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Effect of Wall Roughness on the Dynamics of Unsteady Cavitation

type de publication      article dans une revue internationale avec comité de lecture
date de publication 2005
auteur(s) Coutier Delgosha Olivier; Devillers Jean-François; Pichon Thierry
journal (abréviation) Journal of Fluids Engineering (J Fluid Eng)
volume (numéro) 127 (4)
  
pages 726 – 733
résumé The present paper is devoted to the experimental study of unsteady cavitation on the suction side of a two-dimensional foil section positioned in a cavitation tunnel with a small incidence angle. When the pressure is decreased in the tunnel, a sheet of cavitation characterized by large amplitude fluctuations is obtained on the foil. The present study focuses on the effects of the foil wall roughness on the cavity unsteady behavior. Four different sizes d of irregularities have been tested, from the smooth surface to a 400 µm grain size. The characteristic frequency of the flow unsteadiness is investigated by analyzing the data measured by a pressure transducer mounted flush on one vertical wall of the test section, whereas the mean cavity length is obtained by visual measurements on the foil side. Several types of cloud cavitation are identified in the case of the smooth surface. The effect of roughness is a significant decrease of the cavity length and a large increase of the oscillation frequency. It results in Strouhal numbers higher than the classical values obtained for partial cavity fluctuations. Moreover, the cavitation cycle is disorganized by the increase of the roughness, as it can be detected by the fast fourier transform analysis of the pressure signal. The general effect is a reduction of the pressure fluctuation intensity.
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