Formation of sand ripples under a turbulent liquid flow

TL;DR

This paper presents a linear stability analysis of granular beds under turbulent liquid flow, incorporating key parameters like bed compactness and shear stress, and validates findings with experimental data.

Contribution

It introduces a comprehensive linear stability model that considers previously overlooked parameters such as bed compactness and shear stress thresholds.

Findings

Model predictions align well with experimental results.

Parameters like bed compactness significantly influence ripple formation.

The analysis enhances understanding of sediment transport dynamics.

Abstract

Sand ripples are commonly observed in both nature and industry. For example, they are found on riverbeds and in oil pipelines that transport sand. In both natural and industrial cases, ripples increase friction between the bed and fluid and are related to flooding, high pressure drops, and transients. Ripples appear when sediments are entrained as bed load (a mobile granular layer) and are usually considered to be the result of initial bedforms that eventually saturate. Given the small aspect ratio of the initial bedforms, linear analyses can be used to understand the formation of ripples. This paper presents a linear stability analysis of a granular bed under a turbulent flow of a liquid. This analysis takes into consideration all the main mechanisms and parameters involved in the turbulent liquid case, including some important parameters that have not yet been considered together such as the bed compactness and the bed-load threshold shear stress. The results of this analysis are compared with published experimental results and they show good agreement.