In a semi-batch (water is in batch mode while air is in continuous mode, I.e., the air is sparging from the bottom of the column) two-phase flow condition, when we can use the k-epsilon model? During the simulation, Eulerian multiphase model is chosen. The flow conditions of the air is follows:
air velocity: 0.040 m/s, bubble diameter: 0.001 m, Area of cylindrical sparger through which air is being sparged in the column in the form of the bubble: 5.40*10^-3 m2, viscosity of air: 1.78*10-5 kg/m.s, density of air: 1.225. According to this Re (air) = 4, So, in this condition can I use k-epsilon turbulence equation? In most of the literature, I have seen that people using the k-epsilon turbulence equation at around the same gas velocity (approx. 0.040 m/s) in semi-batch operation.
From data you mentioned Reynolds number is calculated based on air only i would suggest to calculate Reynolds number based on mixture (air+water) i think that laminar case will be ok. No need to use any turbulence model and DNS is enough to handle your problem.
Laminar condition is correct for at inlet location only as flow condition values such as Reynolds number (Re = 4) is given for inlet condition. However, I think when bubbles reach inside the column and start to move up, it interacts with other gas bubbles (which already present in the column) and liquid. Therefore, turbulence must be occur. Hence, I think in order to have a correct result, must incorporate the k-epsilon model.
Dear/Ritesh Prakash
Even if the case reaches to be turbulent flow i would suggest to calculate Reynolds number , if it is under 4000 you may use DNS with adaptive fine mesh without using turbulence model.
Kindly Regards
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