Author(s): Shuolin Li; Gabriel Katul
Linked Author(s):
Keywords: Sediment carrying capacity; Turbulence physics; Zhang Ruijin equation; Universal curve; Suspended sediment transport
Abstract: Zhang Ruijin's equation for the sediment carrying capacity in suspended sediment transport across China has a storied legacy spanning almost a century. Despite its broad applicability, the equation largely remains empirical, built upon a series of ad hoc assumptions derived from gravitational theory. In this presentation, I will cover a mathematical derivation of the sediment carrying capacity factor consistent with turbulence physics, demonstrating that Zhang's formula is a specific case of this factor under limited conditions when Strickler scaling is applicable in turbulent sediment flows. Our study leverages a comprehensive array of both field and laboratory experiments across an expansive range of relative length scales—seven orders of magnitude of lo/H, where H is the stream water depth and lo signifies a scale derived from the energy needed to maintain sediment suspension. This analysis has led to the identification of a universal curve that delineates the sediment carrying factor. This curve is clarified by analyzing the distribution of energy in turbulent vertical velocities and achieving a balance between the production and dissipation of turbulent kinetic energy, alongside managing the turbulent stress budgets. The insights gained from the findings offer a novel and practical representation of the sediment carrying factor, substantially improving our capacity to assess and predict channel vulnerability to scouring and deposition. This knowledge is desirable for the design of more resilient hydraulic structures and for the enhanced management of sediment in river systems.
Year: 2024