Evaluation and Optimization of a Multi-component Planar Doppler Velocimetry System

A Planar Doppler Velocimetry system has been developed for multi-component velocity measurements in large scale subsonic wind tunnel facilities. System components, methodologies and improvements are evaluated and discussed. Data is presented on two component measurements conducted in the flow field above a 70 degree delta wing at an angle of attack of 23 degrees in a Mach 0.2 (69 m/s) free stream. Although only two components of velocity could be resolved, axial and spanwise measurements were made characterizing the velocity field associated with the vortex cores as they developed downstream. Detector placement and system performance was improved in a second test to measure the three dimensional velocity field above a Boeing UCAV model again at 20 degrees angle of attack operated in a Mach 0.2 free stream. The evolution of the three dimensional velocity field created by vortices from the sharp leading edge of the body and the outboard vortex above the wing was characterized. Further optimization of the current system indicated that current levels of uncertainty can be improved by proper camera placement to reduce the sensitivity to laser frequency fluctuations and by improving the linear independence of the measured velocity components as characterized by the condition number of the coefficient matrix. Other considerations of camera placement and considerations to make measurements are also discussed. I