Dynamics of enstrophy of a forced quasi-2D wall-adjacent flow

Abstract

We present an analysis of experimental enstrophy signals obtained from a quasi two-dimensional fluid flow in a wall-bounded spatial domain. The flow under consideration is a zero-pressure gradient Blasius boundary layer, where periodic volumetric forcing is applied near the wall at two distinct streamwise locations. The flow structures produced by the first actuation are advected downstream, subsequently affecting the local generation of enstrophy at the second location. Phase space visualizations of the complex system dynamics are generated using time-delay embedding techniques applied to the experimental time series. The results are examined by considering the projections of the time-delay embedded system onto the singular vectors of the enstrophy signal?s Hankel matrix. With appropriate spatiotemporal forcing, nonlinearities transform the system dynamics from confined orbits to chaotic-like behavior, exhibiting a combination of small orbital and dispersed patterns.