RESEARCH ON SUCTION SURFACES FOR LAMINAR FLOW

Abstract

This chapter presents a critical review of present-day achievements in the design of practical suction surfaces for laminar flow. The design problem is to specify a surface and ducting system whose internal aerodynamics and controls are such as to allow a desired pattern of inflow to be obtained in the presence of an external static pressure distribution. A continuously porous surface is envisaged as the ideal that allows the velocity normal to the surface at the boundary to take some nonzero value. A laminar boundary layer may be kept stable by applying suction at suitable discrete intervals. As the percentage of nonporous region increases, the local inflow velocity correspondingly increases, and it is possible to reduce the porous regions to a series of slots or slits. The ideal porous surface does not exist as the normal velocity at the boundary must of necessity be zero on the matrix between the pores. The permissible distribution of such perforations, whether uniformly over the surface or concentrated into narrow spanwise rows, has, therefore, also been a subject for research.