Towed Underwater PIV Measurement for Free-Surface Wave Effects on Turbulent Wake of a Surface-Piercing Body

摘要

In the present study, a towed underwater particle image velocimetry (PIV) system in Seoul National University Towing Tank was used to identify the free-surface wave effects on the velocity vector field and the turbulent wake behind a simple surface-piercing body. The selected test model was a cylindrical geometry formed by extruding the Wigley hull's waterplane shape with a breadth-length ratio of 1/10 in the vertical direction. The model size was 1 m long, 0.1 m wide and 0.6 m deep. The towing speed of the model was set to Froude numbers of 0.2, 0.3 and 0.4. The corresponding Reynolds numbers were 0.54 million, 0.81 million, and 1.08 million, respectively. 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. Wave braking was observed at Froude number of 0.4 and reverse flow occurred behind trailing edge. In order to provide the accuracy level of the data, uncertainty assessment was done following the International Towing Tank Conference standard procedure.