Turbulent Free-Surface Flow Behind a Surface-Piercing Body: Towed PIV Measurements

Detailed information on the free-surface wave in the turbulent wake of a surface-piercing body is important in various fields of naval architecture and ocean engineering such as designing ship hulls and floating structures. In the present study, a towed underwater particle image velocimetry (PIV) system was used to investigate the free-surface wave effects on the turbulent wake of a simple surface-piercing body. The selected test model was a cylindrical geometry formed by extruding the Wigley hull’s waterplane shape in the vertical direction. The towing speed of the model was set to Froude numbers of 0.2 and 0.4, which represent typical speeds of commercial ships and combatants, respectively. The corresponding Reynolds numbers were 0.541 million and 1.08 million, respectively. Due to the constraints of the two-dimensional PIV system used for the present study, the velocity field measurements were done separately for the vertical and horizontal planes. Using the measured data at several different locations, it was possible to identify the free-surface wave effects on the turbulent wake in terms of the mean velocity components and turbulence quantities. In order to provide the accuracy level of the data, uncertainty assessment was done following the International Towing Tank Conference standard procedure.