Rotorcraft Aerodynamics Group

Flow Visualization of Rotor Wakes Using Density Gradient Methods

Erwin Moedersheim, Mark Daghir, and Dr. Gordon Leishman


A series of shadowgraph and schlieren studies were performed to visualize the wakes of small scale rotors operated at tip Mach numbers between 0.5 and 0.9. The objectives were to examine the relative merits of both techniques in an attempt to gain a better appreciation of the various flow problems that could be studied on rotors, possibly on a larger scale. Various optical and photographic techniques were also explored, with a view to optimizing the techniques for rotor applications. Studies were conducted in hover and descent with various propellers and rotors. Rotor wake/body interactions were also examined using cylindrical body shapes.

Below is a shadowgraph image of a rotor in simulated axial descent conditions in a wind tunnel at the University of Maryland. The rotor is operating close to the vortex ring state, and the tip Mach number is 0.6.

Moedersheim, E.P., Daghir, M.G., Leishman, J.G.: "Flow Visualization of Rotor Wakes Using Shadowgraph and Schlieren Techniques," Paper 31, Proceedings of the 20th European Rotorcraft Forum, Amsterdam, The Netherlands, October 1994.

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Erwin Moedersheim

Last modified: Sat Feb 10 15:01:14 EST 1996 by fencer