Incipient bedforms in a bidirectional wind regime

@article{Gadal2019IncipientBI,
  title={Incipient bedforms in a bidirectional wind regime},
  author={Cyril Gadal and Cl{\'e}ment Narteau and Sylvain Courrech du Pont and Olivier Rozier and Philippe Claudin},
  journal={Journal of Fluid Mechanics},
  year={2019},
  volume={862},
  pages={490 - 516}
}
Most terrestrial sand seas form at ‘horse’ latitudes, where the wind direction exhibits seasonal variation. Here, we extend the two-dimensional linear stability analysis of a flat sand bed associated with a unidirectional wind to the three-dimensional case in order to account for multidirectional wind regimes. Focusing on the simplest case of bidirectional flow regimes, we show that the transition from transverse to oblique or longitudinal patterns is controlled by the transport ratio and the… 

Dune Initiation in a Bimodal Wind Regime

Early‐stage bedforms develop into mature dunes through complex interactions between wind, sand transport, and surface topography. Depending on varying environmental and wind conditions, the

Stabilization of a straight longitudinal dune under bimodal wind with large directional variation.

TLDR
The dynamical stability of isolated dunes using the crest line model is investigated, where the dune dynamics is represented by its crest line motion and it is found that the straight longitudinal dune is stabilized under the large variation of bimodal wind direction.

Local Wind Regime Induced by Giant Linear Dunes: Comparison of ERA5-Land Reanalysis with Surface Measurements

Emergence and growth of sand dunes results from the dynamic interaction between topography, wind flow and sediment transport. While feedbacks between these variables are well studied at the scale of

Bidirectional bedform fields at the head of a submarine canyon (NE Atlantic)

The Effects of Wind Regime and Sand Supply on the Coexistence of Barchans and Linear Dunes in China’s Qaidam Basin

Dunes composed of granular materials are present in deserts and other environments, such as subaqueous environments and environments on other planets, with very different time and length scales for

Coexistence of Two Dune Growth Mechanisms in a Landscape‐Scale Experiment

In landscape‐scale experiments at the edge of the Gobi desert, we show that various dune types develop simultaneously under natural wind conditions. Using 4 years of high‐resolution topographic data,

Direct validation of dune instability theory

TLDR
A landscape-scale experiment with controlled initial and boundary conditions to reveal incipient dune growth under natural action of wind underpins existing theoretical models for the early development of eolian dunes, which can now be used to provide reliable insights into atmospheric and surface processes on Earth and other planetary bodies.

Coarsening Dynamics of 2D Subaqueous Dunes

Fluid flow over an initially flat granular bed leads to the formation of a surface‐wave instability. The sediment bed profile coarsens and increases in amplitude and wavelength as disturbances

Periodicity in fields of elongating dunes

Dune fields are commonly associated with periodic patterns that are among the most recognizable landscapes on Earth and other planetary bodies. However, in zones of limited sediment supply, where

Elongation and Stability of a Linear Dune

Compared to barchan dunes, the morphodynamics of linear dunes that elongate on a nonerodible bed have barely been investigated by means of laboratory experiments or numerical simulations. Using a

References

SHOWING 1-10 OF 88 REFERENCES

Two modes for dune orientation

Earth’s sand seas (dune fields) experience winds that blow with different strengths and from different directions in line with the seasons. In response, dune fields show a rich variety of shapes,

A two-species model of aeolian sand transport

The transport of sand by wind results from the equilibrium between the erosion of grains dragged by the flow and the resulting slow down of the wind velocity. The dynamical mechanisms governing the

Minimal model for aeolian sand dunes.

We present a minimal model for the formation and migration of aeolian sand dunes in unidirectional winds. It combines a perturbative description of the turbulent wind velocity field above the dune

Dune formation under bimodal winds

TLDR
This work presents the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction, and shows that dunes align longitudinally to the resultant wind trend if the angle θw between the wind directions is larger than 90°.

Bedform Alignment in Directionally Varying Flows

TLDR
The fact that many of the experimental bedforms were neither transverse nor parallel to the resultant transport direction suggests that transport directions cannot be accurately determined by presuming such alignment.

Bedforms in a turbulent stream: formation of ripples by primary linear instability and of dunes by nonlinear pattern coarsening

It is widely accepted that both ripples and dunes form in rivers by primary linear instability; the wavelength of the former scaling on the grain size and that of the latter being controlled by the

Measurements of the aeolian sand transport saturation length

Field Evidence for the Upwind Velocity Shift at the Crest of Low Dunes

Flow that is topographically forced by hills and sand dunes accelerates on the upwind (stoss) slopes and reduces on the downwind (lee) slopes. This secondary wind regime, however, possesses a subtle

Formation and stability of transverse and longitudinal sand dunes

The shape of dunes depends on the history of wind regimes and sand availability. In deserts exposed to winds from two different directions but with comparable magnitude, dunes are found to be linear
...