The low- and high-pressure rate constants of n-propanol decomposition via three routes, with the formation of propene and water (R1), methyl and hydroxyethyl radicals (R2), and ethyl and hydroxymethyl radicals (R3), were determined using experimental and theoretical methods. The experiments were performed in a shock tube behind reflected shock waves at a pressure of ∼ 1.3 atm and temperatures of ∼ 1050 to 1250 K. The process was monitored by recording the absorption time profiles of the shock-heated reaction mixture at a wavelength of 197.0 ± 1.0 nm. The experimental results were interpreted within the framework of a kinetic mechanism. The low-pressure rate constants of reactions (R1)–(R3) were calculated based on the density of states of the n-propanol molecule, which, in turn, was obtained by applying the Laplace transform to the partition function of the internal degrees of freedom determined from the NASA polynomials and the external rotation constants (in cm ^3 mol ^-1 s ^-1) : k_1,0 = 5.09× 10^58T^-11.71 exp(-30,224 K/T) , k_2,0 = 4.70 × 10 ^64T^-12.73 exp(−44,277 K/T), and k_3,0 = 2.15 × 10 ^64T^-12.73 exp(−42,268 K/T). The high-pressure rate constant of reaction (R1) was derived from kinetic modeling of our experimental data (in s ^-1) : k_1,∞ = 9.72 × 10 ^14T^-0.6 exp(−30,193 K/T). The high-pressure rate constants of reactions (R2) and (R3) were calculated as the product of the estimated rate constants of the reverse recombination reactions and the relevant equilibrium constants (in s ^-1) : k_2,∞ = 2.66 × 10 ^19T^-0.77 exp(−44,277 K/T) and k_3,∞ = 3.81 × 10 ^20T^-1.27 exp(−42,268 K/T). The high-pressure rate constants of reactions (R2) and (R3) from the present work compare favorably with the calculation results and estimates given in the literature. An analysis of the present study and published data led to the conclusion that a greatly overestimated high-pressure rate constant of reaction (R3) used in some kinetic mechanisms was probably introduced to compensate for a substantially underestimated low-pressure rate constant of this reaction.
Experiments have been carried out in order to detect where and when chemical reactions occur when a shock wave impacts a decane droplet in air initially at 50 kPa. A detonation-driven shock tube produces a Mach 5.3 shock wave with high repeatability, and a piezoelectric device generates a continuous train of droplets with diameters ranging from 148 to 180 m . Schlieren and filtered direct visualization with high-speed cameras allow the extraction of droplet displacement during the atomization process and time-resolved CH^* emission. Chemical reactions start to appear in the droplet wake but have no influence on the leading edge displacement of the droplet. The reactions then propagate toward the leading edge of the droplet after the total breakup time. This, in turn, leads to the complete combustion of the remaining cloud resulting from the atomization and evaporation processes.
The shock dynamics resulting from high-speed droplet impingement on a rigid surface are investigated employing high-resolution schlieren imaging and numerical simulations based on the five-equation model. A key finding is that, in contrast to the common emphasis on jetting-induced dynamics, the long-time shock morphology is governed not by explosive shocks generated during jetting, but rather by the reflection of the droplet’s own shock wave off the solid wall. The resulting shock structure is found to be robust across a wide range of densities and breakup states, and its evolution is shown to depend primarily on the impact Mach number. Axisymmetric and 3D simulations both capture the wall-reflected envelope with high fidelity, despite shared limitations in modeling post-impact jetting dynamics. The presented results clarify the physical mechanisms shaping post-impingement shock evolution and highlight the modeling trade-offs involved in capturing jet-driven transients. This paper provides a unique experimental and numerical dataset that can be used as a reference for future studies.
Afterburning, which is the secondary combustion of detonation products with ambient oxygen, can substantially increase the energy released in confined TNT explosions. Predicting this phenomenon in partially confined environments is considerably more challenging than under ideal, fully confined conditions, yet it is essential for accurate estimation of internal blast loads. This study evaluates afterburning behavior in partially confined scenarios by correlating numerical simulations with experimental data. Numerical modeling is based on previously conducted experiments, serving as a database to assess the afterburning contribution in Viper::Blast CFD simulations. An engineering model is utilized to account for the combustion of fuel-rich detonation products, where the total energy release and characteristic duration are controlled by two key parameters. A theoretical framework is first introduced to estimate the maximum potential afterburning energy under full confinement for both oxygen-rich and oxygen-deficient conditions. Two scenarios are subsequently analyzed: fully confined and partially confined explosions. For the former, simulations show good agreement with published experimental data when the maximum theoretical energy is applied. For the latter, a comprehensive numerical study identifies the effective magnitude and timing of afterburning that best fits the tests, highlighting the significant influence of venting on energy release. Finally, an additional literature-based case study is simulated to further illustrate the effect of venting. The analysis emphasizes the caution required when extrapolating these parameters to different confinement or venting conditions and underscores the need for further experimental and numerical investigation.
The capacity of analytical models to accurately represent real-world phenomena is critical to the study of jet formation physics. Shaped charge performance can be influenced by the detonation wave geometry as it interacts with the liner, making accurate representation of the wavefront essential when evaluating hemispherical liners. Previous work established an analytic foundation for predicting jet characteristics of plane-wave-initiated, hemispherical-lined charges. Extending this framework, the present study introduces a modified set of analytic equations describing the collapse and jet formation of constant-wall-thickness, hemispherical-lined shaped charges initiated on or off the axis of symmetry. The proposed model is first evaluated against experimental data from two on-axis-initiated charges. Agreement between experiments and continuum-based simulations establishes a basis for further assessment, after which model predictions are also compared with simulations of identical configurations. The model is then examined across a matrix of simulations spanning variations in charge geometry and both on- and off-axis initiation locations. Although further research is warranted to identify more appropriate methods for describing collapse velocity profiles, the analytic framework predicts jet characteristics with sufficient accuracy relative to simulations that neglect liner material strength when a well-characterized profile is used as input. For the copper-lined, LX-14 simulation cases neglecting liner material strength and having an explosive-to-liner mass-per-unit-area ratio less than 17.20, the model yields an average coefficient of determination of 0.91 and an average mean absolute error of ± 0.23 km/s. These matrix results, together with the close agreement obtained for simulations of the two experimental configurations neglecting liner material strength, support the validity of the proposed point-initiation model across the configurations evaluated in this study. Comparisons with the experimental data and additional simulations incorporating liner material strength, however, indicate that further refinement is needed to more fully account for material strength effects beyond those represented by the simple empirical jet-tip-truncation approach. Despite this, the present framework provides an efficient and practical method for predicting jet characteristics of point-initiated, hemispherical-lined shaped charges.
