# MultiphaseInterFoam question

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 September 17, 2007, 14:45 Often after the simulation has #1 Senior Member   Srinath Madhavan (a.k.a pUl|) Join Date: Mar 2009 Location: Edmonton, AB, Canada Posts: 703 Rep Power: 14 Sponsored Links Often after the simulation has started, I find that the minimum volume fraction for a certain phase has a negative value which I guess comes from using the limitedLimitedLinear scheme. For instance, here is a transcript of the log file: Courant Number mean: 0.0003676463941223166 max: 0.1433804123149916 deltaT = 5.902777777777798e-05 Time = 0.01246875 smoothSolver: Solving for alphawater, Initial residual = 5.367012678397666e-07, Final residual = 1.657007202694921e-09, No It erations 1 water volume fraction, min, max = 0.500000013666753 -2.476129830158727e-05 1.000241328781609 smoothSolver: Solving for alphaoil, Initial residual = 0.0005141524902777194, Final residual = 1.115623990538466e-09, No Iter ations 3 oil volume fraction, min, max = 0.001774934415791225 -0.0002436711866175406 1.000002660725418 air volume fraction, min, max = 0.4982250519173831 -0.0001213547565864747 1.000021713925952 Is there a way to prevent negative volume fractions such as -0.0002436711866175406 and -0.0001213547565864747 by using a different scheme? Or would grid refinement cause the problem to go away? My current fvSchemes file reads: ddtSchemes { default Euler; } gradSchemes { default Gauss linear; grad(U) Gauss linear; grad(gamma) Gauss linear; } divSchemes { div(rho*phi,U) Gauss upwind; div(phi,alpha) Gauss limitedLimitedLinear 1.0 -0.00001 1.00001; div(phic,alpha) Gauss interfaceCompression; //upwind; } laplacianSchemes { default Gauss linear corrected; } interpolationSchemes { default linear; } snGradSchemes { default corrected; } fluxRequired { default yes; }

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