Application of a Two-Component Bragg-Diffracted Laser Velocimeter to Turbulence Measurements in a Subsonic Jet.
Final rept. Jul 73-May 75,
ARNOLD ENGINEERING DEVELOPMENT CENTER ARNOLD AIR FORCE STATION TENN
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Laser velocimeter LV and hot-wire measurements of turbulence parameters in an isothermal subsonic jet are compared for axial locations up to 40 nozzle diameters downstream of the nozzle exit. Data are presented for the mean axial and radial velocities, axial and radial turbulence intensities, Reynolds stresses, and velocity probability densities. The LV used was a two-component, Bragg-diffracted, individual realization system. Since the flow was unseeded, the measurements relied on naturally occurring flow contaminants to serve as a tracer for the LV system. The LV stress measurements are believed unique in that they are derived from cross-correlation of simultaneous measurements of the axial and radial velocities. Comparisons of the LV results with the hot-wire data show anomalies in the mean radial velocities and turbulence intensities for axial locations less than 10 nozzle diameters downstream. Farther downstream these anomalies vanish, and the two instruments are in good agreement. Those factors influential to the accuracy of the LV results, such as optical alignment, statistical confidence and bias, particle dynamic behavior, and the error characteristics of the LV system, are discussed in light of the results. Author
- Test Facilities, Equipment and Methods
- Fluid Mechanics