Turbulent Vortex Shedding from Hydrofoil

Introduction

The purpose of the thesis is to study the effects of cavitation and boundary layer developement on turbulent vortex shedding from hydrofoil in a uniform flow.

Vortex shedding from bluff body belongs to the family of flows known as shear layer instabilities. The studies into this type of flow are motivated by the abundance of situations where understanding and manipulating vortex shedding are of practical importance. Uniform flow past circular cylinder is a standard configuration for investigating vortex shedding and is well documented at low Reynolds numbers. However and particularly at high Reynolds numbers, the vortex shedding in hydrofoil wake has been studied to much less extent despite its occurrence in numerous practical applications; in ship propulsion and hydropower generation for example.

The lack of experimental data becomes particularly evident today, since engineers tend to use materials to their limits, causing structures to be more flexible, so that the vortex-induced vibrations become one of the primary damage mechanisms. Besides, depending on the pressure level in the flow, cavitation occurs in the shed vortices. However, except for several early studies, the cavitation effects on the vortex street have been ignored. The influence of the boundary layer development along the hydrofoil on the vortex shedding process is also experimentally investigated in the EPFL high speed cavitation tunnel.

Doctoral student : Philippe Ausoni

Wake Flow High Speed Visualization

Cavitation vortex street in the wake of a Naca 0009 hydrofoil for lock-in condition (Torsion mode)

  • High speed visualization: 10’000 frames/sec
  • Free stream velocity: 12 m/s
  • Cavitation number: 0.6