Particle image velocimetry (PIV) measurements around a 7-m-long DDG-51 destroyer model focus on the flow within the attached liquid sheet, upstream of the point at which the bow wave separates from the model. The measurements are performed in Carderock, NSWC's 140-ft model basin at Reynolds number 1.6x10^7 and Froude number 0.30 (both based on ship length L).

The PIV system uses a 1k x 1k submerged digital camera and a 25-mj/pulse dual-head Nd-YAG laser. The data cover a 20-cm x 20-cm area of the flow within the bow wave near the free surface. As the model passes the camera, data are collected at 2.5-cm intervals beginning from upstream of the model until X/L = 0.1.

Individual vector maps show a growing region of negative vorticity originating at the toe of the wave and positive vorticity on the top and forward face of the wave. 92 instantaneous velocity distributions are repeated at X/L = 0.0690 to calculate mean flow and turbulent stresses.

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