Investigation of bed shear stresses subject to external turbulence

• Published in: The International journal of heat and fluid flow Vol. 24; no. 6; pp. 816 - 824
• Main Authors: Cheng, Nian-Sheng, Sumer, B.Mutlu, Fredsøe, Jørgen
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.12.2003; Elsevier Science
• Subjects: Applied fluid mechanics; Bed shear stress; Exact sciences and technology; Fluctuation; Fluid dynamics; Fundamental areas of phenomenology (including applications); Hydrodynamics, hydraulics, hydrostatics; Kurtosis; Lognormal distribution; Physics; Probability density function; Skewness; Turbulence; Turbulence; Fluctuation; Skewness; Probability density function; Kurtosis; Bed shear stress; Lognormal distribution; Statistical analysis; Smooth wall; Hydraulics; Open channel flow; Shear stress; Experimental study; Turbulence structure
• ISSN: 0142-727X; 1879-2278; 1879-2278
• DOI: 10.1016/S0142-727X(03)00088-2

The fluctuating bed shear stress has largely been investigated only for uniform channel flows and boundary layers. In practical engineering, the flow conditions are often modified due to the presence of various hydraulic structures. To what extent the modification affects the known characteristics of the bed shear stress is not clear. This study presents experimental results of the bed shear stress fluctuations, which are obviously subjected to external turbulence generated by superimposing artificial structures in the open channel flows. The statistical analysis of the measurements shows that the probability density function of the bed shear stress can be described by the lognormal function. Some associated relations concerning higher-order moments, skewness and kurtosis, which are derived from the lognormal function, are further compared with the experimental data. Physical implication of the skewed probability density distribution is finally discussed.