Direct numerical simulation of the development of asymmetric perturbations at very late stages of the transition process

Summary

An investigation on the development of asymmetric perturbations at extremely late stages of the transition process, right before the boundary layer becomes fully turbulent, will be presented. The influence of asymmetric disturbances on the time averaged flow and the local flow dynamics close to the original symmetry plane will be demonstrated. We introduce small asymmetric disturbances which mimic small-amplitude random background perturbations that are present in any realistic flow situation. We focus on how the flow is transformed from a symmetric to an asymmetric one by these additional perturbations, and we try to identify instability mechanisms which are responsible for the amplification of these asymmetric disturbances. Thus, the aim of the present investigations is to contribute to a deeper understanding of turbulence production.