SBIR-STTR Award

Aeroacoustic testing of rotors and propellers in wind tunnels fulfills an important role in the design and evaluation of future concepts as well as existing technologies. Laser-based sensors for standoff measurement of aeroacoustic perturbations are required in order to overcome the limitations of traditional microphones that are mounted on struts. AeroMancer Technologies proposes to develop a Laser Rayleigh Aeroacoustic Density Sensor (LRADS) for the measurement of acoustic density perturbations using Rayleigh scattering of laser radiation by air molecules. The relative acoustic density perturbations are directly proportional to the ratio of fluctuations of the intensity of the light received by the detector to the mean light intensity. While wind tunnel pressure and velocity measurements will be contaminated by periodic fluctuations from air turbulence, especially below 1KHz where acoustic measurements are desired, density measurements will not be affected as the turbulence is incompressible. In Phase I, AeroMancer will refine the instrument requirements and develop a simulation of its performance; build and test a breadboard instrument for validating the performance simulation; and develop the preliminary design of the system. AeroMancer will also study the potential for developing a miniature in situ version of the instrument for obtaining higher sensitivity and higher frequency response.

AeroMancer Technologies proposes a Laser Rayleigh Aeroacoustic Density Sensor (LRADS) for the measurement of aeroacoustic density perturbations in anechoic wind tunnels using Rayleigh scattering of laser radiation by air molecules. The relative acoustic density perturbations are directly proportional to the ratio of fluctuations of the intensity of the light received by the detector to the mean light intensity. In Phase I, AeroMancer refined the instrument requirements, developed a simulation of its performance; built and tested a breadboard instrument for validating the performance simulation; and conducted an error analysis to determine the dominant sources of measurement uncertainty. Using these results, AeroMancer developed the preliminary design of a prototype LRADS system that is based on a lidar configuration that can provide range resolved aeroacoustic density measurements along the laser beam to >1 KHz. In Phase II, AeroMancer proposes to finalize the LRADS prototype design; develop a noise and vibration enclosure to isolation the laser and sensitive optics from wind tunnel noise and vibration; fabricate and assemble the prototype; and test, validate and calibrate the system both in the laboratory and operationally in the 40x80 wind tunnel.