Fluctuations of turbulent bed shear stress

• Main Authors: Cheng, Nian-Sheng, Law, Adrian Wing-Keung
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Civil engineering::Water resources; DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: https://hdl.handle.net/10356/92263; http://hdl.handle.net/10220/7642
• Institution: Nanyang Technological University

With the assumption that the bed shear stress fluctuates in a lognormal fashion, the probability density function PDF of the standardized bed shear stress is derived as a function of the relative shear stress intensity. The PDF is more skewed with larger relative intensities, but approaches a Gaussian function when the relative intensity is small. The computed PDF agrees well with the reported experimental data for flows over a smooth boundary. The higher-order moments of the bed shear stress, skewness, and kurtosis, are shown analytically to be also dependent on the relative intensity. The theoretical dependencies are then compared to a number of measurements available in the literature. The Reynolds number effect on the relative intensity is also discussed.