Boundary-layer flow

Article By:

White, Frank M. Department of Mechanical Engineering, University of Rhode Island, Kingston, Rhode Island.

Adams, Thomas M. Department of Mechanical Engineering, Rose-Hulman Institute of Technology, Terre Haute, Indiana.

Last reviewed:July 2022

DOI:https://doi.org/10.1036/1097-8542.092500

Show previous versions

• Boundary-layer flow, published November 2019:Download PDF Get Adobe Acrobat Reader

That portion of a fluid flow near a solid surface where shear stresses are significant and the inviscid-flow assumption, in which viscous-shear and normal stresses are negligible, may not be used. In physics broadly and fluid mechanics specifically, a boundary layer refers to the thin layer of fluid in immediate proximity to a solid surface when there is fluid flowing past the surface. All solid surfaces interact with a viscous fluid flow because of the no-slip boundary condition, which is a physical requirement that the fluid and solid have equal velocities at their interface. Thus, the presence of a fixed solid surface impedes fluid flow. The result is a finite boundary layer that moves slower than the bulk fluid otherwise flowing past the surface and not in direct contact with the surface. Accounting for boundary-layer flow is important in numerous applied fields such as mechanical, marine, and aeronautical engineering, in theoretical fields such as physics, and also in the life sciences. See also: Fluid mechanics; Fluid-flow principles; Fluids; Shear; Stress and strain; Velocity; Viscosity

The content above is only an excerpt.