Bed particle saltation in turbulent wall-shear flow: a review

Abstract

Bed particle saltation in turbulent wall-shear flow remains an intriguing phenomenon in applied hydro-dynamics. In this review, we report the current state of the art of bed particle saltation in turbulent wall-shear flow, highlighting the physical characteristics of bed particle saltation and its mathematical modelling. A critical appraisal of the mechanics of bed particle saltation is presented thorough ample experimental evidence. The salient features of bed particle saltation, encompassing the saltation height, saltation length, particle velocity, saltation duration, particle collision with the bed, particle rotation, particle resting time and particle re-entrainment, are thoroughly discussed. Both the deterministic and computational fluid dynamics approaches in modelling bed particle saltation are summarized, and the subtle role of the hydrodynamic forces is elaborated. The estimation of bedload flux in a fluvial environment, emanating from the mathematical modelling of bed particle saltation, is delineated using different modelling approaches. Finally, the challenges in modelling bed particle saltation are highlighted, and a new look at bed particle saltation is furnished.

Mechanics of bed particle saltation in turbulent wall-shear flow

“…It addresses the temporal delay in the boundary layer development adjoining the surface of the particle. The F B is expressed as follows [1]:…”

“…In a recent review article, Ali & Dey [1] provided a state-of-the-science of bed particle saltation in turbulent wall shear flow, scrutinizing the salient features of bed particle saltation in the light of experimental, theoretical and numerical frameworks (for details, see the references therein). In essence, the computational fluid dynamics schemes have provided an enhanced understanding of the mutual interplay between the near-bed coherent structures and the bed particle motion [2][3][4][5].…”

“…Ali & Dey [1] specifically emphasized that although impressive advances have been made on the topic principally on experimental and numerical grounds, an exclusive theoretical analysis in exploring the mechanics of bed particle saltation requires further attention. To this end, researchers need to seek a generalized force system that would be able to accomplish the key mechanism of the fluid-particle interaction.…”

“…To this end, researchers need to seek a generalized force system that would be able to accomplish the key mechanism of the fluid-particle interaction. Although Ali & Dey [1] put forward explicitly the current challenges in modelling of bed particle saltation from a broader perspective, here we put into focus the major limitations of the existing mathematical models. These are succinctly furnished below.…”

“…Estimation of the characteristic features of bed particle saltation, such as the particle trajectory, saltation height, saltation length and particle velocity has been the primary goal of analytical studies [1]. To fulfil this target, the bottom line is to solve the Lagrangian equations of motion of a particle performing a saltation [20][21][22].…”