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Weakly compressible vs. Incompressible
Posted 9 lug 2017, 17:04 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD) 0 Replies
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I am simulating a natural convection problem coupled with CFD and heat transfer modules. All the fluid properties are given as constants and my Buoyancy term is rho*g*(beta*(T-T0)-1) with Boussinesq approximation.
Now, I am getting two significantly different results with weakly compressible and incompressible settings.
The Manual and some answers online said in weakly compressible setting, properties will be only functions of temperature not pressure, but since I already set them all to be constant, am I supposed to get same results?
In equation views of weakly compressible setting, if rho is constant, then we will have div u = 0, which also makes the momentum equation as the same as the one for incompressible case. If this is the case, it should turn out to be the same results.
I don't believe COMSOL simply eliminate the terms in momentum equations if properties are constant, instead, each terms in equations are actually calculated and I guess the difference I got for two settings may be due to some numerical errors.
I would like to have more information on that, so any comments or explanations would be highly appreciated.
Best,
Yi
Hello Yi Yan
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