The Physics of Sediment Transport Initiation, Cessation, and Entrainment Across Aeolian and Fluvial Environments

IF 25.2 1区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS Reviews of Geophysics Pub Date : 2020-01-05 DOI:10.1029/2019RG000679
Thomas P?htz, Abram H. Clark, Manousos Valyrakis, Orencio Durán
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引用次数: 95

Abstract

Predicting the morphodynamics of sedimentary landscapes due to fluvial and aeolian flows requires answering the following questions: Is the flow strong enough to initiate sediment transport, is the flow strong enough to sustain sediment transport once initiated, and how much sediment is transported by the flow in the saturated state (i.e., what is the transport capacity)? In the geomorphological and related literature, the widespread consensus has been that the initiation, cessation, and capacity of fluvial transport, and the initiation of aeolian transport, are controlled by fluid entrainment of bed sediment caused by flow forces overcoming local resisting forces, whereas aeolian transport cessation and capacity are controlled by impact entrainment caused by the impacts of transported particles with the bed. Here the physics of sediment transport initiation, cessation, and capacity is reviewed with emphasis on recent consensus-challenging developments in sediment transport experiments, two-phase flow modeling, and the incorporation of granular physics' concepts. Highlighted are the similarities between dense granular flows and sediment transport, such as a superslow granular motion known as creeping (which occurs for arbitrarily weak driving flows) and system-spanning force networks that resist bed sediment entrainment; the roles of the magnitude and duration of turbulent fluctuation events in fluid entrainment; the traditionally overlooked role of particle-bed impacts in triggering entrainment events in fluvial transport; and the common physical underpinning of transport thresholds across aeolian and fluvial environments. This sheds a new light on the well-known Shields diagram, where measurements of fluid entrainment thresholds could actually correspond to entrainment-independent cessation thresholds.

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风沙和河流环境中泥沙搬运的开始、停止和夹带的物理学
预测由河流和风成流引起的沉积景观的形态动力学需要回答以下问题:水流是否足够强大以启动泥沙运输,水流是否足够强大以维持泥沙运输,以及在饱和状态下水流运输了多少泥沙(即,运输能力是什么)?在地貌学和相关文献中,广泛的共识是,河流输运的开始、停止和容量以及风成输运的开始是由水流力克服局部阻力引起的河床泥沙的流体夹带控制的,而风成输运的停止和容量是由被输送颗粒与河床碰撞引起的冲击夹带控制的。本文回顾了泥沙输运开始、停止和能力的物理学,重点介绍了泥沙输运实验、两相流建模和颗粒物理概念的结合等方面的最新进展。重点强调了密集颗粒流和沉积物输运之间的相似之处,例如被称为爬行的超慢颗粒运动(发生在任意弱驱动流中)和抵抗床沉积物夹带的系统跨越力网络;湍流波动事件的大小和持续时间在流体夹带中的作用;传统上被忽视的颗粒床冲击在触发河流搬运夹带事件中的作用;以及风成和河流环境中运输阈值的共同物理基础。这为众所周知的希尔兹图提供了新的线索,在希尔兹图中,流体夹带阈值的测量实际上可以对应于夹带无关的停止阈值。
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来源期刊
Reviews of Geophysics
Reviews of Geophysics 地学-地球化学与地球物理
CiteScore
50.30
自引率
0.80%
发文量
28
审稿时长
12 months
期刊介绍: Geophysics Reviews (ROG) offers comprehensive overviews and syntheses of current research across various domains of the Earth and space sciences. Our goal is to present accessible and engaging reviews that cater to the diverse AGU community. While authorship is typically by invitation, we warmly encourage readers and potential authors to share their suggestions with our editors.
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