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

The Korean Society of Mechanical Engineers (대한기계학회)
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Effects of Priodic Blowing Through a Spnnwise Slot on a Turbulent Boundary Layer (I) - Comparison with Steady Blowing -

슬릿을 통한 주기적 국소 가진이 난류경계층에 미치는 영향 (I) - 정상 가진과의 비교 -

  • 김경연 (한국과학기술원 기계공학과) ;
  • 성형진 (한국과학기술원 기계공학과)
  • Published : 2004.01.01
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Abstract

Direct numerical simulations were performed to analyze the effects of time-periodical blowing through a spanwise slot on a turbulent boundary layer. The blowing velocity was varied in a cyclic manner from 0 to 2A$^{+}$(A$^{+}$ =0.25, 0.50 and 1.00) at a fixed blowing frequency of f$^{+}$=0.017. The effect of steady blowing (SB) was also examined, and the SB results were compared with those for periodic blowing (PB). PB reduced the skin friction near the slot, although to a slightly lesser extent than SB. PB was found to generate a spanwise vortical structure in the downstream of the slot. This vortex generates a reverse flow near the wall, thereby reducing the wall shear stress. The wall-normal and spanwise turbulence intensities under PB are increased as compared to those under SB, whereas the streamwise turbulent intensity under PB is weaker than that under SB. PB enhances more energy redistribution than SB. The periodic response of the streamwise turbulence intensity to PB is propagated to a lesser extent than that of the other components of the turbulence intensities and the Reynolds shear stress.

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