Influence des divers types de cavitation sur les bruits, les érosions et les modifications des performances

Effect of various types of cavitation on noise, erosion and performance

Professeur à l'Ecole Nationale Supérieur des Arts et Métiers, Paris.

Résumé

Introduction. An initial reminder is given of a standard terminology and cavitation figure classification complied by No. 3 Working Group of Société Hydrotechnique de France's Cavitation Commission. Applications of this classification are discussed and conclusions are drawn regarding cavitation noise, erosion and effects on performance for each figure. The information in the article is the result of a survey carried out among hydraulic equipment manufacturers and users, and design or research organisations. Analysis of factors involved. The effects of the following factors are discussed : cavitation coefficient, operating point, gas content, flow velocity, Reynolds number, temperature, vapour pressure, surface condition, thickness and type of machine casing and type of cavitation, all of which are likely to affect the development of the cavitation figure or the noise and/or erosion accompanying it. Study of particular cavitation figures. The following figures are discussed : Single bubbles. Bubble clusters. Bubble clouds. Sheets. Vortices. Twisting streamers. Bright streaks. Each figure is illustrated by one or more photographs, with amplifying remarks on the associated noise, erosion and effect on performance. Conclusions. The ambitious yet tremendously important aim of this study is to define the harmful or harmless effect of the various cavitation figures on industrial equipment. Though it has not been possible to reach any definite conclusions for all of them, a certain number of the points established can already serve as a reference basis.