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Weller test case for XiFoam: results discrepancy |
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October 7, 2011, 12:17 |
Weller test case for XiFoam: results discrepancy
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Member
Frederic Collonval
Join Date: Apr 2009
Location: Technische Universitaet Munich - Lehrstuhl fuer Thermodynamik
Posts: 53
Rep Power: 17 |
Dear foamers,
I'm trying to do the simulation used by Weller et al. to validate XiFoam [H.G. Weller et al., 1998, Application of a Flame-Wrinkling LES Combustion Model to a Turbulent Mixing Layer, Twenty-Seventh Symposium (International) on Combustion/The Combustion Institute]. For that first I took simply the tutorial case, refine a bit the mesh at the shear layer and boundary layers and update the U and k file to use the experimental profiles. Then the flame was effectively wrinkled (see XiFoamInit.jpg VS WellerResults.jpg - on the last the top picture is from the experiment). But the temperature and the pressure were crazy. In XiFoamInitTemperature.jpg I use a threshold filter to select the cells with a temperature between 260K and 290K. That range is totally unphysical as the temperature should not go below 293K. So I changed the numerical schemes (cf. attachment). And now the pressure and the temperature are great: p is roughly constant and the minimal temperature is 292.6 K However the instability of the flame is gone. Any suggestions will be appreciate. Thanks, Frederic Additional information about the simulation: * max CFL = 0.5 * no gravitation * the mesh is not has large in the homogeneous direction as in the Weller's paper. The dimensions are those of the tutorial case * the combustion properties are those of the tutorial case * it looks like the wrong smaller temperature was triggering the instabilities due to a bigger density difference between the fresh gas and the burnt one.
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Frederic Collonval Technische Universität München Thermodynamics Dpt. |
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Tags |
rearward step, xifoam |
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