Statistical properties of spherical shock waves propagating through grid turbulence, turbulent cylinder wake, and laminar flow

K. Inokuma, T. Watanabe, K. Nagata, Y. Sakai
Statistical properties of spherical shock waves propagating through grid turbulence, turbulent cylinder wake, and laminar flow
Physica Scripta 94(4) 044004 2019

This article may be found at https://doi.org/10.1088/1402-4896/aafde2.

Abstract

Wind tunnel experiments are reported for a spherical shock wave propagating through turbulent wakes of a single cylinder, double cylinders, grid-turbulence, and a laminar flow, whose influences on the shock wave are compared. Overpressure behind the shock wave is measured on a plate while streamwise velocity is measured at the flow point between the measurement plate and the location of the shock wave ejection. Average of peak-overpressure observed upon arrival of the shock wave is decreased by the mean velocity defect of the cylinder wake. Root mean squared (rms) peak-overpressure fluctuation divided by the averaged peak-overpressure is increased by turbulence, and it becomes larger with the rms velocity fluctuation. Correlation coefficients are calculated between fluctuations of peak-overpressure and low-pass filtered fluid velocity. The strong positive correlation is found for the fluid at the location where the shock ray toward the pressure measurement point passes. The length scale of velocity fluctuation with the strong correlation is related to the integral length scale of turbulence. In the double-cylinder wake experiments, the shock wave that has passed one cylinder wake interacts again with another cylinder wake before it reaches the measurement plate. The correlation coefficient for the velocity fluctuation of the first wake is weakened by the second wake, and this influence becomes more important when the rms velocity fluctuation of the second wake is larger.

日本語訳 (DeepL翻訳)

格子乱流、円柱後流、層流中を伝播する球形衝撃波の統計的性質

球形衝撃波が単円柱あるいは二重円柱の乱流後流，格子乱流，層流中を伝播し，衝撃波に与える影響を比較した風洞実験について報告する．衝撃波の後流の圧力はプレート上で測定し，流速は測定プレートと衝撃波の放出位置の間の流路で測定する．衝撃波到達時に観測されるピーク圧力の平均値は、円柱後流の平均速度欠損で減少する。平均ピーク圧力で割った実効値ピーク圧力変動は，乱流によって増加し，実効値速度変動とともに大きくなる．ピーク圧力の変動とローパスフィルターをかけた流速の相関係数を計算したところ、ピーク圧力の変動とローパスフィルターをかけた流速の変動は強い正の相関があることがわかった。圧力測定点に向かう衝撃波が通過する位置の流体では、強い正の相関が見られた。強い相関を持つ速度変動の長さスケールは、乱流の積分長さスケールと関係がある。二重円柱後流の実験では、一つの円柱後流を通過した衝撃波は、測定板に到達するまでにもう一つの円柱後流と再び相互作用する。このとき、第一後流の速度変動に対する相関係数は第二後流によって弱められ、この影響は第二後流の実効速度変動が大きいほど重要になる。

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