Publications by authors named "Xisheng Luo"

This paper performed a comprehensive study of the thermal nonequilibrium effects of CO/Ar mixtures with various degrees of N2 additions and probed the N2 relaxation behaviors via the CO rovibrational thermometry. The rovibrational temperature time histories of shock-heated CO/N2/Ar mixtures were measured via a laser-absorption technique, and the corresponding vibrational relaxation data were summarized at 1890-3490 K. The measured results were compared with predictions from the Schwartz-Slawsky-Herzfeld (SSH) formula and the state-to-state (StS) approach (treating CO and N2 as pseudo-species).

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A shock-tube facility capable of generating a planar shock with the Mach number higher than 3.0 is developed for studying Richtmyer-Meshkov instability induced by a strong shock wave (referred to as strong-shock RMI). Shock enhancement is realized through the convergence of shock within a channel with the profile determined by using shock dynamics theory.

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Experimental and numerical studies were performed on the vibrational energy relaxation in shock-heated CO/N2/Ar mixtures. A laser absorption technique was applied to the time-dependent rovibrational temperature time-history measurements. The vibrational relaxation data of reflected-shock-heated CO were summarized at 1720-3230 K.

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The time-dependent rotational and vibrational temperatures were measured to study the shock-heated thermal nonequilibrium behaviors of CO with Ar, He, and H2 as collision partners. Three interference-free transition lines in the fundamental vibrational band of CO were applied to the fast, in situ, and state-specific measurements. Vibrational relaxation times of CO were summarized over a temperature range of 1110-2820 K behind reflected shocks.

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The incipient process of water vapor condensation around an insoluble nanoscale particle is studied by a molecular dynamics method, and the emphasis is placed on the effects of particle surface curvature and wettability. With a high initial saturation, two different linear nucleation stages are observed. At the first stage, clusters are formed by the water molecules adsorbed on the surface such that the nucleation rate is significantly affected by both water molecule flux toward the surface and adsorption probability.

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Various methods have been exploited to replicate nacre features into artificial structural materials with impressive structural and mechanical similarity. However, it is still very challenging to produce nacre-mimetics in three-dimensional bulk form, especially for further scale-up. Herein, we demonstrate that large-sized, three-dimensional bulk artificial nacre with comprehensive mimicry of the hierarchical structures and the toughening mechanisms of natural nacre can be facilely fabricated via a bottom-up assembly process based on laminating pre-fabricated two-dimensional nacre-mimetic films.

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We report the first measurements of the perturbation amplitude in the converging Richtmyer-Meshkov instability in a semiannular shock tube. At early stages, the amplitude growth agrees well with the impulsive model considering the geometrical convergence effect. A quick decrease of the growth rate at late time, even to be negative, before the reshock is observed for the first time.

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The Richtmyer-Meshkov (RM) instability of a nominally flat interface (N_{2}/SF_{6}) subjected to a rippled shock, as the counterpart of a corrugated interface interacting with a planar shock, is studied experimentally in a vertical shock tube using both schlieren photography and fog visualization diagnostics. The nonplanar incident shock wave is produced by a planar shock diffracting around a rigid cylinder, and the flat interface is created by a membraneless technique. Three different distances η (the ratio of spacing from cylinder to interface over cylinder diameter) are considered.

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Low-density compressible materials enable various applications but are often hindered by structure-derived fatigue failure, weak elasticity with slow recovery speed and large energy dissipation. Here we demonstrate a carbon material with microstructure-derived super-elasticity and high fatigue resistance achieved by designing a hierarchical lamellar architecture composed of thousands of microscale arches that serve as elastic units. The obtained monolithic carbon material can rebound a steel ball in spring-like fashion with fast recovery speed (∼580 mm s), and demonstrates complete recovery and small energy dissipation (∼0.

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The Richtmyer-Meshkov instability (RMI) of single-mode air-SF(6) interfaces is studied numerically and the emphasis is placed on the effect of the principal curvature on the early evolution of the shocked interface. Two three-dimensional initial interfaces with opposite (3D-) and identical (3D+) principal curvatures and a traditional two-dimensional interface (2D) are considered. The weighted essentially nonoscillatory scheme and the Level-Set method combined with the real ghost fluid method are adopted.

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The Richmyer-Meshkov instability of a three-dimensional (3D) SF_{6}-air single-mode interface with a minimum-surface feature is investigated experimentally. The interface produced by the soap film technique is subjected to a planar shock and the evolution of the shocked interface is captured by time-resolved schlieren photography. Different from the light-heavy single-mode case, a phase inversion occurs in the shock-interface interaction and a bubblelike structure is observed behind the shocked interface, which may be ascribed to the difference in pressure perturbation at different planes.

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A shock tube facility for generating a cylindrical converging shock wave is developed in this work. Based on the shock dynamics theory, a specific wall profile is designed for the test section of the shock tube to transfer a planar shock into a cylindrical one. The shock front in the converging part obtained from experiment presents a perfect circular shape, which proves the feasibility and reliability of the method.

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A kinetic model is developed to describe the heterogeneous condensation of vapor on an insoluble spherical particle. This new model considers two mechanisms of cluster growth: direct addition of water molecules from the vapor and surface diffusion of adsorbed water molecules on the particle. The effect of line tension is also included in the model.

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