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-   -   mixture mass continuity eqn v.s. volumetric mixture continuity eqn (http://www.cfd-online.com/Forums/ansys/89309-mixture-mass-continuity-eqn-v-s-volumetric-mixture-continuity-eqn.html)

kaifu June 9, 2011 08:42

mixture mass continuity eqn v.s. volumetric mixture continuity eqn
 
Hi all,

I am now developing solver for subcooled nucleate boiling with OpenFOAM. And recently I met a big problem. It comes from the mixture mass continuity eqn v.s. volumetric mixture continuity eqn in pressure equation in PISO loop. It was reported that "the lighter phase is poorly conserved when the mixture mass continuity equation is used" and thus the volumetric mixture continuity eqn is adopted in adiabatic case. However we have to use mixture mass continuity equation if phase change term exists. In my adiabatic case (air-water, 2D upward bubbly flow) I tested both of the eqns and I found it works well with volumetric mixture way. And in case of mixture mass eqn, the velocity of both phase diverged. I can see the max velocity is initially generated in vicinity of inlet. It moves from inlet to outlet, and keeps increasing during simulation. I will appreciate if you could give me any suggestions/references since fluent/starcd have already implemented the subcooled nucleate boiling model. Thank you very much.

// Kai


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