Suppression Effect on TLV Cavitation of Overhanging Grooves with Different Tab Orientations: an Experimental Investigation

In this paper, a high speed camera and endoscopic particle image velocimetry system are utilized to investigate the influence of tab orientations of overhanging grooves on the suppression effect of tip-leakage vortex cavitation around a truncated NACA0012 hydrofoil. Four kinds of overhanging grooves (OHGs) with different tab orientations, namely OHGs_1–4, are tested, with the original hydrofoil as a comparison. The results suggest that compared with the baseline, all the overhanging grooves tested in our experiments show the suppression effect on TLV cavitation. However, the tab orientations of overhanging grooves leave significant influence on its effect. OHGs_2 with tabs extending beyond the pressure side surface shows the best suppression effect for all the measured gap sizes, followed by OHGs_1 with tabs extending beyond both the suction and pressure side surfaces. For OHGs_3 and OHGs_4, due to the lack of tabs extending beyond the pressure side surface, the suppression effect is not so good as OHGs_1 and OHGs_2. Further analysis indicates that the reason for the better suppression effect of OHGs_2 is the interference of tabs extending beyond the pressure side surface on the fusion of tip-leakage vortex and tip-separation vortex, which decreases the tip-leakage vortex circulation and increases its radius.