Mass flow requirements for LFC wing design

Abstract

The problem of determining optimum suction mass flow requirements for LFC wings is addressed. Some previous methods for predicting the extent of laminar flow over swept wings with suction are briefly reviewed. These range from the purely empirical to those utilizing tabulated linear stability computations. The present method is described. This method solves the linear, incompressible stability equations by spectral techniques. The maximum temporal amplification of boundary layer crossflow and 2-D disturbances is determined for waves of a given frequency. Group velocities are used to integrate these amplification rates along the wing to yield the logarithmic amplitude ratio or 'N factor' of the disturbance. The 'N factor' calibration of a computer code utilizing this method is described, using experimentally determined transition data. The method is shown to be as consistent as previously used 'fixed wavelength' methods.