Steady state saltation in air

Ungar, J. E.; Haff, P. K.

doi:10.1111/j.1365-3091.1987.tb00778.x

Cited by 365 publications

(420 citation statements)

References 11 publications

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“…Additionally, grain impacts will cause more severe creep if the impacted particles are too large to be moved by reptation, and larger particles will be able to be moved by creep than on Earth. Assuming that the process that governs the scaling of granule ripple wavelength is indeed reptation/creep (e.g., Anderson, 1987;Ungar and Haff, 1987;Yizhaq, 2004), the maximum Fig. 14.…”

Section: Terrestrial Analogs To Tars: Dunes or Granule Ripples?mentioning

confidence: 99%

Transverse Aeolian Ridges (TARs) on Mars

et al. 2008

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Aeolian processes are probably the dominant ongoing surface process on Mars; Large Dark Dunes (LDDs), particularly common aeolian landforms, were first recognized in the early 1970s. Recent, higher resolution images have revealed another, morphologically distinct, large population of smaller, ripple-like aeolian bedforms that have been termed "Transverse Aeolian Ridges" (TARs) as it is unknown whether they formed as large ripples or small dunes. We have begun a new study of TARs that examines their distribution, orientation, and morphology using N 10,000 high-resolution Mars Orbiter Camera (1.5 to 8 m/pixel resolution) images in a 45°longitude wide, pole-to-pole survey. The aim of this study is to assess whether TARs are active, to identify possible sediment sources and pathways, and to determine the volumes of sediment that they comprise. We present results from the first half of this study, in which we examine the northern hemisphere, and describe a new three-part classification scheme used to aid the survey. Our results show that TARs are abundant but not ubiquitous: preferentially forming proximal to friable, layered terrains such as those found in Terra Meridiani -the location of the ongoing Mars Exploration Rover "Opportunity" mission. TAR distribution in the northern hemisphere shows a strong latitudinal dependence with very few TARs being found north of ∼ 30°N. We also find that in most cases TARs are less mobile than LDDs, a conclusion possibly explained by Mars Exploration Rover Opportunity observations that show TARlike ripples to have a core of fine material armored by a monolayer of granule-sized particles. This could disallow significant bedform movement under the current wind regime. That TARs are essentially inactive is confirmed by superposition relations with slope streaks and LDDs and by observations of superposed impact craters. We suggest that observations made by the Opportunity Rover in Terra Meridiani indicate that the small aeolian bedforms common here are ripples and not small dunes. Farther south, these bedforms transition into larger features indistinguishable from TARs, suggesting that TARs (in the Meridiani area at least) are ripples and not dunes.

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Section: Terrestrial Analogs To Tars: Dunes or Granule Ripples?mentioning

confidence: 99%

Transverse Aeolian Ridges (TARs) on Mars

et al. 2008

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“…Recent experiments [9,10] and numerical simulations [11,12,13,14] have focused on the saltation impacts. It is worth recalling the main results.…”

Section: Collision Processmentioning

confidence: 99%

Dynamics of aeolian sand ripples

Csahók

Misbah

Rioual

et al. 2000

The European Physical Journal E

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We analyze theoretically the dynamics of aeolian sand ripples. In order to put the study in the context we first review existing models. This paper is a continuation of two previous papers [3,4], the first one is based on symmetries and the second on a hydrodynamical model. We show how the hydrodynamical model may be modified to recover the missing terms that are dictated by symmetries. The symmetry and conservation arguments are powerful in that the form of the equation is model-independent. We then present an extensive numerical and analytical analysis of the generic sand ripple equation. We find that at the initial stage the wavelength of the ripple is that corresponding to the linearly most dangerous mode. At later stages the profile undergoes a coarsening process leading to a significant increase of the wavelength. We find that including the next higher order nonlinear term in the equation, leads naturally to a saturation of the local slope. We analyze both analytically and numerically the coarsening stage, in terms of a dynamical exponent for the mean wavelength increase. We discuss some future lines of investigations.

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“…This regime, called saltation, is the primary mode of transport in Aeolian sand transport, and has been investigated theoretically (Bagnold 1941, Bagnold 1966, Owen 1964, Ungar & Haff 1987, Sauermann et al 2001, Andreotti 2004, Jenkins et al 2010, experimentally (Bagnold 1941, Nalpanis et al 1993, Foucaut & Stanislas 1997, Iversen & Rasmussen 1999, Ho et al 2014) and numerically (Anderson & Haff 1988, Kok & Renno 2009). More references can be found in recent reviews on Aeolian transport (Durán et al 2011, Kok et al 2012, Valance et al 2015.…”

Section: Introductionmentioning

confidence: 99%

Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

2015

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We determine approximate, analytical solutions for average, periodic trajectories of particles that are accelerated by the turbulent shearing of a fluid between collisions with a hydrodynamically rough bed. We indicate how the viscosity of the fluid may influence the collisions with the bed. The approximate solutions compare well with periodic solutions for average periodic trajectories over rigid-bumpy and erodible beds that are generated numerically. The analytic solutions permit the determination of the relations between the particle flux and the strength of the shearing flow over a range of particle and fluid properties that vary between those for sand in air and sand in water.

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Steady state saltation in air

Cited by 365 publications

References 11 publications

Transverse Aeolian Ridges (TARs) on Mars

Transverse Aeolian Ridges (TARs) on Mars

Dynamics of aeolian sand ripples

Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

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