The laminar sublayer, also called the viscous sublayer, is the region of a mainly-
turbulent flow that is near a
no-slip boundary and in which viscous
shear stresses are important. As such, it is a type of
boundary layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a Boundary (thermodynamic), bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces ...
. The existence of the viscous sublayer can be understood in that the flow velocity decreases towards the no-slip boundary.
The laminar sublayer is important for river-bed
ecology
Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...
: below the laminar-turbulent interface, the flow is stratified, but above it, it rapidly becomes well-mixed. This threshold can be important in providing homes and feeding grounds for
benthic organisms.
Whether the roughness due to the bed sediment or other factors are smaller or larger than this sublayer has an important bearing in
hydraulics and
sediment transport. Flow is defined as
hydraulically rough if the roughness elements are larger than the laminar sublayer (thereby perturbing the flow), and as
hydraulically smooth if they are smaller than the laminar sublayer (and therefore ignorable by the main body of the flow).
[http://www.personal.kent.edu/~amoore5/FST_L_6a.pdf ]
References
Fluid mechanics
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