Active Control of Vortex Shedding Frequency by Side-Jets

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When a bluff body is placed in a flow, the body generates a separated flow region behind the body. That causes the generation of a vortex, which is grown along the flow, and shed into the wake. If the eigen frequency of the body corresponds to the vortex shedding frequency, the lock-in (sympathetic vibration) is occured, that is caused large damages to the body. Therefore, if the vortex shedding frequency could be controlled, it would be very useful in engineering.It this investigation, the control method using side-jets without any other new construction was applied to investigate whether the vortex shedding frequency can be controlled or not. Here the side-jets were inhaled at the point where the separation shear layr was generated. With emphasis on the performance of side-jets on the control of the vortex shedding frequency, both numerical simulation and experiment were carried out.The results are summarized as follows :・In the case of uniform suction side-jets, the characteristic is shown that the vortex shedding frequency is changed immediately in some narrow range with the change of side-jets velocity.・Suction side-jets have more effective influence on both the flow field and the vortex shedding frequency than injection side-jets.