Experimental studies of the turbulent wake behind self-propelled slender bodies

The turbulent wakes behind a drag body, a jet-propelled body, and a propeller-driven body all with the same streamlined forebody shape were studied experimentally in a subsonic wind tunnel at a nominal Reynolds number based on diameter of 6 x 10. The wakes produced by the latter two bodies were momentumless. Mean flow and turbulence data were taken at five axial stations (X/D = 2, 5, 10, 20, and 40) downstream of the sterns of these bodies. The data for the wake behind the drag body compare favorably with previous experiments and establish a rigid reference for the wakes behind the self-propelled configurations. The downstream rate of decay of the velocity defect is essentially the same for the drag and propeller-driven bodies, whereas the decay for the jet-propelled body is substantially faster. The magnitude of the axial turbulence intensity is greater for the jetpropelled model than the other models, and the absolute value of the radial shear stress is greater (beyond X/D= 2) for the propeller-driven model. The rate of decay of the axial turbulence intensity is faster for the propellerdriven model than the jet-propelled model, however the rate of decrease of radial shear stress is faster for the jet propelled model.