
Figure 7shows the vortical structures in the flow, similar toFig. 3for b ¼ 0 deg. The flow is asymmetric with respect to the center plane and the effects of the static drift angle dominate the flow. The crossflow from windward (WW) to leeward (LW) sides generates two primary vortices with counter clockwise rotation due to the sonar dome and WW bilge keel. The experimental **data** inFig. 7(a) clearly display the sonar dome (SDTV) and bilge keel (BKTV) tip vortices whose strength and progression are different from those shown for SDV and FBKV. SDTV is first observed at x ¼ 0.1 and BKTV at x ¼ 0.6. Additional secondary vortices are also observed: counter-rotating WW-and LW-FBKV with same rotation directions as PS and SS for b ¼ 0 deg; clockwise rotation ABKV; WW-and LW-free-surface vortices (FSV) due to wave breaking with clockwise and counter clockwise rotation on the LW and WW. WW-FBKV is first observed at x ¼ 0.2, and LW-FBKV at x ¼ 0.3. ABKV is first observed at x ¼ 0.8. LW-FSV is observed at x ¼ 0.12, and WW-
