Showing papers presented at "AUTOTESTCON in 1979"

Application of laser velocimetry to an unsteady transonic flow

Abstract: Measurements of mean velocity, turbulent kinetic energy, and turbulent shear stress have been obtained in an unsteady but periodic flow. Polystyrene spheres, 0.35-0.55 microns in diameter, were injected into the tunnel settling chamber to seed the flow for a laser velocimeter. Synchronized counters together with an encoding interface and digital-to-analog converters were used to record the data on an analog tape recorder. Profiles of velocity and turbulence quantities are presented for several times during the periodic flow.

Alternative signal processing techniques for a pulsed laser Doppler velocimeter system

Abstract: The laser Doppler velocimeter system (LDV) being tested at NASA MSFC, Alabama, relies on a bank of classical filters for processing the returned lidar signal. Due to the complexity of this conventional filter system, alternative signal processing methods have been proposed for obtaining the Doppler spectrum. The fast Fourier transform (FFT) and the pulse-pair estimator are two techniques which appear to offer some advantages over the existing system. The work reported employs digital computer simulation to compare and evaluate these two processing methods for determining the first and second moments of the LDV velocity spectrum.