Enhanced Visualization of Late-stage Transitional Structures Using Vortex Identiication and Automatic Feature Extraction

The unsteady Navier{Stokes equations ooer a large variety of instantaneous solutions even for rather simple boundary conditions once the relevant spatial and temporal scales of the problem at hand are adequately resolved. This is especially true for DNS (Direct Numerical Simulation) of laminar-turbulent transition, where an initially lam-inar ow, disturbed by some unsteady uctuations \breaks down" into small-scale high-frequency turbulence. When trying to study and understand this process, one faces the problem of identifying the relevant structures to describe the ow which consist of vortices and shear layers, and on their isolation for further investigation. Here, we present a post-processing method based on the vortex deenition proposed by Jeong & Hussain 5] and on Feature Extraction similar to Silver 13] that allows to successfully identify, isolate and track vortical features in a transitional boundary layer.