Cavitation Performance of Confluent Pipe

Abstract

Because of the recent increasing velocity in pipe, the elements in water pipe line systems are in danger of cavitation occurrence. The cavitation causes detrimental phenomena such as noise, vibration and sometimes damage of materials. Therefore, in the plan and design of such pipe line systems, it is very important to evaluate the energy losses as well as to predict the cavitation performances in it. This paper dealt experimentally with the cavitation performances of the confluent pipe with a single lateral pipe. First, for the T-shaped confluent pipe with equal square cross sectional areas of lateral and main pipes, the aspects of cavitation occurrence were observed in detail and its critical conditions were found. Then, the effects of the cross sectional area ratio of lateral to main pipe, the confluent angle, and the roundness at the junction part on the cavitation performance were experimentally investigated. The following conclusions are obtained. 1) Though the cavitation occurs slightly, there is no remarkable change in the loss coefficients for main and lateral flows due to confluence. 2) The desinent cavitation numbers are not so much affected by Reynolds number for the constant ratio of flow rate and expressed only by the ratio of flow rate. 3) For the T-shaped and y-shaped confluent pipes with equal cross sectional areas of lateral and main pipes, the cavitation appears in separating stream from downstream side edge of junction. 4) Increasing the area ratio of lateral to main pipe, decreasing the angle of confluence and rounding off the downstream corner of junction, the cavitation performances become higher. 5) For the T-shaped confluent pipe with a half area ratio of lateral to main pipe, there is not only the separating cavitation but also the vortex cavitation formed by secondary flow at confluent part.