Local description of the three-dimensional wake transitionстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 24 января 2020 г.
Аннотация:Mechanisms affecting the transition to three-dimensionality in a cylinder wake are studied based on the local description of the perturbations development for modes A and B. Early stages of three-dimensional vortex structures growth are simulated by the direct numerical solution of the Navier–Stokes equations. The influence of basic mechanisms (such as vorticity diffusion, stretching and tilting of vortex lines) on the growth and decay of perturbations in fluid particles, and on the change in the direction of generated longitudinal vorticity vectors is considered. The same analysis is carried out for an idealized elliptic flow, which reveals qualitative similarities and differences in the perturbations development inside the forming vortex and for the flow with elliptical streamlines. It was shown that the line, along which perturbations of mode B concentrate, can be approximately found based on a two-dimensional solution. The instability of mode B is studied by introducing a simplified two-dimensional flow, which approximates the flow in the braid shear layer. Based on the linear stability analysis of this flow it can be assumed that the curvature of the braid shear layer plays an important role in the mode B instability.