Basal pressure variations induced by a turbulent flow over a wavy surface

TL;DR

This paper investigates how turbulent flows over wavy surfaces cause pressure variations that influence sediment transport, highlighting the importance of pressure dynamics alongside shear stress in bedform formation.

Contribution

It introduces a reanalysis of existing data to examine pressure variations induced by turbulence, revealing phase lag and components not previously emphasized in sediment transport models.

Findings

Pressure variations lag behind topography.

Pressure exhibits in-phase and out-of-phase components.

Pressure effects are significant alongside shear stress.

Abstract

Turbulent flows over wavy surfaces give rise to the formation of ripples, dunes and other natural bedforms. To predict how much sediment these flows transport, research has focused mainly on basal shear stress, which peaks upstream of the highest topography, and has largely ignored the corresponding pressure variations. In this article, we reanalyze old literature data, as well as more recent wind tunnel results, to shed a new light on pressure induced by a turbulent flow on a sinusoidal surface. While the Bernoulli effect increases the velocity above crests and reduces it in troughs, pressure exhibits variations that lag behind the topography. We extract the in-phase and in-quadrature components from streamwise pressure profiles and compare them to hydrodynamic predictions calibrated on shear stress data.