Observation of the Spray of Prismatic Planing-Hull Models

Abstract

High-speed planing hulls support their weight by the dynamic lift, rather than the buoyancy as in case of displacement ships. The planing hulls, therefore, have a high-pressure region on the hull bottom, which gives rise to a water spray formation, spreading out in both sides of the hull. The spray is considered to be one component of the pressure drag. The present paper describes the results of observations of the spray configuration on prismatic planing-hull models. The flow velocity field on the spray and the flow flux are also measured to obtain the spray thickness and the momentum loss due to the spray. It is found that the spray resistance thus measured has a large part of the total pressure drag of the model hull.