Influence of the impellers' geometry on turbulent von K\'arm\'an swirling flows

TL;DR

This study uses numerical simulations to explore how the shape and rotation direction of impeller blades affect turbulence characteristics in von Kármán swirling flows, revealing differences in turbulence production and anisotropy.

Contribution

It provides new insights into how impeller geometry influences turbulence structure and dynamics in von Kármán flows, highlighting the role of blade shape and rotation direction.

Findings

Turbulence production zones differ with blade geometry.

Turbulent fluctuations show significant anisotropy.

Relative helicity distribution depends on the forcing mechanism.

Abstract

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.