Experimental Investigation on Free Surface Flow Related to Bow Wave Breaking

Abstract

This is a report on experimental study of wave breaking phenomena in front of ship bows. To make clear the flow characteristics of bow near field with wave breaking, the authors conducted the following experiments by using two types of model ship with a blunt and a sharp bow; 1) Observation and measurement of bow wave profiles 2) Measurement of flow field beneath the free surface 3) Visualization of vortices in front of the bows 4) Observation of limiting streamlines on the surface of the bows 5) Measurement of pressure distribution on the surface of the bows. On the basis of experimental results, several considerations are made on free surface flow related to the bow wave breaking. Further, the effect of a bow wing on wave breaking is experimentally investigated. It has been found that the bow wing reduces ship wave resistance by decreasing the turbulence on the free surface of breaking waves. The measurements of the flow field around the bow wing proves that leading edge vortices exist above the wing, which can be observed on swept wings at large angle of attack. A bow wing is attached to a model of a fishing boat, and it is confirmed that the bow wing is also effective for reduction of wave resistance of the practical hull form.