Article
Physics, Multidisciplinary
Hong-Hao Dai, Miao-Hua Xu, Hong-Yu Guo, Ying-Jun Li, Jie Zhang
Summary: In this study, we investigate the Kelvin-Helmholtz instability of two superposed finite-thickness fluid layers with the magnetic field effect taken into account. Analytical formulas are derived to describe this instability. We find that both the thickness and the magnetic field influence the instability, with the effect of thickness being more pronounced at weak magnetic field intensities.
Article
Physics, Multidisciplinary
Galal M. Moatimid, Mona A. A. Mohamed, Khaled Elagamy
Summary: This study investigates the nonlinear stability of a plane interface between two fluids of Walters B type and its importance in engineering and applied physics. Non-perturbative analysis is employed to study the nonlinear stability and a numerical method is used to confirm the solutions. Several non-dimensional physical numbers and instability benchmarks are revealed in the study.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
Fabiola A. Gerosa, Heloise Meheut, Jeremie Bec
Summary: Through 2D direct numerical simulations, it is found that the presence of singularities in turbulent flows affects the clustering of particles, which is crucial for planetesimal formation.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Mechanics
Adam J. K. Yang, E. W. Tedford, J. Olsthoorn, G. A. Lawrence
Summary: The asymmetric Holmboe instabilities that form on an arrested salt wedge were investigated in the laboratory. The appearance of different regions in the flow is determined by the spatial variation in the thickness of the saline layer, the shear layer thickness, and the offset between the density interface and velocity interface. The growth of the instabilities is initially consistent with linear stability theory, but becomes nonlinear when the Holmboe wave reaches a steepness ratio of 5 - 7%. The Holmboe wavelength increases downstream along the salt wedge due to the increase in shear layer thickness and gradual acceleration of the upper layer fluid. The predicted wave speed and wavelength are consistent with the laboratory measurements.
Article
Mechanics
Sung-Ik Sohn
Summary: The undulatory swimming of a fish-like body was studied using an inviscid vortex shedding model, demonstrating self-propulsion and the formation of anti-rotating vortices. It was found that free swimming is more energy-efficient than motions without recoil and with lateral translation, with recoil motions enhancing swimming efficiency.
Article
Physics, Fluids & Plasmas
Jiao Liu, Zhenhua Chai, Baochang Shi
Summary: In this paper, a coupled diffuse-interface lattice Boltzmann method (DI-LBM) was developed to investigate the transport of a charged particle in the Poiseuille flow. The study showed that the electric field has a significant impact on the particle migration, causing the equilibrium position to either drop or move towards the centerline of the channel, depending on the direction of the applied electric field.
Article
Mechanics
Vikas S. Krishnamurthy, Miles H. Wheeler, Darren G. Crowdy, Adrian Constantin
Summary: A new class of exact solutions to the steady, incompressible Euler equation on the plane is presented in this study, forming a theoretical structure known as a Liouville chain. The solutions consist of a set of stationary point vortices embedded in a background sea of Liouville-type vorticity, with parameters leading to the development of new pure point vortex equilibria. The study demonstrates the existence of hybrid equilibria that can have finite or infinite links in the Liouville chain.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
William Bethune
Summary: This study presents a computational framework for studying fluid discontinuities and provides a numerical method along with validation cases. The framework has been successfully applied to magnetohydrodynamic shocks and shear layers, allowing for investigation into how these phenomena are altered in weakly ionized plasmas.
Article
Multidisciplinary Sciences
Galal M. Moatimid, Marwa H. Zekry, Doaa A. Ibrahim
Summary: This study provides an approach to studying the nonlinear stability of a vertical cylindrical interface between two Oldroyd-B prototypes. It considers the influence of an axial electric field and the effects of heat and mass transfer. The methodology involves solving linear equations of motion and applying appropriate nonlinear boundary conditions. Non-dimensional physical numbers are used, and stability conditions are theoretically achieved and numerically verified. The study also derives a Ginzburg-Landau equation and uses both theoretical and numerical methods to achieve nonlinear stability criteria.
SCIENTIFIC REPORTS
(2023)
Article
Astronomy & Astrophysics
Shao-Xia Chen, Bo Li, Mingzhe Guo, Mijie Shi, Hui Yu
Summary: This study focuses on trapped, transverse fundamental, oblique quasi-kink modes in pressureless setups. The system asymmetry results in a nonmonotonic dependence of the damping rates, and resonant absorption only occurs below a certain threshold. The asymmetry of the system also leads to two qualitatively different regimes for the phase and group diagrams.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
D. J. Yu
Summary: Shear flow can affect the stability of magnetohydrodynamic waves. The dissipative instability, also known as negative energy wave instability, can be induced by flow shear below the threshold of Kelvin-Helmholtz instability. By considering viscosity as a dissipation mechanism, an analytical dispersion relation for slow sausage modes in a straight cylinder with a discontinuous boundary is derived. The growth rate of these modes is found to be related to the axial wavenumber and flow shear for both surface and body modes.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Hirakjyoti Das, Sukanta Deb, Amiya Baruah
Summary: In this study, a new technique was introduced to calculate the optimal values of each particle in the Plummer density model, improving the accuracy of gravitational force calculations. Results showed that the errors in force calculations were lower than those estimated from previous studies and remained stable for various considerations of nearest neighboring particles (N-neigh). The adjusted expression of epsilon(lambda,i) exhibited less dependence on N-neigh in the Plummer sphere, remarkably improving both the accuracy and the stability of the gravitational force calculation.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Haomin Sun, Yan Yang, Quanming Lu, San Lu, Minping Wan, Rongsheng Wang
Summary: Using MHD simulations, this study investigates the physical regimes and the role of turbulence in turbulent reconnection. The results show that externally injected turbulence enhances the reconnection rate by converting magnetic energy to kinetic energy. The presence of turbulence also impacts the magnetic energy conversion and the Kelvin-Helmholtz instability in the reconnection process.
ASTROPHYSICAL JOURNAL
(2022)
Article
Optics
I Tazes, S. Passalidis, E. Kaselouris, I Fitilis, M. Bakarezos, N. A. Papadogiannis, M. Tatarakis, V Dimitriou
Summary: This research focuses on the delivery of optically shaped targets through the interaction of nanosecond laser pulses with high-density gas-jet profiles, and the acceleration of protons in the near-critical density regime using magnetic vortex acceleration (MVA). Geometrical alternatives for delivering laser pulses into the gas target were explored to control the density profile. The efficiency of the proposed shaping method was demonstrated through computational and particle-in-cell simulations.
HIGH POWER LASER SCIENCE AND ENGINEERING
(2022)
Article
Mechanics
J. Bouchgl, S. Aniss
Summary: The effect of horizontal periodic oscillation on the interfacial instability of two immiscible and viscous fluids in porous media is investigated through linear stability analysis, leading to the occurrence of Kelvin-Helmholtz instability and parametric resonance. The results show that an increase in oscillation frequency destabilizes Kelvin-Helmholtz instability and shifts the parameter instability regions towards shorter wavelengths perturbation. Factors such as permeability, porosity, and relative heights of fluid layers also affect the instabilities in the system.
INTERNATIONAL JOURNAL OF APPLIED MECHANICS
(2021)