Visualization of the energy-containing turbulent scales

In this study, we explore a novel approach for visualizing the energetic turbulent structures in a flow field. The flow field is generated by a direct numerical simulation (DNS) of a stratified turbulent shear layer instigated by the Kelvin-Helmholtz instability. The use of so-called structure-based tensors combined with volume rendering seems to be a very promising tool to gain new insight into the dynamically most important part of the turbulence. Rendering of these tensors depicts the large-scale structures that carry most of the turbulence energy. This is in distinct contrast to traditional methods based on derivatives of the velocity field, such as those based on the velocity gradient tensor and vorticity. These methods only capture the smaller-scale structures of the flow. Traditionally, statistical measures are used to handle the enormous amount of data generated by DNS, whereby a lot of detailed information is inevitably lost. The rapid increase in computer performance combined with advanced visualization techniques makes it possible to use a non-statistical or deterministical approach to study the kinematic and dynamic properties of turbulent flows. This paper presents a promising first attempt to render structure-based tensors to see how faithfully they can describe the large-scale structures in a stratified turbulent shear flow.