DOI: 10.1016/j.earscirev.2019.03.021
论文题名: The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes
作者: Bohorquez P. ; Cañada-Pereira P. ; Jimenez-Ruiz P.J. ; del Moral-Erencia J.D.
刊名: Earth Science Reviews
ISSN: 00128252
出版年: 2019
卷: 193 起始页码: 91
结束页码: 108
语种: 英语
中文关键词: Dune and antidune
; Linear stability theory
; Missoula and Altai Quaternary flood
; Sediment transport
英文关键词: drainage
; dune
; flow velocity
; glacial lake
; morphodynamics
; paleoflood
; Pleistocene
; sediment transport
; shallow-water equation
; Altay [Russian Federation]
; Missoula
; Montana
; Russian Federation
; United States
英文摘要: Exceptional megaflood-scale bedforms on Earth are commonly associated with the catastrophic draining of glacial lakes in the late Pleistocene. The widest studied events have been the Missoula and Altai floods with 300–700 m flow depth, 1–20 m bedform height and 10–300 m wavelength. Nowadays, the Saint-Venant equations have succeeded at simulating the catastrophic glacial-lake drainage process numerically, but we still lack a depth-averaged morphodynamic theory able to predict the growth of dunes and antidunes. The disparity of spatial scales in megafloods prevents the use of non-depth-averaged rotational flow equations, motivating the present shallow-water theory for the formation of megaflood-scale bedforms. We adopt a non-equilibrium sediment transport equation rooted in Einstein's pioneering work. Here we prove that the bed instability triggers to form dunes and antidunes simply by lagging the entrainment term for sediment mass conservation, or the bottom shear stress, with respect to the depth-averaged flow velocity. We formalise this result using a linear stability theory that captures the existence regions of dune and antidune in addition to the roll wave instability. Furthermore, in the spirit of Kennedy (Annu. Rev. Fluid Mech., vol. 1, 1969, pp. 147–168), we derive a closed-form solution of growth rate and wave speed of the bedform. The nondimensional groups controlling the linear instabilities are the Froude number, ℱr, the Shields parameter, Sh, and the grain roughness relative to flow depth, d. Subsequently, we simulate the drainage of the largest Missoula flood numerically to explain the formation of giant antidunes in the Camas Prairie (Montana, US) during the late stage of the megaflood. Also considered are large fields of gravel dunes in the Kuray-Chuja Lake Basin (Altai Mountains, Siberia). The simulated hydraulic conditions over bedforms in both basins yield values of the nondimensional parameters that lie in the theoretical region of dunes and antidunes according to the proposed theory and in situ measurements in sandy rivers and flume experiments. © 2019 Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165770
Appears in Collections: 气候变化与战略
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作者单位: Centro de Estudios Avanzados en Ciencias de la Tierra (CEACTierra), Universidad de Jaén, Campus de las Lagunillas, Jaén, 23071, Spain; Área de Mecánica de Fluidos, Departamento de Ingeniería Mecánica y Minera, Universidad de Jaén, Campus de las Lagunillas, Jaén, 23071, Spain
Recommended Citation:
Bohorquez P.,Cañada-Pereira P.,Jimenez-Ruiz P.J.,et al. The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes[J]. Earth Science Reviews,2019-01-01,193