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

The Korean Society of Mechanical Engineers (대한기계학회)
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Effect of Two-Frequency Forcing on Flow Behind a Backward-Facing Step

이중주파수 가진이 후향계단 유동에 미치는 영향

  • Yu, Jeong-Yeol (Dept.of Mechanical Aerospace Engineering, Seoul National University) ;
  • Jin, Song-Wan (Dept.of Mechanical Aerospace Engineering, Graduate School of Seoul National University) ;
  • Kim, Seong-Uk (Dept.of Mechanical Aerospace Engineering, Graduate School of Seoul National University) ;
  • Choe, Hae-Cheon (Dept.of Mechanical Aerospace Engineering, Seoul National University) ;
  • Kim, Sa-Ryang
  • 유정열 (서울대학교 기계항공공학부) ;
  • 진송완 (서울대학교 대학원 기계항공공학부) ;
  • 김성욱 (서울대학교 대학원 기계항공공학부) ;
  • 최해천 (서울대학교 기계항공공학부) ;
  • 김사량
  • Published : 2002.03.01
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Abstract

An experimental study is conducted to investigate the effect of two-frequency forcing on turbulent flow behind a backward-facing step at the Reynolds number of 27000 based on the step height. The forcing is provided from a thin slit located at the edge of the backward-facing step to increase mixing behind the backward-facing step and consequently to reduce the reattachment length. With single frequency forcing, the minimum reattachment length is obtained at the non-dimensional forcing frequency (F) of St$\_$h/ = 0.29. With two-frequency forcing, a subharmonic frequency (F/2) or biharmonic frequency (2F) is combined with the fundamental frequency (F), i.e. (F, F/2) or (F, 2F) forcing is applied. In the case of (F, F/2) forcing, the reattachment length is not much sensitive to the phase difference between F and F/2. However, the reattachment length significantly depends on the phase difference between F and 2F in the case of (F, 2F) forcing. At a certain range of the phase difference, the reattachment length becomes smaller than that of the single frequency forcing.

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References

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