Abstract

Characteristics of turbulent flows in rivers can be significantly modified due to the presence of sediment particles and secondary currents/non-uniformity. This paper investigates why the measured vertical distributions of velocity deviate from the log-law. In contrast to previous research which attributed the deviation to Richardson number only, this study demonstrates that, like Reynolds shear stress (- ), momentum flux (uv) caused by the non-zero wall-normal velocity v is also responsible for these deviations. Starting from Reynolds equations, this paper exhibits that the classical log-law can be obtained only when v = 0, otherwise the velocity v results in the deviation. Based on experimental data available in the literature, this study shows that in an open channel v is non-zero due to the coexistence of secondary currents and sediment, subsequently the Reynolds shear stress and streamwise velocity are affected. Equations for these interactions are obtained and solved numerically. The validity of the proposed model has been verified using experimental data, and good agreement between the predicted and observed profiles has been achieved.

Keywords: sediment-laden flow, Karman constant, log-law, Rouse law, velocity profile