Development of a new device to control oblique waves in transitional boundary layers

An experimental attempt to control oblique waves in the transitional boundary layer of a flat plate using small pieces of thin piezo-ceramic actuators attached on the wall surface is carried out. In addition, whether piezo-ceramic actuators are appropriate as a transition-controlling device is examined. The basic idea is to generate waves whose sign are opposite of the incoming oblique waves. Two rows of piezo actuators are used in the experiment. The upstream row is used to generate the intruding waves and the downstream row is used to generate the intercepting waves. From the experimental results, it is shown that the piezo-ceramic actuators are capable of reducing the amplitude of the oblique waves. It is also shown that the strength of waves after control can be estimated as a linear addition of the waves from the upstream and downstream rows of actuators.