正方形断面管路内乱流におけるバースト現象 : VITA法および4象限法によるイベントの検出

概要

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Near-wall bursting has been detected in a fully developed turbulent square-duct flow both by the VITA technique and by quadrant analysis. Discrepancy between these detection schemes is shown, and its possible cause is discussed. Dependence of bursting frequencies and contribution rates to the Reynolds shear stress on threshold parameters is also investigated at the wall bisector, z/H=0.5, and the vicinity of the duct corner, z/H=0.2. In the case of quadrant analysis the bursting frequency at z/H=0.2 is found to be higher than at z/H=0.5 for large threshold values, while in the case of the VITA technique they are nearly identical. It is shown that the contribution rate of ejection at z/H=0.2 is higher than at z/H=0.5, but that of sweep at z/H=0.2 is lower than at z/H=0.5. In addition, a plot of the measured Reynolds shear stress is presented on the wall bisector, and its difference between a square duct and two-dimensional channel is demonstrated.
1995-12-25