Ask A Scientist© Engineering Archive

Index Key:   ENG001
Author:      wildman jackson
Subject:     Boundary layers and airplanes.
What exactly is a Boundary Layer, and what relationship does it have
to planes?  

Response #:  1 of 1
Author:      proach
When a solid body moves through a fluid such as air, there is a thin layer
next to the surface of the body where the fluid moves with the body.  There
is no slip of the fluid with respect to the body in this thin layer.  At
greater distances from the surface, there is some slip, and the fluid is
dragged along at some speed between that of the body and the stationary mass
of fluid.  This layer, in which the fluid is being dragged by the body, is
the boundary layer.  The behavior of this boundary layer is very important
in determining such things as the drag force on the body.  At high speeds,
such as with an airplane, the drag force can be very large.  Understanding
what the boundary layer is doing can help to reduce this force.