and its inertia, velocity, density, and viscosity.
Ludwig Prandtl simplified calculations of aerodynamic flow
by dividing a flow over a bounding surface into two areas,
the first inside a boundary layer near the surface,
where the flow is affected by viscosity,
and the second outside the boundary layer,
where the effects of viscosity can be ignored.
Boundary layers
Heat transferring from a surface
also has a boundary layer.
Design of airplanes, ships, submarines,
and offshore drilling platforms.
The blades of the Tesla turbines and pumps.
Oscillating objects and rotating fluids.
produce laminar or turbulent flows
and all have boundary layers.
Boundary definition
The line where the speed of a flow
is slowed by the drag on a surface
exactly one percent.
The 49th parallel north.
Where it was in my grandfather’s day.
In this business,
one can sometimes choose any number
as long as it’s always the same number.
Especially, of course,
if it comfortably corresponds
to agreed-upon reality.
On interesting thing about mathematical discoveries is that the original problem over time
becomes less important as new uses for it are developed.
The problem with property boundaries is that their definitions are too often
rooted in a history of exploitation and violence, not in the nature of the land.
Gary Snyder has said that political boundaries should outline watersheds,
but governments invested in their arbitrary borders should not be expected to agree.
On interesting thing about mathematical discoveries is that the original problem over time becomes less important as new uses for it are developed. The problem with property boundaries is that their definitions are too often rooted in a history of exploitation and violence, not in the nature of the land. Gary Snyder has said that political boundaries should outline watersheds, but governments invested in their arbitrary borders should not be expected to agree.
See also in The book of science:
Readings on wikipedia: