Model of aerodynamic resistance of three-dimensional distributed roughness

An analytical formulation of the drag characteristics of arbitrary three-dimensional surface roughness in the fully rough regime of turbulent boundary layer flow is introduced. An expression was derived for the equivalent sand grain roughness, introducing a universal roughness correlation parameter. The coefficients of the roughness parameter were determined based on Schlichting's database. This yielded a linear correlation of equivalent sand grain roughness over the complete range of roughness frontal solidity. Applications to regular and irregular distributions were undertaken. Results are presented for a sand-roughened sample, and the data uncertainty and sensitivity to input parameters are determined.