Formation mechanism of hairpin vortices in the wake of a truncated square cylinder in a duct
Vincent Dousset,Alban Pothérat +1 more
TLDR
In this paper, the authors investigated the laminar shedding of hairpin vortices in the wake of a truncated square cylinder placed in a duct, for Reynolds numbers around the critical threshold of the onset of vortex shedding.Abstract:
We investigate the laminar shedding of hairpin vortices in the wake of a truncated square cylinder placed in a duct, for Reynolds numbers around the critical threshold of the onset of vortex shedding. We single out the formation mechanism of the hairpin vortices by means of a detailed analysis of the flow patterns in the steady regime. We show that unlike in previous studies of similar structures, the dynamics of the hairpin vortices are entwined with that of the counter-rotating pair of streamwise vortices, which we found to be generated in the bottom part of the near wake (these are usually referred to as ‘base vortices’). In particular, once the hairpin structure is released, the base vortices attach to it, forming its legs, so these are streamwise, and not spanwise as previously observed in unconfined wakes or behind cylinders of lower aspect ratios. We also single out a trail of Ω-shaped vortices, generated between successive hairpin vortices through a mechanism that is analogous to that active in near-wall turbulence. Finally, we show how the dynamics of the structures we identified determine the evolution of the drag coefficients and Strouhal numbers when the Reynolds number varies.read more
Citations
More filters
Journal ArticleDOI
Dynamic overset CFD simulations of wind turbine aerodynamics
TL;DR: In this article, simulations of the National Renewable Energy Laboratory (NREL) phase VI wind turbine using dynamic oversetgrid technology are presented, with the rotor consisting of the blades and hub.
Journal ArticleDOI
Low-Reynolds-number flow around a wall-mounted square cylinder: Flow structures and onset of vortex shedding
TL;DR: In this article, a direct numerical simulation is applied to investigate three-dimensional unsteady flow characteristics around a finite wall-mounted square cylinder with an aspect ratio of 7 at a Reynolds number (Re) of 40-250.
Journal ArticleDOI
Direct numerical simulation of flow around a surface-mounted finite square cylinder at low Reynolds numbers
TL;DR: In this paper, the authors presented a detailed investigation on the flow around a finite square cylinder at a fixed aspect ratio (AR) of 4 and six Reynolds numbers (Re = 50, 100, 150, 250, 500, and 1000).
Journal ArticleDOI
Unsteady flow past a finite square cylinder mounted on a wall at low Reynolds number
TL;DR: In this paper, the effect of the aspect ratio on the flow field and integral parameters of a finite length square cylinder has been investigated using second order spatial and temporal discretizations.
Journal ArticleDOI
Flat-Plate Interaction with the Near Wake of a Square Cylinder
TL;DR: In this article, the authors explored how low Reynolds number bluff body wake interference can affect the generation of unsteady flow and force in the presence of an infinitely thin flat plate placed in the near wake of a square cylinder.
References
More filters
Journal ArticleDOI
On the identification of a vortex
Jinhee Jeong,Fazle Hussain +1 more
TL;DR: In this article, the authors propose a definition of vortex in an incompressible flow in terms of the eigenvalues of the symmetric tensor, which captures the pressure minimum in a plane perpendicular to the vortex axis at high Reynolds numbers, and also accurately defines vortex cores at low Reynolds numbers.
Journal ArticleDOI
A tensorial approach to computational continuum mechanics using object-oriented techniques
TL;DR: The implementation of various types of turbulence modeling in a FOAM computational-fluid-dynamics code is discussed, and calculations performed on a standard test case, that of flow around a square prism, are presented.
Journal ArticleDOI
Mechanisms for generating coherent packets of hairpin vortices in channel flow
TL;DR: In this article, the evolution of a single hairpin vortex-like structure in the mean turbulent field of a low-Reynolds-number channel flow is studied by direct numerical simulation, and the detailed mechanisms for this upstream process are determined, and they are generally similar to the mechanisms proposed by Smith et al. (1991), with some notable differences in the details.
Journal ArticleDOI
A general classification of three-dimensional flow fields
TL;DR: In this paper, the geometry of solution trajectories for three first-order coupled linear differential equations can be related and classified using three matrix invariants for elementary three-dimensional flow patterns defined by instantaneous streamlines for flow at and away from no slip boundaries for both compressible and incompressible flow.
Journal ArticleDOI
Kinematical studies of the flows around free or surface-mounted obstacles; applying topology to flow visualization
TL;DR: In this paper, the authors show that the zero-shear-stress points on the surface and on the obstacle must be such that the sum of the nodes and the saddles of the saddle must satisfy