Particle transport induced by internal wave beam streaming in lateral boundary layers

TL;DR

This study reveals a novel boundary-layer streaming mechanism induced by internal waves near vertical walls, significantly affecting particle transport in the abyssal sea, supported by laboratory experiments and theoretical analysis.

Contribution

It identifies and characterizes a previously unrecognized lateral boundary-layer streaming mechanism caused by internal waves, extending existing theoretical models.

Findings

Particles experience significant horizontal advection near walls.

The streaming mechanism is most effective for inclined wave beams.

Experimental results agree well with theoretical predictions.

Abstract

Quantifying the physical mechanisms responsible for the transport of sediments, nutrients and pollutants in the abyssal sea is a long-standing problem, with internal waves regularly invoked as the relevant mechanism for particle advection near the sea bottom. This study focuses on internal-wave induced particle transport in the vicinity of (almost) vertical walls. We report a series of laboratory experiments revealing that particles sinking slowly through a monochromatic internal wave beam experience significant horizontal advection. Extending the theoretical analysis by Beckebanze et al (2018a), we attribute the observed particle advection to a peculiar and previously unrecognized streaming mechanism originating at the lateral walls. This vertical boundary-layer streaming mechanism is most efficient for strongly inclined wave beams, when vertical and horizontal velocity components are of comparable magnitude. We find good agreement between our theoretical prediction and experimental results.