A three-velocity-component laser-Doppler velocimeter for measurements inside the linear compressor cascade |
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Authors: | Qing Tian K Todd Lowe Roger L Simpson |
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Affiliation: | (1) Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA;(2) Applied University Research, Inc, Blacksburg, VA 24060, USA |
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Abstract: | A 24′′ (610 mm) access laser-Doppler velocimeter (LDV) system was developed to make simultaneous three-velocity-component
measurements in a low speed linear cascade wind tunnel with moving wall simulation. The probe has a 610 mm access length and
achieves a measurement spatial resolution of 100 μm by using off-axis optical heads. With the relatively large access length,
the LDV probe allows for measurements from the side of a wind tunnel instead of through the tunnel floor, while the high spatial
resolution allows for quality near-wall measurements. The probe has been tested in a zero-pressure gradient 2D turbulent boundary
layer and the test results agree well with the experimental data measured with different LDV systems and hot-wire anemometery
for the boundary layer flows. The energy spectral density was estimated using a slot correlation, and Von Kármán’s model for
the energy-spectrum function was used to analyze the measured spectral data to estimate the turbulent kinetic energy dissipation
rate, which compares favorably with the measured production values in the log-layer region of the turbulent boundary layer.
Measurements are presented for the moving endwall boundary layer at the inlet of the linear compressor cascade facility to
validate the capability of this LDV for tip leakage flow measurements. These results indicate that the moving endwall reduces
velocity gradients in the near-wall region and results in less production of Reynolds stresses and turbulent kinetic energy
compared to the stationary endwall case. |
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