Diagnostic Techniques for Maneuvering Rotorcraft 

Army Research Office

Computations and traditional measurement tools are far too slow and expensive to detect and understand all the aerodynamic interactions encountered by rotorcraft over the vast range of parameters in transitional maneuvers. We are learning to extract instantaneous 2-D velocity fields, vortex trajectories, and configuration geometry from the same video images using inexpensive white-light sources over large areas typical of rotorcraft and wind turbine flows. Besides obvious benefits in aircraft development, this opens up large-area atmospheric boundary layer turbulence phenomena. The issues are in optimizing resolution, and in the possibilities inherent in iterative and interactive analysis of space-and time-dependent multiple property fields. The Spatial Correlation Velocimetry technique offers iterative extraction of turbulence scales and basic flow metrics such as dilatation ( in reacting flows), eddy lifetimes and histories, and rotation, in high-Reynolds number, highly unsteady flows. These techniques use personal computers for initial results, followed by iterations on distributed-processor computers. Recently we have demonstrated successful application of the technique to rotor flowfield measurement in a large industry facility, without using lasers. 

Related Publications:

"Planar Velocimetry Using Digital Cross-Correlations". Developments in Theoretical and Applied Mechanics, Vol. XV, March 1990, p. 471 - 478.

"Planar Velocity by Spatial Cross-Correlation: Theoretical Concepts and Validation". AIAA Paper 90-1634, 21st Fluid Dynamics, Plasmadynamics, and Lasers Conference, Seattle,WA,June'90.

"Spatial Correlation Velocimetry in Unsteady Flows". AIAA 91-0271, Aerospace Sciences Meeting, Jan. '91.

"Spatial Correlation Velocimetry in Large Wind Tunnels". SATA Business Meeting, South Bend, IN, June 1991.

"Quantification of Canard and Wing Interactions Using Spatial Correlation Velocimetry". AIAA Paper 92-2687, June 1992.

"Instantaneous Velocity Fields in a Rotor Wake By Spatial Correlation Velocimetry". AIAA Paper 93-3081, July 1993. 

"Wind Turbulence Measurement Over Large Areas Using Spatial Correlation Velocimetry". Proceedings of the Silver Symposium of the Flight Test Engineers Society, Patuxent River, MD. V-4- V-4-12, August 1994. 

"Modern Diagnostics in an Ancient Wind Tunnel". Annual Meeting of the Subsonic Aerodynamic Testing Association, Auburn Hills, MI, June 1995. 

"Rotor Wake -Induced Flow Separation on a Lifting Surface" Journal of the American Helicopter Society, Vol. 40, No.2, April 1995, p. 24 - 27. 

"Large-Area Velocity Measurement in Low Speed Flows". ICIASF '95 Record, July 1995,p. 20.1 - 20.9. IEEE95-CH34827-95/0000-20.1