プラズマアクチュエータを用いた曲がり管内の音響振動流の制御

抄録

Our purpose is to clarify the effective control method with a plasma actuator to reduce the energy loss in the acoustic oscillatory flow in a curved duct. This flow appears in machinery related with sound such as speakers and thermoacoustic devices. In this study, simulations based on the compressible Navier-Stokes equations were conducted to clarify the flow and acoustic fields in a curved duct under acoustic excitation at the duct end. The excitation frequency was adjusted so that acoustic resonance with a three-quarter wavelength mode occurs in the duct. The curved section was positioned at the anti-node of the velocity fluctuations between straight sections. The acoustic Reynolds number based on the amplitude of velocity fluctuations at the anti-node was varied in the simulations. The predicted flow fields show the periodic occurrence of flow separation leading to the energy loss around the curvature. The flow control by a plasma actuator, which was installed between curved and straight sections, was applied to suppress the flow separation. It was shown that the acoustic energy loss around the curvature was reduced by the intermittent control of the plasma actuator with the duty ratio of 0.5. Moreover, the influence of the phase of the intermittent control with reference to the cross-sectional averaged velocity fluctuations around the curvature on the control effects is discussed.