V-22 Three-Dimensional (3D) Downwash Measurement

The Navy requires measurements of the wake field of helicopters in the vicinity of carrier ships to determine the safe operating envelope for the V-22 and to verify the accuracy of models obtained by computational fluid dynamics. This Phase I SBIR project will examine the feasibility of a laser-based remote sensing technique for recording three dimensional wind fields with high spatial and temporal resolution. A laser beam shines across the flight deck, where some of the light scatters from aerosol particles in the air to a group of at least three optical detectors placed around the measurement region. The motion of the particles encodes information about the wind velocity as a change in frequency of the scattered light. An innovative optical filter converts the frequency information into a signal that is proportional to velocity. The optical filter is simple, inexpensive, and has a wide acceptance angle, permitting the use of fast optics to collect the most light possible. The high signal to noise ratio obtained by this technique allows measurements from stand-off distances of over twenty meters using low-power lasers. Other system features include low electrical power and compact transmitter and receiver assemblies that should facilitate onboard tests.