scholarly journals Effect of time-dependent piston velocity program on vortex ring formation in a piston/cylinder arrangement

2006 ◽  
Vol 18 (3) ◽  
pp. 033601 ◽  
Author(s):  
Michael Shusser ◽  
Moshe Rosenfeld ◽  
John O. Dabiri ◽  
Morteza Gharib
Keyword(s):  
Vortex Ring ◽  
Ring Formation ◽  
Time Dependent ◽  
Piston Velocity ◽  
Piston Cylinder ◽  
Vortex Ring Formation

Vortex Ring Formation in Wall-Bounded Domains

2010 ◽  
Author(s):  
Kelley C. Stewart ◽  
Pavlos P. Vlachos
Keyword(s):  
Vortex Ring ◽  
Propagation Velocity ◽  
Cylindrical Tube ◽  
Ring Formation ◽  
Vortex Rings ◽  
Frequency Noise ◽  
Bounded Domains ◽  
Piston Cylinder ◽  
Vortex Ring Formation ◽  
Wall Interaction

Vortex ring formation and propagation have been studied extensively in quiescent semi-infinite volumes. However, very little is known about the dynamics of vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the effect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube parallel to the piston cylinder arrangement which defined the confined downstream domain. Two different domains were studied with diameters twice and four times the size of the piston cylinder. A semi-infinite unbounded volume with no downstream cylinder was also investigated for comparison. The piston stroke-to-diameter ratio (L/D0) for the studied vortex rings was varied between 0.75 and 3 with corresponding Reynolds numbers, based on circulation, of approximately 500 to 8,000. Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV). The TRDPIV data were processed using an in-house developed cross-correlation PIV algorithm and post processed using Proper Orthogonal Decomposition to remove high frequency noise. The propagation velocity and vorticity were investigated and vortex identification was used to track the changing size, location, and circulation of the vortices. The combination of these parameters was used to investigate the effects of wall interaction on vortex ring formation and propagation.

A Unified Energy Feature of Vortex Rings for Identifying the Pinch-Off Mechanism

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Yang Xiang ◽  
Hong Liu ◽  
Suyang Qin
Keyword(s):  
Vortex Ring ◽  
Critical Value ◽  
Ring Formation ◽  
Experimental Results ◽  
Vortex Rings ◽  
Piston Cylinder ◽  
Dimensionless Energy ◽  
Vortex Ring Formation ◽  
Energy Feature ◽  
Off Time

Owing to the limiting effect of energy, vortex rings cannot grow indefinitely and thus pinch off. In this paper, experiments on the vortex rings generated using a piston-cylinder apparatus are conducted so as to investigate the pinch-off mechanisms and identify the limiting effect of energy. Both theoretical and experimental results show that the generated vortex rings share a unified energy feature, regardless of whether they are pinched-off or not. Moreover, the unified energy feature is quantitatively described by a dimensionless energy number γ, defined as γ=(E/I2Γωmax) and exhibiting a critical value γring = 0.14 ± 0.01 for the generated vortex rings. This unified energy feature reflects the limiting effect of energy and specifies the target of vortex ring formation. Furthermore, based on the tendency of γ during vortex ring formation, criteria for determining the two timescales, i.e., pinch-off time and separation time, which correspond to the onset and end of pinch-off process, respectively, are suggested.

scholarly journals A model for vortex ring formation in a starting buoyant plume

2000 ◽  
Vol 416 ◽  
pp. 173-185 ◽  
Author(s):  
MICHAEL SHUSSER ◽  
MORTEZA GHARIB
Keyword(s):  
Vortex Ring ◽  
Time Scale ◽  
Ring Formation ◽  
Vortex Rings ◽  
Uniform Density ◽  
Dimensionless Time ◽  
Buoyant Plume ◽  
Piston Cylinder ◽  
Vortex Ring Formation ◽  
Formation Number

Vortex ring formation in a starting axisymmetric buoyant plume is considered. A model describing the process is proposed and a physical explanation based on the Kelvin–Benjamin variational principle for steady vortex rings is provided. It is shown that Lundgren et al.'s (1992) time scale, the ratio of the velocity of a buoyant plume after it has travelled one diameter to its diameter, is equivalent to the time scale (formation time) proposed by Gharib et al. (1998) for uniform-density vortex rings generated with a piston/cylinder arrangement. It is also shown that, similarly to piston-generated vortex rings (Gharib et al. 1998), the buoyant vortex ring pinches off from the plume when the latter can no longer provide the energy required for steady vortex ring existence. The dimensionless time of the pinch-off (the formation number) can be reasonably well predicted by assuming that at pinch-of the vortex ring propagation velocity exceeds the plume velocity. The predictions of the model are compared with available experimental results.

scholarly journals Investigation of vortex ring formation with account of generator piston motion

2017 ◽  
Vol 208 ◽  
pp. 012045 ◽  
Author(s):  
I V Khramtsov ◽  
VV Palchikovskiy ◽  
A A Siner ◽  
Yu V Bersenev
Keyword(s):  
Vortex Ring ◽  
Ring Formation ◽  
Piston Motion ◽  
Vortex Ring Formation

scholarly journals Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first

2015 ◽  
Vol 219 (3) ◽  
pp. 392-403 ◽  
Author(s):  
Ian K. Bartol ◽  
Paul S. Krueger ◽  
Rachel A. Jastrebsky ◽  
Sheila Williams ◽  
Joseph T. Thompson
Keyword(s):  
Vortex Ring ◽  
Ring Formation ◽  
Flow Imaging ◽  
Vortex Ring Formation
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