Observation of the whole process of interaction between barchans by flume experiments

Abstract

[1] Through laboratory experiments generating unidirectional water flows, we examine the process of interaction between two moving barchans (sandy bed configurations in a crescentic plan-shape), which may take dozens of years for barchan dunes in the nature. Three types of the interaction were observed. The first type was absorption of two barchans into one. The second was that the upstream fast barchan rode on the downstream slow barchan and simultaneously a newly born barchan was ejected from the lee side of the slow barchan. The third was that the downstream slow barchan was split into two before the upstream fast barchan touched the downstream. The type of the interaction was determined by both relative and absolute size of two barchans.

Migration and Morphology of Asymmetric Barchans in the Central Hexi Corridor of Northwest China

“…During the period of 2002-2004, the available sand material decreased, and the overlying smaller dune moved to the dune crest and then to the leeward slope, which caused the number of smaller dunes on the windward slope to decrease down to 0 on dune d and to 3 on dune e (Figure 10). Such limb collision dynamics had been predicted in numerical studies [33,61] and were observed in a previous field study [1]. In these previous studies, it was shown that the collision involving mainly the dune limb led to an asymmetric barchan dune shape with an elongated limb, such as we observed in the present case study on the barchan dunes of the Hexi Corridor.…”

Remote sensing and spatial analysis of aeolian sand dunes: A review and outlook

“…The importance of dune form evolution has emerged as a top research priority in light of recent progress in numerical modeling and flume experiments (e.g., Schwämmle and Herrmann, 2003;Endo et al, 2004;Hersen et al, 2004;Durán et al, 2005;Hersen, 2005;Hersen and Douady, 2005;Durán et al, 2011;Katsuki et al, 2011). These approaches afford insight into dune dynamics and interactions and can be used to supplement the paucity of field observations.…”

River bedform inception by flow unsteadiness: A modal and nonmodal analysis

“…We must realize that the choice of an appropriate disturbance measure does not only stem from physical arguments but also must satisfy mathematical constraints. In order to arrive at a positive definite energy weight, while capturing a maximum of physical effects, we choose to neglect the last term of (12). As the primary goal of this work is to analyze the morphological instabilities, our focus is on the behavior of the bed response.…”

“…However, it is worth recalling that transverse dunes can decay into a chain of barchans (crescent-shaped dunes) and display a "sea-wave-like" shape with meandering. The formation of barchan dunes is very common and widely studied in an aeolian environment, as demonstrated by a vast body of literature [9][10][11], but has also been detected in subaqueous conditions both in laboratory experiments [12] and in real rivers [13].…”