• Title/Summary/Keyword: 후류 천이지연

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Suppression of Wake Transition and Occurrence of Lock-on Downstream of a Circular Cylinder in a Perturbed Flow in the A-mode Instability Regime (A-mode 불안정성 영역에서 교란유동장에 놓인 원형실린더 후류의 천이지연과 유동공진의 발생)

  • Kim, Soo-Hyeon;Bae, Joong-Hun;Yoo, Jung-Yul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.8
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    • pp.702-710
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    • 2007
  • Direct numerical simulation (DNS) is performed to investigate suppressed wake transition and occurrence of lock-on in the wake of a circular cylinder disturbed by sinusoidal perturbation at the Reynolds number of 220 (A-mode instability regime). The sinusoidal perturbation, of which the frequency is near twice the natural shedding frequency, is superimposed on the free stream velocity. It is shown that the wake transition behind the circular cylinder can be suppressed due to the perturbation of the free stream velocity. This change causes a jump in the Strouhal number from the value corresponding to A-mode instability regime to the value corresponding to retarded wake transition regime (extrapolated from laminar shedding regime) in the Strouhal-Reynolds number relationship. As a result, vortex shedding frequency is locked on the perturbation frequency depending not on the natural shedding frequency but on the modified shedding frequency.