Abstract
Suppression of low-frequency pressure pulsations using vortex generators at the jet nozzle is investigated for a large low-speed open jet wind tunnel. The pressure pulsations are measured for different arrangements of the vortex generators at the jet nozzle. It is found that only generators installed at the corners of the nozzle can reduce low-frequency pressure pulsations and generators installed in the middle parts of the four inner walls of the nozzle not only fail to decrease the pulsations but also excite them outside the jet even more strongly. On the basis of these results, corner vortex generators (CVGs) are adopted for control of low-frequency pressure pulsations in the open jet wind tunnel. After installation of CVGs, both the amplitude of pressure pulsations in the plenum and the turbulence intensity at the center of the test section are significantly reduced.
Highlights
Many in-service open jet wind tunnels1–4 and 3/4 open jet automotive wind tunnels5–9 experience periodic, near-single-frequency low-frequency pressure fluctuations in the plenum over a specific test wind speed range
The 5.5 × 4 m2 large open jet wind tunnel (FL-17) at the China Aerodynamic Research and Development Center (CARDC) was subject to large-amplitude low-frequency pressure pulsations during its early stages of operation,9 and this paper describes a study of the control of such pulsations using vortex generators in the rectangular nozzle of this tunnel
It is found that the locations at which the vortex generators are installed in the rectangular nozzle of the open jet wind tunnel are critical for their effective performance
Summary
Many in-service open jet wind tunnels and 3/4 open jet automotive wind tunnels experience periodic, near-single-frequency low-frequency pressure fluctuations in the plenum over a specific test wind speed range. FKFS besst was successfully applied to low-frequency pulsation control in the 5.8 × 3.8 m2 aeroacoustic wind tunnel at the University of Stuttgart in 2014.36,37 To achieve a maximum test wind speed of more than 80 m/s, extensive nozzle modifications based on different types of vortex generators and Seiferth wings were undertaken in DNW’s 8 × 6 m2 open jet wind tunnel and 1:10 scale model wind tunnel Among these modifications, tetrahedra placed at the inner side of the leading edge of the nozzle achieved good results, increasing the jet velocity by 6% without any noticeable reduction in the core width of the jet..
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