Streaky Structures in a Turbulent Square-Duct Flow. Identification of Streaky Structures by Combined Flow Visualization-Velocity Measurement Techniques.

Kawahara Genta, Ayukawa Kyozo, Ochi Junji, Watanabe Tetsuya

doi:10.1299/kikaib.59.397

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正方形断面管路内乱流におけるストリーク構造　流れの可視化および流速測定による同定
セイホウケイダンメンカンロナイランリュウニオケルストリークコウゾ

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Abstract

Streaky structures have been studied in a fully developed turbulent square-duct flow by using combined dye flow visualization-LDV velocity measurement techniques. Transverse distributions of low-speed streaks and mean streak spacing are shown in the near-wall region, i.e., yu_τ/v < 25. At z/H < 0.16, the transverse distribution of the low-speed streaks is homogeneous and their spacing is about 90v/u_τ, which suggests that the streaky structures near the wall bisector may be similar to those in turbulent boundary layers. In addition, the transverse distance between the visually identified low-speed streak and the velocity-measurement point was measured for each set of visual data. Conditioning the velocity fluctuations on this transverse distance, conditional probability density distributions of the axial, wall-normal and spanwise velocity fluctuations are shown. These distributions suggest the existence of quasi-streamwise vortical motions associated with the visualized streaky structures, their wall-normal dimension and the intermittency of their appearance.

Journal

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B 59 (558), 397-402, 1993

The Japan Society of Mechanical Engineers

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