A grain flow is a type of
sediment-gravity flow in which the fluid can be either air or water, acts only as a lubricant, and grains within the flow remain in suspension due to grain-to-grain collisions that generate a dispersive pressure to prevent further settling. Grain flows are very common in
aeolian settings as grain avalanches on the slip faces of
sand dunes. By contrast, pure grain flows are rare in subaqueous settings, where the grains in a flow are generally held in suspension dominantly by
traction,
saltation, fluid
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...
and/or grain
buoyancy
Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...
when the grains are floating in the clay matrix of a
mud flow. However, grain-to-grain collisions are very important as a contributing process of sediment support in subaqueous, sand-rich,
high-density turbidity currents. The high concentrations of sand that develop at the base of high-density flows brings grains close enough together that frequent grain-to grain collisions are inevitable and result in layers of sediment that are
inverse graded as the smaller grains are able to fall in between larger grains and settle out beneath them.
[Lowe, D.R. (1982), ''Sediment gravity flows: II. Depositional models with special reference to the deposits of high-density turbidity currents,'' Journal of Sedimentology, Society of Economic Paleonotlogists and Mineralogists, v. 52, p. 279-297.]
In metallurgy
In
metallurgy
Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.
Metallurgy encompasses both the ...
, the grain flow refers to the
plastic deformation
In engineering, deformation (the change in size or shape of an object) may be ''elastic'' or ''plastic''.
If the deformation is negligible, the object is said to be ''rigid''.
Main concepts
Occurrence of deformation in engineering application ...
of
crystallite
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel Wikt:longulite ...
s during
rolling
Rolling is a Motion (physics)#Types of motion, type of motion that combines rotation (commonly, of an Axial symmetry, axially symmetric object) and Translation (geometry), translation of that object with respect to a surface (either one or the ot ...
or
forging
Forging is a manufacturing process involving the shaping of metal using localized compression (physics), compressive forces. The blows are delivered with a hammer (often a power hammer) or a die (manufacturing), die. Forging is often classif ...
.
Notes and references
Sedimentology
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