NUMERICAL SIMULATION STUDIES OF TRANSITION PHENOMENA IN INCOMPRESSIBLE, TWO-DIMENSIONAL FLOWS.

Results of stability and transition studies which were obtained by employing an implicit finite difference method for the solution of the complete Navier-Stokes equations are discussed. Emphasis is placed on the discussion of investigations of some aspects of stability and transition for which treatment with other theoretical approaches becomes extremely difficult. In one investigation discussed in this paper, the reaction of a flat-plate boundary layer to periodic disturbances of finite amplitude is studied in order to gain insight into the nonlinear, two-dimensional development of the transition process. In another effort, the numerical model is applied to the investigation of stability and transition in plane Poiseuille flow with special consideration of a nonlinear, spacewise disturbance amplification. A third topic of discussion involves a study of the effects of a single roughness element (backward-facing step) on stability and transition in a boundary layer flow.