乱流自由混合層の影響を受ける円柱の特性 : 表面圧力変動および変動流体力

概要

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Fluctuating pressure on the surface of a circular cylinder in and near a plane turbulent mixing layer was measured as having a Reynolds number of 4.6×10^4, based on the cylinder diameter d and the main-flow velocity ; the diameter being approximately 2 thicknesses δ of the mixing layer. the r.m.s. value and the autocorrelation of fluctuating lift and drag were computed from the r.m.s. value and the circumferential cross-correlation of the surface-pressure fluctuation. The r.m.s. value and the circumferential cross-correlation of the surface-pressure fluctuation. The r.m.s. lift was found to attain a large maximum when the center of the cylinder was located near the high-speed edge of the mixing layer ; the maximum value was much greater than the r.m.s. lift obtained in the main flow. The present data, together with authors' previous results, enables the representation of the maximum r.m.s. lift as a function of the ratio d/δ. It appears that the maximum lift is associated with a bodily lateral oscillation of the mixing layer upstream of the cylinder. The oscillation enhances both the strength of the vortices shed from the cylinder, and the periodicity of the vortex shedding. The disturbance of the enhanced vortex shedding propagates upstream and in turn forces the oscillation of the mixing layer. This is a feed-back mechanism.
一般社団法人日本機械学会の論文
1986-03-25