The Wake of Self-Propelled and Over-Thrusted Slender Bodies Near a Simulated Free Surface

Abstract

Measurements were performed in the turbulent wake of a propeller-driven axisymmetric body with a plane of symmetry. A flat plate strut was attached to the upper surface of the axisymmetric body, giving a configuration like that of a SWATH-type ship, with the free surface replaced by the plane of symmetry. All mean flow and turbulent flow parameters were measured at three streamwise stations. The measurements were performed for the self-propelled condition and 100 percent over-thrust condition. In the far wake, the center of the wake was found to migrate towards the plane of symmetry. Some interactions were noted between the wakes of the propeller-driven axisymmetric body and that of the flat plate strut—yielding lower axial velocities, higher turbulence intensities and larger static pressure changes compared to regions free of such interference. Comparisons of these effects in the self-propelled case, 100 percent over-thrust case and a previous unpropelled case are given. Spectral measurements were also performed in both near-wake and far-wake regions.