Simulation of mountain lee waves in a wind tunnel: technical report

Lin, Jung-Tai, author
Binder, G. J., author
Fluid Mechanics Program, College of Engineering, Colorado State University, publisher
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Mountain lee-waves were simulated in a wind tunnel where the density stratification was produced by heating the ambient air and-cooling the lower boundary. The flow patterns were visualized with smoke and were also determined from mapping of the temperature fields measured point by point with thermocouples and platinum resistance thermometers. The magnitudes of the velocities were measured with a constant temperature hot-wire anemometer. Since this instrument is also temperature sensitive the compensation of this effect at very low velocities (the actual velocities were about 0.5 ft/sec) was experimentally determined. The flow was composed of two layers of which the lower one (thickness 7-8 in.) had the large stability. The Froude number was calculated on the basis of the height, stability and average velocity ih the lower layer. Two bell-shaped model mountains of the same height (4 in.) but of different horizontal scales were used. This simulation experiment reproduced all the main features of mountain lee-waves, namely the wave profile, the rotor below the crest of the first wave, the strong velocity increase on the lee slope (1.5-1.8 times the average upstream velocity). Strong turbulence was found in the upper part of the rotor. The wave length at a fixed elevation of the lee-waves was found to increase linearly with Froude number; the amplitudes did also increase with Froude number.
December 1967.
Includes bibliographical references (pages 67-69).
U.S. Army Research Grant DA-AMC-28-043-65-G20.
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Mountain wave
Wind tunnels
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