대한기계학회논문집 (Transactions of the Korean Society of Mechanical Engineers)
- 제19권9호
- /
- Pages.2328-2341
- /
- 1995
- /
- 1225-5963(pISSN)
DOI QR Code
축대칭 하향단흐름에서 자유흐름 난류강도의 영향
Effects of the free Stream Turbulence Intensity on the Flow Over an Axisymmetric Backward-Facing Step
초록
An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purposes of the present study are to investigate the effect of the free stream turbulence intensity on the reattachment length and to understand the turbulence structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separated and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. As the free stream turbulence intensity increased, the reattachment length became shorter due to the enhanced mixing in the separated shear layer. It was also observed that the reverse flow velocity and turbulent kinetic energy increase with increasing free stream turbulence intensity. Spectral data and flow visualization showed that low-frequency motions occur in the separated flow behind a backward-facing step. These motions have a significant effect on the time-averaged turbulence data.
키워드