Experiments are reported on the formation and migration of isolated dunes in a turbulent channel flow. These have very robust crescentic shape with horns pointing downstream, similar to that barchan observed deserts at much larger scale. Their main geometrical dynamical properties studied detail, for four types grains: conditions their formation, morphology, threshold shear stress motion, velocity, erosion rate, minimum size longitudinal stripes grains hollowed by fluid streaks boundary...

Abstract We investigate experimentally the short‐range interactions occurring between two subaqueous barchans. The experiments were conducted in a water channel of transparent material where controlled grains poured inside, and camera placed on top acquired images bedforms. varied grain types (diameter, density, roundness), pile masses, transverse distances, flow rates, initial conditions. As result, five different patterns identified for both aligned off‐centered configurations, we propose...

Dunes are bedforms found on sandy terrains shaped by fluid flow Earth, Mars, and other celestial bodies. Despite their prevalence, understanding dune dynamics at the grain scale is challenging due to vast number of grains involved. In this study, we demonstrate a novel approach estimate forces acting individual using images. By combining subaqueous experiments, high-speed camera recordings, discrete numerical simulations, specially trained convolutional neural network, can quantify these...

Abstract Sand dunes are ubiquitous in nature, and found abundance on Earth other planetary environments. One of the most common types crescent‐shaped known as barchans, whose mid‐line could be assumed to behave 2D dunes. In this work, we (a) compare morphology 3D barchans with dunes; (b) track evolution while reversing flow conditions. We performed experiments a flume Euler‐Lagrange simulations bedforms. all reversal simulations, initial condition starts conical heap being deformed into...

Accurate geospatial data is fundernental to reliable decision making for sustainable physical development on earth surface. Open-source Digital Elevation Models (DEMs) are imperative many earths’ surface process analysis therefore it necessary subject them accuracy assessment evaluate their suitability different geographical applications. In this study, the elevation quality of DEMs acquired by Surface Radar Topographic Mission 30m resolution (SRTM-30) and Advanced Spaceborne Thermal...

This paper investigates numerically the hydraulic conveying of solids through a 90$^{\circ}$ elbow that changes flow direction from horizontal to vertical, in very-narrow case where ratio pipe particle diameters is less than 5. We performed resolved CFD-DEM (computational fluid dynamics - discrete element method) computations, which we made use IB (immersed boundary) method open-source code CFDEM. investigate effects water and injection rate on transport sedimentation by tracking granular...

Abstract We report an experimental study of the turbulent flow above a barchan dune in channel, from particle image velocimetry measurements, for Reynolds numbers ranging 9000, just below threshold motion, up to 24 000, where moves. Two calculations speed-up over are compared, usual ‘same-elevation’ and more relevant ‘Lagrangian’, showing that latter is smaller by factor two. The two-layer structure disturbance – essentially inviscid outer layer inner thickness ${\delta }_{i} $ assessed. In...

Crescentic shape dunes, known as barchan are formed by the action of a fluid flow on granular bed. These bedforms common in many environments, existing under water or air, and being from grains organized different initial arrangements. Although they frequently found nature industry, details about their development still to be understood. In recent paper [C. A. Alvarez E. M. Franklin, Phys. Rev. E 96, 062906 (2017)], we proposed timescale for equilibrium single barchans based growth horns....

Barchan dunes are crescentic shape with horns pointing downstream. The present paper reports the formation of subaqueous barchan from initially conical heaps in a rectangular channel. Because most unique feature dune is its horns, we associate time scale for appearance to dune. A granular heap was placed on bottom wall closed conduit and it entrained by water flow turbulent regime. After certain time, appear grow, until an equilibrium length reached. Our results show existence scales...

Barchans are eolian dunes of crescent shape found on Earth, Mars and other celestial bodies. Among the different types barchan-barchan interaction, there is one, known as chasing, in which remain close but without touching each other. In this paper, we investigate origins dune repulsion by carrying out grain-scale numerical computations a pair granular heaps deformed fluid flow into barchan that interact with our simulations, data such position, velocity resultant force computed for...

We investigate experimentally the short-range interactions occurring between two subaqueous barchans. The experiments were conducted in a water channel of transparent material where controlled grains poured inside, and camera placed on top acquired images bedforms. varied grain types (diameter, density roundness), pile masses, transverse distances, flow rates initial conditions. As result, five different patterns identified for both aligned off-centered configurations we propose interaction...

Abstract Three dimensional dunes of crescentic shape, called barchans, are commonly found on Earth and other planetary environments. In the great majority cases, barchans organized in large fields which corridors size‐selected observed, where barchan‐barchan interactions play an important role size regulation. Previous studies shed light between by making use monodisperse particles, but nature consist, however, polydisperse grains. this paper, we investigate binary consisting (a) bidisperse...

This paper presents an experimental and numerical investigation of solid-liquid fluidized beds consisting bonded spheres in very narrow tubes, i.e., when the ratio between tube grain diameters is small. In beds, high confinement effects have proved to induce crystallization, jamming different patterns, which can be intensified or modified if some grains are together. order investigate that, we produced duos trios aluminum with diameter 4.8 mm, formed either 150-300 100-200 a 25.4 mm-ID pipe,...

Earth and Space Science Open Archive This work has been accepted for publication in Journal of Geophysical Research - Surface. Version RecordESSOAr is a venue early communication or feedback before peer review. Data may be preliminary. Learn more about preprints. preprintOpen AccessYou are viewing an older version [v1]Go to new versionMorphodynamics barchan-barchan interactions investigated at the grain scaleAuthorsWillian RighiAssisiDErickFrankliniDSee all authors Willian Righi...

Barchans are crescent-shape dunes ubiquitous on Earth and other celestial bodies, which organized in barchan fields where they interact with each other. Over the last decades, satellite images have been largely employed to detect barchans surface of Mars, AI (Artificial Intelligence) becoming an important tool for monitoring those bedforms. However, automatic detection reported previous works is limited isolated does not identify successfully groups interacting barchans. In this paper, we...

In the realm of granular bedforms, barchan dunes are strong attractors that can be found in rivers, terrestrial deserts and other planetary environments. These bedforms characterized by a crescentic shape, which, although robust, presents different scales according to environment they in, their length scale varying from decimeter under water kilometer on Mars. addition transport grains significant differences nature entraining fluid, so growth barchans rests fully understood. Given smaller...

A fluidized bed is basically a suspension of granular material by an ascending fluid in tube, and it has rich dynamics that includes clustering pattern formation. When the ratio between tube grain diameters small, different behaviors can be induced high confinement effects. Some unexpected curious we investigate this paper are crystallization jamming grains liquids with velocities higher than those for incipient fluidization, supposed to maintain fluidized. In our experiments, performed...

Many complex aspects are involved in the morphodynamics of crescent-shaped dunes, known as barchans. One them concerns trajectories individual grains over dune, and how they affect its shape. In case subaqueous barchans, we proposed Alvarez Franklin [Phys. Rev. Lett. 121, 164503 (2018)] that their extremities, called horns, formed mainly by migrating from upstream regions initial pile, exhibit significant transverse displacements. Here, extend our previous work to address dynamics horns...

Corridors of size-selected crescent-shaped dunes, known as barchans, are commonly found in water, air, and other planetary environments. The growth barchans results from the interplay between a fluid flow granular bed, but their size regulation involves intricate exchanges different within field. One size-regulating mechanism is binary interaction nearby when two dunes exchange mass via near field or by direct contact (collision). In recent Letter (Assis Franklin, Geophys. Res. Lett., 2020),...