Hi everyone,

I got a question about using VOF in Fluent6. Is it possible to use this model when the flow is air-water flow in which the air velocity is much higher than the water velocity? i.e shear driven flow where it is possible that the water surface breaks into droplets(e.g.is spinning of liquid in an annulus with inner cylinder rotating).

Or is the VOF model is ONLY suitable for cases when the air is more or less stationary (e.g ocean flow)?

Thanks in advance, Shafidz

you can't use confidently VOF when phase velocities are too different. I would use MAC model but, to my knowledge, there is no commercial implementation of the method.

cheers

Thanks New1,

My situation is that I want to model liquid flow in an annulus with the inner cylinder rotating at high speed. The liquid is injected into the annulus at speed much less than the rotating air flow inside it. In this case, the assumption that the the two phases moving at the same velocity will be invalid. Experiment shows that the liquid will accumulate - i.e free surface.

I tried to look into the mixture model and Eulerian model in Fluent6. Can't these models simulate cases where the two phases are continuous? Because from what I have seen, the models will ask for the diameter of the secondary phase - which implies that they can only be used for continuous-dispersed flow, whereas in my case it should be continuous-continuous flow.

Is this correct?

Norshah

Fluent can be used for shear flow, such as two-layer, wave, couette flow, drop/bubble deformation and breakup, jet flow, and other immiscible flows, it's should be ok for your case.