S054044 音波による長方形噴流の制御 : 渦構造に及ぼす励起パターンの影響([S05404]噴流,後流,およびはく離流れの基礎と応用:最前線(4))

概要

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Active control of a rectangular jet has been attempted to manipulate the vortex shedding interval in the major shear layer. The aspect ratio of the nozzle cross-section is 15, and the Reynolds number based on the shorter side length of the nozzle is 6700. It is considered essential that the vortex distribution along the each major shear layer plays an important role to characterize a rectangular jet behavior. In the present investigation, it was remarkably observed that the jet spreads more widely in the minor direction and contracts more greatly in major direction by the asymmetric excitation than that of the non-excited jet. Hot wire measurement was conducted, and could provide the mean, coherent and random velocity components from the instantaneous velocity signal. The measurement results showed that the coherent vortices are generated in synchronization with the excitation frequency and the mode. In addition, it was revealed that the inclined vortex rings are formed and interacted with each other only when the jet was excited by asymmetric mode. The jet spreading is attributed to the tilting alignment of the vortex ring, and the jet contracting in minor direction is due to the self-induced deformation of the rectangular vortex ring.
2011-09-11