[RAJDEEP]

Hello everyone,

I am carrying out the simulation of Multiphase fluids(water and air) under rotation.
While carrying out the simulation, I observed that there is not clear interface between water and air like water volume fraction changes from 0 to 1 over appreciable length.

Is there any option which will help in getting the distinct interface between water and air?

Thanks and Regards

[ghorrocks]

There are many options for modelling multphase flows - free surface, drops, mist, bubbles, foam an so on. They are all modelled differently. You have to choose the right multiphase model for the regime of multiphase flow you have.

If you have a free surface flow then choose the free surface options (obviously). To see how to set that, look at the CFX tutorial titled "free surface flow over a bump".

[AtoHM]

I think he set it up already but is wondering about the interface height. The mesh resolution in the region of the free surface can influence the interface height. If you want a sharper interface, you can try to refine the mesh in that region. In any case I guess it is common practise to assume the free surface at volume fraction 0.5 of the phases.

[RAJDEEP]

I am carrying out the simulation of multiphase fluid under rotation.
The interface is clear at the outer end whereas it is more of diffused kind on inner side.
The attached screenshot depicts the same that, water volume fraction changes smoothly at outer end(right side) whereas it changes on inner side over comparable length(left side).

I am using standard homogeneous model for multiphase in CFX and interface model as free surface as I am not at all expecting any bubble formation.

And the mesh is almost of same nature on inner and outer sides.

[ghorrocks]

Please post your output file and an image of your mesh.