Article
Mechanics
Peder A. Tyvand, Jonas Kristiansen Noland
Summary: Transient nonlinear convection in a finite Prandtl number fluid heated uniformly from below is studied in a simple square cavity with normal-mode compatible boundary conditions. The study considers two independent initial conditions for thermal and flow amplitude, with two ways of initiation: soft start with small initial amplitude, or kick-started transient convection with larger initial amplitudes. The complex transient flow transitions into a steady convection due to the symmetry and antisymmetry properties of the temperature perturbation and flow field.
Article
Astronomy & Astrophysics
Shahar Hod
Summary: Recent research has shown that spinning black holes can support acoustic 'clouds', with analytical techniques being used to prove a no-short hair theorem for composed acoustic black hole scalar-clouds configurations. It has been demonstrated that the effective lengths of the stationary bound-state corotating acoustic scalar clouds are bounded by specific inequalities involving the horizon radius of the black hole and the radius of the corotating null circular geodesic.
Article
Astronomy & Astrophysics
Ben Kain
Summary: In this study, we derived and examined the pulsation equations for spherically symmetric boson stars, considering self-interacting boson stars with varying values of the self-coupling constant. By numerically evolving boson stars and Fourier transforming dynamic solutions, we independently computed radial oscillation frequencies and verified the results obtained from the pulsation equations, finding excellent agreement between the two methods.
Article
Physics, Fluids & Plasmas
Olga Shapoval, Remi Lehe, Maxence Thevenet, Edoardo Zoni, Yinjian Zhao, Jean-Luc Vay
Summary: By using a CFL-free analytical spectral solver and mitigating additional numerical instabilities that arise at large timestep, this study shows the potential to overcome traditional limitations on the timestep, thereby realizing the full potential of the boosted-frame technique over a much wider range of parameters.
Article
Physics, Multidisciplinary
V. Valenzuela-Villaseca, L. G. Suttle, F. Suzuki-Vidal, J. W. D. Halliday, S. Merlini, D. R. Russell, E. R. Tubman, J. D. Hare, J. P. Chittenden, M. E. Koepke, E. G. Blackman, S. V. Lebedev
Summary: We conducted pulsed-power driven plasma experiments to simulate astrophysical disks and jets. Angular momentum is injected by ablation flows from a wire array Z pinch, rather than boundary forces. An upward rotating plasma jet is launched by axial pressure gradients and confined by ram, thermal, and magnetic pressure. The jet has a subsonic rotation with a maximum velocity of 23 +/- 3 km/s, following a quasi-Keplerian profile with a positive Rayleigh discriminant kappa 2 proportional to r-2.8 +/- 0.8 rad2/s2. The plasma completes 0.5-2 full rotations within the experimental time frame (approximately 150 ns).
PHYSICAL REVIEW LETTERS
(2023)
Article
Geosciences, Multidisciplinary
Yue Zhou, Jih-Hong Shue, Hiroshi Hasegawa, Jianyong Lu, Ming Wang, Hanxiao Zhang
Summary: Using data from the ARTEMIS spacecraft near the Moon, this study statistically analyzes the properties of Kelvin-Helmholtz (KH) waves and the thickness of initial velocity shear layers on the magnetopause at lunar distance. The results show that at lunar distance, the KH waves have a larger wavelength and thickness compared to those at near-Earth magnetopause. The ratio of wavelength to thickness at lunar distance exceeds the range predicted by the linear theory, indicating that the observed KH waves are not consistent with the fastest growing mode according to linear theory. This study provides insights into the generation and development of KH waves at lunar distance.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Mechanics
Claudiu Patrascu, Corneliu Balan
Summary: This paper examines the stability of planar liquid sheets surrounded by another immiscible liquid and finds that in the limit of dominant viscous stresses, the dispersion relation yields negative growth rates for instability across all wavenumbers. The study also shows that planar liquids in liquid systems are stable regardless of viscosity mismatch under certain conditions.
Article
Physics, Mathematical
Davit Karagulyan, Jing Zhou
Summary: This paper presents the existence of an infinite measure set of exponentially escaping orbits for a resonant Fermi accelerator. The resonant accelerator is realized as a square billiard with a periodically oscillating platform. Normal forms are used to describe the energy change in a period, and techniques from the theory of hyperbolic systems with singularities are employed to demonstrate the exponential drift given by these normal forms on a divided time-energy phase.
COMMUNICATIONS IN MATHEMATICAL PHYSICS
(2023)
Article
Mechanics
Haifei Wang, Guo Chen
Summary: This study investigates the stability of an anisotropic rotor partially filled with viscous incompressible fluid, proposing a new analytical prediction model. Results show that dimensionless damping and stiffness have significant effects on stability, with a single stable region existing at low values. By comparing isotropic and anisotropic conditions, the correctness of the proposed analytical method is verified.
Article
Mechanics
Souradip Chattopadhyay
Summary: The study examines the stability of a thin viscous Newtonian fluid with broken time-reversal-symmetry draining down a slippery inclined plane. The odd viscosity coefficient introduces new characteristics in fluid flow and modifies the pressure gradient. The presence of odd viscosity impacts the flow system parameters and influences the stability of the fluid, with larger odd viscosity leading to higher critical Reynolds number and higher slip length promoting instability.
Article
Mechanics
Zaijie Liu, Teng Zhou, Yuhan Lu, Chao Yan
Summary: This paper presents a method to control the first-mode oblique breakdown in a Mach 2.0 supersonic boundary layer using micro-groove coating strips. The study shows that the micro-groove coating strip can significantly suppress the oblique breakdown and the stability effect increases with certain parameters. The stabilization mechanism varies depending on the location of the micro-groove coating strip, with the early and late nonlinear development regions having a more effective stabilization effect compared to the strip itself.
Article
Physics, Fluids & Plasmas
Mohit Singh, Neha Gawande, Y. S. Mayya, Rochish Thaokar
Summary: The experimental and numerical results demonstrate that a charged drop undergoes asymmetric, subcritical Rayleigh fission in an AC quadrupole trap, with a jet ejected upwards opposite to gravity. Gravity-induced shape oscillations, combined with out-of-phase center-of-mass oscillations, act as triggers for the subcritical instability and lead to the upward fission of the drop. This finding suggests that nanodrop generation in electrospray devices generally occurs through similar asymmetric, subcritical Rayleigh fission events.
Article
Physics, Multidisciplinary
C. Nore, L. Cappanera, J-L Guermond, T. Weier, W. Herreman
Summary: By combining theoretical arguments and numerical simulations, we have shown that metal pad roll instability can occur in a centimeter-scale setup with reasonable values of magnetic field and electrical current, using metal pairs that are liquid at room temperature. We have investigated two fluid pairs: gallium with mercury (immiscible pair) or gallium with GaInSn eutectic alloy (miscible pair).
PHYSICAL REVIEW LETTERS
(2021)
Article
Mechanics
Luo Xie, Hai-bao Hu, Feng Ren, Xiao Huang, Peng Du, Jun Wen
Summary: The EVCVPF model is developed to analyze the electrohydrodynamic instability of an electrified leaky-dielectric viscous jet. It resolves the discrepancy between non-zero irrotational viscous and electric tangent stresses by introducing a pressure correction to compensate for neglected viscous dissipation. The model has been validated for charged jets with low and moderate viscosities, showing good agreement with the exact normal-mode solution and improving adequacy when studying the electrohydrodynamic instability.
Article
Mechanics
Ranislav M. Bulatovic
Summary: Merkin's theorem states that the equilibrium stability of a potential system with the same natural frequencies is destroyed after the addition of arbitrarily small linear non-conservative positional forces. A new generalization of this theorem has been developed in this study, which does not require commutativity of potential and circulatory matrices, providing an advantage over previous works.
Article
Engineering, Civil
Jian Xue, Weiwei Zhang, Jing Wu, Chao Wang, Hongwei Ma
Summary: This study integrates a plate-type local resonator with varying free boundaries within a plate to convert the initial low-order global vibration modes into localized vibration modes. A novel semi-analytical method is proposed to analyze the free vibration of the plate with thickness and displacement discontinuities. The results show that by applying free boundary conditions, the low-order localized vibration frequencies can be significantly reduced without affecting the low-order global frequencies.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Merve Tunay
Summary: In recent years, there has been an increasing number of studies on the mechanical properties of sandwich structures manufactured with the Fused Deposition Modeling (FDM) method. However, there is still a lack of experimental data on the mechanical characteristics of FDM-manufactured sandwich structures under different thermal aging durations. In this experiment, the energy absorption capabilities of sandwich structures with different core geometries were investigated under various thermal aging durations. The results showed that the core topology significantly influenced the energy absorption abilities of the sandwich structures.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Zi-qin Jiang, Zi-yao Niu, Ai-Lin Zhang, Xue-chun Liu
Summary: This paper proposes a crosssection corrugated plate steel special-shaped column (CCSC) that improves the bearing capacity and overall stability of structural columns by using smaller material input. Through theoretical analysis and numerical simulation, the overall stability of the CCSC under axial compression is analyzed. The design method and suggestions for the stability of CCSC are put forward. Compared with conventional square steel tube columns, the CCSC has obvious advantages in overall stability and steel consumption.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Yong Zhang, Yangang Chen, Jixiang Li, Jiacheng Wu, Liang Qian, Yuanqiang Tan, Kunyuan Li, Guoyao Zeng
Summary: A hybrid TPMS method was proposed to develop a new TPMS structure, and the mechanical properties of different TPMS structures were studied experimentally and numerically. Results showed that the hybrid TPMS structure had higher energy absorption and lower load-carrying capacity fluctuation. Further investigations revealed that the topological shape and material distribution had significant influence on mechanical properties, and the hybrid additive TPMS structure exhibited significant crashworthiness advantage in in-plane crushing condition.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Tongfei Sun, Ye Liu, Kaoshan Dai, Alfredo Camara, Yujie Lu, Lijie Wang
Summary: This paper presents a series of experimental and numerical studies on the performance of a novel double-stage coupling damper (DSCD). The effects of damper configuration, friction-yield ratio (Rfy), and loading protocol on the hysteresis performance of the DSCD are investigated. The test results demonstrate that the arrangement of ribs in the DSCD increases its energy dissipation capacity. Numerical analysis reveals that the length of the friction mechanism and the clearance between the yield segment and the restraining system affect the energy dissipation and stability of the damper.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Jeonghwa Lee, Young Jong Kang
Summary: This study investigates the local buckling behavior and strength of I-shape structural sections by considering flange-web interactions through three-dimensional finite element analysis. The study provides a more reasonable estimation of local buckling strength by considering the ratio of flange-web slenderness and height-to-width ratio, and presents design equations for flange local and web-bend buckling coefficients.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Yizhe Chen, Wenfeng Xiang, Qingsong Zhang, Hui Wang, Lin Hua
Summary: This study investigates the surface modification of a nickel plate to improve the bonding strength with carbon fiber-reinforced plastics (CFRP). The results show that different surface modification methods, including sandblasting, coupling agent treatment, and compound coupling agent treatment, significantly enhance the bonding strength of CFRP/Ni joints. The research provides insights into improving the connection between nickel and CFRP, as well as other heterogeneous materials.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Agha Intizar Mehdi, Fengping Zhang, Moon-Young Kim
Summary: A spatial stability theory of mono-symmetric thin-walled steel beams pre-stressed by spatially inclined cables is derived and its validity is demonstrated through numerical examples. The effects of initial tension, deviator numbers, inclined cable profiles, and bonded/un-bonded conditions on lateral-torsional buckling of the pre-stressed beams are investigated, with a specific emphasis on the effects of increasing initial tension.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Teng Ma, Jinxiang Wang, Liangtao Liu, Heng Li, Kui Tang, Yangchen Gu, Yifan Zhang
Summary: The structural response of water-back plate under the combined action of shock wave and bubble loads at water depths of 1-300 m was numerically investigated using an arbitrary Lagrange-Euler method. The accuracy of the numerical model was validated by comparing with experimental and theoretical results. The influences of water depth and length-to-diameter ratio of the charge on the combined damage effect were analyzed. The results show that as water depth increases, the plastic deformation energy of the water-back plate decreases, and the permanent deformation mode changes from convex to concave. When the charge has a large length-to-diameter ratio, the plastic deformation energy of the radial plate is higher than that of the axial plate, and the difference decreases with increasing water depth. Increasing the length-to-diameter ratio enhances the combined damage effect in the radial direction in deep-water environments.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Qiu-Yun Li, Ben Young
Summary: This paper investigates the flexural performance of CFS zed section members bent about the neutral axis parallel to the flanges through experimental and numerical analysis. The results show that the current direct strength method generally provides conservative predictions for the flexural strength of unstiffened zed section members, but slightly unconservative design for edge-stiffened zed section beams. The nominal flexural strengths of zed section members with edge stiffeners were found to be underestimated by 17% to 21% on average. Modified DSM formulae are recommended for the design of CFS zed section beams.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Weinan Gao, Bo Song, Xueyan Chen, Guochang Lin, Huifeng Tan
Summary: This paper presents a precise method for predicting deformation in large-scale inflatable structures, utilizing finite element modeling and laser scanning technique. The study shows a good agreement between the predictive model and non-contact measurement results.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Fei Gao, Zongyi Wang, Rui Zhu, Zhenming Chen, Quanxi Ye, Yaqi Duan, Yunlong Jia, Qin Zhang
Summary: This research investigates the mechanical properties of high-strength ring groove rivet assemblies and the load resistances of riveted T-stubs. Experimental tests reveal that Grade 10.9 rivets have higher yield strength and strain, and lower ultimate strain, making them suitable for high-strength ring groove rivet connections. Increasing the rivet diameter benefits the T-stubs, while increasing the flange thickness is not always advantageous. The Eurocode 3 method is not suitable for T-stubs connected through ring groove rivets, while the Demonceau method is conservative.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Shangchun Jiang, Liangfeng Sun, Haifei Zhan, Zhuoqun Zheng, Xijian Peng, Chaofeng Lue
Summary: This study investigates the bending behavior of two-dimensional nanomaterials, diamane and its analogous structure TBGIB, through atomistic simulations. It reveals that diamane experiences structural failure under bending, while TBGIB bends elastically before undergoing structural failure. The study provides valuable insights for the application of these materials in flexible electronics.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Qiang Zhang, Jianian Wen, Qiang Han, Hanqing Zhuge, Yulong Zhou
Summary: In this study, the mechanical properties of Q690 steel H-section columns under bi-directional cyclic loads are investigated, considering the time-varying characteristics of corrosion. A refined finite element (FE) model is built to analyze the degradation of mechanical property and failure mechanisms of steel columns with different design parameters during the whole life-cycle. The study proposes a quantitative calculation method for the ultimate resistance and damage index of steel columns, taking into account the ageing effects. The findings emphasize the importance of considering the ageing effects of steel columns in seismic design.
THIN-WALLED STRUCTURES
(2024)
Article
Engineering, Civil
Yuda Hu, Qi Zhou, Tao Yang
Summary: The magneto-thermo-elastic coupled free vibration of functionally graded materials cylindrical shell is investigated in this study. The vibration equation in multi-physical field is established and solved using the Hamilton principle and the multi-scale method. The numerical results show that the natural frequency is influenced by various factors such as volume fraction index, initial amplitude, temperature, and magnetic induction intensity.
THIN-WALLED STRUCTURES
(2024)