Abstract
Cloud cavitation shows an unsteady periodic tendency under a certain flow condition. In a cavitating water jet flow with cavitation clouds, the cavities or the clouds produce high impact at their collapse. In order to make clear a mechanism of the periodic cavity behavior, we experimentally examine the behavior in a transparent cylindrical convergent-divergent nozzle using a high-speed video camera. An effect of upstream pressure fluctuation due to a plunger pump is investigated from a viewpoint of unsteady behavior in a cavitating water jet. As a result, it is found that the cavitating flow has two kinds of oscillation patterns in the cavity length (cavitation cloud region). One is due to the upstream pressure fluctuation caused by the plunger pump. The other is much shorter periodic motion related to the characteristic oscillation of cavitation clouds accompanied with the shrinking (reentrant), growing and shedding motion of the clouds.
Highlights
Cloud cavitation is typically observed in a separated flow field
An effect of upstream pressure fluctuation due to a plunger pump is investigated from a viewpoint of unsteady behavior in a cavitating water jet
One is due to the upstream pressure fluctuation caused by the plunger pump
Summary
Cloud cavitation is typically observed in a separated flow field. In many cases, the cloud cavitation shows an unsteady periodic tendency with a periodic shedding of cavitation clouds and a reentrant motion in a cavity. It is found that a reentrant motion on the inside of a cavity and the following formation of periodic cloud cavitation are caused by pressure waves occurrence and its propagation due to a collapse of a cavitation cloud shed downstream [2,3]. The cavitation cloud behavior is investigated using a relatively large convergent-divergent nozzle made of a transparent acrylic-resin cylinder installed in a Cav-WJ apparatus. It is observed that the high-speed water jet accompanied with periodic cavitation clouds is formed in the axisymmetric nozzle. A water jet apparatus is pressurized by a plunger pump This kind of high-pressure pump system can affect upstream flow condition due to the periodic pressure pulsation. The other is due to cavitation cloud by nature, which is not affected by plunger unsteadiness
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