Computational investigation of confined turbulent swirling flows exhibiting vortex breakdown

The paper deals with the computational analysis of confined incompressible turbulent swirling flows, exhibiting vortex breakdown. For modelling turbulence, the Reynolds Stress Model-based (RSM) Unsteady Reynolds Averaged Numerical Simulations (URANS), Large Eddy Simulations (LES) and Detached Eddy Simulations (DES) approaches are adopted. Emphasis is placed upon the predictability of the sub and. super-critical vortex core states. Results are assessed by comparison with experiments for a laboratory water test rig. It is observed that better results are obtained using the RSM-based URANS approach. DES is also observed to perform better than LES. The rather unsatisfactory performance of LES may be attributed to inaccuracies in formulating the boundary conditions, and/or because there was too a coarse a cut-off scale for the simple sub-grid model adopted. Although the present work shows that remarkable improvements can be achieved compared with traditional FANS-based approaches, comparisons of the predictions with the measurements indicate that further improvements are necessary in order to achieve a satisfactory predictive capability for turbulent swirling flows.