A LAMINAR ROUGHNESS BOUNDARY-CONDITION

A modified slip boundary condition is obtained to represent the effect s of small roughness-like perturbations to an otherwise-plane fixed wa ll which is acting as a boundary to steady laminar flow of a viscous f luid. In its simplest form, for low local Reynolds number and small ro ughness slope, this boundary condition involves a constant apparent ba ckflow at the mean surface or, equivalently, represents a shift of the apparent plane boundary toward the flow domain. Extensions of the the ory are also made to include finite local Reynolds number and finite r oughness slope.