Experiments with fluid friction in roughened pipes

Abstract
Nikuradse (1933; Prandtl 1933), experimenting with pipes roughened internally by a uniform layer of sand, found that such pipes were indistinguishable from perfectly smooth ones, provided that the pressure gradient was less than that given by pV * k / μ = 4, where V = √( T 0 / p ), T 0 = shear stress at wall, p = density of fluid, μ , —- viscosity of fluid, k = diameter of roughness grains. With lesser flows neither the resistance nor the distribution of velocity was measurably influenced by the size of the roughness grains, and the observed resistance law was satisfactorily of the type required by the Kármán-Prandtl theory for smooth surfaces. This law is usually expressed in the following form:

This publication has 0 references indexed in Scilit: