回転する単独平板翼近傍後流中の周期的速度変動成分による広帯域騒音の音圧レベル予測

概要

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Typical periodic velocity fluctuation in a near-wake flow of a flat-plate blade is caused by the Karman vortex shedding from its trailing edge. The Karman vortex shows a cellular structure in the spanwise direction in a rotating flow field. The Karman vortex street produces discrete frequency noise. A theory to estimate the sound pressure level (SPL) due to Karman vortex shedding is proposed. The spectral distribution of SPL is predicted by superposing SPLs due to each vortex shedding with different frequency in the near-wake flow along the blade span. SPL strongly depends on the intensity of velocity fluctuation and the spanwise scale of a vortex cell, which is experimentally determined by measuring the cross correlation along the blade span of the near-wake flow. The calculated spectral distribution agrees well with the experimental data.
1995-01-25