Triplet of helical vortices

Abstract

In the present study, the stability of a helical vortex triplet has been predicted theoretically for the first time, and its existence proven experimentally as well as numerically. As basic flow configuration, swirling flows induced by a rotating cover in a closed cylinder have been considered. The experimental investigation was carried using simultaneously two diagnostics methods: Particle Image Velocimetry (PIV) to determine velocity fields by particle tracks and Laser Doppler Anemometry (LDA) to establish time-histories. The flow was systematically investigated for flow structures and, as a result, the existence of a stable vortex triplet was found at operating conditions corresponding to those predicted by the theoretical stability analysis. For the same flow regime, the 3D unsteady Navier-Stokes equations were solved numerically to identify the 3D structure of the vortex triplet. © 2008 Springer.