Etude du sillage d'une poche de cavitation partielle se développant sur un profil hydraulique bi-dimensionnel

Study relating to a partial cavitation wake pocket forming on a bidimensional hydraulic profile

Institut de machines hydrauliques et de mécaniques des fluides, Ecole polytechnique fédérale de Lausanne

Abstract

The formation of a partial cavitation pocket at the entrance of the turbine blades of a hydraulic machine is a situation which represents the highest risk of erosion. Therefore, we have decided to study this situation inside the IMHEF high speed cavitation tunnel on a NACA bidimensional profile. With a 0.81 cavitation figure, a 2.5^o incidence and a speed varying from 20 to 35 m/s, the cavitation speed corresponds to that which can be observed at the entrance of the centrifugal pump.XML_RICH/1988/05/lhb1988044.xml After having given a brief description of the experimental means used, details are given concerning the mechanisms which generate and convect the transistory cavities into the wake of the partial cavitation. The pressure measurements carried out at various speeds reveal a remarkable influence of the Reynold's numbers of the flow along the length of the pocket.