Analyzing the vortex dynamics in bluff-body wakes by Helmholtz decomposition of the velocity field

2006 ◽  
Vol 38 (7) ◽  
pp. 431-451 ◽  
Author(s):  
F L Ponta
Keyword(s):  
Velocity Field ◽  
Vortex Dynamics ◽  
Bluff Body ◽  
Helmholtz Decomposition

scholarly journals Turbulent flame-vortex dynamics of bluff-body premixed flames

2021 ◽  
Vol 223 ◽  
pp. 28-41
Author(s):  
Marissa K. Geikie ◽  
Cal J. Rising ◽  
Anthony J. Morales ◽  
Kareem A. Ahmed
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body ◽  
Turbulent Flame ◽  
Premixed Flames

Helmholtz decomposition of velocity field of a mixing layer: Application to the analysis of acoustic sources

2006 ◽  
pp. 513-520 ◽  
Author(s):  
M. Cabana ◽  
V. Fortuné ◽  
P. Jordan ◽  
F. Golanski ◽  
Eric Lamballais ◽  
...  
Keyword(s):  
Velocity Field ◽  
Mixing Layer ◽  
Helmholtz Decomposition ◽  
Acoustic Sources

Numerical and Experimental Evaluation of Lift Forces in Flows Around Surface-Mounted Bluff Bodies

2002 ◽  
Author(s):  
T. Stengel ◽  
F. Ebert ◽  
M. Fallen
Keyword(s):  
Velocity Field ◽  
Bluff Body ◽  
Recirculation Zone ◽  
Separation Zone ◽  
Laser Doppler Anemometry ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
The Body ◽  
Bluff Bodies ◽  
Large Eddy

The flow around a surface-mounted bluff body with cuboid shape is investigated. Therefore, the velocity field including the distribution of the turbulent kinetic energy is computed and compared with experimental Laser Doppler Anemometry data. Several different turbulence models, namely the standard k-ε model, the Wolfshtein two-layer k-ε model and a Large-Eddy approach are validated. Since the Large-Eddy model remains the only model representing the flow accurate, it is chosen for further investigations. The pressure distribution on the body and on the carrying surface around the body is analysed. The lift coefficients are computed for Reynolds numbers, ranging from 1.1 × 104 up to 4.4 × 104. The lengths of the separation zone above and the recirculation zone downstream the body are evaluated.

scholarly journals Study of the Turbulent Velocity Field in the Near Wake of a Bluff Body

2016 ◽  
Vol 97 (3) ◽  
pp. 715-728 ◽  
Author(s):  
Juan José Cruz Villanueva ◽  
Luís Fernando Figueira da Silva
Keyword(s):  
Velocity Field ◽  
Bluff Body ◽  
Turbulent Velocity ◽  
Near Wake ◽  
Turbulent Velocity Field

Effect of nonharmonic forcing on bluff-body vortex dynamics

2009 ◽  
Vol 79 (4) ◽  
Author(s):  
E. Konstantinidis ◽  
D. Bouris
Keyword(s):  
Vortex Dynamics ◽  
Bluff Body

Transition to bluff-body dynamics in the wake of vertical-axis wind turbines

2017 ◽  
Vol 813 ◽  
pp. 346-381 ◽  
Author(s):  
Daniel B. Araya ◽  
Tim Colonius ◽  
John O. Dabiri
Keyword(s):  
Velocity Field ◽  
Circular Cylinder ◽  
Large Scale ◽  
Wind Farm ◽  
Bluff Body ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Cylinder Wake ◽  
Vertical Axis Wind Turbine ◽  
Far Wake

We present experimental data to demonstrate that the far wake of a vertical-axis wind turbine (VAWT) exhibits features that are quantitatively similar to that of a circular cylinder with the same aspect ratio. For a fixed Reynolds number ($Re\approx 0.8\times 10^{5}$) and variable tip-speed ratio, two-dimensional particle image velocimetry (PIV) is used to measure the velocity field in the wake of four different laboratory-scale models: a 2-bladed, 3-bladed and 5-bladed VAWT, as well as a circular cylinder. With these measurements, we use spectral analysis and proper orthogonal decomposition (POD) to evaluate statistics of the velocity field and investigate the large-scale coherent motions of the wake. In all cases, we observe three distinct regions in the VAWT wake: (i) the near wake, where periodic blade vortex shedding dominates; (ii) a transition region, where growth of a shear-layer instability occurs; (iii) the far wake, where bluff-body wake oscillations dominate. We define a dynamic solidity parameter, $\unicode[STIX]{x1D70E}_{D}$, that relates the characteristic scales of the flow to the streamwise transition location in the wake. In general, we find that increasing $\unicode[STIX]{x1D70E}_{D}$ leads to an earlier transition, a greater initial velocity deficit and a faster rate of recovery in the wake. We propose a coordinate transformation using $\unicode[STIX]{x1D70E}_{D}$ in which the minimum velocity recovery profiles of the VAWT wake closely match that of the cylinder wake. The results have implications for manipulating VAWT wake recovery within a wind farm.

PIV-POD Investigation of the Wake of a Sharp-Edged Flat Bluff Body Immersed in a Shallow Channel Flow

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Arindam Singha ◽  
A.-M. Shinneeb ◽  
Ram Balachandar
Keyword(s):  
Velocity Field ◽  
Channel Flow ◽  
Bluff Body ◽  
Maximum Flow ◽  
Velocity Fields ◽  
Central Plane ◽  
Mean Flow ◽  
Mean Velocity ◽  
Near Surface ◽  
The Mean

This paper reports particle-image velocimetry measurements of instantaneous velocity fields in the wake of a sharp-edged bluff body immersed vertically in a shallow smooth open channel flow. The maximum flow velocity was 0.19 m/s and the Reynolds number based on the water depth was 18,270. The purpose of the present study is to show the vertical variation of the velocity field in the near region of a shallow wake. Measurements of the flow field in the vertical central plane and in the horizontal near-bed, mid-depth, and near-surface planes were taken. Then, the mean flow quantities such as the mean velocity, turbulence intensity, and Reynolds stress fields were investigated. In addition, the proper orthogonal decomposition technique was used to reconstruct the velocity fields to investigate the energetic vortical structures. The results showed that the largest recirculation zone in the mean velocity fields occurred in the mid-depth velocity field, while the smallest one occurred near the bed. Also, the fluid was entrained from the sides toward the wake central plane in the three horizontal velocity fields but with different rates. This behavior was attributed to the existence of quasi-streamwise vortices near the boundaries. In addition, patterns of ejection and sweep events near the free surface similar to the features commonly observed near the wall-bounded flows were observed.

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