Feedback control of instability waves in a transitional flat-plate boundary layer |
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Authors: | Y Fukunishi T Sakai K Sasaki S Izawa A K Xiong |
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Institution: | 1. Department of Mechanical Systems and Design, Tohoku University, 980-8579, Sendai, Japan 2. Hokkaido Railway Company, 060-0011, Sapporo, Japan
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Abstract: | A semi-automatic and active control of T-S waves and oblique waves in a transitional flat plate boundary layer is carried
out in a wind-tunnel experiment and a numerical simulation. An array of piezo-ceramic actuators attached on a surface is used
to generate counter waves that cancel the incoming instability waves. The actuator’s operating amplitudes and phases are successively
updated using the velocity fluctuations monitored downstream by a rake of hotwires. Experimental results show that the system
is effective in weakening these waves when their inclination angles are less than 15 degrees. However, the system encountered
difficulty in controlling the waves of large inclination angles. In the numerical simulation, it is shown that the control
can be accomplished much easier. The numerical results show that controllability of the large inclination angle waves can
be improved by shortening the spanwise length each actuator piece. The danger of pursuing this kind of research solely by
a numerical simulation is pointed out. |
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Keywords: | |
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