Boundary Layer Adjustment as an Initial Value Problem

Abstract

Previous investigations of boundary layer adjustment, such as those by Panofsky and Townsend, and more recently by Townsend, have been based upon similarity arguments. In this paper, however, the adjustment of a neutrally stratified boundary layer to a sudden change in surface roughness is treated as an initial value problem. Changes in wind speed obtained from the numerical integration of a set of nonlinear boundary layer equations are significantly larger than previous theoretical predictions. Numerical results comparable to the similarity predictions can be obtained by neglecting the effects of vertical motion. Numerical techniques such as those developed herein should be of value in modeling nonuniform boundary layer flows that are beyond the scope of current similarity solutions.