Evaluation of drag reduction by turbulence control devices

Abstract

A method is given for determining the drag reduction achieved by a given passive turbulence-control device located within the turbulent boundary layer on the surface for which the drag is to be reduced for given flow conditions, the length of the surface being treated as a variable. The simplest version of the method results in a description of the performance in terms of two parameters which can be interpreted as asymptotic or peak drag reduction rate (drag reduction/original drag) and half-drag-reduction length. Application of the method to published experimental data shows the first parameter to vary from about 5 to 30 percent and the second parameter from rather small distances to about 15 m.