A study of inner-outer interactions in turbulent channel flows by interactive POD

• 作者: Hongping Wang Qi Gao
• 来源期刊: 力学快报（英文版）
• 年，卷（期）: 2021,（1）
• 页码范围: 2-13
• 页数: 12页
• 语种: 英文
• DOI: 10.3969/j.issn.2095-0349.2021.01.002

摘要

The amplitude and frequency modulation of near-wall flow structures by the large-scale motions in outer regions is studied in turbulent channel flows. The proper orthogonal decomposition (POD) method is ap- plied to investigate the interactions between the near-wall motions and the large-scale flow modes of the outer regions based on two datasets from direct numerical simulation of turbulent channel flows at Reynolds numbers of 550–1000. The fluctuations in the fields u + , v + , w + and Reynolds shear stress ? (u v ) + are studied to understand the mechanism of amplitude and frequency modulation of the near- wall structures by the outer large-scale motions. The amplitude modulation coefficient of the Reynolds shear stress is larger than that of the velocity components. The frequency modulation effect has an op- posite influence in the spanwise direction compared to the streamwise direction. The streamwise char- acteristic frequency increases with increasing large-scale velocity. However, the spanwise characteristic frequency exhibits a decreasing trend with increasing large-scale velocity in the near-wall region.