Affiliations: Department of Mechanical Systems and Design, Tohoku
University, Sendai, 980-8579, Japan. E-mail:
[email protected] | Hokkaido Railway Company, Sapporo, 060-0011,
Japan
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.