We present measurements of wind velocity and sand flux performed on the windward side of a large barchan dune in Jericoacoara, northeastern Brazil. From the measured profile, we calculate the air shear stress using an analytical approximation and treat the problem of flow separation by an heuristic model. We find that the results from this approach agree well with our field data. Moreover, usin...

Elucidating cardiac evolution has been frustrated by lack of fossils. One celebrated enigma in cardiac evolution involves the transition from a cardiac outflow tract dominated by a multi-valved conus arteriosus in basal actinopterygians, to an outflow tract commanded by the non-valved, elastic, bulbus arteriosus in higher actinopterygians. We demonstrate that cardiac preservation is possible in...

An asteroid spun up to its critical limit has unique surface mechanical properties that gravity and the centrifugal force largely balance, creating a relaxation environment where low-energy events such as mass shedding may trigger subsequent long complex motion of an asteroid's regolith grains. Exploring evolution process provide key clues for understanding early formation multi-asteroid system...

We present a novel approach for numerical simulation of uid ow and sediment transport past evolutionary landforms, with emphasis on sand dunes developing in extreme winds. Time-dependent curvilinear coordinates are employed to fully couple ow aloft with the developing landform. The conservation law that de nes shape of the lower boundary depends on details of local surface stress, thereby favou...

The paper is of great interest. It introduces a 3D model coupling effects between wind and snow particles. The coupled model is evaluated on a flat erodible snow surface under various wind conditions and is compared to wind tunnel experiments, the results of which are published in the literature. The model takes into account all involved physical processes and allows to better understand behavi...

We extend the model of surface granular flow proposed in [1] to account for the effect of an external ‘wind’, which acts as to dislodge particles from the static bed, such that a stationary state of flowing grains is reached. We discuss in detail how this mechanism can be described in a phenomenological way, and show that a flat bed is linearly unstable against ripple formation in a certain reg...