Vortical Structures: Some Aspects of the Recent Identification Schemes

Vaclav KOLAR¹; Jakub SISTEK²

¹ Institute of Hydrodynamics, Academy of Sciences of the Czech Republic, Prague 6, Czech Republic; ² Institute of Mathematics, Academy of Sciences of the Czech Republic, Prague 1, Czech Republic

doi:10.20906/CPS/COB-2015-0288

Resumo

The contribution deals with the recent vortex-identification schemes (proposed by the present authors) compared on the background of some widely used methods from the literature. It concentrates on their physical and kinematic aspects and presents some comparison results based on a straightforward application of these schemes to the 3-D outcome of numerical simulation (including a transonic flow past a turbine cascade and a flow around an impulsively started flat plate). The main aspects of vortex identification discussed are: the local corotation of line segments near a point, vorticity decomposition and the so-called residual vorticity, the effect of shear, the role of the axial-stretching rate, pressure aspects, applicability of identification schemes to compressible flows, the need for a local vortex intensity with an easy kinematic interpretation and linear response, and limited applicability of integral vortex strength in terms of the circulation along the vortex boundary.

Palavras-chave: vortical structures; vortex identification; vortices