: An experimental investigation was conducted in a water tunnel to explore the application of Coanda-effect circulation control to low aspect ratio wings. The facility was the Large Cavitation Channel in Memphis, TN. The intended application is to high-lift control surfaces (appendages) on underwater naval vehicles. Test results are interpreted in light of both theory and the extensive experience with circulation control (CC) technology at NSWCCD. The semi-span wing test model with a taper ratio of 0.76 was mounted on a load cell; a reflection plane provided for an effective aspect ratio of 2. Dual upper/lower trailing edge tangential jet slots were incorporated for bi-directional force generation. Findings include: finite-span effects on CC augmented lift are consistent with the effects on conventional lift-due-to-angle-of-attack, and cavitation in the Coanda wall jet region does not result in jet detachment or an abrupt lift stall. Wing lift augmentation ratios are up to 36 and meet expectations. Unexpected virtues of a dual-slotted configuration were found that enhance the value of CC to ship and VSTOL aircraft applications. A small flow from the second slot will significantly extend the lift capability beyond that of single slot operation by preventing what is believed to be the adverse effects of excessive turning of the wall jet at high momentum coefficients. Dual slot flow produces a merger of the two wall jets into a free planar jet that enables static thrust vectoring of the jet momentum flux over the full 0-360 degree range. This steerable-jet provides a jet-flap mode of lift development for use at very low vehicle speeds, as an extension of the high efficiency CC mode.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA436473&Location=U2&doc=GetTRDoc.pdf

Characteristics of a Dual-Slotted Circulation Control Wing of Low Aspect Ratio Intended for Naval Hydrodynamic Applications

: This document is the written version of a lecture presented in the 1975 Short Course on High Lift Technology at the University of Tennessee Space Institute.

https://calhoun.nps.edu/bitstream/10945/29446/1/oscillatingjetfl00plat.pdf

The oscillating jet flap

: The results of an analytical study to determine the application of a blown flap device called the Variable Deflection Thruster (VDT) to a helicopter rotor are presented and analyzed. The study is part of a longer-range program to investigate and develop control techniques for stabilization of the higher harmonic modes of helicopter rotor blades. A high-speed digital computer program was used to calculate the aerodynamic characteristics and performance of a Sikorsky CH-34 rotor system as though equipped with a blown two-dimensional section. The study was made over a range of rotor flight profiles and operating parameters including advance ratio, shaft angle of attack, blade pitch, tip Mach number, jet deflection angle and blowing rate. Performance of the blown rotor is compared to the conventional CH-34 rotor to illustrate VDT application effectiveness. Results show that the operating lift capability and propulsive force of the CH-34 rotor are increased when the rotor is equipped with a blown device. A preliminary analysis of the attenuation of rotor hub-shear variation by programmed blowing is also shown. In all cases, improved performance through application of blown control requires additional power. (Author)

Jeffrey M. Hammer

Papers

Helicopter Application Studies of the Variable Deflection Thruster Jet Flap.