Near wall vortex structures in an inclined cylinder wake

1998 ◽  
Author(s):  
Takaaki Shizawa ◽  
Shinji Honami ◽  
Kotaro Miyauchi
Keyword(s):  
Vortex Structures ◽  
Cylinder Wake ◽  
Near Wall

scholarly journals The Formation of Vortex Structures in a Screen Cylinder Wake

2017 ◽  
Vol 234 ◽  
pp. 012015 ◽  
Author(s):  
Azlin Mohd Azmi ◽  
Yucen Lu ◽  
Tongming Zhou
Keyword(s):  
Vortex Structures ◽  
Cylinder Wake

Study of Buoyancy Induced Suppression of Cylinder Wake Instability Using Schlieren-Interferometry

2007 ◽  
Author(s):  
S. K. Singh ◽  
P. K. Panigrahi
Keyword(s):  
Vortex Shedding ◽  
Heat Input ◽  
Richardson Number ◽  
Shear Layers ◽  
Vortex Structures ◽  
Schlieren Image ◽  
Cylinder Wake ◽  
Mean Flow ◽  
Experimental Conditions ◽  
Thermal Buoyancy

The control of horizontal square cylinder wake using thermal buoyancy has been experimentally investigated at low Reynolds numbers. The cylinder with an aspect ratio of 60 is mounted in a vertical test cell. The cylinder is electrically heated such that the buoyancy aids to the inertia of the mean flow. The operating parameters i.e. Reynolds number (87–118) and Richardson number (0.065–0.171) are varied to examine the flow behaviour over a range of experimental conditions. Laser schlieren-interferometry has been used for visualization and analysis of flow structures. The complete vortex shedding sequence has been recorded using a highspeed camera. The suppression of vortex shedding by heat input has been demonstrated by schlieren image visualization, time traces of light intensity, corresponding power spectra and Strouhal number. The study provides new experimental information on processes and mechanisms involved in the heat-induced changes of the vortex structures under the influence of buoyancy. The formation length of the vortex structures increases with increase in Richardson number i.e. heating level. The sequence of instantaneous schlieren images show that shape of vortex structures becomes slender at a sufficiently high Richardson number and the vortices from opposite shear layers rub with each other without increasing the circulation level and the two shear layers combine to form a single plume. The plume becomes steady at critical value of heat input leading to suppression of vortex shedding. The corresponding spectra evolve from having a clear peak at the vortex shedding frequency to broadband spectra when vortex shedding is suppressed.

Longitudinal vortex structures in a cylinder wake

1994 ◽  
Vol 6 (9) ◽  
pp. 2883-2885 ◽  
Author(s):  
J. Wu ◽  
J. Sheridan ◽  
M. C. Welsh ◽  
K. Hourigan ◽  
M. Thompson
Keyword(s):  
Vortex Structures ◽  
Longitudinal Vortex ◽  
Cylinder Wake

Hairpin vortex structures in a supersonic, separated, longitudinal cylinder wake

2020 ◽  
Vol 32 (4) ◽  
pp. 046103 ◽  
Author(s):  
Branden M. Kirchner ◽  
Gregory S. Elliott ◽  
J. Craig Dutton
Keyword(s):  
Vortex Structures ◽  
Hairpin Vortex ◽  
Cylinder Wake

Initial growth of a disturbance in a boundary layer influenced by a circular cylinder wake

2013 ◽  
Vol 718 ◽  
pp. 116-130 ◽  
Author(s):  
Guosheng He ◽  
Jinjun Wang ◽  
Chong Pan
Keyword(s):  
Boundary Layer ◽  
Circular Cylinder ◽  
Growth Stage ◽  
Plate Boundary ◽  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Wall Region ◽  
Initial Growth ◽  
Cylinder Wake ◽  
Near Wall

AbstractThe initial growth of a disturbance induced by a near-wall circular cylinder in a flat-plate boundary layer is experimentally investigated using both particle image velocimetry and hydrogen bubble visualization techniques. The secondary spanwise vortices appear in the near-wall region as a direct response to the outside passing wake vortices, consistent with previous studies on similar models (Pan et al., J. Fluid Mech., vol. 603, 2008, pp. 367–389; Mandal & Dey, J. Fluid Mech., vol. 684, 2011, pp. 60–84). The streamwise variation of the total disturbance energy within the boundary layer shows a two-stage growth, which characterizes the initial transition process: the first exponential growth stage, followed by a region with slower growth rate. It is revealed that these two stages of growth are related to the formation and the destabilization of the secondary vortex in the near-wall region. The technique of dynamic mode decomposition is used to decompose the total disturbance into temporally orthogonalized modes, and it shows that the first growth stage largely results from the increased disturbance at the same frequency as that of the wake vortex shedding, while the second growth stage comprises the disturbance growth in a number of frequencies, especially the lower ones.

Experimental study on dominant vortex structures in near-wall region of turbulent boundary layer based on tomographic particle image velocimetry

2019 ◽  
Vol 874 ◽  
pp. 426-454 ◽  
Author(s):  
Chengyue Wang ◽  
Qi Gao ◽  
Jinjun Wang ◽  
Biao Wang ◽  
Chong Pan
Keyword(s):  
Particle Image Velocimetry ◽  
Particle Image ◽  
Three Dimensional ◽  
Vortex Structures ◽  
Wall Region ◽  
Tomographic Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Inclination Angles ◽  
The Difference ◽  
Near Wall

Vortex structures are very popular research objects in turbulent boundary layers (TBLs) because of their prime importance in turbulence modelling. This work performs a tomographic particle image velocimetry measurement on the near-wall region ($y<0.1\unicode[STIX]{x1D6FF}$) of TBLs at three Reynolds numbers $Re_{\unicode[STIX]{x1D70F}}=1238$, 2286 and 3081. The main attention is paid to the wall-normal evolution of the vortex geometries and topologies. The vortex is identified with swirl strength ($\unicode[STIX]{x1D706}_{ci}$), and its orientation is recognized by using the real eigenvector of the velocity gradient tensor. The vortex inclination angles in the streamwise–wall-normal plane and in the streamwise–spanwise plane as functions of wall-normal positions are investigated, which provide useful information to speculate on the three-dimensional shape of the vortex tubes in a TBL. The difference between the orientations of vorticity and swirl is discussed and their inherent relationship is revealed based on the governing equation of vorticity. Linear stochastic estimation (LSE) is further deployed to directly extract three-dimensional vortex models. The LSE velocity fields for ejection events happening at different wall-normal positions shed light on the evolution of the topologies for the vortices dominating ejection events. LSE based on a centred prograde spanwise vortex provides a typical packet model, which indicates that the population density of the packets in a TBL is large enough to leave footprints in conditionally averaged flow fields. This work should help to settle the severe debate on the existence of packet structures and also lays some foundation for the TBL model theory.

Numerical Investigation of Vortex Ring Ground Plane Interactions

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
K. Bourne ◽  
S. Wahono ◽  
A. Ooi
Keyword(s):  
Vortex Ring ◽  
Ground Plane ◽  
Vortex Structures ◽  
Vortex Rings ◽  
Angle Of Incidence ◽  
Flow Conditions ◽  
Single Vortex ◽  
Wall Flow ◽  
The Impact ◽  
Near Wall

The interaction between multiple laminar thin vortex rings and solid surfaces was studied numerically so as to investigate flow patterns associated with near-wall flow structures. In this study, the vortex–wall interaction was used to investigate the tendency of the flow toward recirculatory behavior and to assess the near-wall flow conditions. The numerical model shows very good agreement with previous studies of single vortex rings for the case of orthogonal impact (angle of incidence, θ = 0 deg) and oblique impact (θ = 20 deg). The study was conducted at Reynolds numbers 585 and 1170, based on the vortex ring radius and convection velocity. The case of two vortex rings was also investigated, with particular focus on the interaction of vortex structures postimpact. Compared to the impact of a single ring with the wall, the interaction between two vortex rings and a solid surface resulted in a more highly energized boundary layer at the wall and merging of vortex structures. The azimuthal variation in the vortical structures yielded flow conditions at the wall likely to promote agitation of ground based particles.

scholarly journals Coherent Streamwise Vortex Structure of a Three-Dimensional Wall Jet

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 35
Author(s):  
Lhendup Namgyal ◽  
Joseph W. Hall
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Three Dimensional ◽  
Streamwise Vortex ◽  
Relative Strength ◽  
Vortex Structures ◽  
Wall Jet ◽  
Streamwise Vorticity ◽  
Lateral Velocity ◽  
Near Wall

The dynamics of the coherent structures in a turbulent three-dimensional wall jet with an exit Reynolds number of 250,000 were investigated using the Snapshot Proper Orthogonal Decomposition (POD). A low-dimensional reconstruction using the first 10 POD modes indicates that the turbulent flow is dominated by streamwise vortex structures that grow in size and relative strength, and that are often accompanied by strong lateral sweeps of fluid across the wall. This causes an increase in the bulging and distortions of streamwise velocity contours as the flow evolves downstream. The instantaneous streamwise vorticity computed from the reconstructed instantaneous velocities has a high level of vorticity associated with these outer streamwise vortex structures, but often has a persistent pair of counter-rotating regions located close to the wall on either side of the jet centerline. A model of the coherent structures in the wall jet is presented. In this model, streamwise vortex structures are produced in the near-field by the breakdown of vortex rings formed at the jet outlet. Separate structures are associated with the near-wall streamwise vorticity. As the flow evolves downstream, the inner near-wall structures tilt outward, while the outer streamwise structures amalgamate to form larger streamwise asymmetric structures. In all cases, these streamwise vortex structures tend to cause large lateral velocity sweeps in the intermediate and far-field regions of the three-dimensional wall jet. Further, these structures meander laterally across the jet, causing a strongly intermittent jet flow.

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