Scaling Laws in Aeolian Sand Transport

Ho, Tuan Duc; Valance, Alexandre; Dupont, Pascal; Moctar, Ahmed Ould El

doi:10.1103/physrevlett.106.094501

Cited by 142 publications

(264 citation statements)

References 10 publications

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“…As already noticed in the experiments (Ho et al 2011) and in the analysis of Jenkins & Valance (2014) on Aeolian transport over rigid beds, there is a maximum horizontal particle flux Q max that the fluid can sustain at a given Shields parameter: the maximum transport capacity of the flow. Our analysis suggests that this observation holds irrespective of the density ratio.…”

Section: Y Q C Lxmentioning

confidence: 71%

“…The latter can be equivalently replaced by the mass hold-up, as in Jenkins & Valance (2014); or by the horizontal particle flux Q =  0 L, as in the experiments (Ho et al 2011); or by the vertical velocity after the rebound 0 y x + , the take-off velocity, as in the present work. In any case, there is a range of possible particle fluxes that can be steadily sustained at a given strength of the fluid flow.…”

Section: Trajectory Equationsmentioning

confidence: 99%

“…9 are the experimental values obtained by Creyssels et al (2009) andHo et al (2011) for sand in air. The analytical solution for  = 2500 and St = 3000, as in the experiments, is indistinguishable from that for  = 1000 and St = 1000.…”

Section: Approximate Analytical Solution: Periodic Saltation Over An mentioning

confidence: 99%

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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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Section: Y Q C Lxmentioning

confidence: 71%

Section: Trajectory Equationsmentioning

confidence: 99%

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Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

2015

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“…The experiments reported here were performed in a 6.6m long wind tunnel with a cross-section of dimensions 0.27m × 0.27m where the nominal air velocity U ∞ (i.e., the air speed outside from the boundary layer) can be varied between 0 to 20m s (see Ho et al [2011Ho et al [ , 2014 for further details). At the upwind edge of the tunnel, a hopper is installed on the roof of the wind-tunnel and delivers a constant and prescribed upwind sand flux Q 0 (see Fig.…”

Section: Experimental Set-up and Protocolmentioning

confidence: 99%

“…Pähtz and co-workers [Pähtz et al, 2013[Pähtz et al, , 2014[Pähtz et al, , 2015 recently proposed an expression of the saturation length based on the saltation length L salt and thus governed by the average speed of sand particles traveling above the sand bed: L sat ∝ L salt ≈ V 2 p g. As the grain velocity in steady regime of saltation is invariant with the wind speed [Ho et al, 2011;Valance et al, 2015], the saltation length is expected to be independent on the wind strength like the drag length.…”

Section: Introductionmentioning

confidence: 99%

Aeolian Sand Transport in Out‐of‐Equilibrium Regimes

Selmani

Valance

Moctar

et al. 2018

Geophysical Research Letters

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We investigate the relaxation process toward the equilibrium regime of saltation transport in the context of nonuniform conditions. Relaxation phenomena can be described in terms of a characteristic length scale that measures the distance for the particle flux to adapt to a spatial change in flow or boundary conditions. We conducted wind tunnel experiments to document the influence of the upwind mass flux on the relaxation process. For zero upwind mass flux conditions, the relaxation process is monotone and the relaxation length is independent of the wind strength. In contrast, for nonzero upwind flux conditions (obtained by releasing particles in the flow from a finite height), the relaxation process is nonmonotone and is well captured by damped harmonic oscillations. Importantly, the relaxation length increases with increasing air flow velocity but is almost insensitive to the magnitude of the upwind flux. Our experimental outcomes clearly indicate that the relaxation of far from equilibrium transport regimes strongly deviates from a simple exponential behavior.

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Temperature and humidity within a mobile barchan sand dune, implications for microbial survival

Louge

Valance

Moctar

et al. 2013

J. Geophys. Res. Earth Surf.

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[1] Although microorganisms play an important role in biological soil crusts and plant rhizospheres in deserts, it is unclear whether temperature and moisture deep within relatively fast moving hyperarid mobile dunes present a suitable habitat for microbes. To inform this question, we report measurements of temperature and humidity from probes initially sunk below the leeward avalanche face of a mobile barchan dune in the Qatar desert, emerging windward after 15 months of deep burial. Despite large diurnal variations on the surface, temperature within this dune of 5.6 m height is predictable, as long as dune advection is properly considered. It evolves on smaller amplitude and longer timescale than the surface, lagging average seasonal atmospheric conditions by about 2 months. We contrast these deep thermal records with measurements of diurnal variations of the temperature profile just below the surface, which we calculate with a thermal model predicting the relative roles of wind-driven convective heat transfer and net radiation flux on the dune. Observations and analyses also suggest why random precipitation on the leeward face produces a more unpredictable moisture patchwork on the windward slope. By rapidly reaching sheltered depths, small quantities of rain falling on that face escape evaporation and endure within the dune until resurfacing upwind. At depths below 10 cm, we show that moisture, rather than temperature, determines the viability of microbes and we provide initial microscopic and respiration-based evidence of their presence below the windward slope.

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Scaling Laws in Aeolian Sand Transport

Cited by 142 publications

References 10 publications

Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

Periodic saltation over hydrodynamically rough beds: aeolian to aquatic

Aeolian Sand Transport in Out‐of‐Equilibrium Regimes

Temperature and humidity within a mobile barchan sand dune, implications for microbial survival

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