On Laminar and Turbulent Friction

von Karman, Th.

The theoretical treatment of surface friction of liquids or gases at a solid wall encounters serious difficulties as soon as the processes are no longer defined by the viscosity of the fluid alone, but also involve the forces of inertia with the probably exception of the flow phenomena in capilaries and the problems of lubricant friction -- as is the case in nearly all practical problems. All the same, two substantial advances have been achieved in this domain within the last decades; namely, by Prandtl's "boundary layer theory' and Blasius' confirmation of the previously supected nature of the friction loss in smooth pipes.

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