Reducing Drag and Oscillation of Spheres Used for Buoyancy in Oceanographic Moorings

Abstract

Numerical and laboratory results of the drag characteristics are presented for different configurations of an underwater buoyancy package. It is shown that the drag and oscillation of an underwater sphere can be reduced substantially with the addition of a shaped cowling. The influence of several different cowling shapes on the drag and lift are determined. The results from a numerical fluid dynamical calculation are compared and laboratory measurements are scaled. Both the dynamic and static components of drag and lift are presented. The drag force for an underwater sphere can be reduced by more than 80% for a full teardrop-shaped cowling. A truncated teardrop, more practical for real applications, will still reduce the drag by 60%?70%. In addition to the drag, the amplitude of oscillations driven by eddy shedding is similarly reduced.