Numerical analysis of Goldschmied geometry with boundary-layer suction

Abstract

An effort is made to implement the phenomenon called the Aerodynamic Pressure Thrust (APT) for the purpose of effective propulsion of underwater vehicle. The two dimensional Goldschmied body with boundary-layer ingestion near the stern section is considered for this purpose. This particular shape, which up to this point is being considered mainly for aerodynamic propulsion, can be preferred for autonomous underwater vehicles over conventional streamlined bodies for their large volume-to-Iength ratio. The wind-tunnel experiments of 1960's by Fabio R. Goldschmied paved a way for development of energy efficient propulsion through proper interaction of aerodynamic design and engine power. Decades later, this eventually led to the development of several futuristic crafts which exploit the Pressure Thrust technique. Similar idea is attempted here to obtain improved pressure recovery behind the aft of a blunt underwater vehicle to generate additional thrust. In the present study, a simplified version of the Goldschmied geometry is considered with a single slot for suction between the fore-body and the stern. The computations are carried out utilizing commercial CFD solver Ansys Fluent. The axi-symmetric shape of the Goldschmied body is employed to generate a fully-structured mesh throughout the entire domain. The simulations are carried out for a range of Reynolds number and the suction pressure. The distribution of pressure at different radial locations is examined and plotted, similar to the original work by Goldschmied, to illustrate the alternate zones of drag and thrust produced along the radius. A sizeable portion of the thrust region in the plot is required to overcome the drag force and to achieve self-propulsion solely by means of boundary layer suction. The results of the computational study indicate a trend in that direction.