Classical Physics
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Showing new listings for Tuesday, 26 November 2024
- [1] arXiv:2411.15507 [pdf, html, other]
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Title: Acoustic forces near elastic substrateJournal-ref: 10.1063/5.0233891 Appl. Phys. Lett. 125, 212203 (2024)Subjects: Classical Physics (physics.class-ph)
In this work, we study the acoustic forces acting on particles due to sound scattering at the interface with an elastic substrate. Utilizing the Green's function formalism, we predict that excitation of leaking Rayleigh wave results in strong modification of the acoustic pressure force acting on a monopole scatterer and changes the equilibrium position of particles above the substrate surface. We also showed that the presence of a substrate changes the configuration of the acoustical binding of two particles due to multiple rescattering of acoustic wave from the interface. The reported results propose the method of acoustic manipulation via surface waves excitation and demonstrate the effect from elastic media in acoustical trapping of microobjects.
- [2] arXiv:2411.15588 [pdf, html, other]
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Title: Decay of amplitude of a harmonic oscillator with weak nonlinear dampingComments: It is likely that there will be some refinement in the next version, but the basic ideas are hereSubjects: Classical Physics (physics.class-ph)
We demonstrate how to derive approximate expressions for the amplitude decay of a weakly damped harmonic oscillator in case of a damping force with constant magnitude (sliding friction) and in case of a damping force quadratic in velocity (air resistance), without solving the associated equations of motion. This is achieved using a basic understanding of the undamped harmonic oscillator and the connection between the damping force's power and the energy dissipation rate. Our approach is based on adapting the trick of adding the energy dissipation rates corresponding to two specific pairs of initial conditions, which was recently used to derive the exponential decay of the amplitude in case of viscous damping, to these two types of damping. We obtain two first-order differential equations from which we get the time-dependent amplitudes corresponding to both damping forces. By comparing our approximate solutions with the exact solutions in the case of sliding friction and with the approximate solutions given by a another well-known method in the case of air resistance, we find that our solutions describe well the dynamics of the oscillator in the regime of weak damping with these two forces. The physical concepts and mathematical techniques we employ are well-known to first-year undergraduates.
New submissions (showing 2 of 2 entries)
- [3] arXiv:2411.15266 (cross-list from astro-ph.IM) [pdf, html, other]
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Title: Continuous Design and Reprogramming of Totimorphic Structures for Space ApplicationsSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Disordered Systems and Neural Networks (cond-mat.dis-nn); Materials Science (cond-mat.mtrl-sci); Robotics (cs.RO); Classical Physics (physics.class-ph)
Recently, a class of mechanical lattices with reconfigurable, zero-stiffness structures has been proposed, called Totimorphic structures. In this work, we introduce a computational framework that allows continuous reprogramming of a Totimorphic lattice's effective properties, such as mechanical and optical properties, via continuous geometric changes alone. Our approach is differentiable and guarantees valid Totimorphic lattice configurations throughout the optimisation process, thus providing not only specific configurations with desired properties but also trajectories through configuration space connecting them. It enables re-programmable structures where actuators are controlled via automatic differentiation on an objective-dependent cost function, altering the lattice structure at all times to achieve a given objective - which is interchangeable to achieve different functionalities. Our main interest lies in deep space applications where harsh, extreme, and resource-constrained environments demand solutions that offer flexibility, resource efficiency, and autonomy. We illustrate our framework through two proofs of concept: a re-programmable metamaterial as well as a space telescope mirror with adjustable focal length, both made from Totimorphic structures. The introduced framework is easily adjustable to a variety of Totimorphic designs and objectives, providing a light-weight model for endowing physical prototypes of Totimorphic structures with autonomous self-configuration and self-repair capabilities.
Cross submissions (showing 1 of 1 entries)
- [4] arXiv:2305.08884 (replaced) [pdf, html, other]
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Title: A coordinate-free guide to the mechanics of thin shellsSubjects: Classical Physics (physics.class-ph)
In this tutorial, we provide a coordinate-free derivation of the system of equations that govern equilibrium of a thin shell that can undergo shear. This system involves tensorial fields representing the internal force and couple per unit length that adjacent parts of the shell exchange at their common boundary. By an appropriate decomposition of those quantities, we obtain a representation of the internal power in terms of time derivatives of suitable strain measures. Subsequently, we propose constitutive equations that employ these strain measures as independent variables. After specializing the theory to the case of unshearable shells, we linearize the resulting equations. As an application, we study the free vibrations of a pressurized spherical shell, showcasing the advantages of a coordinate-free perspective, which simplifies both the deduction and the solution of the final governing equations.
- [5] arXiv:2410.07221 (replaced) [pdf, html, other]
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Title: Measurement, self-similarity, and TNT equivalence of blasts from exploding wiresSubjects: Classical Physics (physics.class-ph)
Reduced-scale experiments offer a controlled and safe environment for studying the effects of blasts on structures. Traditionally, these experiments rely on the detonation of solid or gaseous explosive mixtures, with only limited understanding of alternative explosive sources. This paper presents a detailed investigation of the blasts produced by exploding aluminum wires for generating shock waves of controlled energy levels. We meticulously design the experiments to ensure a precise quantification of the underlying uncertainties and conduct comprehensive parametric studies. We draw practical relationships of the blast intensity with respect to the stand-off distance and the stored energy levels. The analysis demonstrates self-similarity of blasts with respect to the conventional concept of the scaled distance, a desirable degree of sphericity of the generated shock waves, and high repeatability. Finally, we quantify the equivalence of the reduced-scale blasts from exploding wires with high explosives, including TNT. The present experimental setup and study demonstrate the high degree of robustness and effectiveness of exploding aluminum wires as a tool for controlled blast generation and reduced-scale structural testing.