scholarly journals Energy contents and vortex dynamics in Mode-C transition of wired-cylinder wake

2013 ◽  
Vol 25 (5) ◽  
pp. 054103 ◽  
Author(s):  
I. Yildirim ◽  
C. C. M. Rindt ◽  
A. A. van Steenhoven
Keyword(s):  
Vortex Dynamics ◽  
Cylinder Wake

scholarly journals Vortex dynamics in a wire-disturbed cylinder wake

2010 ◽  
Vol 22 (9) ◽  
pp. 094101 ◽  
Author(s):  
I. Yildirim ◽  
C. C. M. Rindt ◽  
A. A. Steenhoven
Keyword(s):  
Vortex Dynamics ◽  
Cylinder Wake

Flow about a circular cylinder between parallel walls

2001 ◽  
Vol 440 ◽  
pp. 1-25 ◽  
Author(s):  
LUIGINO ZOVATTO ◽  
GIANNI PEDRIZZETTI
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Vortex Dynamics ◽  
Lift Force ◽  
The Body ◽  
Cylinder Wake ◽  
Regime Changes ◽  
Wall Boundary Layer ◽  
Karman Street ◽  
The Mean

The flow about a body placed inside a channel differs from its unbounded counterpart because of the effects of wall confinement, shear in the incoming velocity profile, and separation of vorticity from the channel walls. The case of a circular cylinder placed between two parallel walls is here studied numerically with a finite element method based on the vorticity–streamfunction formulation for values of the Reynolds number consistent with a two-dimensional assumption.The transition from steady flow to a periodic vortex shedding regime has been analysed: transition is delayed as the body approaches one wall because the interaction between the cylinder wake and the wall boundary layer vorticity constrains the separating shear layer, reducing its oscillations. The results confirm previous observations of the inhibition of vortex shedding for a body placed near one wall. The unsteady vortex shedding regime changes, from a pattern similar to the von Kármán street (with some differences) when the body is in about the centre of the channel, to a single row of same-sign vortices as the body approaches one wall. The separated vortex dynamics leading to this topological modification is presented.The mean drag coefficients, once they have been normalized properly, are comparable when the cylinder is placed at different distances from one wall, down to gaps less than one cylinder diameter. At smaller gaps the body behaves similarly to a surface-mounted obstacle. The lift force is given by a repulsive component plus an attractive one. The former, well known from literature, is given by the deviation of the wake behind the body. Evidence of the latter, which is a consequence of the shear in front of the body, is given.

Vortex dynamics for flow over a circular cylinder in proximity to a wall

2017 ◽  
Vol 812 ◽  
pp. 698-720 ◽  
Author(s):  
Guo-Sheng He ◽  
Jin-Jun Wang ◽  
Chong Pan ◽  
Li-Hao Feng ◽  
Qi Gao ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Shear Layer ◽  
Flat Plate ◽  
Vortex Shedding ◽  
Vortex Dynamics ◽  
Wake Vortex ◽  
Secondary Vortex ◽  
Cylinder Wake ◽  
Gap Ratio ◽  
Shedding Frequency

The dynamics of vortical structures in flow over a circular cylinder in the vicinity of a flat plate is investigated using particle image velocimetry (PIV). The cylinder is placed above the flat plate with its axis parallel to the wall and normal to the flow direction. The Reynolds number $Re_{D}$ based on the cylinder diameter $D$ is 1072 and the gap $G$ between the cylinder and the flat plate is varied from gap-to-diameter ratio $G/D=0$ to $G/D=3.0$. The flow statistics and vortex dynamics are strongly dependent on the gap ratio $G/D$. Statistics show that as the cylinder comes close to the wall ($G/D\leqslant 2.0$), the cylinder wake becomes more and more asymmetric and a boundary layer separation is induced on the flat plate downstream of the cylinder. The wake vortex shedding frequency increases with decreasing $G/D$ until a critical gap ratio (about $G/D=0.25$) below which the vortex shedding is irregular. The deflection of the gap flow away from the wall and its following interaction with the upper shear layer may be the cause of the higher shedding frequency. The vortex dynamics is investigated based on the phase-averaged flow field and virtual dye visualization in the instantaneous PIV velocity field. It is revealed that when the cylinder is close to the wall ($G/D=2.0$), the cylinder wake vortices can periodically induce secondary spanwise vortices near the wall. As the cylinder approaches the wall ($G/D=1.0$) the secondary vortex can directly interact with the lower wake vortex, and a further approaching of the cylinder ($G/D=0.5$) can result in more complex interactions among the secondary vortex, the lower wake vortex and the upper wake vortex. The breakdown of vortices into filamentary debris during vortex interactions is clearly revealed by the coloured virtual dye visualizations. For $G/D<0.25$, the lower shear layer is strongly inhibited and only the upper shear layer can shed vortices. Investigation of the vortex formation, evolution and interaction in the flow promotes the understanding of the flow physics for different gap ratios.

Vortex Dynamics in the Turbulent Wake of a Single Step Cylinder

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
C. Morton ◽  
S. Yarusevych
Keyword(s):  
Vortex Dynamics ◽  
Turbulent Wake ◽  
Single Step ◽  
Cylinder Wake ◽  
Near Wake ◽  
Vortex Interactions ◽  
Direct Cross ◽  
Half Loop ◽  
Turbulent Vortex Shedding ◽  
Different Diameters

The turbulent wake development of a circular cylinder with a single stepwise discontinuity in diameter was investigated experimentally using flow visualization and two-component Laser Doppler Velocimetry (LDV). A single step cylinder is comprised of two cylinders of different diameters (D and d). Experiments were performed at a Reynolds number (ReD) of 1050 and a diameter ratio (D/d) of two. A combination of hydrogen bubble and laser induced fluorescence techniques allowed visualization of complex vortex dynamics in the near wake. The results show that turbulent vortex shedding from a single step cylinder occurs in three distinct cells of constant shedding frequency. The differences in frequency and strengths between vortices in the cells lead to complex vortex interactions at the cell boundaries. The results demonstrate that vortex splitting, half-loop vortex connections, and direct cross-boundary vortex connections occur near the cell boundaries. A comparative analysis of flow visualizations and velocity measurements is used to characterize the main vortex cells and the attendant vortex interactions, producing a simplified model of vortex dynamics in the step cylinder wake for ReD = 1050 and D/d = 2.

Sign in / Sign up

Export Citation Format

Share Document