Development of an alternative to the e to the 9th power procedure for predicting boundary-layer transition

A method has been devised which can be used in conjunction with linear-stability theory for predicting boundary-layer transition. As with the classical 'e to the 9th power' procedure, for a given frequency the growth of a disturbance is computed downstream of the initial point of instability using the linearized equations of motion. In contrast to the e to the 9th power procedure in which the linearized equations are used all the way to the inferred transition point, an approximate set of long-time averaged equations which account for nonlinearity is used to describe the ultimate nonlinear growth of the disturbance. Because the method accounts for nonlinear processes it holds promise for determining the point at which a boundary layer undergoes transition to turbulence.