The groove at blade tip designed for suppression of tip-leakage vortex may bring the risk of inducing new cavitation

Previous research showed that slotting at the tip section of a rotating machinery blade could suppress the tip-leakage vortex (TLV) by forming a new groove flow, while the possible adverse effects caused by the discontinuous tip section have not fully been studied. In this Letter, unfavorable effects due to an extra cavitation caused by the groove found in the standard incipient cavitation experiments are reported. Then, this anomaly is clarified by using large eddy simulation that the grooves cause step-like flows and induce low-pressure areas behind the groove near the pressure surface. This increased risk of inducing new cavitation deserves special attention when the medium is water.