Sea Bottom Pressure Fields Produced by Yawed Vessels

Abstract

An understanding of the flow pattern about an ellipsoid immersed at rest in a parallel stream is often of value in aerodynamic and hydrodynamic studies. The steady flow, without circulation, about an ellipsoid immersed at rest in an infinite half-space of perfect fluid is discussed. A uniform stream flow is considered in which the centroid of the ellipsoid remains at a finite distance h from the plane boundary of the half-space. The major axis of the ellipsoid is taken to be parallel to the plane boundary and to make an angle θ with the direction of the undisturbed flow. Approximation equations are given for the velocity and pressure distributions on the plane boundary. These equations are based upon the method of images and the well-known theory of the flow pattern about a stationary ellipsoid in an infinite fluid medium. A procedure for obtaining the lines of equipressure change on the boundary is also described. The sea bottom pressure distribution produced by slowly moved yawed surface vessels in advance of the upstream hull-line may be approximated from computations based on formulae developed for the ellipsoid model. These approximations should hold when the ship proceeds through calm water of moderate depth at an angle of yaw sufficiently large to produce a wake, say θ greater than 20○. As an illustration of the application of the theory certain results of calculations of sea bottom pressure distributions and lines of equipressure change are given for a representative case.