Article
Mechanics
Luca Galantucci, Michele Sciacca, Nick G. Parker, Andrew W. Baggaley, Carlo F. Barenghi
Summary: This article discusses the leapfrogging of coaxial vortex rings in ultra-cold atomic gases and quantum fluids. Using the two-dimensional point vortex model and solving the Gross-Pitaevskii equation for a Bose-Einstein condensate, it was found that the dynamics of leapfrogging in narrow channels is richer than in unbounded domains, with new regimes identified. The differences between classical and quantum vortex leapfrogging were also discussed, especially when the quantum healing length and compressibility effects become significant.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
S. Advaith, K. T. Aswathi, Saptarshi Basu
Summary: This paper quantitatively investigates the topology and formation mechanisms of vortex rings under externally modulated parameters, predicting vortex characteristics and validating them through experiments. The study shows that external parameters can be collapsed into a universal variable, providing insights into vortex roll-up characteristics and energy distribution variations.
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS
(2022)
Article
Mechanics
Yunxing Su, Monica M. Wilhelmus, Roberto Zenit
Summary: Vortex rings are crucial for generating thrust underwater. This study investigates the evolution of isolated vortex rings crossing a stable two-layer system and examines how their translation direction relative to gravity affects their behavior. The production of baroclinic vorticity is found to significantly impact the propagation of vortex rings at the density interface. The results highlight the breakdown of symmetry between vortex rings traveling from dense to light fluids and from light to dense fluids, with the maximum penetration depth occurring when the vortex propagates against the density gradient.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Jie Yao, Weiyu Shen, Yue Yang, Fazle Hussain
Summary: The dynamics of two slender Hopf-linked vortex rings were studied at different vortex Reynolds numbers, revealing that at high Re, the vortex rings reconnected to form smaller rings that then broke up into turbulent clouds. The global helicity H was not conserved at very high Re, with twist playing a significant role in helicity dynamics at high Re.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Rigoberto Ortega-Chavez, Lian Gan, Philip H. H. Gaskell
Summary: The controlled discharge of fluid with swirl promotes the breakdown of the leading vortex ring structure, resulting in significant negative azimuthal vorticity generation. The interaction between vortex breakdown and swirl increases the radius of the primary vortex core, decreases the self-induced propagation velocity of the leading ring, and increases vortex stretching along the circular primary vortex core. These effects lead to an increased dimensionless kinetic energy for the primary ring and a decrease in the circulation based formation number, F.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Aerospace
John A. Valdez, Charles E. Tinney
Summary: This study investigates the trade-off between near-field acoustics and thrust of a coaxial, corotating rotor in hover, and proposes the concept of optimal index angle to maximize the thrust. High-speed digital schlieren and particle image velocimetry were used to measure the flowfield, and the interaction of the upper and lower rotor vortices was analyzed.
Article
Mechanics
Manas Ranjan Behera, Anirvan Dasgupta, Sudipto Chakraborty
Summary: The evolution of a vortex ring generated by drop impinging on a liquid pool was studied experimentally, numerically, and analytically. A novel analytical model for a finite vortex core was developed and validated with experimental results. The controlling parameters governing the viscous diffusion-driven evolution of the vortex ring were uncovered. The study provided valuable insights into the formation and viscous diffusion process of the vortex ring through a combination of experimental, numerical, and analytical approaches.
Article
Mechanics
Guillaume de Guyon, Karen Mulleners
Summary: Explored the energy of starting vortex rings and its non-universal value of 0.33, proposed a model based on self-similar vortex sheet roll-up and spiralling shear layer to predict the non-dimensional energy of vortex rings, and validated the model with different velocity profiles of the vortex generator.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mathematics, Applied
Weiwei Ao, Yehui Huang, Yong Liu, Juncheng Wei
Summary: New finite energy traveling wave solutions with small speed are constructed for the three dimensional Gross-Pitaevskii equation, having the shape of 2n + 1 vortex rings. The locations of these rings are described by roots of a sequence of polynomials, which can be regarded as a generalization of the classical Adler-Moser polynomials.
SIAM JOURNAL ON MATHEMATICAL ANALYSIS
(2021)
Article
Mechanics
F. J. Foronda-Trillo, J. Rodriguez-Rodriguez, C. Gutierrez-Montes, C. Martinez-Bazan
Summary: The turbulent breakup of bubbles is a complex phenomenon, and simplified models are essential for understanding the interaction between turbulent eddies and bubbles. Numerical simulations show that slightly larger vortices can efficiently break bubbles, and bubbles migrate to the vortex core when the Weber number is sufficiently large. The interaction between bubbles and vortices destabilizes the vortex ring and leads to an increase in enstrophy and a rapid decrease in kinetic energy.
INTERNATIONAL JOURNAL OF MULTIPHASE FLOW
(2021)
Article
Mechanics
Lei Wang, Li-Hao Feng
Summary: This study investigates the interaction between synthetic jet vortex rings and a water-oil interface in different flow regimes. It is found that the vortex rings undergo three distinct stages of evolution, leading to the generation of secondary vortex rings and hairpin vortices through the interaction with the interface. The complex interaction between the primary vortex ring and hairpin vortices enhances the vortex ring instability, especially in the presence of stratification. Additionally, the analysis of interface deformation and interfacial waves reveals the destabilization effect caused by the radial development of perturbations stemming from the vortex ring instability.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Mechanics
Van Luc Nguyen, Toai Tuyn Phan, Viet Dung Duong, Nam T P Le
Summary: The study simulated the collision of two vortex rings initially arranged in axis-offset and orthogonal configurations to investigate turbulent energy cascade associated with their reconnection. As Reynolds number increases, the energy of formed small vortices raises and their wavenumber range enlarges, approaching a k(-5/3) slope of the Kolmogorov hypotheses at low wavenumbers. The energy spectrum evolves differently for the two collision configurations, with the axis-offset collision showing better turbulent mixing performance.
Article
Chemistry, Multidisciplinary
Thai Dinh, Thomas Cubaud
Summary: This study investigates the influence of interfacial tension on liquid/liquid microflows, with various flow regimes observed through experiments. Analysis of multiphase materials reveals the relationship between interfacial dynamics and fluid properties, providing insights into the evolution of flow patterns with changing interfacial tension.
Article
Mechanics
P. Svancara, M. La Mantia
Summary: This study investigates the propagation of macroscopic vortex rings in superfluid 4He at different conditions using the extremely small kinematic viscosity of the fluid. The results show that the shape and circulation of the rings are related to the traveled distance within a certain range. Additionally, the velocity and circulation of the rings appear to be influenced by a single experimental parameter that combines the liquid temperature with the magnitude and duration of the power pulse.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Engineering, Chemical
Li-Mei Guo, Ming Lu, Zhi Ning
Summary: A mathematical model for the stability of a viscous liquid jet in a coaxial twisting compressible airflow has been developed, considering the effects of twist, compressibility, and gas-liquid velocity difference on the jet stability. The study shows that the jet instability decreases first and then increases with the increase of airflow axial velocity, and the airflow rotation strength has different effects on jet stability under different modes. The results indicate that changing the circumferential velocity of the surrounding airflow when it twists does not facilitate jet breakup.
Article
Mechanics
M. Cheng, J. Lou, T. T. Lim
Article
Mechanics
K. B. Lua, H. Lu, X. H. Zhang, T. T. Lim, K. S. Yeo
Article
Mechanics
J. H. Ng, R. K. Jaiman, T. T. Lim
Article
Mechanics
M. Cheng, J. Lou, T. T. Lim