대한기계학회논문집B (Transactions of the Korean Society of Mechanical Engineers B)

  • 제38권10호
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  • Pages.859-864
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  • 2014
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  • 1226-4881(pISSN)
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  • 2288-5324(eISSN)
대한기계학회 (The Korean Society of Mechanical Engineers)
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상류에 있는 물체의 직경변화에 따라 후류 물체가 받는 영향

Effects of Downstream Cylinder by Changing Upstream Object's Diameter

  • Kim, Sang Il (Dept. of Mechanical Engineering, Kangwon Nat'l Univ.)
  • 투고 : 2014.06.30
  • 심사 : 2014.08.07
  • 발행 : 2014.10.01
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초록

본 연구는 상류 쪽에 설치된 물체의 직경 변화에 따른 후류에 존재하는 하류 쪽 물체의 영향에 대해 조사한 실험적 연구이다. 풍동의 측정부에서 상류 쪽에는 알파벳 V자 형태의 물체를 삽입하고, 하류 쪽에는 로드셀을 장착한 원기둥을 설치하여 상류 쪽 물체의 직경 변화에 따라 후류의 유속분포가 어떻게 변화하는지를 조사하였다. 그리고 후류에 존재하는 원기둥의 위치를 변화시키면서 원기둥의 변동양력과 카르만 와류 방출 주파수를 조사하므로서 다음과 같은 결론을 얻었다. i) 후류의 유속은 주유속보다 작다. ii) 상류 쪽 물체의 직경이 하류 쪽 물체의 직경보다 클 때 록크-인 현상이 일어난다. iii) 후류에 있는 원기둥의 변동양력이 최대가 되는 위치는 상류 쪽 물체의 직경의 변화에 따라 위치도 함께 변해야 한다.

This experimental study investigates the effects of a downstream cylinder in the wake change on upstream object's diameter. A V-shaped object is placed in the upstream of the test section and a circular cylinder containing a load-cell is placed in the downstream. The velocity distribution of the wake generated from the upstream object with a change in its diameter is investigated. Further, the fluctuation in the lift coefficient and Karman-vortex emission frequency with a change in the position of the downstream cylinder is examined. The study results reveal the following. i) The flow velocity in the wake is smaller than that in the main stream. ii) The lock-in phenomenon occurs when the diameter of the upstream object is larger than that of the downstream cylinder. iii) To generate maximum fluctuating lift force of the downstream cylinder in the wake, the position of the downstream cylinder must be moved with changing diameter of the upstream object together.

키워드

참고문헌

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