Influence of the impellers' geometry on turbulent von K\'arm\'an   swirling flows
  We report numerical evidences of the influence of the blades' shape and of their direction of rotation on turbulent flows generated by counter-rotating bladed-disks enclosed in a cylinder, known as the von K\'arm\'an swirling flow. We show that, although the mean flows generated by stirrers with straight or curved blades can be topologically similar, turbulence production occurs in different zones. The structure and intensity of the turbulent fluctuating field also varies with the geometry, and retains significant anisotropy. From the direct numerical simulations fields, we analyse the dynamics of enstrophy and we show that the distribution of relative helicity h depends on the forcing mecanism of turbulence. 
Cl\'ement Jause-Labert and Fabien S. Godeferd
physics.flu-dyn