Skin friction

Article By:

Schetz, Joseph A. Department of Aerospace and Ocean Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.627300

The shear stress exerted on a solid surface by a flowing viscous fluid. Skin friction is also termed wall shear stress. One can also consider cases where the flowing fluid is replaced by a moving granular solid such as soil or a moving fabric, but such situations will not be discussed here. The subject is of great practical importance because it is manifested (1) as a significant component of the drag of airplanes, ships, and other vehicles, and also birds and fish; and in (2) the loss of pressure in piping systems, including pulmonary and circulatory systems; (3) the health of artery walls; (4) weather prediction; (5) sediment transport; (6) food and chemical processing; and (7) many other situations in engineering and nature. To put this in perspective, about 50% of the drag of a well-designed, modern transport airplane results from skin friction, and the yearly fuel cost expended to overcome that drag is enormous. Skin-friction information is also a critical component in the modeling of turbulent flows implemented in computational fluid dynamics (CFD) tools, which are playing increasingly important roles in engineering design, weather prediction, and many other areas. See also: Aircraft icing; Aircraft laminar flow control; Airplane; Boundary-layer flow; Computational fluid dynamics; Fuel efficiency and laminar flow control; High-speed train aerodynamics; Ship powering, maneuvering, and seakeeping; Turbulent flow; Vortex dynamics in supersonic mixing flows

The content above is only an excerpt.