Three dimensional flow motions in the viscous sublayer

• 作者: S.Santosh Kumar Xinyi Huang Xiang Yang Jiarong Hong
• 来源期刊: 力学快报（英文版）
• 年，卷（期）: 2021,（2）
• 所属期刊栏目: Fluid Mechanics
• 页码范围: 105-109
• 页数: 5页
• 语种: 英文
• DOI: 10.3969/j.issn.2095-0349.2021.02.008

摘要

We employ novel digital Fresnel reflection holography to capture the 3D flows within the viscous sublayer of a smooth-wall turbulent channel flow at Re τ= 400. The measurements reveal unsteady and diverse flow patterns in the sublayer including nearly uniform high and low speed flows and strong small-scale (on the order of viscous wall units) spanwise meandering motions. The probability density functions (PDFs) of wall shear stresses show a clear discrepancy in high stress range with those from direct numerical simu- lation (DNS), which is attributed to the unresolved streamwise and spanwise motions by DNS. Moreover, the PDF of Lagrangian particle accelerations yields a stretched exponential shape like that in homogenous isotropic turbulence, indicating strong intermittency in the sublayer. We find a significant fraction of high accelerations is associated with the small-scale meandering motions. Our study helps explain the effect of sublayer-scale roughness on reducing drag and flow separation reported in the literature.