Generation of velocity fluctuations in a boundary layer by a piezoelectric actuator

Hajime Okawa, Shigenori Kondo, Masaya Shigeta, Seiichiro Izawa, Yu Fukunishi

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


A feedforward control system for suppressing the instability waves in a boundary layer has been examined and improved. An array of piezoelectric actuators attached on a flat-plate surface was used as an active control device of the feedforward control system. Previous works have demonstrated that an array of piezoelectric actuators was able to generate controlling waves that were 180 degrees out-of-phase with the target instability waves, but finding the optimum timing and amplitude for driving the actuators depended on the experience and skill of the experimenters. To resolve this problem, we focused our attention on the process of generating these artificial waves. First, the flow field near an actuator was measured in detail in order to clarify the wave-generating process. It was found that the velocity fluctuation pattern started to appear from the actuator's surface, not from its trailing edge. Next, the effect of the driving signal waveform on the control was examined by comparing two different waveforms, sinusoidal and rectangular. A difference was found only in the third harmonic component of the generated velocity fluctuations, where the peak in the rectangular case was higher than that in the sinusoidal case. This suggested that it was not necessary to operate the actuators by a sinusoidal signal. Finally, a new semi-automatic algorithm for determining the control parameters was proposed and applied in an active feedforward control experiment. Our new algorithm demonstrated its ability to reduce the amplitude of the incoming oblique waves.

Original languageEnglish
Title of host publicationASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011
Number of pages7
EditionPARTS A, B, C, D
Publication statusPublished - 2011
EventASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011 - Hamamatsu, Japan
Duration: 2011 Jul 242011 Jul 29

Publication series

NameASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011
NumberPARTS A, B, C, D


ConferenceASME-JSME-KSME 2011 Joint Fluids Engineering Conference, AJK 2011


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