In most hydraulic applications (turbines, pumps, water intakes, propellers) the appearance of gas filled vortices, either caused by cavitation or air entrainment from a free surface, is usually associated with increase of losses, vibrations, noise and erosion risk. However, a correct prediction of the vortex characteristics (most importantly, of the pressure at the core) by numerical simulations may be challenging. A common example is the over-prediction of the vortex dissipation, which leads to wrong estimation of the gas core collapse location.
In the present paper we assess the numerical requirements necessary to compute vortex characteristics comparable to experimental results. As a first step, we evaluate the influence of the mesh resolution for different turbulence models (SST, SAS and RMS), in the case of a vortex generated by an elliptical wing.
Secondly, we compare the efficiency of several popular vortex identification techniques (helicity, Q, λ, Δ, etc…) to designate the mesh refinement regions, thus adapting the mesh to successfully compute the vortex characteristics, in the case of a vortex created in a cylindrical container with tangential inflow and central outflow.
Therefore, we are able to present effective guidelines for the correct computation of the above mentioned two phase problems, that can also be applied to leakage flow in gas turbomachines, wing-tip vortices, and more generally all computations where a high quality resolution of the vortices is necessary.