Detonation Shock Research Articles

Investigation of the Effect of Nozzle on Underwater Detonation Shock Wave and Bubble Pulsation

The subject of a gas jet generated by underwater detonation is an important issue in the field of underwater propulsion. The experimental system of underwater detonation is established, which utilizes a high-speed camera to record the morphological changes in bubbles and various pressure sensors to measure the flow field pressure. The effect of nozzles and the pressure of the flow field are analyzed thoroughly. The comparison of the bubble and field pressure shows that the shrinking nozzle increases the peak pressure of the transmitted shock wave generated by underwater detonation compared with that of the straight nozzle. Simultaneously, the water–air mixing phenomenon caused by the gas jet is enhanced. Under the influence of the reflected shock wave and the converging angle of the nozzle, the pulsation process of the bubble is inhibited enormously, which results in the bubble energy being substantially below that of the straight nozzle. The bubble pulsation period is 24.2 ms when the shrinking nozzle is installed, and the pressure of the bubble pulsation is quite small, only 9.8 kPa. On the contrary, the expansion angle increases the velocity of the gas jet, suppressing the water–gas mixing phenomenon while enhancing the bubble pulsation process. The bubble pulsation period is 33.0 ms when the expanding nozzle is equipped, which is larger than the 31.2 ms of the straight nozzle and the bubble pulsation pressure is higher, at 26.1 kPa. Although the bubble energy is increased when the expanding nozzle is installed, thus generating a higher pulsation pressure, the peak pressure and direction of the shock wave are changed in the water.

A Color Mapping Automatic Tuning Framework for Complex Simulation Datasets

Real-world simulations of physical effects generate complex data with extremely uneven numerical distributions and a large amount of background noise. Linear color mapping method to convert these data to color make it difficult to obtain visual results with clear physical features. A color mapping framework based on automatic tuning of color control points is proposed, including information-based removal of background data, distribution-based position tuning of color control points, and luminance-based color recognition enhancement. Three real-world simulation data, including detonation shock wave, electromagnetic environment, and high-power microwave, are used for the experimental tests in this paper. The results show the effectiveness of proposed framework, which can obtain visual results with high-quality detailed features, and the color recognition can be improved by an order of magnitude.

A large scale parallel fluid‐structure interaction computing platform for simulating structural responses to a detonation shock

AbstractDue to the intrinsic nature of multi‐physics, it is prohibitively complex to design and implement a simulation software platform for study of structural responses to a detonation shock. In this article, a partitioned fluid‐structure interaction computing platform is designed for parallel simulating structural responses to a detonation shock. The detonation and wave propagation are modeled in an open‐source multi‐component solver based on OpenFOAM and blastFoam, and the structural responses are simulated through the finite element library deal.II. To capture the interaction dynamics between the fluid and the structure, both solvers are adapted to preCICE. For improving the parallel performance of the computing platform, the inter‐solver data is exchanged by peer‐to‐peer communications and the intermediate server in conventional multi‐physics software is eliminated. Furthermore, the coupled solver with detonation support has been deployed on a computing cluster after considering the distributed data storage and load‐balancing between solvers. The 3D numerical result of structural responses to a detonation shock is presented and analyzed. On 256 processor cores, the speedup ratio of the simulations for a detonation shock reach 178.0 with 5.1 million of mesh cells and the parallel efficiency achieve 69.5%. The results demonstrate good potential of massively parallel simulations. Overall, a general‐purpose fluid‐structure interaction software platform with detonation support is proposed by integrating open source codes. And this work has important practical significance for engineering application in fields of construction blasting, mining, and so forth.

Effect of Pressure of Supercritical CO2 on Perfusion Explosive with Foamed SF‐3 Propellant

AbstractIn this paper, an SF‐3 double‐base propellant was treated by a supercritical carbon dioxide foaming process. Effects of the pressure of supercritical carbon dioxide on the morphology, energy level, and ingredients of the foamed SF‐3 double‐base propellant and the detonation performance of a perfusion explosive with the foamed SF‐3 double‐base propellant were studied. Results show that, with the increase of the pressure, the number of pores in the foamed SF‐3 double‐base propellant gradually increased, and some of the pores were connected to form a small amount of cracks. In the foaming process, the pressure had a small effect on the energy of foamed SF‐3, and the formation of dense pores increased the volume of the sample. The dense pores acted as “hotspots” during the detonation process of the perfusion explosive, allowing the explosive to have better detonation performance, as compared with the perfusion explosive with unfoamed SF‐3 which could not detonate effectively. When the pressure of supercritical CO2 was 8 MPa, the perfusion explosive with foamed SF‐3 had a shock wave energy of 1.06 kJ g−1 and a detonation velocity of 6521 m s−1. When the pressure was 11 MPa, the detonation velocity and shock wave energy of the perfusion explosive were 2.9 % and 6.6 % respectively higher than those under the pressure of 8 MPa. Therefore, with the increase of pressure, the detonation velocity and the shock wave energy of the perfusion explosive with foamed SF‐3 were increased, proving that increasing the pressure can effectively improve the detonation performance of perfusion explosives with foamed SF‐3.

Differences of chamber pressure variations during stage separation between flight and detonation-shock-tube-based ground tests

Interstage separation is a key link in the flight process of a solid rocket; however, the ground test often cannot cover the environmental conditions of the flight state during interstage separation. Therefore, it is necessary to master the difference between flight and ground tests during this process for the ground test results to reflect the flight environment effectively. With the new detonation-shock-tube-based ground test technology as the research background, combined with a theoretical model and numerical simulation, this paper studies the similarity law of pressure variation in the chamber and the difference of the effect of initial pressure and density conditions between flight and ground tests. In addition, it illustrates the requirement for equivalent-simulating stage separation through the detonation shock tube.

Overdriven detonation

Shock pressure of overdriven detonation is above the CJ pressure. We use here our reactive flow model TDRR (=Temperature Dependent Reaction Rate) to calculate examples of overdriven detonation, including details of the reaction zone. The explosive is PBX-9502, and the detonation shock pressure for different examples is below and above the intersection pressure of the reactant and products Hugoniot curves. We find that: 1) below that intersection, as well as above it, the reaction zone is on the corresponding Rayleigh line, like for a CJ detonation; 2) below the intersection, pressure decreases along the reaction zone, as for a CJ detonation, but above the intersection, pressure increases along the reaction zone; 3) for a shock pressure above the intersection point, the reaction zone is continuous, smooth, and without any peculiarities.

A Constitutive Modeling and Experimental Effect of Shock Wave on the Microstructural Sub-strengthening of Granular Copper

Micro-sized copper powder (99.95%; O≤0.3) has been shock-processed with explosives of high detonation velocities of the order of 7.5km/s to observe the structural and microstructural sub-strengthening. Axisymmetric shock-consolidation technique has been used to obtain conglomerates of granular Cu. The technique involves the cylindrical compaction system wherein the explosive-charge is in direct proximity with the powder whereas the other uses indirect shock pressure with die-plunger geometry. Numeric simulations have been performed on with Eulerian code dynamics. The simulated results show a good agreement with the experimental observation of detonation parameters like detonation velocity, pressure, particle velocity and shock pressure in the reactive media. A pin contactor method has been utilized to calculate the detonation pressure experimentally. Wide angled x-ray diffraction studies reveal that the crystalline structure (FCC) of the shocked specimen matches with the un-shocked specimen. Field emissive scanning electron microscopic examination of the compacted specimens show a good sub-structural strengthening and complement the theoretical considerations. Laser diffraction based particle size analyzer also points towards the reduced particle size of the shock-processed specimen under high detonation velocities. Micro-hardness tests conducted under variable loads of 0.1kg, 0.05kg and 0.025kg force with diamond indenter optical micrographs indicate a high order of micro-hardness of the order of 159Hv. Nitrogen pycnometry used for the density measurement of the compacts shows that a compacted density of the order of 99.3% theoretical mean density has been achieved.

Characterization of the Detonation Pressure of a PETN Based PBX with the Optical Active Method

AbstractDetonation metrology is essential for the development of energetic materials, to characterize existing explosives, and to characterize materials behavior under high pressures. The optical active method (OAM), based on PMMA optical fibers (250 μm diameter) and their radiation transmission loss when shocked, was used to characterize the detonation wave (DW) and shock wave (SW) in inert barriers and applied to measure the detonation pressure in condensed explosives. The detonation velocity and detonation pressure of a PBX based on PETN (86 % PETN, 14 % Sylgard), known as Seismoplast were measured. The OAM with protected optical probes (POP) was used to determine the mean detonation velocity (7337 m s−1), whereas the OAM with bare optical probes (BOP) was used to measure the induced shock velocities generated by Seismoplast on different thicknesses of PMMA (1–9 mm), aluminum and copper (1–7 mm). Based on the shock velocities at the interfaces between the explosive and the inert barriers, the CJ pressure of Seismoplast was determined as 21.2 GPa.

An improved Kirkwood–Bethe model for calculating near-field shockwave propagation of underwater explosions

To calculate the near-field shockwave propagation of underwater explosions for different explosives quickly and accurately, an improved calculation model, based on the Kirkwood–Bethe theory, is proposed. Based on the detonation theory and shock jump conditions, the model establishes initial equilibrium conditions and an initial shockwave-front state of the explosion bubble interface. By incorporating a second-order Mach-precision bubble dynamics equation, the model determines the physical parameters and enthalpy change functions at the initial expanding stage in real time. By solving the isentropic flow of the enthalpy change function G at varying delay times, a functional relation was established between the enthalpy change function and the pressure at arbitrary flow points and times. The model obtained the near-field shockwave-front peak-pressure spatial distributions of underwater explosions and the pressure decay time constants at arbitrary flow points. The results indicated that the proposed method can quickly and accurately determine the near-field shockwave propagation of underwater explosions for different explosives, with satisfactory agreement with experimental data. The proposed method relates the explosive detonation, explosion bubble expansion, and shockwave propagation, thus connecting the explosive parameters with the shockwave front state parameters.

An engineering application of Prosperetti and Lezzi equation to solve underwater explosion bubbles

The dynamic behaviors of underwater explosion bubbles differ for different explosives. The explosive characteristic parameters will result in a greater impact on the motion characteristics of the bubbles. Based on the bubble dynamics equation established by Prosperetti and Lezzi [“Bubble dynamics in a compressible liquid. Part 1. First-order theory,” J. Fluid Mech. 168, 457âĂŞ-478 (1986); “Bubble dynamics in a compressible liquid. Part 2. Second-order theory,” J. Fluid Mech. 185, 289âĂŞ-321 (1987)], we proposed an initial condition and an equation of state (EOS) form applicable for calculating the underwater explosion bubble dynamics of different explosives. With the assumption of instantaneous detonation and initial shock wave formation at the gas–liquid boundary, we calculated the initial state of the bubble boundary and established the initial condition for calculating explosion bubbles. Using the Jones–Wilkins–Lee EOS for different explosives, we constructed an isentropic EOS with a polytropic exponent that varied with density. We calculated and analyzed the differences in the initial expansions and the subsequent oscillations of underwater explosion bubbles with different explosives as well as the effects of different explosive parameters on the explosion bubble dynamics. This study showed that the proposed initial condition and the EOS form with a polytropic exponent that varied with density yielded good calculation accuracy and achieve close association of the underwater explosion bubbles with the properties of the explosive detonation and the characteristics of the detonation products. In addition, the explosion bubbles differed in the initial expansion, where the bubbles produced by explosives with higher densities and greater detonation velocities expanded more rapidly.

Innovative Potential of Gas Detonation

Introduction. Explosive technologies are widely used in the extraction industries, in mechanical engineering for welding, hardening, etc. However, the use of solid explosives is limited, above all, by safety requirements. Therefore, the use of a safer and more convenient source of energy, gas detonation, is attracting much attention. Pressures, temperatures, and velocities in detonation waves or shock waves in gases close to them in terms of intensity, as well as the pulse nature of the influence of these factors determine a high potential of their technical and technological use. Problem Statement. In many technical systems, deflagration modes of burning prevail. However, a more thermodynamically advantageous method of combustion and conversion of chemical energy of fuel into useful work is the detonation mode of combustion. This ensures the feasibility of development, research and wider implementation of various technologies and devices using controlled gas detonation. Purpose. Systematization and analysis of the main trends in the development and design of detonation gas technologies and devices in Ukraine and throughout the world. Materials and Methods. Systematization and analysis of scholarly research publications and patents on the practical application of gas detonation in various sectors of the economy. Results. The tendencies of practical use of gas detonation in different branches of industry have been revealed and analyzed. Priority developments in the technological application of the method in mechanical engineering have been performed in Ukraine. However, in many technical areas Ukraine has fallen behind the world leaders in terms of the creation of detonation gas technologies and devices. Conclusions. For the practical use of the potential of gas detonation, it is necessary to develop fundamentally new devices that ensure reliable, safe, and controlable generation and propagation of detonation waves in gases and sprayed fuels. Gas detonation is promising for the creation of more advanced technologies and equipment.

Detonation performance of the CL-20-based explosive LX-19

The generation of constitutive detonation performance model components for high explosives (HEs) invariably involves reference to experiment, as reliable first-principles determinations of these models are beyond our current capability. Whatever its form or complexity, the detonation performance model must be able to accurately capture the detonation wave timing and the energy release that it triggers upon arrival. Specifically, the HE products equation-of-state (EOS), which largely determines the detonating HE’s ability to do useful work on its surroundings, is typically inferred from cylinder expansion tests where metal-confined HE cylinders are detonated and the ensuing outer confiner wall-expansion trajectory is recorded. Expensive, iterative comparisons to multimaterial hydrodynamic (or “hydrocode”) simulations of these experiments are then used to constrain the parameters of the chosen EOS form. Here, we report on new detonation performance experiments produced for the highly-ideal, plastic-bonded explosive and CL-20-based LX-19 which are used to produce a new sub-scale detonation performance model for the explosive. This includes new products EOS and a new Detonation Shock Dynamics front propagation law. We also confirm the capability of two new, non-hydrocode-based products EOS generation techniques to accelerate the HE model parameterization process. This latter development is particularly significant for detonation performance modeling of new HE formulations.

The influence of multi-layer confinement on detonation propagation in condensed-phase explosives

We examine, via multi-material simulation in a two-dimensional planar geometry, the effects on steady detonation propagation of the presence of a low-density intermediate layer between a condensed-phase high explosive (HE) and a high-density metallic confiner of finite thickness. Such elastomer intermediate layers are often added to eliminate air-gaps and the associated jetting effects that can arise due to machining imprecisions, or to prevent HE cracking due to environmental changes. Without an intermediate layer, the flow structure of a steady detonation/metal confiner interaction is well understood. In particular, there is no reflected wave passed into the HE due to the metal confinement. With the elastomer layer present, we find that, as the intermediate layer width increases, a complex wave interaction and communication path develops between the HE, intermediate, and metal layers. For thin intermediate layers, a shock-driven subsonic flow develops in the intermediate layer, passing information from the metal layer to the HE, with the detonation speed decreasing as the intermediate layer width increases. For wider intermediate layers, a Mach stem configuration develops in the intermediate layer, forcing a shock to be reflected into the HE. Simultaneously, a localized Prandtl-Meyer fan emerges from the intersection of the detonation shock with the HE-intermediate layer material interface. These HE structures are shown to have a substantial effect on the structure of the detonation driving zone. The Prandtl-Meyer fan becomes the dominant structure for critically large intermediate layer widths, wherein the presence of the metal layer does not affect the detonation propagation. We examine the detonation propagation speed and reaction and driving zone structure as a function of varying intermediate layer width. Two confinement metals are examined, along with two high explosive and three metal layer widths.

Determination of JWL parameters from underwater explosion test of spherical explosives by continuous velocity probe

ABSTRACT Underwater explosion test has been proven to be a simple way to measure the equation of state of detonation products. In order to further develop this technology, a new method for determining Jones-Wilkins-Lee equation of state (JWL-EOS) by underwater explosion test with spherical charge was designed based on the self-developed pressure-conducted velocity probe in this paper. First of all, we established an experimental system for the measurement of near-field shock wave of spherical charge using the novel probe, which made it possible to continuously record the velocities of detonation wave and shock wave in a given direction. Four field tests were performed using powdery cyclotrimethylene trinitramine (RDX) and the time history curves of detonation-shock wave front were obtained, by which we determined the velocity of detonation (VoD) and initial shock wave velocity. Besides, the detonation pressure was calculated applying impedance matching technique based on interface continuity conditions and acoustic approximation. We also analyzed the attenuation law of peak pressure of near-field shock wave by fitting the full-scale shock wave data. Applying numerical calculation and test-and-error process, we adjusted the six JWL-EOS parameters (A, B, C, R 1, R 2, and ω) constantly to make the error between numerical and experimental attenuation coefficients of peak pressure of shock wave fall within ±1%. Finally, the JWL-EOS parameters of powdery RDX of each test were determined, and the adiabatic curves of pressure versus relative volume were plotted as well.

Detonation shock dynamics modeling and calibration of the HMX-based conventional high explosive PBX 9501 with application to the two-dimensional circular arc geometry

A surface evolution model is developed for the detonation propagation dynamics of the HMX-based conventional high explosive PBX 9501, which relates the normal surface speed Dn to its local surface curvature κ. Such surface evolution models are important for the understanding and modification of engineering design calculations for high explosive applications. We describe a series of unconfined PBX 9501 slab geometry experiments of varying thickness, and detail how the steady axial detonation speed and detonation front shape data are obtained. A merit-function based calibration process is then described that uses both the PBX 9501 thickness effect and front shape data to parametrize the Dn−κ propagation law. The time-dependent PBX 9501 Dn−κ surface evolution law is then applied to detonation wave propagation in two-dimensional circular arc geometries, systematically examining the effect of arc thickness, inner radius, relaxation dynamics to steady-state propagation and confinement.

A Fast-Response Calorimeter with Dynamic Corrections for Transient Heat Transfer Measurements

Robust fast-response transient calorimeters with novel calorimeter elements have attracted the attention of researchers as new synthetic materials have been developed. This sensor uses diamonds as the calorimeter element, and a platinum film resistance is sputtered on the back to measure the temperature. The surface heat flux is obtained based on the calorimetric principle. The sensor has the advantages of high sensitivity and not being prone to erosion. However, non-ideal conditions, such as heat dissipation from the calorimeter element to the surroundings, can lead to measurement deviation and result in challenges for sensor miniaturization. In this study, a novel transient calorimeter (NTC) with two different sizes was developed using air or epoxy as the back-filling material. Numerical simulations were conducted to explain the complex heat exchange between the calorimeter element and its surroundings, which showed that it deviated from the assumption of an ideal calorimeter sensor. Accordingly, a dynamic correction method was proposed to compensate for the energy loss from the backside of the calorimeter element. The numerical results showed that the dynamic correction method significantly improved the measurement deviation, and the relative error was within 2.3% if the test time was smaller than 12 ms in the simulated cases. Detonation shock tunnel experiments confirmed the results of the dynamic correction method and demonstrated a practical method to obtain the dynamic correction coefficient. The accuracy and feasibility of the dynamic correction method were verified in a single detonation shock tunnel and under shock tube conditions. The NTC calorimeter exhibited good repeatability in all experiments.

Computation of the mean hydrodynamic structure of gaseous detonations with losses

In this paper, computations of gaseous detonations in several configurations are performed and discussed. The objective is to investigate the detonation characteristics, specially the influence of losses, through a quantitative analysis of the mean hydrodynamic structure. The results are divided into two parts: The first one relates to the propagation of ideal detonations without losses and to their characterization for a specific set of thermodynamic parameters, and the second part investigates the influence of losses on the averaged hydrodynamic structure of detonations. This is achieved by means of a specific and canonical configuration, in which a detonation wave propagates in a reactive layer bounded by an inert gas. This topology is investigated through a comparison of the instantaneous flow-field, cellular structure, and averaged quantities such as the mean curvature and the hydrodynamic thickness. This configuration may be regarded as non-ideal, as the detonation experiences losses due to the expansion of the detonation products toward the inert layer. The prediction of the detonation characteristics, as well as the conditions at which quenching occurs, remains a challenge when losses are involved. The main objective is to assess to what extent the hydrodynamic thickness can be used as a relevant length scale in the analysis of the resulting database. The results also highlight the key features of this configuration, which isolates a specific issue related to the rotating detonation engines. The temperature of the inert layer strongly affects the structure of the detonation–shock combined wave. For a high-temperature inert gas confinement, a detached shock appears in the upper layer and a jet of fresh mixture develops downstream of the front. For this condition, we observed a reduction in the critical dimensions by a factor of two. The degree of regularity of the detonation structure, from weakly unstable to mildly unstable cases, through the variation of the reduced activation energy, was investigated. The hydrodynamic thickness appears to be a useful characteristic length scale for the detonation, as it allows a better analysis of the results and a scaling of data. Moreover, the detonation velocity deficit can be globally expressed as a function of the ratio of the hydrodynamic thickness to the mean radius of curvature at the bottom of the wall.

Інноваційні можливості газової детонації

Introduction. Explosive technologies are widely used in the extraction industries, in mechanical engineering for welding, hardening, etc. However, the use of solid explosives is limited, above all, by safety requirements. Therefore, the use of a safer and more convenient source of energy, gas detonation, is attracting much attention. Pressures, temperatures, and velocities in detonation waves or shock waves in gases close to them in terms of intensity, as well as the pulse nature of the influence of these factors determine a high potential of their technical and technological use. Problem Statement. In many technical systems, deflagration modes of burning prevail. However, a more thermodynamically advantageous method of combustion and conversion of chemical energy of fuel into useful work is the detonation mode of combustion. This ensures the feasibility of development, research and wider implementation of various technologies and devices using controlled gas detonation. Purpose. Systematization and analysis of the main trends in the development and design of detonation gas technologies and devices in Ukraine and throughout the world. Materials and Methods. Systematization and analysis of scholarly research publications and patents on the practical application of gas detonation in various sectors of the economy. Results. The tendencies of practical use of gas detonation in different branches of industry have been revealed and analyzed. Priority developments in the technological application of the method in mechanical engineering have been performed in Ukraine. However, in many technical areas Ukraine has fallen behind the world leaders in terms of the creation of detonation gas technologies and devices. Conclusions. For the practical use of the potential of gas detonation, it is necessary to develop fundamentally new devices that ensure reliable, safe, and controlable generation and propagation of detonation waves in gases and sprayed fuels. Gas detonation is promising for the creation of more advanced technologies and equipment.

Numerical modeling of a high-enthalpy shock tunnel driven by gaseous detonation

A detonation-driven shock tunnel is useful as a ground test facility for hypersonic flow research. Numerical modeling of the shock tunnel is an easy way to extract precise test flow conditions and generate predictions of new operating conditions. In this study, a quasi-one-dimensional modeling of a detonation-driven shock tunnel is described. The model accounts for the viscous effects within a shock tube by adding a source term. The simulations of the particular conditions of the detonation shock tunnel are then presented and compared with the experimental results. The simulations provide good estimates for both the shock speed and pressure distributions. Detailed information on the gas dynamic processes over the full length of the facility is also obtained and discussed. The results also show that the approach is valid and ideal for the development of new tunnel operating conditions. It is also an ancillary tool for characterization of the reservoir parameters in a shock tube/tunnel, especially for the total temperature which are difficult to measure in such facilities.

Steady detonation propagation in thin channels with strong confinement

We examine asymptotically the dynamics of two-dimensional, steady detonation wave propagation and failure for a strongly confined high explosive (HE), in which the width of the explosive is small relative to the reaction zone length. An energy balance equation is derived, which shows how the longitudinal acceleration of subsonic flow behind the detonation shock is influenced both by chemical reaction and by the effects of HE boundary streamline deflection, specifically via the induced rate of change of mass flux through the detonation wave. The latter serves to either counteract or reinforce the acceleration of longitudinal flow, depending on the sign of the gradient of the boundary streamline deflection at the detonation shock. The analysis is valid for general equations of state and chemical reaction rates in the HE. The asymptotically derived form of the energy equation represents an eigenvalue problem for the determination of the steady detonation propagation speed, solved via a shooting method. We explore specific results for ideal and stiffened equations of state, along with a pressure-dependent reaction rate for which changes in the pressure exponent and reaction order are also studied. We consider the influences of both straight and curved HE boundary streamline shapes. The asymptotic analysis reveals significant physical insights into how detonation propagation and failure are affected by strong confinement.