The flow near a surface piercing, symmetric body with a long draft is examined, focusing in particular on the structure of the shoulder wave and the separated region behind it. The experiments are pefformed in a towing tank at Fr_L=0.25, and include velocity measurements using PIV as well as video and film photography above and below the free surface. At Fr_L>=0.15, formation of the shoulder wave is preceded by impingement of the flow on the model, a process associated with the bow wave, which generates a turbulent, bubbly wake. Consequently, the origin of the shoulder wave consists of severai powerful counter-rotating vortices which entrain bubbles from the free surface. The wave crest becomes milder and eventually irrotational with increasing distance from the model. Behind the shoulder wave, at x/L=0.7, boundary layer separation begins, but only near the free surface. The separated zone contains several large scale streamwise vortices that detach from the model; the first one from the intersection with the free surface, and later ones from below the free surface. At Fr_L=0.25, there is no reverse flow within the separated region, but at Fr_L>0.30, flow reversal does occur. The entire process involves considerable energy dissipation.
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