Etude numérique des tourbillons de Karman à grand nombre de Reynolds

Numerical study of Karman vortices shedding at high Reynolds number

ALSTOM Power Hydra, Centre de Technologie Turbine, 82 avenue Léon Blum, BP 75, 38041 Grenoble Cedex 9, France

Auteurs de correspondance : thierry.chiappa@power.alstom.com jean-loup.deniau@power.alstom.com

Abstract

Unsteady loading of the hydraulic turbine components remains an important design parameter. Among these unsteady loadings, the specific problem of dynamic stresses on stay vanes is still important. In fact, in this case, the fluctuating flow due to the Karman vortex street occuring downstream the stay vanes is a source of periodic mechanical stress that can be, in lock-in conditions, the cause of fatigue/corrosion phenomena and may introduce blade cracking and failures. The master of such phenomena needs a good understanding of the fluctuating wakes behaviour. Then, the direct simulation by viscous calculations is the only method that can help in the understanding of the unsteady characteristics of the wakes. This article presents a numerical analysis of Karman vortex shedding thanks to unsteady Navier-Stokes calculations (CFX-TASC flow(r) [11] ) of flows downstream profiles such as cylinder and truncated NACA profile for both laminar and turbulent conditions.