مبانی کاویتاسیون

Why are propeller blades of speedboats strongly eroded? Why does a syringe have to be filled slowly in order to avoid the formation of a vapour cavity near the piston? Why does a pump for watering the garden not work efficiently if it is placed too high above the ground water level? These questions, and many others taken from day to day experience, refer to situations which apparently have no connection between them, except for the fact that the motion of a liquid in part of the system plays an essential role.Cavitation science is that part of liquid physics which addresses the motion of liquids near -or beyond- the limit of vaporization. Generally, vaporization occurs if liquid velocities are large, causing pressure to decrease below a critical value at which the liquid continuum is broken at one or several points. Vapor cavities appear there and various unexpected effects follow for the system such as noise, lower performance, vibrations, wall erosion For a long time, it was believed that cavitation phenomena should be avoided entirely because of the generally negative character of their consequences. However, over the years it appeared that such a constraint could be costly, though not necessarily justified on scientific grounds. A limited development of cavitation – if carefully defined and controlled – can be allowed. This promotes the development of high speed hydrodynamics and hydraulics.The present book is aimed at providing a comprehensive presentation of cavitation phenomena in liquid flows. It is further backed up by the experience, both experimental and theoretical, of the authors whose expertise has been internationally recognized. A special effort is madeto place the various methods of investigation in strong relation with the fundamental physics of cavitation, enabling the reader to treat specific problems independently. Furthermore, it is hoped that a better knowledge of the cavitation phenomenon will allow engineers to create systems using it positively. Examples in the literature show the feasibility of this approach.