From lab to landscape-scale experiments for the morphodynamics of sand dunes

Abstract

We review the main processes that drive the morphodynamics of dunes, i.e. their growth in height, migration and elongation, and emphasise the contribution of experiments to the understanding of these mechanisms. The main control parameters are the sediment flux $Q$ and the saturation length $L_{\mathrm{sat}}$ associated with the spatial relaxation of the flux towards the transport capacity. The other relevant quantities are essentially dimensionless: fluid response to a bed perturbation, dune geometry (orientation, aspect ratio), transport ratios under multi-directional wind regimes. We argue that laboratory experiments dealing with sedimentary bedforms in water flows are good analogues to study the morphodynamics of aeolian dunes at reduced length and time scales, as $L_{\mathrm{sat}}$ and $L_{\mathrm{sat}}^2/Q$ are expected to be smaller for subaqueous bedload. Besides, dune shape and dynamics are mainly governed by flow and boundary conditions, independent of the transport mode. We discuss different experimental set-ups and results, especially concerning dune pattern orientation and dune interaction. Under natural wind regimes in terrestrial deserts, we show the potential of field experiments in which the control of initial and boundary conditions allows for the quantification of all the relevant mechanisms involved in dune growth. We emphasise the general agreement between observations, measurements and theoretical predictions, which indicates a robust comprehension of the underlying processes. This understanding can serve as a foundation for further investigations, including the interpretation of dune landscapes and the resolution of inverse problems.

35 pages, 13 figures, Contribution to the Special Issue `Geophysical and astrophysical fluid dynamics in the laboratory'

References in corpus (22)

• A scaling law for aeolian dunes on Mars, Venus, Earth, and for subaqueous ripples
• Vegetation against dune mobility
• The physics of sediment transport initiation, cessation, and entrainment across aeolian and fluvial environments
• A unified model of ripples and dunes in water and planetary environments
• Barchan dune corridors: field characterization and investigation of control parameters
• Giant ripples on comet 67P/Churyumov-Gerasimenko sculpted by sunset thermal wind
• Dissolution instability and roughening transition
• Methane storms as a driver of Titan's dune orientation
• A lower-than-expected saltation threshold at Martian pressure and below
• A comprehensive picture for binary interactions of subaqueous barchans
• Elongation and stability of a linear dune
• Direct validation of dune instability theory
• Spatial and temporal development of incipient dunes
• Local Wind Regime Induced by Giant Linear Dunes: Comparison of ERA5-Land Reanalysis with Surface Measurements
• Aeolian sand transport: Scaling of mean saltation length and height and implications for mass flux scaling
• Dune initiation in a bimodal wind regime
• Morphology and displacement of dunes in a closed-conduit flow
• Coexistence of two dune growth mechanisms in a landscape-scale experiment
• Scaling laws for planetary sediment transport from DEM-RANS numerical simulations
• Hydrodynamic roughness induced by a multiscale topography
• Barchan dunes cruising dune-size obstacles
• Out of equilibrium stationary states, percolation, and sub-critical instabilities in a fully non conservative system