Linear stability analysis of transverse dunes

Melo, Hygor P. M.; Parteli, Eric J. R.; Andrade, José S.; Herrmann, Hans J.

doi:10.1016/j.physa.2012.05.042

Cited by 27 publications

(22 citation statements)

References 60 publications

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“…In view of this, it could be useful to apply a similar analysis for other morphological instabilities in which flow unsteadiness plays an important role, such as aeolian dunes [10]. As the barchan shape transition in the aeolian dune environment is very relevant, a nonmodal analysis could be used for improving existing studies on this transversal instability.…”

Section: Discussionmentioning

confidence: 99%

“…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].…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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River bedforms arise as a result of morphological instabilities of the stream-sediment interface. Dunes and antidunes constitute the most typical patterns, and their occurrence and dynamics are relevant for a number of engineering and environmental applications. Although flow variability is a typical feature of all rivers, the bedform-triggering morphological instabilities have generally been studied under the assumption of a constant flow rate. In order to partially address this shortcoming, we here discuss the influence of (periodic) flow unsteadiness on bedform inception. To this end, our recent one-dimensional validated model coupling Dressler's equations with a refined mechanistic sediment transport formulation is adopted, and both the asymptotic and transient dynamics are investigated by modal and nonmodal analyses.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…Based on the results presented here, it would be interesting to perform systematic investigations in order to improve the quantitative assessment of the wind flow over different barchan morphologies, and to quantify the discrepancies between predictions of wind speed-up obtained from the full three-dimensional model and using the equivalent transverse dune. Furthermore, the implications of our results for dune dynamics should be also investigated by coupling the wind model with a sand transport model 10 32 38 39 40 41 42 .…”

Section: Discussionmentioning

confidence: 99%

Two-dimensional airflow modeling underpredicts the wind velocity over dunes

Strobl

Parteli

Pöschel

2015

Sci Rep

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We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected.

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“…Theoretical studies also have been conducted, employing various approaches, such as linear and nonlinear stability analyses (e.g., Melo et al 2012;Andreotti et al 2012); first-principle calculations for fluids and/or grains (e.g., Wippermann and Gross 1986;Schwämmle and Herrmann 2003;Duran et al 2014); simulations with simplified continuous models, such as a defect-crest line dynamics model (Werner and Kocurek 1999), a skeleton model (Niiya et al 2010), and a single-dune-based particle model (Parteli and Herrmann 2003;Diniega et al 2010); and simulations with various cellular automaton (CA) models (e.g., Nishimori and Ouchi 1993;Werner 1995;Momiji et al 2000;Katsuki et al 2005). Even with increased computing speeds, CA models of bedforms remain useful for complicated settings that are time consuming when other methods are used (Barchyn and Hugenholtz 2012;Barrio-Parra and Rodríguez-Santalla 2014;Rozier and Narteau 2014).…”

Section: Introductionmentioning

confidence: 99%

Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

Endo

2016

Prog. in Earth and Planet. Sci.

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A simple stochastic cellular automaton model is proposed for simulating bedload transport, especially for cases with a low transport rate and where available sediments are very sparse on substrates in a subaqueous system. Numerical simulations show that the bed type changes from sheet flow through sand patches to ripples as the amount of sand increases; this is consistent with observations in flume experiments and in the field. Without changes in external conditions, the sand flux calculated for a given amount of sand decreases over time as bedforms develop from a flat bed. This appears to be inconsistent with the general understanding that sand flux remains unchanged under the constant-fluid condition, but it is consistent with the previous experimental data. For areas of low sand abundance, the sand flux versus sand amount (flux-density relation) in the simulation shows a single peak with an abrupt decrease, followed by a long tail; this is very similar to the flux-density relation seen in automobile traffic flow. This pattern (the relation between segments of the curve and the corresponding bed states) suggests that sand sheets, sand patches, and sand ripples correspond respectively to the free-flow phase, congested phase, and jam phase of traffic flows. This implies that sand topographic features on starved beds are determined by the degree of interference between sand particles. Although the present study deals with simple cases only, this can provide a simplified but effective modeling of the more complicated sediment transport processes controlled by interference due to contact between grains, such as the pulsatory migration of grain-size bimodal mixtures with repetition of clustering and scattering.

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Linear stability analysis of transverse dunes

Cited by 27 publications

References 60 publications

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

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

Two-dimensional airflow modeling underpredicts the wind velocity over dunes

Simple stochastic cellular automaton model for starved beds and implications about formation of sand topographic features in terms of sand flux

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