COMPARING LOCAL AND MARCHING ANALYSES OF GORTLER INSTABILITY

Two methods of solving the partial differential equations describing Gortler instability are compared. Local separation-of-variable analysis predicts growth rates independently of any assumptions about initial disturbances. Global marching analysis requires initial-disturbance assumptions but is shown to provide results that are not affected after sufficient marching. The local analysis results are compared to the marching results and are seen to consistently overestimate growth rates by modest amounts. The distance required for different disturbances to collapse onto one common curve is estimated from several examples. The first neutral point cannot be clearly identified by the marching analysis because convergence to the asymptotic curve is too slow and because the most unstable disturbance changes rapidly with streamwise position upstream of the neutral point. Different measures of growth give slightly different results because of the changing disturbance shape. © 1990 American Institute of Aeronautics and Astronautics, Inc., All rights reserved.