A study of the counter rotating vortex rings interacting with the primary vortex ring in shock tube generated flows

2013 ◽  
Vol 45 (2) ◽  
pp. 025506 ◽  
Author(s):  
T Murugan ◽  
S De ◽  
C L Dora ◽  
D Das ◽  
P Prem Kumar
Keyword(s):  
Shock Tube ◽  
Vortex Ring ◽  
Vortex Rings ◽  
Primary Vortex

On the structure of vortex rings from inclined nozzles

2011 ◽  
Vol 686 ◽  
pp. 451-483 ◽  
Author(s):  
Trung Bao Le ◽  
Iman Borazjani ◽  
Seokkoo Kang ◽  
Fotis Sotiropoulos
Keyword(s):  
Vortex Ring ◽  
Vortex Sheet ◽  
Vortex Rings ◽  
Cylinder Wall ◽  
Primary Vortex ◽  
Vortical Structures ◽  
Ambient Flow ◽  
Piston Cylinder ◽  
Axial Stretching ◽  
Vortex Tubes

AbstractWe carry out numerical simulations to investigate the vortex dynamics of laminar, impulsively driven flows through inclined nozzles in a piston–cylinder apparatus. Our simulations are motivated by the need to provide a complete description of the intricate vortical structures and governing mechanisms emerging in such flows as documented in the experiments of Webster & Longmire (Phys. Fluids, vol. 10, 1998, pp. 400–416) and Troolin & Longmire (Exp. Fluids, vol. 48, 2010, pp. 409–420). We show that the flow is dominated by the interaction of two main vortical structures: the primary inclined vortex ring at the nozzle exit and the secondary stopping ring that arises due to the entrainment of the flow into the cylinder when the piston stops moving. These two structures are connected together with pairs of vortex tubes, which evolve from the continuous vortex sheet initially connecting the primary vortex ring with the interior cylinder wall. In the exterior of the nozzle the key mechanism responsible for the breakup of the vortical structure is the interaction of the stronger inclined primary ring with the weaker stopping ring near the longest lip of the nozzle. In the interior of the nozzle the dynamics is governed by the axial stretching of the secondary ring and the ultimate impingement of this ring on the cylinder wall. Our simulations also clarify the kinematics of the azimuthal flow along the core of the primary vortex ring documented in the experiments by Lim (Phys. Fluids, vol. 10, 1998, pp. 1666–1671). We show that the azimuthal flow is characterized by a pair of two spiral saddle foci at the long and short lips of the nozzle through which ambient flow enters and exits the primary vortex core.

Interaction of a laminar vortex ring with a thin permeable screen

2012 ◽  
Vol 707 ◽  
pp. 260-286 ◽  
Author(s):  
Christian Naaktgeboren ◽  
Paul S. Krueger ◽  
José L. Lage
Keyword(s):  
Kinetic Energy ◽  
Vortex Ring ◽  
Large Scale ◽  
Symmetry Axis ◽  
Wire Mesh ◽  
Nonlinear Dependence ◽  
Vortex Rings ◽  
Solid Boundary ◽  
Primary Vortex ◽  
Special Cases

AbstractThe canonical case of a vortex ring interacting with a solid surface orthogonal to its symmetry axis exhibits a variety of intricate behaviours, including stretching of the primary vortex ring and generation of secondary vorticity, which illustrate key features of vortex interactions with boundaries. Replacing the solid boundary with a permeable screen allows for new behaviour by relaxing the no-through-flow condition, and can provide a useful analogue for the interaction of large-scale vortices with permeable structures or closely spaced obstructions. The present investigation considers the interaction of experimentally generated vortex rings with a thin permeable screen. The vortex rings were generated using a piston-in-cylinder mechanism using piston stroke-to-diameter ratios ($L/ D$) of 1.0 and 3.0 (nominal) with jet Reynolds numbers ($R{e}_{j} $) of 3000 and 6000 (nominal). Planar laser-induced fluorescence and digital particle image velocimetry (DPIV) were used to study the interaction with wire-mesh screens having surface open-area ratios ($\phi $) in the range 0.44–0.79. Solid surfaces ($\phi = 0$) and free vortex rings ($\phi = 1$) were also included as special cases. Measurement of the vortex trajectories showed expansion of the vortex ring diameter as it approached the boundary and generation of secondary vorticity similar to the case of a solid boundary, but the primary vortex diameter then began to contract towards the symmetry axis as the flow permeated the screen and reorganized into a transmitted vortex downstream. The trajectories were highly dependent on $\phi $, with little change in the incident ring trajectory for $\phi = 0. 79$. Measurement of the hydrodynamic impulse and kinetic energy using DPIV showed that the change between the average upstream and downstream values of these quantities also depended primarily on $\phi $, with a slight decrease in the relative change as $L/ D$ and/or ${\mathit{Re}}_{j} $ were increased. The kinetic energy dissipation ($ \mrm{\Delta} E$) was much more sensitive to $\phi $, with a strongly nonlinear dependence, while the decrease in impulse ($ \mrm{\Delta} I$) was nearly linear in $\phi $. A simple model is proposed to relate $ \mrm{\Delta} E$ and $ \mrm{\Delta} I$ in terms of bulk flow parameters. The model incorporates the decrease in flow velocity during the interaction due to the drag force exerted by the screen on the flow.

scholarly journals Lattice Boltzmann Study of a Vortex Ring Impacting Spheroidal Particles

2014 ◽  
Vol 6 (4) ◽  
pp. 461-477 ◽  
Author(s):  
Chunlong Yu ◽  
Haibo Huang ◽  
Xiyun Lu
Keyword(s):  
Vortex Ring ◽  
Lattice Boltzmann ◽  
Prolate Spheroid ◽  
Vortex Rings ◽  
Secondary Vortex ◽  
Short Axis ◽  
Primary Vortex ◽  
Important Research Topic ◽  
Multiple Relaxation Time ◽  
Boltzmann Method

AbstractInteraction of vortex rings with solid is an important research topic of hydrodynamic. In this study, a multiple-relaxation time (MRT) lattice Boltzmann method (LBM) is used to investigate the flow of a vortex ring impacting spheroidal particles. The MRT-LBM is validated through the cases of vortex ring impacting a flat wall. The vortex evolution due to particle size, the aspect ratio of a prolate particle, as well as Reynolds (Re) number are discussed in detail. When the vortex ring impacting a stationary sphere, the primary and secondary vortex rings wrap around each other, which is different from the situation of the vortex ring impacting a plate. For the vortex ring impacting with a prolate spheroid, the secondary vortex ring stretches mainly along the long axis of the ellipsoid particle. However, it is found that after the vortex wrapping stage, the primary vortex recovers along the short axis of the particle faster than that in the long axis, i.e., the primary vortex ring stretches mainly along the short axis of the particle. That has never been address in the literature.

Investigations Of Pressure Pulsations In A Model Of Draft Tube Of Hydraulic Turbine Caused By Vortex Rings

2016 ◽  
Vol 11 (4) ◽  
pp. 25-32
Author(s):  
Sergey Skripkin ◽  
Mikhail Tsoy ◽  
Sergey Shtork ◽  
Pavel Kuibin
Keyword(s):  
Vortex Ring ◽  
High Speed ◽  
Draft Tube ◽  
Hydraulic Turbine ◽  
Vortex Rings ◽  
Experimental Investigations ◽  
Visualization Technique ◽  
Vortex Rope ◽  
Hydro Turbine ◽  
Hydraulic Turbines

Current work is devoted to experimental investigations of behavior of precessing vortex rope in a draft tube model of hydraulic turbine. We used combination of stationary and freely rotating swirlers as a hydro turbine model. Such construction provides velocity distribution on the draft tube inlet close to distribution in natural hydraulic turbines operated at non-optimal conditions. The phenomenon of precessing vortex rope reconnection with further formation of vortex ring was founded in this experimental research using high-speed visualization technique. Synchronization of highspeed visualization and pressure measurements allowed us to relate pressure shock on the draft tube wall with vortex ring moving along wall.

Laminar to Turbulent Buoyant Vortex Ring Regime in Terms of Reynolds Number, Bond Number, and Weber Number

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Xueying Yan ◽  
Rupp Carriveau ◽  
David S. K. Ting
Keyword(s):  
Reynolds Number ◽  
Vortex Ring ◽  
Weber Number ◽  
High Speed ◽  
Reynolds Numbers ◽  
Bond Number ◽  
Vortex Rings ◽  
Transition Regime ◽  
Turbulent Vortex ◽  
Buoyant Vortex Rings

When buoyant vortex rings form, azimuthal disturbances occur on their surface. When the magnitude of the disturbance is sufficiently high, the ring will become turbulent. This paper establishes conditions for categorization of a buoyant vortex ring as laminar, transitional, or turbulent. The transition regime of enclosed-air buoyant vortex rings rising in still water was examined experimentally via two high-speed cameras. Sequences of the recorded pictures were analyzed using matlab. Key observations were summarized as follows: for Reynolds number lower than 14,000, Bond number below 30, and Weber number below 50, the vortex ring could not be produced. A transition regime was observed for Reynolds numbers between 40,000 and 70,000, Bond numbers between 120 and 280, and Weber number between 400 and 800. Below this range, only laminar vortex rings were observed, and above, only turbulent vortex rings.

Ionic Wind Application to Vortex Ring Generator and its Transportation Efficiency

2019 ◽  
Author(s):  
Kengo Fukunaga ◽  
Masayoshi Satake ◽  
Noboru Maeda ◽  
Kazushi Shikata ◽  
Tomohisa Ezaka
Keyword(s):  
Kinetic Energy ◽  
Mechanical System ◽  
Electric Power ◽  
Vortex Ring ◽  
Energy Conversion Efficiency ◽  
Target Distance ◽  
Vortex Rings ◽  
Experimental Measurements ◽  
Ionic Wind ◽  
External Turbulence

Abstract In this study, ionic wind generated in corona discharge is focused for producing an air flow without having mechanical actuators. First, the kinetic energy conversion efficiency to ionic wind from electric power is experimentally estimated to be 0.32%. Then, it is confirmed that intermittent blows of ionic wind enable to produce vortex rings without using mechanical system. We adopt novel sub-chamber structure to avoid the concentration of the substance in a vortex ring low, so that the substance concentration transported to the target distance of 200 mm increases by 9%. As an application, the efficiency for moisture transportation is evaluated through experimental measurements. As a result, it is shown that the substance (moisture) can be transported at an efficiency of about 85% to target distance of 200 mm under conditions where the influence of external turbulence is small.

Circulation Generation and Vortex Ring Formation by Conic Nozzles

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Moshe Rosenfeld ◽  
Kakani Katija ◽  
John O. Dabiri
Keyword(s):  
Vortex Ring ◽  
Vortex Generator ◽  
Ring Formation ◽  
Vortex Rings ◽  
Two Dimensional ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Vortex Ring Formation ◽  
Exit Nozzle ◽  
Two Dimensional Flow

Vortex rings are one of the fundamental flow structures in nature. In this paper, the generation of circulation and vortex rings by a vortex generator with a static converging conic nozzle exit is studied numerically. Conic nozzles can manipulate circulation and other flow invariants by accelerating the flow, increasing the Reynolds number, and by establishing a two-dimensional flow at the exit. The increase in the circulation efflux is accompanied by an increase in the vortex circulation. A novel normalization method is suggested to differentiate between two contributions to the circulation generation: a one-dimensional slug-type flow contribution and an inherently two-dimensional flow contribution. The one-dimensional contribution to the circulation increases with the square of the centerline exit velocity, while the two-dimensional contribution increases linearly with the decrease in the exit diameter. The two-dimensional flow contribution to the circulation production is not limited to the impulsive initiation of the flow only (as in straight tube vortex generators), but it persists during the entire ejection. The two-dimensional contribution can reach as much as 44% of the total circulation (in the case of an orifice). The present study offers evidences on the importance of the vortex generator geometry, and in particular, the exit configuration on the emerging flow, circulation generation, and vortex ring formation. It is shown that both total and vortex ring circulations can be controlled to some extent by the shape of the exit nozzle.

Sign in / Sign up

Export Citation Format

Share Document