Detonation of a three-dimensional reactive non-isotropic molecular crystal is modeled using molecular dynamics simulations. The detonation process is initiated by an impulse, followed by the creation of a stable fast reactive shock wave. The terminal shock velocity is independent of the initiation conditions. Further analysis shows supersonic propagation decoupled from the dynamics of the decomposed material left behind the shock front. The dependence of the shock velocity on crystal nonlinear compressibility resembles solitary behavior. These properties categorize the phenomena as a weak detonation. The dependence of the detonation wave on microscopic potential parameters was investigated. An increase in detonation velocity with the reaction exothermicity reaching a saturation value is observed. In all other respects the model crystal exhibits typical properties of a molecular crystal.
Videos of the molecular dynamics simulations of a colliding hard disk reactive medium. A simple event-driven algorithm is used to simulate these colliding hard disks allowing for the study of detonations at the microscopic level. This video was submitted as party of the Gallery of Fluid Motion for the American Physical Society 63rd Annual DFD Meeting.
Self-sustained detonation waves in flake aluminum dust/air mixtures have been studied in a tube of diameter 199 mm and length 32.4 m. A pressure sensor array of 32 sensors mounted around certain circumferences of the tube was used to measure the shape of the detonation front in the circumferential direction and pressure histories of the detonation wave. A two-head spin detonation wave front was observed for the aluminum dust/air mixtures, and the cellular structure resulting from the spinning movement of the triple point was analyzed. The variations in velocity and overpressure of the detonati…
The study investigates detonations with multiple quasi-steady velocities that have been observed in the past in systems with multi-peaked thermicity, using Fickett's detonation analogue. A steady state analysis of the travelling wave predicts multiple states, however, all but the one with the highest velocity develop a singularity after the sonic point. Simulations show singularities are associated with a shock wave which overtakes all sonic points, establishing a detonation travelling at the highest of the predicted velocities. Under a certain parameter range, the steady-state detonation can …
A numerical study is carried out on the droplet-laden two-phase rotating detonation wave (RDW) of kerosene/oxygen-enriched air at normal temperature. Two types of combustors without and with the inlet mixing section (IMS) are constructed to illustrate the effect of IMS on the combustion characteristics of two-phase RDW. The important role of the preheating zone in the IMS after the back-propagation shock on the droplet evaporation is analyzed. The parameter sensitivity of RDW propagation stability to the average droplet diameter d0 is further discussed. Results show that the droplets mainly ev…
Detonation propagation in a compressible medium wherein the energy release has been made spatially inhomogeneous is examined via numerical simulation. The inhomogeneity is introduced via step functions in the reaction progress variable, with the local value of energy release correspondingly increased so as to maintain the same average energy density in the medium, and thus a constant Chapman Jouguet (CJ) detonation velocity. A one-step Arrhenius rate governs the rate of energy release in the reactive zones. The resulting dynamics of a detonation propagating in such systems with one-dimensional…
State Key Laboratory of High-Temperature Gas Dynamics (LHD), Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所）；Department of Mechanical Engineering, City University of Hong Kong（香港城市大学机械工程系）；School of Engineering Sciences, University of Chinese Academy of Sciences（中国科学院大学工程科学学院）
Liquid-fueled Oblique Detonation Stabilized by a Transverse Jet
Institute of Mechanics, Chinese Academy of Sciences（中国科学院力学研究所）；City University of Hong Kong（香港城市大学）；University of Chinese Academy of Sciences（中国科学院大学）
The turbulent structure of an irregular detonation is studied through very high resolution numerical simulations of 600 points per half reaction length. The aim is to explore the nature of the transverse waves during the collision and reflection processes of the triple point with the channel walls. Consequently the formation and consumption mechanism of unreacted gas pockets is studied. Results show that as the triple point collides with the wall, the transverse shock interacts with the unreacted pocket. After reflection of the triple point off the wall, the transverse wave interacts with the …
Space-time adaptive ADER-DG finite element method with LST-DG predictor and a posteriori sub-cell ADER-WENO finite-volume limiting for multidimensional detonation waves simulation
In this work, oblique detonation of n-heptane/air mixture in high-speed wedge flows is simulated by solving the reactive Euler equations with a two-dimensional (2D) configuration. This is a first attempt to model complicated hydrocarbon fuel ODWs with a detailed chemistry (44 species and 112 reactions). Effects of freestream equivalence ratios and velocities are considered, and the abrupt and smooth transition from oblique shock to detonation are predicted. Ignition limit, ODW characteristics, and predictability of the transition mode are discussed. Firstly, homogeneous constant-volume ignitio…
Detonation propagation in the limit of highly spatially discretized energy sources is investigated. The model of this problem begins with a medium consisting of a calorically perfect gas with a prescribed energy release per unit mass. The energy release is collected into sheet-like sources that are now embedded in an inert gas that fills the spaces between them. The release of energy in the first sheet results in a planar blast wave that propagates to the next source, which is triggered after a prescribed delay, generating a new blast, and so forth. The resulting wave dynamics as the front pas…
We show experimentally and numerically that when a weak shock interacts with a finger flame in a narrow channel, an extremely efficient mechanism for deflagration to detonation transition occurs. This is demonstrated in a 19-mm-thick channel in hydrogen-air mixtures at pressures below 0.2 atm and weak shocks of Mach numbers 1.5 to 2. The mechanism relies primarily on the straining of the flame shape into an elongated alligator flame maintained by the anchoring mechanism of Gamezo in a bifurcated lambda shock due to boundary layers. The mechanism can increase the flame surface area by more than…
Weakly-compressible particle-based discretization methods, utilized for the solution of the subsonic Navier-Stokes equation, are gaining increasing popularity in the fluid dynamics community. One of the most popular among these methods is the weakly-compressible smoothed particle hydrodynamics (WCSPH). Since the dynamics of a single numerical particle is determined by fluid dynamic transport equations, the particle per definition should represent a homogeneous fluid element. However, it can be easily argued that a single particle behaves only pseudo-Lagrangian as it is affected by volume parti…
We investigate by Molecular-Dynamics simulations the fast mobility - the rattling amplitude of the particles temporarily trapped by the cage of the neighbors - in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable We investigate by Molecular-Dynamics simulations the fast mobility - the rattling amplitude of the particles temporarily trapped by the cage of the neighbors - in mi…
Classical molecular-dynamics simulations (CMDS) have been conducted to investigate one of the main mechanism responsible for absorption of radiation by matter namely stimulated inverse bremsstrahlung. CMDS of two components plasmas (electrons and ions) for a large range of electron densities, electron temperatures, for ionization $Z=1$, were carried out with 2 million particles using the code LAMMPS. A parameterized model (with 6 adjustable constants), which encompasses most theoretical models proposed in the past to quantify heating rate by stimulated inverse bremsstrahlung, serves as a refer…
