Hongping Zhang

A Lagrangian method is presented for solving linear perturbations of elastic solids in cylindrical and spherical geometry. The model consists of one-dimensional base equations and linearly perturbed modal component equations, and the elasticity constitutive equations and its linearized form are considered. The component equations based on perturbation expansions are described uniformly under different geometries and perturbation assumptions. In the numerical format of a linearly perturbed system, the radial and transverse numerical fluxes based on the Godunov discretization format use the same Riemann solver to ensure the consistency of the numerical scheme, and the time-step constraint scheme is empirical. Based on this method, this paper investigates the Rayleigh–Taylor instability at the interface of elastic solids in cylindrical and spherical geometries, analyzes the differences between the initial and asymptotic phases of perturbation development, and compares it with the two-dimensional theory. Furthermore, we point out the effects of pseudo-three-dimensional perturbations and finite thickness, which cannot be ignored.

The laser ablation pressure is often estimated by an exponential scaling law, which is determined by integral averaging of 1–2 ns short pulses. Here, we report a direct, continuous measurement of ablation pressure of a 3–10 ns ramp 351-nm laser pulse. Aluminum is deposited on LiF window, ablation pressure is inferred from the particle velocity of interface using the backward integration method, combined with incident ramp shaped laser intensity, and the real-time laser-driven ablation pressure as a function of incident laser power density on an aluminum target is obtained. For the same ablation pressure scale, when intensity is higher than 1TW/cm2, the surface illuminated intensity of laser should be modified with the cosine of incident angle, which agrees well with the modified Manheimer model [Scheiner and Schmitt, Phys. Plasmas 26(2), 024502 (2019)]. On the other hand, the incidence angle has the least effect when the intensity is below 0.1 TW/cm2. In the range of 0.1–1 TW/cm2, a significant loss in ablation pressure is observed, deviating notably from the exponential scaling relationship. This characteristic makes the laser direct drive ramp loading technique unfriendly to elastoplastic and phase transition problems.

Ion evaporation from a conductive meniscus has been of significant interest in the theoretical investigation of electro-hydrodynamics and application exploration across various fields. This study focuses on developing a fluid-fluid methodology for the dynamical simulation of a conductive meniscus undergoing ion evaporation and uncovering the interaction between the plume and meniscus using the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate as a case study. In the fluid-fluid model, we propose a simplified fluid plume model to acquire the charge distribution in free space, and validate it against a particle plume model and a full fluid plume model. The meniscus evolution is described by expanding the leaky dielectric model to account for charge conservation in the liquid as well as self-heating and inhomogeneous physical properties. The arbitrary Lagrangian–Eulerian method is used to track the sharp liquid–vacuum interface. Dynamic simulation with the simplified fluid plume model is more than 150 times faster than that with the full fluid plume model. The electrohydrodynamic process of the meniscus evolving to form a droplet is analyzed, with a detailed discussion on the space charge effect caused by evaporated ions. Results indicate that neglecting the space charge effect during conical meniscus formation leads to a singular meniscus tip. Instead, the reverse electric field induced by the space charge suppresses this singularity, assisting the conical meniscus to produce a jet. Additionally, the high-throughput ion evaporation significantly enlarges the diameter of droplet formed on the conical meniscus due to the reverse electric field of space charge.