Control of natural laminar instability waves on an axisymmetric body

Abstract

Abstract : An experimental investigation of the control of natural laminar instability waves on an axisymmetric body was conducted in the NOSC high speed water tunnel. The body was a 9:1 ellipsoid of revolution, 50mm in diameter at the midsection. Control perturbations were introduced into the boundary layer through a suction/blowing slot of 0.075mm width at 130mm from the nose. Hot film sensors before and after the slot were used to measure the passage and attenuation of the instability waves. A very simple invert and delay control loop was used to control a speaker embedded in the suction/blowing slot. At a freestream velocity of 8.67m/sec, and approximately 50 percent reduction in the RMS fluctuations of the instability waves was achieved after control. At this velocity the frequency of the instability waves was about 1kHz. The experimental run conditions corresponded to Reynolds numbers, at the slot location, of 1.24 million and 1520 based on axial location and boundary layer displacement thickness respectively. Torpedo systems, Subsystems, Components, Propellers.