Cavitation at Sharp Edge Multi-Hole Baffle Plates

Abstract

This paper reports results of an experimental investigation of cavitation caused by water flow through sharp edge multi-hole baffle plates at high speeds and large pressure drops. Such cavitation can be destructive to industrial systems due to the induced pipe wall vibrations that result. Incipient and critical cavitation numbers are design limits that are frequently needed in the design of systems implementing baffle plate type geometries to prevent adverse cavitation effects. The overall baffle plate loss coefficient, point of cavitation inception, and point where critical cavitation occurs are functions of baffle hole size, number of holes, and plate thickness. Sixteen total baffle plates were considered in the study with hole sizes ranging from 0.16 cm to 2.54 cm, total through area ranging between 11% and 60%, plate thickness ranging from 0.32–0.635 cm, and number of holes ranging from 4 to 1800. The plates were mounted in the test section of a 10.2 cm diameter schedule 40 pipe closed water flow loop. The focus of this paper is on how the influencing parameters affect the loss coefficient and the point of cavitation inception. The results show a complex dependency between the baffle plate loss coefficient with total through area ratio and the thickness to baffle hole diameter ratio. In general the loss coefficient decreases with increasing openness and increasing thickness to hole diameter ratio. A model based on the data is proposed to predict the loss coefficient for multi-holed baffle plates. Further, the data show that the cavitation number at the point of cavitation inception increases with increasing openness. However, with regard to the thickness to hole diameter ratio, the cavitation number at inception exhibits a local maximum at a ratio between 0.5 and 1.0. Models to allow prediction of the point of cavitation inception and the point where critical cavitation begins are presented in the paper.