STATIC CONTROL OF DRAG-REDUCING AIR CAVITIES WITH VARIABLE CAVITATOR SHAPE

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K I Matveev

Abstract

Air ventilation of submerged surfaces of ship hulls is a promising technique for drag reduction. To ensure high performance of air cavities in a broad range of operational conditions, the cavity properties can be controlled with help of compact hydrodynamic actuators. In this study, a potential flow theory is applied to model an air cavity formed behind a wedge-shaped cavitator under a horizontal wall imitating a ship bottom. By varying the wedge angle, it is possible to achieve states with maximum drag reduction at given operational conditions. The dependence of the optimal wedge angle on Froude number and hull trim is investigated. The air-cavity ability to reduce frictional drag is found to increase with rising flow speed and bow-down hull trim.

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