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An experimental study has been conducted on the effects of initial swirl and high turbulence in the exhaust of a circular jet injected from a flat plate at a 90-deg angle into a crossflow. The different jet types studied were low-exit turbulence (3%), high-exit turbulence (>10°7o), and 40 and 58% swirl. Surface pressure distributions and mean velocity vector plots were obtained for all of these cases. For the surface pressure distribution tests, the jet to crossflow velocity ratios R were 2.2, 4, and 8 for most of the jet types. For the mean velocity vector plots, R = 4 was chosen. Turbulence information in the jet plume was also obtained for the low-exit turbulence case at R = 4. The results showed that the higher-exit turbulence reduced the penetration height, and it also reduced the surface area influenced by negative pressures. The swirl-caused asymmetric pressure distributions and the swirl effects were more pronounced for lower-velocity ratios.

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Performance characteristics and velocity field of a ducted propeller in hover and axial flight conditions are investigated experimentally. Five different circular duct shapes has been tested. Effect of duct geometry is studied by means of measurements at various flow conditions. Velocity field upstream and downstream of the propeller, axial force acting on each component of the propulsive system, rotor speed and torque are measured. Pressure distribution on duct inner and outer surfaces is also investigated. Experimental results obtained for open and ducted propellers are compared. Nomenclature= duct inner diameter at propeller plane J = advance ratio (U ∞C /nD) K P = pressure coefficient L = duct length n = revolutions per second N = revolutions per minute P = power (2nQ) Q = torque T = thrust U = mean velocity U ∞ = free stream velocity U ∞C = corrected free stream velocity x = axial direction r = radial direction η = efficiency