list: ddtSchemes { // Default scheme default Euler; } // Gradient discretisation schemes gradSchemes { // Default gradient scheme default Gauss linear; grad(U) Gauss linear; grad(gamma) Gauss linear; } // Convection discretisation schemes divSchemes { div(rho*phi,U) Gauss upwind; div(phi,gamma) Gauss Gamma201 0.2; div(phirb,gamma) Gauss Gamma201 1; } // Laplacian discretisation schemes laplacianSchemes { // Default scheme default Gauss linear corrected; } // Interpolation schemes interpolationSchemes { // Default scheme default linear; } // Surface normal gradient schemes snGradSchemes { // Default scheme default corrected; } // Calculation of flux fluxRequired { // Create storage for flux for all solved variables? default no; pd; pcorr; gamma; } I will try to do some tests with different schemes. Thanks.

 August 16, 2005, 04:49 I don't think your choice of s #5 Senior Member   Join Date: Mar 2009 Posts: 854 Rep Power: 15 I don't think your choice of schemes are appropriate for thise case, in particular upwind on U will cause a lot of unnecessary damping and given that your case is low Re you could probably use linear of if that gives trouble Gamma2V 1. However, this will not affect the fragmentation of the interface, to see if this is real or numerical try with div(phi,gamma) Gauss Gamma01 1; div(phirb,gamma) Gauss Gamma01 1;

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