An Investigation into the Applicability of Friction Velocity Estimation Methods for the Channel with A Deposit Body

TL;DR

This paper evaluates the effectiveness of classical and turbulence-based models for estimating friction velocity in river sections with deposit bodies, highlighting the influence of flow non-uniformity and turbulence on friction characteristics.

Contribution

It assesses the applicability of classical uniform flow friction models and introduces turbulence-based models for deposit body sections, providing new insights into friction estimation in non-uniform flows.

Findings

Turbulence-based models effectively capture flow field impacts on friction.

Friction velocity is mainly influenced by turbulence intensity.

Deposit body resistance increases with larger deposit proportions.

Abstract

This study investigates how the deposit body influences friction characteristics by altering local flow fields, which is closely related to bed shear stress. Using generalized flume experiments, the study assesses the applicability of classical uniform flow friction models in deposit body river sections, revealing frictional changes induced by flow field non-uniformity. Initially, based on \( \frac{u_*}{\sqrt{\overline{w'^2}}} = 0.85 \sim 1.15 \) under uniform flow conditions as the judgment basis, the reliability of the classical model is verified. Four models are then applied to estimate near-bed friction velocity in deposit body sections. Results show a significant alignment between the longitudinal velocity gradient and the peak friction velocity derived from the turbulent kinetic energy method (TKE). Dimensional analysis of friction indicators reveals that: (a) friction velocity is primarily influenced by turbulence intensity, with constricted and narrowed sections resembling uniform flow, while the expansion section forms a peak; (b) models incorporating flow field fluctuations (TKE, Vertical Turbulence Kinetic Energy (TKE w'), Reynolds shear stress method (RSS)) effectively capture the impact of non-uniform flow fields on friction characteristics; (c) when energy states are low or when deposit body proportions are large, the deposit body's resistance ratio increases, and peak friction velocity rises. This study provides theoretical insights into friction estimation and sediment transport in non-uniform flow fields of deposit bodies.