Modal interactions in a Bickley jet: comparison of theory with direct numerical simulation

This study is concerned with three-dimensional transition in plane wakes and jets. Nonlinear stability theory has predicted that interactions between different instability modes can play an important role in that transition. In this paper, we consider interactions between varicose and sinuous oblique disturbances in the Bickley jet, using both nonlinear stability theory (in its nonlinear critical layer form) and direct numerical simulation using a spectral method. We will first present an overview of the nonlinear stability theory which indicates that a (nonlinear) interaction between the modes should occur, and then present simulations that appear to support the theory.