A comprehensive picture for binary interactions of subaqueous barchans

TL;DR

This study experimentally explores how subaqueous barchans interact in water, revealing patterns and factors influencing their behavior, which enhances understanding of their size regulation on Earth and other planets.

Contribution

It provides new experimental interaction maps and insights into the dynamics of subaqueous barchan collisions under various conditions.

Findings

Identified five interaction patterns based on experimental parameters.

Proposed interaction maps depending on grain ratio, Shields number, and alignment.

Indicated that ejected barchans can have similar mass to impacting ones.

Abstract

We investigate experimentally the short-range interactions occurring between two subaqueous barchans. The experiments were conducted in a water channel of transparent material where controlled grains were poured inside, and a camera placed on the top acquired images of the bedforms. We varied the grain types (diameter, density and roundness), pile masses, transverse distances, water flow rates and initial conditions. As a result, five different patterns were identified for both aligned and off-centered configurations and we propose interaction maps that depend basically on the ratio between the number of grains of each dune, Shields number and alignment of barchans. In addition, we show experimental indications that an ejected barchan has roughly the same mass of the impacting one in some cases, and that in wake-dominated processes the asymmetry of the downstream dune is large. The present results shed light on the size regulation of barchans found on Earth and other planets.