Wavelength selection of rolling-grain ripples in the laboratory.

Physical distinction between rolling-grain ripples and vortex ripples: an experimental study.

We have performed an experimental study of the transition of rolling-grain ripples toward vortex ripples. In particular, we have looked for the influence of the grains' diameter, the frequency of oscillation, and the grains' cohesion. We demonstrate that the rolling-grain ripples are transient patterns which do appear as soon as we are close to the threshold for grain motion, whereas vortex rip...

A particle model of rolling grain ripples under waves

Direct numerical simulations of aeolian sand ripples.

Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns...

Bedforms in a turbulent stream. Part 2: Formation of ripples by primary linear instability and of dunes by non-linear 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, that of the latter being controled by the water depth. We revisit here this problem, using the computation of the turbulent flow over a wavy bottom performed in Part 1. A multi-scale description of the problem is proposed, in which the details o...

Magnificent Grain Refinement of Al-Mg2Si Composite by Hot Rolling

The effect of chemical composition and the hot rolling operations on the microstructure and mechanical properties of in situ aluminum matrix composite with Mg2Si phase as the reinforcement was studied. It was revealed that the modification by phosphorous results in the rounder (more spherical) primary and secondary (eutectic) magnesium silicide intermetallics. During hot rolling, the primary pa...