Secondary-Flow-Related Vortex Cavitation.

摘要

A study is presented of a vortex formed near the inner wall of a rotor operating within a boundary layer. Experimental critical cavitation data and Laser Doppler Anomometer measurements obtained downstream of the rotor plane are given for many flow configurations. In addition, rotor inlet and outlet velocity profiles were measured. Experimental results show an influence of inlet velocity gradient near the inner wall on the critical cavitation number of the vortex. Secondary flow vorticity equations are developed and employed to calculate the vorticity in the blade passage near the inner wall of a rotor. In order to calculate the streamwise vorticity, an approximate method was developed to calculate the streamlines through a rotor. Cavitation data are correlated with the calculated exit passage streamwise vorticity using a simple vortex model. Results show the importance of the additional secondary vorticity on the exit streamwise vorticity near the inner wall of a rotor. The secondary vorticity induces an additional component of tangential velocity which was found to increase the flow turning near the inner wall. This increased tangential velocity profile compared favorably with the measured vortex profile outside of the vortex core region. (Author)