Simulation of Blast Waves with Headwind
Olsen, Michael E.; Lawrence, Scott W.; Klopfer, Goetz H.; Mathias, Dovan; Onufer, Jeff T.
2005-01-01
The blast wave resulting from an explosion was simulated to provide guidance for models estimating risks for human spacecraft flight. Simulations included effects of headwind on blast propagation, Blasts were modelled as an initial value problem with a uniform high energy sphere expanding into an ambient field. Both still air and cases with headwind were calculated.
Device for Underwater Laboratory Simulation of Unconfined Blast Waves
Courtney, Elijah; Courtney, Michael
2015-01-01
Shock tubes simulate blast waves to study their effects in air under laboratory conditions; however, few experimental models exist for simulating underwater blast waves that are needed for facilitating experiments in underwater blast transmission, determining injury thresholds in marine animals, validating numerical models, and exploring mitigation strategies for explosive well removals. This method incorporates an oxy-acetylene driven underwater blast simulator which creates peak blast pressures of about 1860 kPa. Shot-to-shot consistency was fair, with an average standard deviation near 150 kPa. Results suggest peak blast pressures from 460 kPa to 1860 kPa are available by adjusting the distance from the source.
Simulation of the detector system's response under nuclear blast wave
International Nuclear Information System (INIS)
Using the pressure-time curve that produced from the simulator loaded to the model to check the ability of some detector system against the blast wave. On the basis of numerical simulation and the results of the test, the finite element analysis software-DYTRAN is used to simulate the static load and the dynamic load. Then, several methods are analyzed and draw a conclusion that the numerical simulation of the dynamic load can fully reflect the interaction between the blast wave and the object. (authors)
A $55 Shock Tube for Simulated Blast Waves
Courtney, Elijah; Courtney, Michael
2015-01-01
Shock tubes are commonly employed to test candidate armor materials, validate numerical models, and conduct simulated blast experiments in animal models. As DoD interests desire to field wearable sensors as blast dosimeters, shock tubes may also serve for calibration and testing of these devices. The high blast pressures needed for experimental testing of candidate armors are unnecessary to test these sensors. An inexpensive, efficient, and easily available way of testing these pressure sensors is desirable. It is known that releasing compressed gas suddenly can create a repeatable shock front, and the pressures can be finely tuned by changing the pressure to which the gas is compressed. A Crosman 0.177 caliber air pistol was used (without loading any pellets) to compress and release air in one end of a 24 inch long 3/4 inch diameter standard pipe nipple to simulate a blast wave at the other end of the tube. A variable number of pumps were used to vary the peak blast pressure. As expected, the trials where 10...
Needham, Charles E
2010-01-01
The primary purpose of this text is to document many of the lessons that have been learned during the author’s more than forty years in the field of blast and shock. The writing therefore takes on an historical perspective, in some sense, because it follows the author’s experience. The book deals with blast waves propagating in fluids or materials that can be treated as fluids. It begins by distinguishing between blast waves and the more general category of shock waves. It then examines several ways of generating blast waves, considering the propagation of blast waves in one, two and three dimensions as well as through the real atmosphere. One section treats the propagation of shocks in layered gases in a more detailed manner. The book also details the interaction of shock waves with structures in particular reflections, progressing from simple to complex geometries, including planar structures, two-dimensional structures such as ramps or wedges, reflections from heights of burst, and three-dimensional st...
A $55 Shock Tube for Simulated Blast Waves
Courtney, Elijah; Courtney, Amy; Courtney, Michael
2015-01-01
Shock tubes are commonly employed to test candidate armor materials, validate numerical models, and conduct simulated blast experiments in animal models. As DoD interests desire to field wearable sensors as blast dosimeters, shock tubes may also serve for calibration and testing of these devices. The high blast pressures needed for experimental testing of candidate armors are unnecessary to test these sensors. An inexpensive, efficient, and easily available way of testing these pressure senso...
Nguyen-Dinh, Maxime; Gainville, Olaf; Lardjane, Nicolas
2015-10-01
We present new results for the blast wave propagation from strong shock regime to the weak shock limit. For this purpose, we analyse the blast wave propagation using both Direct Numerical Simulation and an acoustic asymptotic model. This approach allows a full numerical study of a realistic pyrotechnic site taking into account for the main physical effects. We also compare simulation results with first measurements. This study is a part of the french ANR-Prolonge project (ANR-12-ASTR-0026).
Numerical simulation on dynamic response of the chest wall loaded by the blast wave
Kang, Jianyi; Yu, Chunxiang; Li, Huimin; Chen, Jing; Liu, Hai
2015-01-01
In this paper, a three-dimensional finite element model of the human thorax was constructed using Mimics software and Icem CFD software. This model was loaded with a 100-kPa blast wave and constructed to analyze the dynamic response of the chest wall. The simulation results have shown that a blast wave can cause stress concentration on the ribs and ribs inward movement. The third, fourth, and fifth ribs have the maximum inward moving velocity of 1.6 m / s without any injury for the human body...
Directory of Open Access Journals (Sweden)
Hristov Nebojša
2015-02-01
Full Text Available Simulation and measurements of muzzle blast overpressure and its physical manifestations are studied in this paper. The use of a silencer can have a great influence on the overpressure intensity. A silencer is regarded as an acoustic transducer and a waveguide. Wave equations for an acoustic dotted source of directed effect are used for physical interpretation of overpressure as an acoustic phenomenon. Decomposition approach has proven to be suitable to describe the formation of the output wave of the wave transducer. Electroacoustic analogies are used for simulations. A measurement chain was used to compare the simulation results with the experimental ones.
Directory of Open Access Journals (Sweden)
Dengfeng Su
2016-01-01
Full Text Available As one of the most serious “side effects” of blast excavation, blast-induced vibration must be controlled for existing buildings and human beings. This paper proposes a method for blast-induced vibration reduction with water jet assistance according to the cutting characters of low-noised, environment-friendly water jet. The mechanism of vibration-isolation with water jet assistance was analyzed, and the stress wave energy attenuation models were established based on blasting theory and stress wave theory. Influence law on shock wave attenuation by vibration-isolation slot was studied by numerical simulation. Simulation results agree with the theoretical analysis roughly. The results of this study put forward a method for blast-induced vibration near blasting source and provide a certain theoretical basis.
Directed Relativistic Blast Wave
Gruzinov, Andrei
2007-01-01
A spherically symmetrical ultra-relativistic blast wave is not an attractor of a generic asymmetric explosion. Spherical symmetry is reached only by the time the blast wave slows down to non-relativistic velocities, when the Sedov-Taylor-von Neumann attractor solution sets in. We show however, that a directed relativistic explosion, with the explosion momentum close to the explosion energy, produces a blast wave with a universal intermediate asymptotic -- a selfsimilar directed ultra-relativi...
Simulation of blast-induced, early-time intracranial wave physics leading to traumatic brain injury.
Energy Technology Data Exchange (ETDEWEB)
Taylor, Paul Allen; Ford, Corey C. (University of New Mexico, Albuquerque, NM)
2008-04-01
U.S. soldiers are surviving blast and impacts due to effective body armor, trauma evacuation and care. Blast injuries are the leading cause of traumatic brain injury (TBI) in military personnel returning from combat. Understanding of Primary Blast Injury may be needed to develop better means of blast mitigation strategies. The objective of this paper is to investigate the effects of blast direction and strength on the resulting mechanical stress and wave energy distributions generated in the brain.
Simulation of the reflected blast wave from a C-4 charge
Howard, W. Michael; Kuhl, Allen L.; Tringe, Joseph
2012-03-01
The reflection of a blast wave from a C4 charge detonated above a planar surface is simulated with our ALE3D code. We used a finely-resolved, fixed Eulerian 2-D mesh (167 μm per cell) to capture the detonation of the charge, the blast wave propagation in nitrogen, and its reflection from the surface. The thermodynamic properties of the detonation products and nitrogen were specified by the Cheetah code. A programmed-burn model was used to detonate the charge at a rate based on measured detonation velocities. Computed pressure histories are compared with pressures measured by Kistler 603B piezoelectric gauges at 7 ranges (GR = 0, 5.08, 10.16, 15.24, 20.32, 25.4, and 30.48 cm) along the reflecting surface. Computed and measured waveforms and positive-phase impulses were similar, except at close-in ranges (GR < 5 cm), which were dominated by jetting effects.
Krause, G; Francile, C; Costa, A; Elaskar, S; Schneiter, M
2015-01-01
We examine the capability of a coronal flare ignited blast wave scenario to reproduce the chromospheric phenomenon. We numerically simulate the Moreton event of December 06, 2006 considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock -able to generate a detectable chromospheric Moreton wave- a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that the flare ignited blast wave scenario is capable to reproduce the observations.
Curved characteristics behind blast waves.
Laporte, O.; Chang, T. S.
1972-01-01
The behavior of nonisentropic flow behind a propagating blast wave is theoretically studied. Exact solutions, expressed in closed form in terms of elementary functions, are presented for three sets of curved characteristicseind a self-similar, strong blast wave.
Numerical simulation of laser--target interaction and blast wave formation
International Nuclear Information System (INIS)
A numerical hydrodynamics chemistry model to simulate the laser--target interaction experiment at the Naval Research Laboratory's PHAROS Laser interaction and elated Plasma henomena (Plenum, New York, 1986), Vol. 7, p. 857] is presented. Both laser--target and debris--background interactions are modeled, solving mass continuity, total momentum, and separate ion and electron internal energy equations. The model is appropriate for background densities≥1 Torr. To accurately treat both the early-time planar ablation and the later spherical expansion of the blast wave, as well as the rear-side shock front, an oblate spheroidal coordinate system was adopted. The aluminum target ablates into and interacts with an ambient nitrogen gas, filling the facility chamber. The simulation models the target continuously from the solid state to the state of a highly ionized nonequilibrium plasma, including all charge states of aluminum and all charge states of the nitrogen background. The laser beam has a wavelength of 1 μ, a approximately 5 nsec full width at half-maximum (FWHM), an intensity at the target surface approximately 1013 W/cm2, and total energy varying from 20--100 J. The model accurately reproduces the measured time-of-flight profile and the mass of ablated aluminum. Expansion of the blast wave in the model follows the ideal Sedov relation until radiation losses force a deviation due to a failure in the constant energy assumption. In the shock wave region the simulations show electron density of a few times 1018 cm/sup -3/, temperatures ranging from 10--20 eV, and dominant nitrogen species of N+3 and N+4, all in agreement with experimental measurement
TWO-DIMENSIONAL BLAST-WAVE-DRIVEN RAYLEIGH-TAYLOR INSTABILITY: EXPERIMENT AND SIMULATION
International Nuclear Information System (INIS)
This paper shows results from experiments diagnosing the development of the Rayleigh-Taylor instability with two-dimensional initial conditions at an embedded, decelerating interface. Experiments are performed at the Omega Laser and use ∼5 kJ of energy to create a planar blast wave in a dense, plastic layer that is followed by a lower density foam layer. The single-mode interface has a wavelength of 50 μm and amplitude of 2.5 μm. Some targets are supplemented with additional modes. The interface is shocked then decelerated by the foam layer. This initially produces the Richtmyer-Meshkov instability followed and then dominated by Rayleigh-Taylor growth that quickly evolves into the nonlinear regime. The experimental conditions are scaled to be hydrodynamically similar to SN1987A in order to study the instabilities that are believed to occur at the He/H interface during the blast-wave-driven explosion phase of the star. Simulations of the experiment were performed using the FLASH hydrodynamics code.
Energy Technology Data Exchange (ETDEWEB)
Ford, Corey C. (University of New Mexico, Albuquerque, NM); Taylor, Paul Allen
2008-02-01
The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm{sup 3} voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.
Simulations of Magnetic Field Generation in Laser-Produced Blast Waves
Lamb, D.; Fatenejad, M.; Gregori, G.; Miniati, F.; Park, H.-S.; Remington, B.; Ravasio, A.; Koenig, M.; Murphy, C. D.
2011-10-01
Magnetic fields are ubiquitous in the Universe. The origin of these fields and process by which they are amplified are not fully understood, although amplification is thought to involve turbulence. Experiments being conducted at medium-scale laser facilities (such as the LULI laser the Janus laser) can investigate the self-generation of magnetic fields under conditions that resemble astrophysical shocks. In these experiments, two 527 nm, 1.5 ns long laser beams are focused onto a 500 μm diameter graphite rod producing an explosion and asymmetric blast wave into a Helium filled chamber. A variety of diagnostics measure the velocity, electron density, and show that a large scale magnetic field is produced. We report preliminary hydrodynamic and MHD simulations using FLASH of a simplified version of the experiment. The results provide insights into the origin and generation of the magnetic field. This work was partially supported by the US DOE, the European Research Council, and Laserlab Europe.
A three-phase soil model for simulating stress wave propagation due to blast loading
Wang, Zhongqi; Hao, Hong; Lu, Yong
2004-01-01
A three-phase soil model is proposed to simulate stress wave propagation in soil mass to blast loading. The soil is modelled as a three-phase mass that includes the solid particles, water and air. It is considered as a structure that the solid particles form a skeleton and their voids are filled with water and air. The equation of state (EOS) of the soil is derived. The elastic-plastic theory is adopted to model the constitutive relation of the soil skeleton. The damage of the soil skeleton is also modelled. The Drucker-Prager strength model including the strain rate effect is used to describe the strength of the soil skeleton. The model is implemented into a hydrocode Autodyn. The recorded results obtained by explosion tests in soil are used to validate the proposed model. Copyright
Numerical simulation of the fluid-structure interaction between air blast waves and soil structure
Umar, S.; Risby, M. S.; Albert, A. Luthfi; Norazman, M.; Ariffin, I.; Alias, Y. Muhamad
2014-03-01
Normally, an explosion threat on free field especially from high explosives is very dangerous due to the ground shocks generated that have high impulsive load. Nowadays, explosion threats do not only occur in the battlefield, but also in industries and urban areas. In industries such as oil and gas, explosion threats may occur on logistic transportation, maintenance, production, and distribution pipeline that are located underground to supply crude oil. Therefore, the appropriate blast resistances are a priority requirement that can be obtained through an assessment on the structural response, material strength and impact pattern of material due to ground shock. A highly impulsive load from ground shocks is a dynamic load due to its loading time which is faster than ground response time. Of late, almost all blast studies consider and analyze the ground shock in the fluid-structure interaction (FSI) because of its influence on the propagation and interaction of ground shock. Furthermore, analysis in the FSI integrates action of ground shock and reaction of ground on calculations of velocity, pressure and force. Therefore, this integration of the FSI has the capability to deliver the ground shock analysis on simulation to be closer to experimental investigation results. In this study, the FSI was implemented on AUTODYN computer code by using Euler-Godunov and the arbitrary Lagrangian-Eulerian (ALE). Euler-Godunov has the capability to deliver a structural computation on a 3D analysis, while ALE delivers an arbitrary calculation that is appropriate for a FSI analysis. In addition, ALE scheme delivers fine approach on little deformation analysis with an arbitrary motion, while the Euler-Godunov scheme delivers fine approach on a large deformation analysis. An integrated scheme based on Euler-Godunov and the arbitrary Lagrangian-Eulerian allows us to analyze the blast propagation waves and structural interaction simultaneously.
Feasibility of a blast wave attenuation structure
Hartmann, Dale Richard
1997-01-01
This thesis begins with an overview of bombings in the United States, followed by the introduction of the Rankine Hugoniot equations for blast wave pressure. The subsequent chapters develop the one dimensional and two dimensional Euler equations. These equations are the solved using the MacCormack finite difference algorithm. The basis of the investigation then begins by placing pole, shear plate and wedge obstacles in the path of the blast wave. The results of these simulations are interpret...
Prediction of blast wave effects on a developed site
Benselama, Adel M.; William-Louis, Mame J.-P.; Monnoyer, François
2010-01-01
Abstract The guidelines for protecting against and mitigating explosion hazards require knowledge and either the experimental or theoretical evaluation of blast wave parameters. To this end, this article proposes a numerical method for simulating blast wave propagation in complex geometries. This method permits an on-the-ground TNT-like explosion and the subsequent blast wave to be simulated, with the possibility of modifying the ground topology by adding a number of obstacles. The...
Interactions of Blast Waves with Perturbed Interfaces
Henry de Frahan, Marc; Johnsen, Eric
2015-11-01
Richtmyer-Meshkov and Rayleigh-Taylor instabilities induce hydrodynamic mixing in many important physical systems such as inertial confinement fusion, supernova collapse, and scramjet combustion. Blast waves interacting with perturbed interfaces are prevelant in such applications and dictate the mixing dynamics. This study increases our understanding of blast-driven hydrodynamic instabilities by providing models for the time-dependent perturbation growth and vorticity production mechanisms. The strength and length of the blast wave determine the different growth regimes and the importance of the Richtmyer-Meshkov or Rayleigh-Taylor growth. Our analysis is based on simulations of a 2D planar blast wave, modeled by a shock (instantaneous acceleration) followed by a rarefaction (time-dependent deceleration), interacting with a sinusoidal perturbation at an interface between two fluids. A high-order accurate Discontinuous Galerkin method is used to solve the multifluid Euler equations.
Simulating geometrically complex blast scenarios
Directory of Open Access Journals (Sweden)
Ian G. Cullis
2016-04-01
Full Text Available The effects of blast waves generated by energetic and non-energetic sources are of continuing interest to the ballistics research community. Modern conflicts are increasingly characterised by asymmetric urban warfare, with improvised explosive devices (IEDs often playing a dominant role on the one hand and an armed forces requirement for minimal collateral effects from their weapons on the other. These problems are characterised by disparate length- and time-scales and may also be governed by complex physics. There is thus an increasing need to be able to rapidly assess and accurately predict the effects of energetic blast in topologically complex scenarios. To this end, this paper presents a new QinetiQ-developed advanced computational package called EAGLE-Blast, which is capable of accurately resolving the generation, propagation and interaction of blast waves around geometrically complex shapes such as vehicles and buildings. After a brief description of the numerical methodology, various blast scenario simulations are described and the results compared with experimental data to demonstrate the validation of the scheme and its ability to describe these complex scenarios accurately and efficiently. The paper concludes with a brief discussion on the use of the code in supporting the development of algorithms for fast running engineering models.
Simulating geometrically complex blast scenarios
Institute of Scientific and Technical Information of China (English)
Ian G. CULLIS; Nikos NIKIFORAKIS; Peter FRANKL; Philip BLAKELY; Paul BENNETT; Paul GREENWOOD
2016-01-01
The effects of blast waves generated by energetic and non-energetic sources are of continuing interest to the ballistics research community. Modern conflicts are increasingly characterised by asymmetric urban warfare, with improvised explosive devices (IEDs) often playing a dominant role on the one hand and an armed forces requirement for minimal collateral effects from their weapons on the other. These problems are characterised by disparate length-and time-scales and may also be governed by complex physics. There is thus an increasing need to be able to rapidly assess and accurately predict the effects of energetic blast in topologically complex scenarios. To this end, this paper presents a new QinetiQ-developed advanced computational package called EAGLE-Blast, which is capable of accurately resolving the generation, propagation and interaction of blast waves around geometrically complex shapes such as vehicles and buildings. After a brief description of the numerical methodology, various blast scenario simulations are described and the results compared with experimental data to demonstrate the validation of the scheme and its ability to describe these complex scenarios accurately and efficiently. The paper concludes with a brief discussion on the use of the code in supporting the development of algorithms for fast running engineering models.
Stability of Relativistic Blast Waves
Ogura, Jun; Kojima, Yasufumi
2000-01-01
A spherical blast wave with relativistic velocity can be described by a similarity solution, that is used for theoretical models of gamma-ray bursts. We consider the linear stability of such a relativistic blast wave propagating into a medium with density gradient. The perturbation can also be expressed by a self-similar form. We show that the shock front is unstable in general, and we evaluate the growth rate.
Computation of blast wave-obstacle interactions
Champney, J. M.; Chaussee, D. S.; Kutler, P.
1982-01-01
Numerical simulations of the interaction of a planar blast wave with various obstacles are presented. These obstacles are either ground structures or vehicles flying in the atmosphere. For a structure on the ground, the blast wave encounter is side-on, while for the flying vehicles the encounter is either head-on or oblique. Second-order accurate, finite-difference, and shock-capturing procedures are employed to solve the two-dimensional, axisymmetric, and three-dimensional unsteady Euler equations. Results are presented for the flow field consisting of blast wave striking obstacles that are at rest, moving subsonically and moving supersonically. Comparison of the numerical results with experimental data for a configuration at rest substantiates the validity of this approach and its potential as a flow analysis tool.
Blast waves in rotating media.
Rossner, L. F.
1972-01-01
The model investigated involves a cylindrically symmetric blast wave generated by an infinitely long line explosion in a cold and homogeneous gas rotating rigidly in its self-gravitational field. It is found that within the context of rotation in a gravitational field a blast wave will not adopt the one-zone form familiar from similarity solutions but, rather, a two-zone form. The inner compression zone arises as a response to the presence of the restoring force, which drives a rarefaction wave into the outer compression zone.
Rodriguez, R.; Espinosa, G.; Gil, J. M.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.
2015-12-01
Radiative shock waves are ubiquitous throughout the universe and play a crucial role in the transport of energy into the interstellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible conditions. In some laboratory experiments radiative blast waves are launched in clusters of gases by means of the direct deposition of the laser energy. In this work, by using a collisional-radiative model, we perform an analysis of the plasma level populations and radiative properties of a blast wave launched in a xenon cluster. In particular, for both the shocked and unshocked material, we study the influence of different effects such as LTE, steady-state or time-dependent NLTE simulations, plasma self-absorption or external radiation field in the determination of those properties and also in the diagnosis of the electron temperature of the blast wave.
Blast Wave Characteristics and Equivalency
Sochet, Isabelle; Schneider, Helmut
2010-01-01
The characteristics of blast waves generated by detonation of gas clouds are studies theoretically and validated by both small-scale and large-scale experiments with ethylene-air mixtures of different equivalence ratio. The mixtures were confined in hemispherical or spherical balloons made from thin polyethylene foils of 0.75 m³ and 15 m³ in volume. The detonation of gas mixtures was initiated by a solid explosive. The characteristics of the blast wave in terms of overpressure, impulse and du...
International Nuclear Information System (INIS)
Radiative shock waves play a pivotal role in the transport energy into the stellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible laboratory conditions and their study has been highlighted as an area requiring further experimental investigations. Low density material with high atomic mass is suitable to achieve radiative regime, and, therefore, low density xenon gas is commonly used for the medium in which the radiative shocks such as radiative blast waves propagate. In this work, by means of collisional-radiative steady-state calculations, a characterization and an analysis of microscopic magnitudes of laboratory blast waves launched in xenon clusters are made. Thus, for example, the average ionization, the charge state distribution, the cooling time or photon mean free paths are studied. Furthermore, for a particular experiment, the effects of the self-absorption and self-emission in the specific intensity emitted by the shock front and that is going through the radiative precursor are investigated. Finally, for that experiment, since the electron temperature is not measured experimentally, an estimation of this magnitude is made both for the shock shell and the radiative precursor. -- Highlights: •We analyze microscopic magnitudes of plasmas for typical conditions found in laboratory blast waves in clusters of gases. •A particular experiment of blast waves launched in xenon is analyzed. •We perform a collisional-radiative steady-state diagnostics of the temperature of the blast wave. •We study the opacity effects in the kinetics calculations and the intensity in the shock shell of the blast wave. •We analyze self-absorption and self-emission in the radiative precursor
Radiative shell thinning in intense laser-driven blast waves
International Nuclear Information System (INIS)
The structural evolution of blast waves launched by intense laser pulses in gases is investigated. These blast waves exhibit significant energy loss through radiation while propagating in xenon as evidenced by interferometric imaging revealing radiative precursors and deceleration parameters well below those of an energy-conserving wave. Thinning of the blast wave shell from radiative cooling is observed through comparison of shocks launched in gases of differing atomic number. Shell thinning is also measured when the gas density is altered, indicating the influence of conditions within the preshock medium. These results are compared with radiative-hydrodynamic simulations.
Relativistic blast waves that accelerate
International Nuclear Information System (INIS)
An approximate analytical similarity solution is derived for the problem of an ultrarelativistic, adiabatic blast wave which results from a point explosion at the origin of a cold (i.e., nonrelativistic), spherically symmetric gas in which the density decreases fast enough with radius to accelerate the shock wave toward larger radii. This solution includes both the shock propagation law and the details of the postshock flow. It is revelant to models of compact, extragalactic radio sources involving relativistic shock waves, as well as to the supernova shock model for cosmic ray acceleration
From blast wave to observation
Eerten, van, H.; Wijers, R. A. M. J.
2008-01-01
Gamma-ray burst (GRB) afterglows are well described by synchrotron emission originating from the interaction between a relativistic blast wave and the external medium surrounding the GRB progenitor. We introduce a code to reconstruct spectra and light curves from arbitrary fluid configurations, making it especially suited to study the effects of fluid flows beyond those that can be described using analytical approximations. As a check and first application of our code we use it to fit the sca...
Radiation from cosmic blast waves
International Nuclear Information System (INIS)
A study is made of the dynamics of blast waves, of their internal structure and of the Bremsstrahlung radiation from the shocked plasma in conditions when the cooling time is longer than the expansion time. Models appropriate for the interpretation of the X-ray sources associated with supernova remnants and with the explosive activity of the radiogalaxies in clusters of galaxies are computed and discussed; the inverse Compton emission from continuously injected relativistic electrons is included. (orig.)
Blast wave parameters at diminished ambient pressure
Silnikov, M. V.; Chernyshov, M. V.; Mikhaylin, A. I.
2015-04-01
Relation between blast wave parameters resulted from a condensed high explosive (HE) charge detonation and a surrounding gas (air) pressure has been studied. Blast wave pressure and impulse differences at compression and rarefaction phases, which traditionally determine damage explosive effect, has been analyzed. An initial pressure effect on a post-explosion quasi-static component of the blast load has been investigated. The analysis is based on empirical relations between blast parameters and non-dimensional similarity criteria. The results can be directly applied to flying vehicle (aircraft or spacecraft) blast safety analysis.
The laboratory simulation of unmagnetized supernova remnants Absence of a blast wave
Borovsky, J. E.; Pongratz, M. B.; Roussel-Dupre, R. A.; Tan, T.-H.
1984-01-01
Supernova remnants are experimentally simulated by irradiating spherical targets with eight-beam carbon dioxide laser in a chamber containing finite amounts of neutral gas, the gas being ionized by radiation from the hot target. The expansion velocities of the target plasmas are approximately the same as the expansion velocities of supernova ejecta and the experiment is successfully scaled to the case of a supernova remnant in an unmagnetized, low-density, interstellar medium. No sweep-up of the ambient plasma is detected, indicating that no hydrodynamic shock wave is formed to couple the target ejecta to the ambient gas. The experiment implies that if supernova ejecta couple to the interstellar medium, magnetic-field effects may be crucial to the physical description.
Self-similar Ultrarelativistic Jetted Blast Wave
Keshet, Uri; Kogan, Dani
2015-12-01
Following a suggestion that a directed relativistic explosion may have a universal intermediate asymptotic, we derive a self-similar solution for an ultrarelativistic jetted blast wave. The solution involves three distinct regions: an approximately paraboloid head where the Lorentz factor γ exceeds ˜ 1/2 of its maximal, nose value; a geometrically self-similar, expanding envelope slightly narrower than a paraboloid; and an axial core in which the (cylindrically, henceforth) radial flow {{u}} converges inward toward the axis. Most (˜80%) of the energy lies well beyond the leading, head region. Here, a radial cross section shows a maximal γ (separating the core and the envelope), a sign reversal in {{u}}, and a minimal γ, at respectively ˜1/6, ˜1/4, and ˜3/4 of the shock radius. The solution is apparently unique, and approximately agrees with previous simulations, of different initial conditions, that resolved the head. This suggests that unlike a spherical relativistic blast wave, our solution is an attractor, and may thus describe directed blast waves such as in the external shock phase of a γ-ray burst.
International Nuclear Information System (INIS)
In this work several relevant parameters and properties for krypton and xenon plasmas are analyzed, such as, for example, the average ionization, the plasma thermodynamic regimes, the radiative power losses and the mean opacities. This analysis is performed in a range of density and temperature typically found in laboratory experiments to generate radiative blast waves in laser-heated clustered plasmas. A polynomial fit of those parameters is also presented. Finally an analysis of the thermal cooling instability is performed. (paper)
Electrical Blast simulator (e-BLAST): design, development and first operational tests
PERONI MARCO; SOLOMOS George; PEGON Pierre; CAVERZAN ALESSIO
2015-01-01
The Electrical Blast Simulator (e-BLAST) activity involves the development of an apparatus capable of reproducing the effects of a blast pressure wave on large-scale structural components (such as columns, walls, etc.) with the objective of improving their strength in such severe loading situations. The work relates to the BUILT-CIP project which deals with the protection and resilience of the built environment (critical buildings, transportation and energy infrastructure etc.) under catastr...
Cygnus Loop Supernova Blast Wave
1993-01-01
This is an image of a small portion of the Cygnus Loop supernova remnant, which marks the edge of a bubble-like, expanding blast wave from a colossal stellar explosion, occurring about 15,000 years ago. The HST image shows the structure behind the shock waves, allowing astronomers for the first time to directly compare the actual structure of the shock with theoretical model calculations. Besides supernova remnants, these shock models are important in understanding a wide range of astrophysical phenomena, from winds in newly-formed stars to cataclysmic stellar outbursts. The supernova blast is slamming into tenuous clouds of insterstellar gas. This collision heats and compresses the gas, causing it to glow. The shock thus acts as a searchlight revealing the structure of the interstellar medium. The detailed HST image shows the blast wave overrunning dense clumps of gas, which despite HST's high resolution, cannot be resolved. This means that the clumps of gas must be small enough to fit inside our solar system, making them relatively small structures by interstellar standards. A bluish ribbon of light stretching left to right across the picture might be a knot of gas ejected by the supernova; this interstellar 'bullet' traveling over three million miles per hour (5 million kilometres) is just catching up with the shock front, which has slowed down by ploughing into interstellar material. The Cygnus Loop appears as a faint ring of glowing gases about three degrees across (six times the diameter of the full Moon), located in the northern constellation, Cygnus the Swan. The supernova remnant is within the plane of our Milky Way galaxy and is 2,600 light-years away. The photo is a combination of separate images taken in three colors, oxygen atoms (blue) emit light at temperatures of 30,000 to 60,000 degrees Celsius (50,000 to 100,000 degrees Farenheit). Hydrogen atoms (green) arise throughout the region of shocked gas. Sulfur atoms (red) form when the gas cools to
Swift GRBs and the blast wave model
Curran, P. A.; Horst, van der, C.M.A.M.; Starling, R.L.C.; Wijers, R. A. M. J.
2008-01-01
The complex structure of the light curves of Swift GRBs has made their interpretation and that of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to constrain the blast wave parameters: electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multi-wavelength light curves and X-ray spectra of a Swift sample to the predictions of the blast wave model. We ca...
On the Propagation and Interaction of Spherical Blast Waves
Kandula, Max; Freeman, Robert
2007-01-01
The characteristics and the scaling laws of isolated spherical blast waves have been briefly reviewed. Both self-similar solutions and numerical solutions of isolated blast waves are discussed. Blast profiles in the near-field (strong shock region) and the far-field (weak shock region) are examined. Particular attention is directed at the blast overpressure and shock propagating speed. Consideration is also given to the interaction of spherical blast waves. Test data for the propagation and interaction of spherical blast waves emanating from explosives placed in the vicinity of a solid propellant stack are presented. These data are discussed with regard to the scaling laws concerning the decay of blast overpressure.
Dynamics and stability of relativistic GRB blast waves
Meliani, Z.; Keppens, R.
2010-01-01
In gamma-ray-bursts (GRB), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving power, following the GRB jet during the entire afterglow phase. We investigate the ...
Blast wave diagnostic for the Petawatt laser system
International Nuclear Information System (INIS)
We report on a diagnostic to measure the trajectory of a blast wave propagating through a plastic target 400 μm thick. This blast wave is generated by the irradiation of the front surface of the target with ∼400 J of 1 μm laser radiation in a 20 ps pulse focused to a ∼50 μm diameter spot, which produces an intensity in excess of 1018W/cm2. These conditions approximate a point explosion and a blast wave is predicted to be generated with an initial pressure nearing 1 Gbar which decays as it travels approximately radially outward from the interaction region. We have utilized streaked optical pyrometry of the blast front to determine its time of arrival at the rear surface of the target. Applications of a self-similar Taylor - Sedov blast wave solution allows the amount of energy deposited to be estimated. The experiment, LASNEX design simulations and initial results are discussed. copyright 1999 American Institute of Physics
Dynamic Modelling of Fault Slip Induced by Stress Waves due to Stope Production Blasts
Sainoki, Atsushi; Mitri, Hani S.
2016-01-01
Seismic events can take place due to the interaction of stress waves induced by stope production blasts with faults located in close proximity to stopes. The occurrence of such seismic events needs to be controlled to ensure the safety of the mine operators and the underground mine workings. This paper presents the results of a dynamic numerical modelling study of fault slip induced by stress waves resulting from stope production blasts. First, the calibration of a numerical model having a single blast hole is performed using a charge weight scaling law to determine blast pressure and damping coefficient of the rockmass. Subsequently, a numerical model of a typical Canadian metal mine encompassing a fault parallel to a tabular ore deposit is constructed, and the simulation of stope extraction sequence is carried out with static analyses until the fault exhibits slip burst conditions. At that point, the dynamic analysis begins by applying the calibrated blast pressure to the stope wall in the form of velocities generated by the blast holes. It is shown from the results obtained from the dynamic analysis that the stress waves reflected on the fault create a drop of normal stresses acting on the fault, which produces a reduction in shear stresses while resulting in fault slip. The influence of blast sequences on the behaviour of the fault is also examined assuming several types of blast sequences. Comparison of the blast sequence simulation results indicates that performing simultaneous blasts symmetrically induces the same level of seismic events as separate blasts, although seismic energy is more rapidly released when blasts are performed symmetrically. On the other hand when nine blast holes are blasted simultaneously, a large seismic event is induced, compared to the other two blasts. It is concluded that the separate blasts might be employed under the adopted geological conditions. The developed methodology and procedure to arrive at an ideal blast sequence can
Modeling of Laser-generated Radiative Blast Waves
International Nuclear Information System (INIS)
We simulate experiments performed with the Falcon laser at Lawrence Livermore National Laboratory to generate strong, cylindrically diverging blast waves of relevance to astrophysics. In particular, we are interested in producing and modeling radiative shocks. We compare numerical simulations with the data and with an analytic approximation to blast-wave propagation with a radiative-loss term included. Our goal is to develop a laboratory setting for studying radiative shocks of relevance to supernova remnants, gamma-ray burst afterglows, and other high-energy astrophysics phenomena. We will show that a good degree of agreement exists between the experimental data and the numerical simulations, demonstrating that it is indeed possible to generate radiative shocks in the laboratory using tabletop femtosecond lasers. In addition, we show how we can determine the energy-loss rate from the blast-wave evolution. This analytic method is independent of the exact mechanism of radiative cooling and is scalable to both the laboratory and astrophysical radiative blast waves. (c) 2000 The American Astronomical Society
Blast waves with cosmic-ray pressure
International Nuclear Information System (INIS)
The effects of cosmic-ray pressure on the dynamics of self-similar, spherical blast waves and driven waves are investigated on the assumptions that the ratio of relativistic cosmic-ray pressure to total pressure at the shock front is a constant w and the the cosmic rays and thermal gas evolve as independent adiabatic fluids in the postshock flow. For blast waves from a point explosion in a uniform medium, the cosmic rays dominate the pressure near r = 0 if w>0. The solutions show that, if w is small, the ratio of cosmic-ray energy to total energy in the blast wave is several times w. The solutions are used to make specific predictions of the pion-decay γ-ray flux from a blast wave as a function of w. If w is large, the predicted fluxes from supernova remnants are close to the current observational limits. It is also noted that cosmic rays may limit the compression in the radiative shock waves of supernova remnants. The addition of cosmic pressure does not change the geneal nature of the driven wave self-similar solutions. The solutions are used to predict the pion-decay γ-ray flux from a young Type II supernova interacting with circumstellar material. Observations these γ-rays from extragalactic supernovae are not promising, but a galactic supernova could be very bright in γ-rays
Isothermal blast wave model of supernova remnants
International Nuclear Information System (INIS)
The validity of the ''adiabatic'' assumption in supernova remnant calculations is examined, and the alternative extreme of an isothermal blast wave is explored. It is concluded that, because of thermal conductivity, the large temperature gradients predicted by the adiabatic model probably are not maintained in nature. Self-similar solutions to the hydrodynamic equations for an isothermal blast wave have been found and studied. These solutions are then used to determine the relationship between X-ray observations and inferred parameters of supernova remnants. A comparison of the present results with those for the adiabatic model indicates differences which are less than present observational uncertainties. It is concluded that most parameters of supernova remnants inferred from X-ray measurements are relatively insensitive to the specifics of the blast wave model
Isothermal blast wave model of supernova remnants
Solinger, A.; Buff, J.; Rappaport, S.
1975-01-01
The validity of the 'adiabatic' assumption in supernova-remnant calculations is examined, and the alternative extreme of an isothermal blast wave is explored. It is concluded that, because of thermal conductivity, the large temperature gradients predicted by the adiabatic model probably are not maintained in nature. Self-similar solutions to the hydrodynamic equations for an isothermal blast wave have been found and studied. These solutions are then used to determine the relationship between X-ray observations and inferred parameters of supernova remnants. A comparison of the present results with those for the adiabatic model indicates differences which are less than present observational uncertainties. It is concluded that most parameters of supernova remnants inferred from X-ray measurements are relatively insensitive to the specifics of the blast-wave model.
Dynamics of a spark produced blast wave
International Nuclear Information System (INIS)
The expansion of a spark produced plasma was studied with a simple model and compared to experiments. The model and experiments were performed using a 11.2 nF capacitor bank charged up to 10kV corresponding to a total energy of 0.6 J. The nanosecond shadow pictures revealed detail structure of the shock waves, giving trajectory, speed and blast wave pressure ratios. Conversions of energy into motion and light wave were estimated
An Abridged Review of Blast Wave Parameters
Directory of Open Access Journals (Sweden)
Manmohan Dass Goel
2012-09-01
Full Text Available In case of blast loading on structures, analysis is carried out in two stages, first the blast loading on a particular structure is determined and second, an evaluation is made for the response of the structure to this loading. In this paper, a review of the first part is presented which includes various empirical relations available for computation of blast load in the form of pressure-time function resulting from the explosion in the air. Different empirical techniques available in the form of charts and equations are reviewed first and then the various blast wave parameters are computed using these equations. This paper is providing various blast computation equations, charts, and references in a concise form at a single place and to serve as base for researchers and designers to understand, compare, and then compute the blast wave parameters. Recommendations are presented to choose the best suitable technique from the available methods to compute the pressure-time function for obtaining structural response.Defence Science Journal, 2012, 62(5, pp.300-306, DOI:http://dx.doi.org/10.14429/dsj.62.1149
The blast wave of Tycho's supernova remnant
Cassam-Chenai, Gamil; Hughes, John P.; Ballet, Jean; Decourchelle, Anne
2007-01-01
We use the Chandra X-ray Observatory to study the region in the Tycho supernova remnant between the blast wave and the shocked ejecta interface or contact discontinuity. This zone contains all the history of the shock-heated gas and cosmic-ray acceleration in the remnant. We present for the first time evidence for significant spatial variations of the X-ray synchrotron emission in the form of spectral steepening from a photon index of 2.6 right at the blast wave to a value of 3.0 several arcs...
Study of high Mach number laser driven blast waves
International Nuclear Information System (INIS)
The study of blast waves produced by intense lasers in gases is motivated by the desire to explore astrophysically relevant hydrodynamic phenomena in the laboratory. A systematic scan of laser produced blast waves was performed and the structure of blast waves was examined over a wide range of drive laser energy. Lasers with energies ranging from 10-1000 J illuminated a pin target in either xenon or nitrogen gas, creating a spherical blast wave. A strongly radiating blast wave in xenon gas is observed while blast waves in nitrogen more closely approximate a pure Taylor-Sedov wave. It is also found that at all laser energies, blast waves traveling through xenon gas had their hydrodynamic evolution significantly affected by the passage of illumination laser
Close-in Blast Waves from Spherical Charges*
Howard, William; Kuhl, Allen
2011-06-01
We study the close-in blast waves created by the detonation of spherical high explosives (HE) charges, via numerical simulations with our Arbitrary-Lagrange-Eulerian (ALE3D) code. We used a finely-resolved, fixed Eulerian 2-D mesh (200 μm per cell) to capture the detonation of the charge, the blast wave propagation in air, and the reflection of the blast wave from an ideal surface. The thermodynamic properties of the detonation products and air were specified by the Cheetah code. A programmed-burn model was used to detonate the charge at a rate based on measured detonation velocities. The results were analyzed to evaluate the: (i) free air pressure-range curves: Δps (R) , (ii) free air impulse curves, (iii) reflected pressure-range curves, and (iv) reflected impulse-range curves. A variety of explosives were studied. Conclusions are: (i) close-in (R Detonation'' of the explosive (because close-in, there is not enough time to fully couple the chemical energy to the air via piston work); (iii) instead they are related to the detonation conditions inside the charge. Scaling laws will be proposed for such close-in blast waves.
Blast wave propagation and the influence of obstacles
International Nuclear Information System (INIS)
Pressure characteristics of blast waves simulating unconfined gas explosions are investigated through a series of laboratory-scale experiments and larger scale field tests. Initially, the distance attenuation and the degree of rotational symmetry close to the source was investigated for the gas filled latex balloons used in these experiments, and for the field tests, the influence of different atmospheric condtions has primarily been established by using high-explosives detonators. The interaction between the blast wave and different boundaries and obstacles have been investigated in both laboratory-scale and field tests, and it is shown, that the influence is a very localized effect, leaving the blast wave unaffected at larger distances. The interaction with groups of building-like structures has been investigated in laboratory-scale tests, and it is shown that the pressures measured on the obstacle surfaces apparently are affected by both reflection and diffraction of the incoming blast wave. Pressure distribution and reflection factors for a single wall has been determined in the field tests, and relatively large reflected pressures have been measured. Correspondingly large pressures have been measured at certain locations at a group of buildings. (author)
The use of computer blast simulations to improve blast quality
International Nuclear Information System (INIS)
Atomic Energy of Canada Limited is constructing an Underground Research Laboratory (URL) as part of a comprehensive program to evaluate the concept of nuclear fuel waste disposal deep in crystalline rock formations. Careful blasting methods have been used to minimize damage to the excavation surfaces. Good wall quality is desirable in any excavation. In excavations required for nuclear waste disposal, the objective will be to minimize blast-induced fractures which may complicate the sealing requirements necessary to control subsequent movement of groundwater around a sealed disposal vault. The construction of the URL has provided an opportunity for the development of controlled blasting methods, especially for drilling accuracy and optimization of explosive loads in the perimeter and cushion holes. The work has been assisted by the use of blast simulations with the mathematical model Blaspa. This paper reviews the results of a recent project to develop a controlled method of full-face blasting, and compares the observed field results with the results of a blast simulator called Blaspa. Good agreement is found between the two, and the Blaspa results indicate quantitatively how the blasting may induce damage in the final excavation surface. In particular, the rock in the final wall may be stressed more severely by the cushion holes than by the perimeter holes. Bootleg of the rock between the perimeter and cushion rows occurs when the burst-out velocity imparted to it by the explosive loads in the perimeter holes is inadequate. In practice, these findings indicate that quantitative rock stress and rock burst-out velocity criteria can be established to minimize wall damage and bootleg. Thus, blast simulations become an efficient way to design controlled blasting and to optimize quality of the excavation surface
Numerical Study on Blast Wave Propagation Driven by Unsteady Ionization Plasma
International Nuclear Information System (INIS)
Understanding the dynamics of laser-produced plasma is essential for increasing the available thrust and energy conversion efficiency from a pulsed laser to a blast wave in a gas-driven laser-propulsion system. The performance of a gas-driven laser-propulsion system depends heavily on the laser-driven blast wave dynamics as well as on the ionizing and/or recombining plasma state that sustains the blast wave. In this study, we therefore develop a numerical simulation code for a laser-driven blast wave coupled with time-dependent rate equations to explore the formation of unsteady ionizing plasma produced by laser irradiation. We will also examine the various properties of blast waves and unsteady ionizing plasma for different laser input energies
Blast loading of masonry infills: testing and simulation
Pereira, João Miguel; Campos, José de; Lourenço, Paulo B.
2015-01-01
This work intends to present a newly developed test setup for dynamic out-of-plane loading using underWater Blast Wave Generators (WBWG) as loading source. Underwater blasting operations have been, during the last decades, subject of research and development of maritime blasting operations (including torpedo studies), aquarium tests for the measurement of blasting energy of industrial explosives and confined underwater blast wave generators. WBWG allow a wide range for the produced blast impu...
Directory of Open Access Journals (Sweden)
Chenzhi Wang
Full Text Available Human exposure to blast waves without any fragment impacts can still result in primary blast-induced traumatic brain injury (bTBI. To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human female. The finite element head model was partially validated and was subjected to the blast waves of five blast intensities from the anterior, right lateral, and posterior directions at a stand-off distance of one meter from the detonation center. Simulation results show that the blast wave directly transmits into the head and causes a pressure wave propagating through the brain tissue. Intracranial pressure (ICP is predicted to have the highest magnitude from a posterior blast wave in comparison with a blast wave from any of the other two directions with same blast intensity. The brain model predicts higher positive pressure at the site proximal to blast wave than that at the distal site. The intracranial pressure wave invariably travels into the posterior fossa and vertebral column, causing high pressures in these regions. The severities of cerebral contusions at different cerebral locations are estimated using an ICP based injury criterion. Von Mises stress prevails in the cortex with a much higher magnitude than in the internal parenchyma. According to an axonal injury criterion based on von Mises stress, axonal injury is not predicted to be a cause of primary brain injury from blasts.
Wang, Chenzhi; Pahk, Jae Bum; Balaban, Carey D; Miller, Mark C; Wood, Adam R; Vipperman, Jeffrey S
2014-01-01
Human exposure to blast waves without any fragment impacts can still result in primary blast-induced traumatic brain injury (bTBI). To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human female. The finite element head model was partially validated and was subjected to the blast waves of five blast intensities from the anterior, right lateral, and posterior directions at a stand-off distance of one meter from the detonation center. Simulation results show that the blast wave directly transmits into the head and causes a pressure wave propagating through the brain tissue. Intracranial pressure (ICP) is predicted to have the highest magnitude from a posterior blast wave in comparison with a blast wave from any of the other two directions with same blast intensity. The brain model predicts higher positive pressure at the site proximal to blast wave than that at the distal site. The intracranial pressure wave invariably travels into the posterior fossa and vertebral column, causing high pressures in these regions. The severities of cerebral contusions at different cerebral locations are estimated using an ICP based injury criterion. Von Mises stress prevails in the cortex with a much higher magnitude than in the internal parenchyma. According to an axonal injury criterion based on von Mises stress, axonal injury is not predicted to be a cause of primary brain injury from blasts. PMID:25409326
Concerning isothermal self-similar blast waves
International Nuclear Information System (INIS)
The two-dimensional self-similar flow behind a blast wave from a line explosion in a medium whose density varies with distance as rsup(-ω) is investigated with the assumption that the flow is isothermal. If ω ω > 0, no critical points exist and a continuous solution passing through both the origin and the shock is shown to exist. If 16/9 = 2 no physically acceptable solution exists since the mass behind the shock is infinite. The dependence of the solutions which have zero flow velocity at the origin on the parameter ω is analytic for ω > 0 so that interpolation between neighboring values of ω is permitted. The stability of these isothermal blast waves is investigated to two-dimensional but non-self-similar perturbations. (Auth.)
Dynamics of adiabatic blast waves in media of finite mass
International Nuclear Information System (INIS)
A basic formulation is developed to describe the mass motion for nonrelativistic, spherically symmetric blast waves. The formulation is quite general in the sense that it applies to blast waves generated by either a strong explosion or a continuous energy injection, and in that it applies to an arbitrary density distribution. A simple method is developed to describe the motion of the shock by modifying the Kompaneets approximation. The formulation is applied to blast waves in specific density distributions, including an exponential medium, a Gaussian medium, and a medium with density distribution which asymptotically approaches a power law. Comparisons with numerical results for spherically symmetric blast waves are made. The one-dimensional formulation is generalized to nonspherically symmetric blast waves by making the assumption that the blast wave expands radially. Comparisons are made with numerical results for an adiabatic supershell in a plane-parallel medium. 32 refs
Boundary-layer theory for blast waves
Kim, K. B.; Berger, S. A.; Kamel, M. M.; Korobeinikov, V. P.; Oppenheim, A. K.
1975-01-01
It is profitable to consider the blast wave as a flow field consisting of two regions: the outer, which retains the properties of the inviscid solution, and the inner, which is governed by flow equations including terms expressing the effects of heat transfer and, concomitantly, viscosity. The latter region thus plays the role of a boundary layer. Reported here is an analytical method developed for the study of such layers, based on the matched asymptotic expansion technique combined with patched solutions.
PERONI MARCO; SOLOMOS George; Viaccoz, Bernard
2013-01-01
The Blast Simulator project involves the development of an apparatus able to reproduce the effects of a blast pressure wave on large scale structural components (such as columns, walls, etc.) with the objective to improve their strength in these severe loading situations. This technical report presents the setting up and the performance assessment of the prototype blast actuator developed at the JRC. The first preliminary tests performed have been described and evaluated. Satisfactory result...
The use of computer blast simulations to improve blast quality
International Nuclear Information System (INIS)
An underground research laboratory (URL) has been constructed as part of a comprehensive program to evaluate the concept of nuclear fuel waste disposal in deep crystalline rock formations. Careful blasting methods have been used to minimize damage to the excavation surfaces. This paper reviews the results of the program to develop controlled blasting for the full-face method, comparing the field observed results achieved with the simulated theoretical results. The simulated results indicate how the blasting may damage the excavation surface. Results suggest that the rock around the final wall is stressed more severely by the cushion holes than by the perimeter holes and that bootleg of the rock between the perimeter and cushion rows occurs when the burst-out velocity imparted to it by the explosive loads in the perimeter holes is inadequate
Behavior of blast wave in nuclear fuel cycle facility
International Nuclear Information System (INIS)
Based on some recent explosion accidents in nuclear fuel cycle facilities, the blast wave propagation in complex path and interactions between blast wave and complex media are ones of the important research topics of the safety. Then, in order to investigate the blast wave propagation in nuclear facility, optical experiment using the micro explosives and pressure measurements are conducted. And, numerical calculation is performed to compare with the experimental results. This paper describes how to conduct the experiments and results are summarized. Finally, behavior of blast wave in complex path will be discussed. (author)
Significance of blast wave studies to propulsion.
Oppenheim, A. K.
1971-01-01
Brief survey of experimental methods currently used for the study of blast wave phenomena with emphasis on high rate exothermic processes. The experimental techniques have used such devices as divergent test sections in shock or detonation tubes, employment of proper test gases, as in marginal detonations, and a variety of explosion systems from finite source explosion apparatus to devices where virtually point explosions are obtained by local breakdown initiated by means of focused laser irradiation. Other methods used are detonation tubes where pressure waves are generated by accelerating flames or by exothermic reactions developed behind reflected shocks, as well as a variety of converging shock and implosion vessels.
International Nuclear Information System (INIS)
Experimental investigations into the dynamics of cylindrical, laser-driven, high-Mach-number shocks are used to study the thermal cooling instability predicted to occur in astrophysical radiative blast waves. A streaked Schlieren technique measures the full blast-wave trajectory on a single-shot basis, which is key for observing shock velocity oscillations. Electron density profiles and deceleration parameters associated with radiative blast waves were recorded, enabling the calculation of important blast-wave parameters including the fraction of radiated energy, ε, as a function of time for comparison with radiation-hydrodynamics simulations
Numerical investigation on optimizing blast wave focusing effects for multiple munitions
Qiu, Shi; Eliasson, Veronica
2015-11-01
The phenomenon of blast wave focusing onto a specified target has been studied. Simulations were performed in which multiple munitions were placed in a circular pattern around a target. The number of munitions was varied through multiple cases while the total energy distributed among all munitions was held constant. Previous research shows that there exits an optimal number of munitions to produce the most extreme conditions at the target while simultaneously reducing collateral damage. Two numerical approaches, inviscid Euler equations and geometrical shock dynamics were used to study the interaction between blast waves in order to further investigate the optimization problem. To generate initial conditions for geometrical shock dynamics simulations on interaction between blast waves, it was found that a transition point between regular reflection and irregular reflection needs to be determined in advance. Both experimental and theoretical investigation is included to study the transition condition. Optimization strategy for focusing blast waves is also discussed.
Experimental Investigation of a Novel Blast Wave Mitigation Device
Su, Zhenbi; Peng, Wen; Zhang, Zhaoyan; Gogos, George; Skaggs, Reed; Cheeseman, Bryan; Yen, Chian Fong
2009-01-01
A novel blast wave mitigation device was investigated experimentally in this paper. The device consists of a piston-cylinder assembly. A shock wave is induced within the cylinder when a blast wave impacts on the piston. The shock wave propagates inside the device and is reflected repeatedly. The shock wave propagation process inside the device lengthens the duration of the force on the base of the device to several orders of magnitude of the duration of the blast wave, while it decreases the ...
Numerical and experimental study of blast wave shape in tunnels
Pennetier, Olivier; Langlet, André; William-Louis, Mame J.-P.
2012-01-01
When an explosion occurs in a tunnel, the study of the blast wave quickly becomes complicated, due to the multiple propagation patterns of the blast wave (Incident wave, regular and Mach reflections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, one can see the well known free-field pressure wave. This overpressure, during its propagation, after multiple reflections on the tunnel's walls, can behave like a one-dimensional wave. ...
Self-similar solutions of laser produced blast waves
Reddy, KPJ
1996-01-01
The aerodynamics of the blast wave produced by laser ablation is studied using the piston analogy. The unsteady one-dimensional gasdynamic equations governing the flow an solved under assumption of self-similarity. The solutions are utilized to obtain analytical expressions for the velocity, density, pressure and temperature distributions. The results predict. all the experimentally observed features of the laser produced blast waves.
Computation of viscous blast wave flowfields
Atwood, Christopher A.
1991-01-01
A method to determine unsteady solutions of the Navier-Stokes equations was developed and applied. The structural finite-volume, approximately factored implicit scheme uses Newton subiterations to obtain the spatially and temporally second-order accurate time history of the interaction of blast-waves with stationary targets. The inviscid flux is evaluated using MacCormack's modified Steger-Warming flux or Roe flux difference splittings with total variation diminishing limiters, while the viscous flux is computed using central differences. The use of implicit boundary conditions in conjunction with a telescoping in time and space method permitted solutions to this strongly unsteady class of problems. Comparisons of numerical, analytical, and experimental results were made in two and three dimensions. These comparisons revealed accurate wave speed resolution with nonoscillatory discontinuity capturing. The purpose of this effort was to address the three-dimensional, viscous blast-wave problem. Test cases were undertaken to reveal these methods' weaknesses in three regimes: (1) viscous-dominated flow; (2) complex unsteady flow; and (3) three-dimensional flow. Comparisons of these computations to analytic and experimental results provided initial validation of the resultant code. Addition details on the numerical method and on the validation can be found in the appendix. Presently, the code is capable of single zone computations with selection of any permutation of solid wall or flow-through boundaries.
Blast-wave snapshots from RHIC
Tomasik, Boris
2003-01-01
I present fits with the so-called blast-wave model to single-particle spectra and HBT correlations from Au+Au collisions at a CMS energy of 130 AGeV. There is only little choice of freeze-out temperature and transverse flow velocity for which the model fits both the identified spectra and the correlation radii just well enough not to be excluded. The observed steep M_t dependence of R_side leads to a temperature which it is problematic to interpret. The applicability of the model for the free...
Cosmic Ray Origins in Supernova Blast Waves
Bell, A R
2014-01-01
We extend the self-similar solution derived by Chevalier for a Sedov blast wave accelerating cosmic rays (CR) to show that the Galactic CR population can be divided into: (A) CR with energies above ~200GeV released upstream during CR acceleration by supernova remnants (SNR), (B) CR advected into the interior of the SNR during expansion and then released from the SNR at the end of its life to provide the Galactic CR component below ~200GeV. The intersection between the two populations may correspond to a measured change in the Galactic CR spectral index at this energy.
Non-equilibrium ionized blast wave
Wu, S. T.
1974-01-01
The structure of a cylindrical blast wave with ionization at non-LTE conditions was calculated using equations previously developed by Wu and Fu (1970). The degree of ionization was predicted by a modified Saha equation. Temperature profiles show that the temperature at non-LTE conditions is lower than at LTE near the shock front. This corresponds to a higher degree of ionization for the non-LTE limit, which indicates that the neutral gas absorption is much more efficient at non-LTE than at the LTE limit. The decaying velocity under non-LTE is approximately 15% less than under LTE.
On the Interaction and Coalescence if Spherical Blast Waves
Kandula, Max; Freeman, Robert J.
2005-01-01
The scaling and similarity laws concerning the propagation of isolated spherical blast waves are briefly reviewed. Both point source explosions and high pressure gas explosions are considered. Test data on blast overpressure from the interaction and coalescence of spherical blast waves emanating from explosives in the form of shaped charges of different strength placed in the vicinity of a solid propellant stack are presented. These data are discussed with regard to the scaling laws concerning the decay of blast overpressure. The results point out the possibility of detecting source explosions from far-field pressure measurements.
A Thoracic Mechanism of Mild Traumatic Brain Injury Due to Blast Pressure Waves
Courtney, Amy; Courtney, Michael
2008-01-01
The mechanisms by which blast pressure waves cause mild to moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating b...
Modeling of aqueous foam blast wave attenuation
Directory of Open Access Journals (Sweden)
Domergue L.
2011-01-01
Full Text Available The use of aqueous foams enables the mitigation of blast waves induced by the explosion of energetic materials. The two-phase confinement gives rise to interphase interactions between the gaseous and liquid phases, which role have been emphasized in shock-tube studies with solid foams [1, 2]. Multifluid formalism enables the thermo-mechanical disequilibria between phases to be taken into account. The flow model ensures the correct estimation of the acoustic impedance of the two-phase media. As for the numerical scheme, Riemann solvers are used to describe the microscopic fluid interactions, the summation of which provides the multiphase flux. The role of the different transfer mechanisms is evaluated in the case where the liquid ligaments of the foam matrix have been shattered into droplets by the shock impingement. Characteristics of blast waves in heterogeneous media leads to a decrease of overpressure. The numerical results have been compared favorably to experimental data [3, 4].
Krause, G.; Cécere, M.; Francile, C.; Costa, A.; Elaskar, S.; Schneiter, M.
2015-11-01
We examine the capability of a blast-wave scenario - associated with a coronal flare or to the expansion of CME flanks - to reproduce a chromospheric Moreton phenomenon. We also simulate the Moreton event of 2006 December 06, considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock - able to generate a detectable chromospheric Moreton wave - a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that a flare ignited blast-wave or the expansion of the CME flanks emulated as an instantaneous or a temporal piston model, respectively, are capable to reproduce the observations.
The tank's dynamic response under nuclear explosion blast wave
International Nuclear Information System (INIS)
To weapons and equipment, blast wave is the primary destructive factor. In this paper, taken the real model-59 tank as an example, we try to transform the damage estimation problem into computing a fluid structure interaction problem with finite element method. The response of tank under nuclear explosion blast wave is computed with the general-coupling algorithm. Also, the dynamical interaction of blast wave and tank is reflected in real time. The deformation of each part of the tank is worked out and the result corresponds to the real-measured data. (authors)
Relativistic blast waves in two dimensions. I - The adiabatic case
Shapiro, P. R.
1979-01-01
Approximate solutions are presented for the dynamical evolution of strong adiabatic relativistic blast waves which result from a point explosion in an ambient gas in which the density varies both with distance from the explosion center and with polar angle in axisymmetry. Solutions are analytical or quasi-analytical for the extreme relativistic case and numerical for the arbitrarily relativistic case. Some general properties of nonplanar relativistic shocks are also discussed, including the incoherence of spherical ultrarelativistic blast-wave fronts on angular scales greater than the reciprocal of the shock Lorentz factor, as well as the conditions for producing blast-wave acceleration.
Investigation of Ultrafast Laser-Driven Radiative Blast Waves
International Nuclear Information System (INIS)
We have examined the evolution of cylindrically symmetric blast waves produced by the deposition of femtosecond laser pulses in gas jets. In high-Z gases radiative effects become important. We observe the production of an ionization precursor ahead of the shock front and deceleration parameters below the adiabatic value of 1/2 (for a cylinder), an effect expected when the blast wave loses energy by radiative cooling. Despite significant radiative cooling, the blast waves do not appear to develop thin shell instabilities expected for strongly radiative waves. This is believed to be due to the stabilizing effect of a relatively thick blast wave shell resulting in part from electron thermal conduction effects
BARYON LOADED RELATIVISTIC BLAST WAVES IN SUPERNOVAE
International Nuclear Information System (INIS)
We provide a new analytic blast wave solution which generalizes the Blandford-McKee solution to arbitrary ejecta masses and Lorentz factors. Until recently relativistic supernovae have been discovered only through their association with long-duration gamma-ray bursts (GRBs). The blast waves of such explosions are well described by the Blandford-McKee (in the ultra-relativistic regime) and Sedov-Taylor (in the non-relativistic regime) solutions during their afterglows, as the ejecta mass is negligible in comparison to the swept-up mass. The recent discovery of the relativistic supernova SN 2009bb, without a detected GRB, opens up the possibility of highly baryon loaded, mildly relativistic outflows which remains in nearly free-expansion phase during the radio afterglow. In this work, we consider a massive, relativistic shell, launched by a Central Engine Driven EXplosion (CEDEX), decelerating adiabatically due to its collision with the pre-explosion circumstellar wind profile of the progenitor. We compute the synchrotron emission from relativistic electrons in the shock amplified magnetic field. This models the radio emission from the circumstellar interaction of a CEDEX. We show that this model explains the observed radio evolution of the prototypical SN 2009bb and demonstrate that SN 2009bb had a highly baryon loaded, mildly relativistic outflow. We discuss the effect of baryon loading on the dynamics and observational manifestations of a CEDEX. In particular, our predicted angular size of SN 2009bb is consistent with very long baseline interferometric (VLBI) upper limits on day 85, but is presently resolvable on VLBI angular scales, since the relativistic ejecta is still in the nearly free-expansion phase.
Spike Penetration in Blast-Wave-Driven Instabilities
Drake, R. Paul
2010-05-01
Recent experiments by C. Kuranz and collaborators, motivated by structure in supernovae, have studied systems in which planar blast waves encounter interfaces where the density decreases. During the Rayleigh-Taylor (RT) phase of such experiments, they observed greater penetration of the RT spikes than tends to be seen in simulations. Here we seek to employ semi-analytic theory to understand the general nature and regimes of spike penetration for blast-wave-driven instabilities. This problem is not trivial as one must account for the initial vorticity deposition at the interface, for its time-dependent deceleration, for the expansion of the shocked material in time and space, and for the drag on the broadened tips of the spikes. We offer here an improved evaluation of the material expansion in comparison to past work. The goal is to use such models to increase our ability to interpret the behavior of simulations of such systems, in both the laboratory and astrophysics. Supported by the US DOE NNSA under the Predictive Sci. Academic Alliance Program by grant DE-FC52-08NA28616, the Stewardship Sci. Academic Alliances program by grant DE-FG52-04NA00064, and the Nat. Laser User Facility by grant DE-FG03-00SF22021.
Blast wave radiation source measurement experiments on Z
International Nuclear Information System (INIS)
The Dynamic Hohlraum (DH) radiation on the Z facility at Sandia National Laboratories is a bright source of radiant energy that has proven useful for High Energy Density (HED) physics experiments. To be useful for HED experiments, where computer simulations need to be compared with experimental measurements, the radiation output from a DH on Z needs to be well-known. We present in this paper a new method for measuring the delivered radiation energy deposited in an experiment, specifically, an experiment driven by a Z DH. This technique uses a blast wave produced in a SiO2 foam, which is initially super-sonic but transitions to sub-sonic, producing a shock at the transition point that is observable via radiography. The position of this shock is a sensitive measure of the radiation drive energy from the Z DH. Computer simulations have been used to design and analyze a Z foam blast wave experiment. This experiment has been shot on Z and experimental results compare favorably with the computations. (authors)
High-fidelity simulations of blast loadings in urban environments using an overset meshing strategy
Wang, X.; Remotigue, M.; Arnoldus, Q.; Janus, M.; Luke, E.; Thompson, D.; Weed, R.; Bessette, G.
2016-07-01
Detailed blast propagation and evolution through multiple structures representing an urban environment were simulated using the code Loci/BLAST, which employs an overset meshing strategy. The use of overset meshes simplifies mesh generation by allowing meshes for individual component geometries to be generated independently. Detailed blast propagation and evolution through multiple structures, wave reflection and interaction between structures, and blast loadings on structures were simulated and analyzed. Predicted results showed good agreement with experimental data generated by the US Army Engineer Research and Development Center. Loci/BLAST results were also found to compare favorably to simulations obtained using the Second-Order Hydrodynamic Automatic Mesh Refinement Code (SHAMRC). The results obtained demonstrated that blast reflections in an urban setting significantly increased the blast loads on adjacent buildings. Correlations of computational results with experimental data yielded valuable insights into the physics of blast propagation, reflection, and interaction under an urban setting and verified the use of Loci/BLAST as a viable tool for urban blast analysis.
Characterising the acceleration phase of blast wave formation
International Nuclear Information System (INIS)
Intensely heated, localised regions in uniform fluids will rapidly expand and generate an outwardly propagating blast wave. The Sedov-Taylor self-similar solution for such blast waves has long been studied and applied to a variety of scenarios. A characteristic time for their formation has also long been identified using dimensional analysis, which by its very nature, can offer several interpretations. We propose that, rather than simply being a characteristic time, it may be interpreted as the definitive time taken for a blast wave resulting from an intense explosion in a uniform media to contain its maximum kinetic energy. A scaling relation for this measure of the acceleration phase, preceding the establishment of the blast wave, is presented and confirmed using a 1D planar hydrodynamic model
Blast wave parameters for spherical explosives detonation in free air
2011-01-01
Several formulations have been published to define the characteristic parameters of an incident blast wave. In almost all previous work, the charge examined has been TNT explosive and overpressure has been the main parameter examined. In this paper, we describe an investigation based on three explosives, TNT, PETN and ANFO, which has been conducted by considering three parameters: overpressure, duration and impulse of the positive blast wave phase. Calculations of the three parameters were co...
Evidence for a blast wave from compressed nuclear matter
International Nuclear Information System (INIS)
Central collisions of heavy nuclei at c.m. kinetic energies of a few hundred MeV per nucleon produce fireballs of hot, dense nuclear matter. Each fireball explodes, producing a blast wave of nucleons and pions. Several features of the observed cross sections for pions and protons from Ne on Na F at 0.8 GeV/nucleon (lab) are explained by the blast wave, but contradict earlier, purely thermal models. The available energy is equally divided between translational energy of the blast, and thermal motion of the particles in the exploding matter
High-speed measurement of firearm primer blast waves
Courtney, Michael; Daviscourt, Joshua; Eng, Jonathan; Courtney, Amy
2012-01-01
This article describes a method and results for direct high-speed measurements of firearm primer blast waves employing a high-speed pressure transducer located at the muzzle to record the blast pressure wave produced by primer ignition. Key findings are: 1) Most of the lead styphnate based primer models tested show 5.2-11.3% standard deviation in the magnitudes of their peak pressure. 2) In contrast, lead-free diazodinitrophenol (DDNP) based primers had standard deviations of the peak blast p...
Blast wave interaction with a rigid surface
International Nuclear Information System (INIS)
A simple model used to investigate blast wave interactions with a rigid surface is presented. The model uses a constant volume energy source analogue to predict pressure histories at gauges located directly above the charge. A series of two-dimensional axi-symmetric CFD calculations were performed, varying the height of the charge relative to the ground. Pressure histories, along with isopycnic plots are presented to evaluate the effects of placing a charge in close proximity to a rigid surface. When a charge is placed near a solid surface the pressure histories experienced at gauges above the charge indicate the presence of two distinct pressure peaks. The first peak is caused by the primary shock and the second peak is a result of the wave reflections from the rigid surface. As the distance from the charge to the wall is increased the magnitude of the second pressure peak is reduced, provided that the distance between the charge and the gauge is maintained constant. The simple model presented is able to capture significant, predictable flow features. (author)
Self-similar ultra-relativistic jetted blast wave
Keshet, Uri
2015-01-01
Following a suggestion that a directed relativistic explosion may have a universal intermediate asymptotic, we derive a self-similar solution for an ultra-relativistic jetted blast wave. The solution involves three distinct regions: an approximately paraboloid head where the Lorentz factor $\\gamma$ exceeds $\\sim1/2$ of its maximal, nose value; a geometrically self-similar, expanding envelope slightly narrower than a paraboloid; and an axial core in which the radial flow $U$ converges inward towards the axis. Most ($\\sim 80\\%$) of the energy lies well beyond the head. Here, a radial cross section shows a maximal $\\gamma$ (separating the core and the envelope), a sign reversal in $U$, and a minimal $\\gamma$, at respectively $\\sim 1/6$, $\\sim1/4$, and $\\sim3/4$ of the shock radius. The solution is apparently unique, and approximately agrees with previous simulations, of different initial conditions, that resolved the head. This suggests that unlike a spherical relativistic blast wave, our solution is an attracto...
High resolution imaging of colliding blast waves in cluster media
International Nuclear Information System (INIS)
Strong shocks and blast wave collisions are commonly observed features in astrophysical objects such as nebulae and supernova remnants. Numerical simulations often underpin our understanding of these complex systems, however modelling of such extreme phenomena remains challenging, particularly so for the case of radiative or colliding shocks. This highlights the need for well-characterized laboratory experiments both to guide physical insight and to provide robust data for code benchmarking. Creating a sufficiently high-energy-density gas medium for conducting scaled laboratory astrophysics experiments has historically been problematic, but the unique ability of atomic cluster gases to efficiently couple to intense pulses of laser light now enables table top scale (1 J input energy) studies to be conducted at gas densities of >1019 particles cm-3 with an initial energy density >5 x 109 J g-1. By laser heating atomic cluster gas media we can launch strong (up to Mach 55) shocks in a range of geometries, with and without radiative precursors. These systems have been probed with a range of optical and interferometric diagnostics in order to retrieve electron density profiles and blast wave trajectories. Colliding cylindrical shock systems have also been studied, however the strongly asymmetric density profiles and radial and longitudinal mass flow that result demand a more complex diagnostic technique based on tomographic phase reconstruction. We have used the 3D magnetoresistive hydrocode GORGON to model these systems and to highlight interesting features such as the formation of a Mach stem for further study
An Abridged Review of Blast Wave Parameters
Manmohan Dass Goel; Vasant A. Matsagar; Gupta, Anil K.; Steffen Marburg
2012-01-01
In case of blast loading on structures, analysis is carried out in two stages, first the blast loading on a particular structure is determined and second, an evaluation is made for the response of the structure to this loading. In this paper, a review of the first part is presented which includes various empirical relations available for computation of blast load in the form of pressure-time function resulting from the explosion in the air. Different empirical techniques available in th...
Instabilities and the adiabatic and isothermal blast wave models for supernova remnants
International Nuclear Information System (INIS)
Isenberg as well as lerche and Vasyliunas proposed the existence of an instability to radial perturbations in adiabatic and isothermal models of self-similar supernova blast waves. Their derivations fail to impose the physical conservation laws at the shock (i.e., the Rankine-Hugoniot jump conditions) as boundary conditions, and their claim of an instability is unsubstantiated. Although as analytic demonstration of the stability of the adiabatic self-similar solution does not presently exist, the cumulative result of three decades of gas dynamic experimentation and numerical simulation provides unmistakable evidence for the stabilty of self-similar blast waves
Dynamics and stability of relativistic gamma-ray-bursts blast waves
Meliani, Z.; Keppens, R.
2010-01-01
Aims. In gamma-ray-bursts (GRBs), ultra-relativistic blast waves are ejected into the circumburst medium. We analyse in unprecedented detail the deceleration of a self-similar Blandford-McKee blast wave from a Lorentz factor 25 to the nonrelativistic Sedov phase. Our goal is to determine the stability properties of its frontal shock. Methods. We carried out a grid-adaptive relativistic 2D hydro-simulation at extreme resolving power, following the GRB jet during the entire afterglow phase. We ...
Numerical study of laser-induced blast wave coupled with unsteady ionization processes
International Nuclear Information System (INIS)
We present the results of the numerical simulation of laser-induced blast wave coupled with rate equations to clarify the unsteady property of ionization processes during pulse heating. From comparison with quasi-steady computations, the plasma region expands more widely, which is sustained by the inverse-bremsstrahlung since an ionization equilibrium does not establish at the front of the plasma region. The delayed relaxation leads to the rapid expansion of the driving plasma and enhances the energy conversion efficiency from a pulse heating laser to the blast wave
Near-Field Characterization of Radial and Axial Blast Waves From a Cylindrical Explosive Charge
McNesby, Kevin; Homan, Barrie
This paper uses experiment (high speed imaging) and simulation (ALE-3D) to investigate radial and axial blast waves produced by uncased, cylindrical charges of TNT (trinitrotoluene). Recently there has been work reported on predicting secondary blast waves in the explosive mid-field (approximately 1 meter from charge center of mass) for cylindrical charges of RDX (trimethylenetrinitramine)/binder formulations. The work we will present seeks to provide complementary information in the explosive near-field, including the approach to chemical ``freeze out'', for end-detonated, right circular cylinders of TNT. Additionally, this work attempts to retrieve state variables (temperature, pressure, velocities) from high-definition images of the explosive event. Keywords: cylindrical charges, blast, shock waves
SPIKE PENETRATION IN BLAST-WAVE-DRIVEN INSTABILITIES
International Nuclear Information System (INIS)
The problem of interest is the unstable growth of structure at density transitions affected by blast waves, which arise in natural environments such as core-collapse supernovae and in laboratory experiments. The resulting spikes of dense material, which penetrate the less dense material, develop broadened tips, but the degree of broadening varies substantially across both experiments and simulations. The variable broadening presumably produces variations in the drag experienced by the spike tips as they penetrate the less dense material. The present work has used semianalytic theory to address the question of how the variation in drag might affect the spike penetration, for cases in which the post-shock interface deceleration can be described by a power law in a normalized time variable. It did so by following the evolution of structure on the interface through the initial shock passage, the subsequent small-amplitude phase of Rayleigh-Taylor instability growth, and the later phase in which the spike growth involves the competition of buoyancy and drag. In all phases, the expansion of the system during its evolution was accounted for and was important. The calculated spike length is strongly affected by the drag attributed to spike tip broadening. One finds from such a calculation that it is not unreasonable for narrow spikes to keep up with the shock front of the blast wave. The implication is that the accuracy of prediction of spike penetration and consequent structure by simulations very likely depends on how accurately they treat the broadening of the spike tips and the associated drag. Experimental validation of spike morphology in simulations would be useful.
Masonry infill walls under blast loading using confined underwater blast wave generators (WBWG)
Pereira, João M.; Campos, José de; Lourenço, Paulo B.
2015-01-01
The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The behaviour of masonry infill walls subjected to dynamic out-of-plane loading was experimentally investigated in this work. Using confined underwater blast wave generators (WBWG), applying the extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, allowed a surface area distribution avoiding also the generation...
Institute of Scientific and Technical Information of China (English)
ZHANG Xiuhua; DUAN Zhongdong; ZHANG Chunwei
2008-01-01
The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA.The multi-material Eulerian and Lagrangian coupling algorithm was adopted.A fluid-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground,multiple ALE element for simulating air and TNT explosive material.Numerical simulations of the blast pressure wave propagation,structural dynamic responses and deformation,and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed.The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure.The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation.The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic deformation subjected to intensive blast waves,and columns lost carrying capacity,subsequently leading to the collapse of the whole structure.The approach coupling influence between structural deformation and fluid load well simulated the progressive collapse process of structures,and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.
Measurement of Blast Waves from Bursting Pressureized Frangible Spheres
Esparza, E. D.; Baker, W. E.
1977-01-01
Small-scale experiments were conducted to obtain data on incident overpressure at various distances from bursting pressurized spheres. Complete time histories of blast overpressure generated by rupturing glass spheres under high internal pressure were obtained using eight side-on pressure transducers. A scaling law is presented, and its nondimensional parameters are used to compare peak overpressures, arrival times, impulses, and durations for different initial conditions and sizes of blast source. The nondimensional data are also compared, whenever possible, with results of theoretical calculations and compiled data for Pentolite high explosive. The scaled data are repeatable and show significant differences from blast waves generated by condensed high-explosives.
Spike morphology in blast-wave-driven instability experiments
International Nuclear Information System (INIS)
The laboratory experiments described in the present paper observe the blast-wave-driven Rayleigh-Taylor instability with three-dimensional (3D) initial conditions. About 5 kJ of energy from the Omega laser creates conditions similar to those of the He-H interface during the explosion phase of a supernova. The experimental target is a 150 μm thick plastic disk followed by a low-density foam. The plastic piece has an embedded, 3D perturbation. The basic structure of the pattern is two orthogonal sine waves where each sine wave has an amplitude of 2.5 μm and a wavelength of 71 μm. In some experiments, an additional wavelength is added to explore the interaction of modes. In experiments with 3D initial conditions the spike morphology differs from what has been observed in other Rayleigh-Taylor experiments and simulations. Under certain conditions, experimental radiographs show some mass extending from the interface to the shock front. Current simulations show neither the spike morphology nor the spike penetration observed in the experiments. The amount of mass reaching the shock front is analyzed and potential causes for the spike morphology and the spikes reaching the shock are discussed. One such hypothesis is that these phenomena may be caused by magnetic pressure, generated by an azimuthal magnetic field produced by the plasma dynamics.
Heat precursor of the blast wave in weakly ionized plasma
International Nuclear Information System (INIS)
Electron temperature distributions in weakly ionized plasma are numerically calculated for the blast-type shock waves. Comparison with experimental data obtained in glow discharge in Ar, as well as in shock waves with constant pressure in HF low-pressure discharge plasma in air is made
Radiative precursors driven by converging blast waves in noble gases
International Nuclear Information System (INIS)
A detailed study of the radiative precursor that develops ahead of converging blast waves in gas-filled cylindrical liner z-pinch experiments is presented. The experiment is capable of magnetically driving 20 km s−1 blast waves through gases of densities of the order 10−5 g cm−3 (see Burdiak et al. [High Energy Density Phys. 9(1), 52–62 (2013)] for a thorough description). Data were collected for Ne, Ar, and Xe gas-fills. The geometry of the setup allows a determination of the plasma parameters both in the precursor and across the shock, along a nominally uniform line of sight that is perpendicular to the propagation of the shock waves. Radiation from the shock was able to excite NeI, ArII, and XeII/XeIII precursor spectral features. It is shown that the combination of interferometry and optical spectroscopy data is inconsistent with upstream plasmas being in LTE. Specifically, electron density gradients do not correspond to any apparent temperature change in the emission spectra. Experimental data are compared to 1D radiation hydrodynamics HELIOS-CR simulations and to PrismSPECT atomic physics calculations to assist in a physical interpretation of the observations. We show that upstream plasma is likely in the process of being radiatively heated and that the emission from a small percentage of ionised atoms within a cool background plasma dominates the emission spectra. Experiments were carried out on the MAGPIE and COBRA pulsed-power facilities at Imperial College London and Cornell University, respectively
Tailored blast wave formation: Developing experiments pertinent to laboratory astrophysics
International Nuclear Information System (INIS)
The first production of 'tailored' blast waves in a cluster media using an intense, 2x1016 W cm-2, laser pulse is reported. This new technique produces cylindrical blast waves with a strong axial modulation of variable spatial frequency as a seed for instability growth. Spherical or cylindrical colliding blast waves can also be produced. Energy deposition in the cluster medium was modified using moderate-power (15 W cm-2) 'laser-machining', which destroyed clusters in selected regions while keeping the atomic density constant. Electron density profiles track the time evolution showing the production of strongly modulated blast waves and the development of a thin shell after ≅6 ns in H2. Similarity parameters suggest that the hydrogen results are hydrodynamically scalable, but instabilities are precluded by the lack of radiation and low Reynolds number. Similar argon and xenon experiments do not form blast waves on the studied time scale, but indicate that radiation might become influential later in the evolution
Spectroscopic diagnostics in a colliding-blast-wave experiment
International Nuclear Information System (INIS)
Visible spectral lines from n=3, Δn=0 transitions in N+ and N2+ ions are used for measuring the plasma electron density and temperature in a region of two colliding blast waves, propagating through a 1.5--10-Torr nitrogen atmosphere. The blast waves originate at the tips of two aluminum rods irradiated with two beams of the Naval Research Laboratory (NRL) Pharos-III 1.054-μm-wavelength Nd:glass laser operated at an energy of 200--430 J for each beam in 5-ns pulses. An electron density in the colliding-blast-wave region of Ne∼1018 cm-3 was deduced from Stark broadening of spectral lines from N+ ions. An electron temperature of Te∼4 eV was measured in this region from a spectral-line intensity ratio between N2+ and N+ ions. Near one target, an electron density of Ne∼8x1020 cm-3 was determined from series-limit x-ray spectral-line merging; a mean electron temperature of kTe∼225 eV was determined from x-ray line-intensity ratios. Some evidence was found for enhanced velocities for blast waves propagating through a plasma formed by a preceding blast wave
THE EARLY BLAST WAVE OF THE 2010 EXPLOSION OF U SCORPII
International Nuclear Information System (INIS)
Three-dimensional hydrodynamic simulations exploring the first 18 hr of the 2010 January 28 outburst of the recurrent nova U Scorpii have been performed. Special emphasis was placed on capturing the enormous range in spatial scales in the blast. The pre-explosion system conditions included the secondary star and a flared accretion disk. These conditions can have a profound influence on the evolving blast wave. The blast itself is shadowed by the secondary star, which itself gives rise to a low-temperature bow shock. The accretion disk is completely destroyed in the explosion. A model with a disk gas density of 1015 cm-3 produced a blast wave that is collimated and with clear bipolar structures, including a bipolar X-ray emitting shell. The degree of collimation depends on the initial mass of ejecta, energy of explosion, and circumstellar gas density distribution. It is most pronounced for a model with the lowest explosion energy (1043 erg) and mass of ejecta (10-8 M sun). The X-ray luminosities of three of six models computed are close to, but consistent with, an upper limit to the early blast X-ray emission obtained by the Swift satellite, the X-ray luminosity being larger for higher circumstellar gas density and higher ejecta mass. The latter consideration, together with estimates of the blast energy from previous outbursts, suggests that the mass of ejecta in the 2010 outburst was not larger than 10-7 M sun.
Energy Technology Data Exchange (ETDEWEB)
Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T. [Center for High Energy Density Science, Department of Physics, The University of Texas at Austin, C1510, Austin, Texas 78712 (United States)
2013-12-15
Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.
International Nuclear Information System (INIS)
Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics
Some properties of adiabatic blast waves in preexisting cavities
Cox, D. P.; Franco, J.
1981-01-01
Cox and Anderson (1982) have conducted an investigation regarding an adiabatic blast wave in a region of uniform density and finite external pressure. In connection with an application of the results of the investigation to a study of interstellar blast waves in the very hot, low-density matrix, it was found that it would be desirable to examine situations with a positive radial density gradient in the ambient medium. Information concerning such situations is needed to learn about the behavior of blast waves occurring within preexisting, presumably supernova-induced cavities in the interstellar mass distribution. The present investigation is concerned with the first steps of a study conducted to obtain the required information. A review is conducted of Sedov's (1959) similarity solutions for the dynamical structure of any explosion in a medium with negligible pressure and power law density dependence on radius.
Nineteen-Foot Diameter Explosively Driven Blast Simulator; TOPICAL
International Nuclear Information System (INIS)
This report describes the 19-foot diameter blast tunnel at Sandia National Laboratories. The blast tunnel configuration consists of a 6 foot diameter by 200 foot long shock tube, a 6 foot diameter to 19 foot diameter conical expansion section that is 40 feet long, and a 19 foot diameter test section that is 65 feet long. Therefore, the total blast tunnel length is 305 feet. The development of this 19-foot diameter blast tunnel is presented. The small scale research test results using 4 inch by 8 inch diameter and 2 foot by 6 foot diameter shock tube facilities are included. Analytically predicted parameters are compared to experimentally measured blast tunnel parameters in this report. The blast tunnel parameters include distance, time, static, overpressure, stagnation pressure, dynamic pressure, reflected pressure, shock Mach number, flow Mach number, shock velocity, flow velocity, impulse, flow duration, etc. Shadowgraphs of the shock wave are included for the three different size blast tunnels
Stress Wave Interaction Between Two Adjacent Blast Holes
Yi, Changping; Johansson, Daniel; Nyberg, Ulf; Beyglou, Ali
2016-05-01
Rock fragmentation by blasting is determined by the level and state of stress in the rock mass subjected to blasting. With the application of electronic detonators, some researchers stated that it is possible to achieve improved fragmentation through stress wave superposition with very short delay times. This hypothesis was studied through theoretical analysis in the paper. First, the stress in rock mass induced by a single-hole shot was analyzed with the assumptions of infinite velocity of detonation and infinite charge length. Based on the stress analysis of a single-hole shot, the stress history and tensile stress distribution between two adjacent holes were presented for cases of simultaneous initiation and 1 ms delayed initiation via stress superposition. The results indicated that the stress wave interaction is local around the collision point. Then, the tensile stress distribution at the extended line of two adjacent blast holes was analyzed for a case of 2 ms delay. The analytical results showed that the tensile stress on the extended line increases due to the stress wave superposition under the assumption that the influence of neighboring blast hole on the stress wave propagation can be neglected. However, the numerical results indicated that this assumption is unreasonable and yields contrary results. The feasibility of improving fragmentation via stress wave interaction with precise initiation was also discussed. The analysis in this paper does not support that the interaction of stress waves improves the fragmentation.
Shock Tube Design for High Intensity Blast Waves for Laboratory Testing of Armor and Combat Materiel
Courtney, Elijah; Courtney, Michael
2015-01-01
Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ~1 MPa to ~5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods were investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which works by increasing the turbulent flow of the deflagration wave, thus increasing its speed and pressure. This approach increased the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increased the peak pressure from 1.17 MPa to 2.25 MPa. Using a 1...
Blast Wave Initiation of a Sheet Explosive Covered with Metal Plates.
H. S. Yadav; S. G. Sundaram; P. V. Kamat; M. W. Kulkarni
1996-01-01
Initiationof RDX-based sheetexplosiveby a normalincident blast wavehas been studied. Explosive sheets : (i) bare (ii) aluminium foil-covered and (iii) sandwiched between different thicknesses of aluminium alloy metal plates, were impacted by the blast wave. The blast wave was produced by detonating a cylindrical plastic explosive charge kept symmetrically over the sheet at different stand-off distances in the air for varying the intensity of the blast wave. The values of critical distances, p...
Blast waves produced by interactions of femtosecond laser pulses with water
International Nuclear Information System (INIS)
The behaviors of the blast waves produced by femtosecond laser-water interactions, and the blast waves induced by laser self-focusing in air, have been investigated using optical shadowgraphy at a maximum intensity of 1x1016 W/cm2. The temporal evolution of the blast wave launched by the water plasma can be described by a planar blast wave model including source mass. An aneurismlike structure, due to the quick propagation inside a hollow channel formed by laser self-focusing, is observed. The expansion of the channel in air is found to agree with a cylindrical self-similar blast wave solution
A systematic exposition of the conservation equations for blast waves.
Oppenheim, A. K.; Lundstrom, E. A.; Kuhl, A. L.; Kamel, M. M.
1971-01-01
In order to provide a rational background for the analysis of experimental observations of blast wave phenomena, the conservation equations governing their nonsteady flow field are formulated in a general manner, without the usual restrictions imposed by an equation of state, and with proper account taken, by means of source terms, of other effects which, besides the inertial terms that conventionally dominate these equations, can affect the flow. Taking advantage of the fact that a blast wave can be generally considered as a spatially one-dimensional flow field whose nonsteady behavior can be regarded, consequently, as a function of just two independent variables, two generalized blast wave coordinates are introduced, one associated with the front of the blast wave and the other with its flow field. The conservation equations are accordingly transformed into this coordinate system, acquiring thereby a comprehensive character, in that they refer then to any frame of reference, being applicable, in particular, to problems involving either space or time profiles of the gas-dynamic parameters in the Eulerian system, or time profiles in the Lagrangian system.
Supernova-blast waves in wind-blown bubbles, turbulent, and power-law ambient media
Haid, Sebastian; Naab, Thorsten; Seifried, Daniel; Mackey, Jonathan; Gatto, Andrea
2016-01-01
Supernova (SN) blast waves inject energy and momentum into the interstellar medium (ISM), control its turbulent multiphase structure and the launching of galactic outflows. Accurate modelling of the blast wave evolution is therefore essential for ISM and galaxy formation simulations. We present an efficient method to compute the input of momentum, thermal energy, and the velocity distribution of the shock-accelerated gas for ambient media with uniform (and with stellar wind blown bubbles), power-law, and turbulent density distributions. Assuming solar metallicity cooling, the blast wave evolution is followed to the beginning of the momentum conserving snowplough phase. The model recovers previous results for uniform ambient media. The momentum injection in wind-blown bubbles depend on the swept-up mass and the efficiency of cooling, when the blast wave hits the wind shell. For power-law density distributions with $n(r) \\sim$ $r^{-2}$ (for $n(r) > n_{_{\\rm floor}}$) the amount of momentum injection is solely r...
A study of combined particle and blast wave loading of structures
Elgy, I. D.; Pope, D. J.; Pickup, I. M.
2006-08-01
In structural dynamics there are many instances where an appreciation of the combined effect of particulate and air blast loading are essential if an accurate prediction of structural response is to be attained. Examples include: the loading of structures via the detonation of cased munitions; the interaction of blast waves and secondary fragmentation with internal building components after an external contact explosion and the loading of vehicle bellies via the detonation of mines buried in soil. As an analytical simplification, engineers often incorporate the effect of particulate loading by applying a load factor to calculations of the blast component alone. In some cases the fragmentation, can indeed be considered as merely incidental but in others, analysis and experiments have indicated that the presence of inert matter within or in close proximity to a detonated explosive can alter the magnitude, spatial distribution and duration of loading applied to a structure. This paper describes a series of numerical simulations, conducted using the AUTODYN hydrocode, in which the effect of detonating an explosive within a matrix of particles, and the subsequent blast and particulate interaction with a target, was simulated. The total momentum transferred to a target and the spatial momentum distribution is evaluated for both mines buried under soil and confined air blasts. The momentum transferred is investigated as a function of the technique used to model particulation and detonation proximity. These comparisons offer an insight into the mechanisms by which buried blast mines load structures and lead to explanations of differences observed in thin plates deforming under simulated mine blast attacks.
Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel
Institute of Scientific and Technical Information of China (English)
Elijah COURTNEY; Amy COURTNEY; Michael COURTNEY
2014-01-01
Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from w1 MPa to w5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral prim-ing section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform). The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.
Shock tube design for high intensity blast waves for laboratory testing of armor and combat materiel
Directory of Open Access Journals (Sweden)
Elijah Courtney
2014-06-01
Full Text Available Shock tubes create simulated blast waves which can be directed and measured to study blast wave effects under laboratory conditions. It is desirable to increase available peak pressure from ∼1 MPa to ∼5 MPa to simulate closer blast sources and facilitate development and testing of personal and vehicle armors. Three methods are experimentally investigated to increase peak simulated blast pressure produced by an oxy-acetylene driven shock tube while maintaining suitability for laboratory studies. The first method is the addition of a Shchelkin spiral priming section which supports a deflagration to detonation transition. This approach increases the average peak pressure from 1.17 MPa to 5.33 MPa while maintaining a relevant pressure-time curve (near Friedlander waveform. The second method is a bottleneck between the driving and driven sections. Coupling a 79 mm diameter driving section to a 53 mm driven section increases the peak pressure from 1.17 MPa to 2.25 MPa. A 103 mm driving section is used to increase peak pressure to 2.64 MPa. The third method, adding solid fuel to the driving section with the oxy-acetylene, results in a peak pressure increasing to 1.70 MPa.
Indoor propagation and assessment of blast waves from weapons using the alternative image theory
Kong, B.; Lee, K.; Lee, S.; Jung, S.; Song, K. H.
2016-03-01
Blast waves generated from the muzzles of various weapons might have significant effects on the human body, and these effects are recognized as being more severe when weapons are fired indoors. The risk can be assessed by various criteria, such as waveform, exposed energy, and model-based types. This study introduces a prediction model of blast wave propagation for estimating waveform parameters related to damage risk assessment. To simulate indoor multiple reflections in a simple way, the model is based on the alternative image theory and discrete wavefront method. The alternative theory is a kind of modified image theory, but it uses the image space concept from a receiver's perspective, so that it shows improved efficiency for indoor problems. Further, the discrete wavefront method interprets wave propagation as the forward movement of a finite number of wavefronts. Even though the predicted results show slight differences from the measured data, the locations of significant shock waves indicate a high degree of correlation between them. Since the disagreement results not from the proposed techniques but from the assumptions used, it is concluded that the model is appropriate for analysis of blast wave propagation in interior spaces.
Reflection and diffraction phenomena of blast wave propagation in nuclear fuel cycle facility
International Nuclear Information System (INIS)
Based on some recent explosion accidents in nuclear fuel cycle facilities, it is thought that the blast wave propagation which was caused by the explosion accident in nuclear fuel cycle facility and interactions between blast wave and complex media are ones of the important research topics of the safety. Then, in order to investigate the blast wave propagation in nuclear fuel cycle facility, optical experiments using the micro explosives and pressure measurements in scaled Plexiglas model are conducted. And, numerical simulation is performed to compare with the experimental results. As the results, typical wave propagation in closed model and time dependent tendency of pressure are confirmed. Effect by reflection on the walls and no attenuation of pressure are observed conspicuously in closed space. Diffracted wave attack the walls weakly, and it is confirmed that the pressure peaks appear at the corner of closed space. These results inform important data for safety to plan the performance of facility and to design the facility considering the mitigation of explosion accident. (author)
RESONANT AMPLIFICATION OF TURBULENCE BY THE BLAST WAVES
International Nuclear Information System (INIS)
We discuss the idea of whether spherical blast waves can amplify by a nonlocal resonant hydrodynamic mechanism inhomogeneities formed by turbulence or phase segregation in the interstellar medium. We consider the problem of a blast-wave-turbulence interaction in the Linear Interaction Approximation. Mathematically, this is an eigenvalue problem for finding the structure and amplitude of eigenfunctions describing the response of the shock-wave flow to forced oscillations by external perturbations in the ambient interstellar medium. Linear analysis shows that the blast wave can amplify density and vorticity perturbations for a wide range of length scales with amplification coefficients of up to 20, with increasing amplification the larger the length. There also exist resonant harmonics for which the gain becomes formally infinite in the linear approximation. Their orbital wavenumbers are within the range of macro- (l ∼ 1), meso- (l ∼ 20), and microscopic (l > 200) scales. Since the resonance width is narrow (typically, Δl < 1), resonance should select and amplify discrete isolated harmonics. We speculate on a possible explanation of an observed regular filamentary structure of regularly shaped round supernova remnants such as SNR 1572, 1006, or 0509-67.5. Resonant mesoscales found (l ≈ 18) are surprisingly close to the observed scales (l ≈ 15) of ripples in the shell's surface of SNR 0509-67.5
Impact of complex blast waves on the human head: a computational study.
Tan, Long Bin; Chew, Fatt Siong; Tse, Kwong Ming; Chye Tan, Vincent Beng; Lee, Heow Pueh
2014-12-01
Head injuries due to complex blasts are not well examined because of limited published articles on the subject. Previous studies have analyzed head injuries due to impact from a single planar blast wave. Complex or concomitant blasts refer to impacts usually caused by more than a single blast source, whereby the blast waves may impact the head simultaneously or consecutively, depending on the locations and distances of the blast sources from the subject, their blast intensities, the sequence of detonations, as well as the effect of blast wave reflections from rigid walls. It is expected that such scenarios will result in more serious head injuries as compared to impact from a single blast wave due to the larger effective duration of the blast. In this paper, the utilization of a head-helmet model for blast impact analyses in Abaqus(TM) (Dassault Systemes, Singapore) is demonstrated. The model is validated against studies published in the literature. Results show that the skull is capable of transmitting the blast impact to cause high intracranial pressures (ICPs). In addition, the pressure wave from a frontal blast may enter through the sides of the helmet and wrap around the head to result in a second impact at the rear. This study recommended better protection at the sides and rear of the helmet through the use of foam pads so as to reduce wave entry into the helmet. The consecutive frontal blasts scenario resulted in higher ICPs compared with impact from a single frontal blast. This implied that blast impingement from an immediate subsequent pressure wave would increase severity of brain injury. For the unhelmeted head case, a peak ICP of 330 kPa is registered at the parietal lobe which exceeds the 235 kPa threshold for serious head injuries. The concurrent front and side blasts scenario yielded lower ICPs and skull stresses than the consecutive frontal blasts case. It is also revealed that the additional side blast would only significantly affect ICPs at
Study of high Mach number laser driven blast waves in gases
International Nuclear Information System (INIS)
A series of experiments were performed examining the evolution of blast waves produced by laser irradiation of a target immersed in gas. Blast waves were produced by illumination of wires by 1 kJ, 1 ns laser pulses from the Z-Beamlet laser at Sandia National Laboratories. The blast waves were imaged by probe laser pulses at various times to examine the trajectory, radiative precursor, and induced perturbations on the blast wave front. Well defined perturbations were induced on the blast wave front with arrays of wires placed in the gas and the results of the experiments are compared to the theoretical predictions for the Vishniac overstability. It is found that the experimental results are in general agreement with these theoretical predictions on thin blast wave shells and are in quantitative agreement in the simplest case.
Blast wave loading pathways in heterogeneous material systems-experimental and numerical approaches.
Selvan, Veera; Ganpule, Shailesh; Kleinschmit, Nick; Chandra, Namas
2013-06-01
Blast waves generated in the field explosions impinge on the head-brain complex and induce mechanical pressure pulses in the brain resulting in traumatic brain injury. Severity of the brain injury (mild to moderate to severe) is dependent upon the magnitude and duration of the pressure pulse, which in turn depends on the intensity and duration of the oncoming blast wave. A fluid-filled cylinder is idealized to represent the head-brain complex in its simplest form; the cylinder is experimentally subjected to an air blast of Friedlander type, and the temporal variations of cylinder surface pressures and strains and fluid pressures are measured. Based on these measured data and results from computational simulations, the mechanical loading pathways from the external blast to the pressure field in the fluid are identified; it is hypothesized that the net loading at a given material point in the fluid comprises direct transmissive loads and deflection-induced indirect loads. Parametric studies show that the acoustic impedance mismatches between the cylinder and the contained fluid as well as the flexural rigidity of the cylinder determine the shape/intensity of pressure pulses in the fluid. PMID:23699714
Shaoqin Huang; Lifeng Luan; Wanli Xing; Qunyi Liu
2015-01-01
This paper uses improved technology for dynamic strain measurement to investigate the dynamic strain signals of blasting wave action tested in the range of 8–16 cm from the central blast. Based on the blasting mechanism and on the analysis of signal characteristics, blasting waves are recognized and divided into three zones, namely, shock wave zone, stress wave zone, and gas-expanding zone. This paper studies the relationships between stress, strain, and time of every zone. The tensile and co...
Stability of the Sedov-Taylor blast wave solutions
International Nuclear Information System (INIS)
Isenberg has obtained the surprising result that the Sedov-Taylor similarity solutions for spherical blast waves are unstable against radial perturbations. However, he assumed for his linearized normal mode analysis that the shock strength was unchanged by perturbations behind the shock, and therefore did not consider convective losses in the wave energy at the shock. As the first-order change in the shock strength must be included in the stability analysis, it is premature to conclude that the Sedov-Taylor solution is generally unstable
Supernova-blast waves in wind-blown bubbles, turbulent, and power-law ambient media
Haid, S.; Walch, S.; Naab, T.; Seifried, D.; Mackey, J.; Gatto, A.
2016-05-01
Supernova (SN) blast waves inject energy and momentum into the interstellar medium (ISM), control its turbulent multiphase structure and the launching of galactic outflows. Accurate modelling of the blast wave evolution is therefore essential for ISM and galaxy formation simulations. We present an efficient method to compute the input of momentum, thermal energy, and the velocity distribution of the shock-accelerated gas for ambient media (densities of 0.1 ≥ n0 [cm-3 ≥ 100) with uniform (and with stellar wind blown bubbles), power-law, and turbulent (Mach numbers M from 1 - 100) density distributions. Assuming solar metallicity cooling, the blast wave evolution is followed to the beginning of the momentum conserving snowplough phase. The model recovers previous results for uniform ambient media. The momentum injection in wind-blown bubbles depend on the swept-up mass and the efficiency of cooling, when the blast wave hits the wind shell. For power-law density distributions with n(r) ˜ r-2 (for n(r) > nfloor) the amount of momentum injection is solely regulated by the background density nfloor and compares to nuni = nfloor. However, in turbulent ambient media with log-normal density distributions the momentum input can increase by a factor of 2 (compared to the homogeneous case) for high Mach numbers. The average momentum boost can be approximated as p_{_turb}/p_{0} =23.07 (n_{_{0,turb}}/1 cm^{-3})^{-0.12} + 0.82 (ln (1+b2M2))^{1.49}(n_{_{0,turb}}/1 cm^{-3})^{-1.6}. The velocity distributions are broad as gas can be accelerated to high velocities in low-density channels. The model values agree with results from recent, computationally expensive, three-dimensional simulations of SN explosions in turbulent media.
Supernova blast waves in wind-blown bubbles, turbulent, and power-law ambient media
Haid, S.; Walch, S.; Naab, T.; Seifried, D.; Mackey, J.; Gatto, A.
2016-08-01
Supernova (SN) blast waves inject energy and momentum into the interstellar medium (ISM), control its turbulent multiphase structure and the launching of galactic outflows. Accurate modelling of the blast wave evolution is therefore essential for ISM and galaxy formation simulations. We present an efficient method to compute the input of momentum, thermal energy, and the velocity distribution of the shock-accelerated gas for ambient media (densities of 0.1 ≥ n0 [cm- 3] ≥ 100) with uniform (and with stellar wind blown bubbles), power-law, and turbulent (Mach numbers M from 1to100) density distributions. Assuming solar metallicity cooling, the blast wave evolution is followed to the beginning of the momentum conserving snowplough phase. The model recovers previous results for uniform ambient media. The momentum injection in wind-blown bubbles depend on the swept-up mass and the efficiency of cooling, when the blast wave hits the wind shell. For power-law density distributions with n(r) ˜ r-2 (for n(r) > nfloor) the amount of momentum injection is solely regulated by the background density nfloor and compares to nuni = nfloor. However, in turbulent ambient media with lognormal density distributions the momentum input can increase by a factor of 2 (compared to the homogeneous case) for high Mach numbers. The average momentum boost can be approximated as p_{turb}/{p_{{0}}} =23.07 (n_{{0,turb}}/1 cm^{-3})^{-0.12} + 0.82 (ln (1+b2{M}2))^{1.49}(n_{{0,turb}}/1 cm^{-3})^{-1.6}. The velocity distributions are broad as gas can be accelerated to high velocities in low-density channels. The model values agree with results from recent, computationally expensive, three-dimensional simulations of SN explosions in turbulent media.
Blast wave protection of aqueous foams
International Nuclear Information System (INIS)
The primary intention of the present study is to present new contribution of shock tube tests to the problem of particle related stabilization and enhanced mitigation action of the wet particulate foams. The experiments reported were designed to examine (i) the reflection of a shock wave from an air/foam face, (ii) the transmission of the shock wave through the air/foam face and (iii) propagation and dispersion of the transmitted shock wave inside the foam column. Because wet aqueous foam of desired specification is difficult to reproduce, handle and quantitatively characterize the fact that experiments on all the above aspects were conducted in a single facility is a potentially important consideration. Moreover vertical position of shock tube simplified the issues since the gradient of the liquid fraction in draining foam coincides with the shock wave propagation. Under these, much simplified test conditions resulted flows could be treated as one-dimensional and the shock wave mitigation depends on three parameters: the intensity of the incident shock wave, s M , the duration of the foam decay, ∆t and on the particle concentration, n
The physical properties of the blast wave produced by a stoichiometric propane/oxygen explosion
Dewey, M. C.; Dewey, J. M.
2014-11-01
The trajectory of the primary shock produced by the explosion of a nominal 18.14 t (20 tn) hemispherical propane/oxygen charge was analysed previously to provide the physical properties immediately behind the shock, but gave no information about the time-resolved properties throughout the blast wave. The present study maps all the physical properties of the wave throughout and beyond the positive durations for a range of distances from about 1.6-18 m scaled to a 1 kg charge at NTP. The physical properties were calculated using a hydro-code to simulate the flow field produced by a spherical piston moving with a specific trajectory. This technique has been used extensively to determine the physical properties of blast waves from a variety of sources for which the piston path was determined by high-speed photography of smoke tracers established close to the charges immediately before detonation. In the case of the propane/oxygen explosion, smoke tracer data were not available to determine the trajectory of the spherical piston. An arbitrary piston path was used and its trajectory iteratively adjusted until it produced a blast wave with a primary shock whose trajectory exactly matched the measured trajectory from the propane/oxygen explosion. Throughout the studied flow field the time histories of hydrostatic pressure, density and particle velocity are well described by fits to the modified Friedlander equation. The properties are presented as functions of scaled radius and are compared with the properties of the blast wave from a 1 kg TNT surface burst explosion, and with other measurements of the same explosion.
A parametric study of self-similar blast waves.
Oppenheim, A. K.; Kuhl, A. L.; Lundstrom, E. A.; Kamel, M. M.
1972-01-01
Comprehensive examination of self-similar blast waves with respect to two parameters, one describing the front velocity and the other the variation of the ambient density immediately ahead of the front. All possible front trajectories are taken into account, including limiting cases of the exponential and logarithmic form. The structure of the waves is analyzed by means of a phase plane defined in terms of two reduced coordinates. Loci of extrema of the integral curves in the phase plane are traced, and loci of singularities are determined on the basis of their intersections. Boundary conditons are introduced for the case where the medium into which the waves propagate is at rest. Representative solutions, pertaining to all the possible cases of blast waves bounded by shock fronts propagating into an atmosphere of uniform density, are obtained by evaluating the integral curves and determining the corresponding profiles of the gasdynamic parameters. Particular examples of integral curves for waves bounded by detonations are given, and all the degenerate solutions corresponding to cases where the integral curve is reduced to a point are delineated.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Extensive use of carbon based fuel is the main inducement for global warming and more extreme weather.Reducing carbon dioxide emission and enhancing energy use is a common subject in steel industry.In the integrated steel plant,decreasing carbon dioxide emission must consider energy balance in the whole iron and steel works,and secondary energy must be actively utilized.As promising blast-furnaces,top gas recovery blast furnace(TGR-BF) and oxygen blast furnace have been investigated.In this paper,conceptual TGR blast furnace and oxygen blast furnace are proposed.Base on the idea of blast furnace gas de-CO2 circulating as reducing agent and the idea of pure oxygen blast decreasing the thermal reserve zone temperature,process modeling is conducted with ASPEN Plus.It is shown that the developed model reasonably describes the energy balance and mass balance feature of the furnace,and provides basic thermodynamic condition for furnaces.The effects of changes in different operation conditions are studied by sensitivity analysis and reference data from simulation.
Pennetier, Olivier; William-Louis, Mame; Langlet, André
2015-01-01
When an explosion occurs in a tunnel, the study of the blast wave quickly becomes complicated, owing to the multiple propagation patterns of the blast wave (Incident wave, regular and Mach reections) and to the geometrical conditions. Considering this problem, two patterns can be revealed. Near the explosive, the well known free-eld pressure wave can be observed. After multiple reections on the tunnel's walls, this overpressure behaves like a one-dimensional (1D) wave. One aim of this paper i...
NO FLARES FROM GAMMA-RAY BURST AFTERGLOW BLAST WAVES ENCOUNTERING SUDDEN CIRCUMBURST DENSITY CHANGE
International Nuclear Information System (INIS)
Afterglows of gamma-ray bursts are observed to produce light curves with the flux following power-law evolution in time. However, recent observations reveal bright flares at times on the order of minutes to days. One proposed explanation for these flares is the interaction of a relativistic blast wave with a circumburst density transition. In this paper, we model this type of interaction computationally in one and two dimensions, using a relativistic hydrodynamics code with adaptive mesh refinement called RAM, and analytically in one dimension. We simulate a blast wave traveling in a stellar wind environment that encounters a sudden change in density, followed by a homogeneous medium, and compute the observed radiation using a synchrotron model. We show that flares are not observable for an encounter with a sudden density increase, such as a wind termination shock, nor for an encounter with a sudden density decrease. Furthermore, by extending our analysis to two dimensions, we are able to resolve the spreading, collimation, and edge effects of the blast wave as it encounters the change in circumburst medium. In all cases considered in this paper, we find that a flare will not be observed for any of the density changes studied
Blast Wave Exposure Impairs Memory and Decreases Axon Initial Segment Length
Baalman, Kelli L.; Cotton, R. James; Rasband, S. Neil; Rasband, Matthew N.
2013-01-01
Exposure to a blast wave has been proposed to cause mild traumatic brain injury (mTBI), with symptoms including altered cognition, memory, and behavior. This idea, however, remains controversial, and the mechanisms of blast-induced brain injury remain unknown. To begin to resolve these questions, we constructed a simple compressed air shock tube, placed rats inside the tube, and exposed them to a highly reproducible and controlled blast wave. Consistent with the generation of a mild injury, 2...
Blast Shock Wave Mitigation Using the Hydraulic Energy Redirection and Release Technology
Chen, Yun; Huang, Wei; Constantini, Shlomi
2012-01-01
A hydraulic energy redirection and release technology has been developed for mitigating the effects of blast shock waves on protected objects. The technology employs a liquid-filled plastic tubing as a blast overpressure transformer to transfer kinetic energy of blast shock waves into hydraulic energy in the plastic tubings. The hydraulic energy is redirected through the plastic tubings to the openings at the lower ends, and then is quickly released with the liquid flowing out through the ope...
Blast Loaded Aluminium Plates : Experiments and numerical simulations
Melby, Emil Arne; Eide, Hilde Olaug Stakvik
2013-01-01
Light and flexible protective constructions in aluminium could be subjected to a blast load. In this thesis the effect of blast loading on aluminium plates of the type 1050A ? H14 was studied through experiments and numerical simulations. The effect of fragmentation was idealized with predrilled holes. The thesis was written at the Structural Impact Laboratory (SIMLab) at NTNU in collaboration with the Norwegian Defence Estates Agency (NDEA).Tensile tests revealed a clearly anisotropic behavi...
Formation of supernova remnants: The pre-blast-wave phase
International Nuclear Information System (INIS)
The effect of stellar structure on supernova remnant formation is studied with a series of computer models of a 1051 erg explosion in a 15 M/sub sun/ star. We find that immediately after the explosion shock wave travels down a steep density gradient, the material in the gradient goes into free expansion, forming a collapsible piston. At the outer edge of such a piston are two shock waves: the expanding supernova shock and a reverse shock moving back into the collapsible piston. Until the piston is completely collapsed it is Rayleigh-Taylor stable, but after collpse the inner material behaves as a massive piston and the interface is R-T unstable. If there is a significant mass in an external density gradient, the material between the supernova shock moving out through the interstellar medium and the reverse shock will be a singificant source of x-rays during the pre--blast-wave phase of remnant formation
On pulsar-driven isothermal blast-wave models of supernova remnants
International Nuclear Information System (INIS)
The 'equilibrium' and stability of spherically-symmetric self-similar isothermal blast waves with a continuous post-shock flow velocity expanding into a medium whose density varies as rsup(-ω) ahead of the blast wave, and which are powered by a central source (a pulsar) whose power output varies with time as tsup(phi-3) are investigated. (Auth.)
Improved models for the dynamical overstability of radiative blast waves
International Nuclear Information System (INIS)
Further developments in atomic physics calculations of radiative cooling designed to interpret experimental observations of overstability in radiating decelerating blast waves by Grun et al. [Phys. Rev. Lett. 66, 2738 (1991)] are described. A previous paper on the subject [Laming and Grun, Phys. Rev. Lett. 89, 125002 (2002)] showed that in order to be overstable, shocked gas must cool significantly in a distance downstream from the shock similar to the width of the shock transition itself. In this paper a more realistic model for the shock jump is employed, and significantly improved agreement between theory and experiment is found
Rigby, S.E.; Tyas, A; Fay, S.D.; Clarke, S.D.; Warren, J. A.
2014-01-01
A considerable amount of scientific effort has been expended over many decades on developing means of predicting the loading generated when a blast wave impinges on a structure. Semi-empirical ‘look-up’ predictive methods, such as those incorporated in the UFC-3-340-02 manual, the ConWep code or the *LOAD_BLAST module of LS-DYNA, offer a simple means for predicting the blast loading generated in geometrically simple scenarios. However, reported test data frequently show considerable spread an...
Numerical simulations of near-field blast effects using kinetic plates
International Nuclear Information System (INIS)
Numerical simulations using two hydrocodes were compared to near-field measurements of blast impulse associated with ideal and non-ideal explosives to gain insight into testing results and predict untested configurations. The recently developed kinetic plate test was designed to measure blast impulse in the near-field by firing spherical charges in close range from steel plates and probing plate acceleration using laser velocimetry. Plate velocities for ideal, non-ideal and aluminized explosives tests were modeled using a three dimensional hydrocode. The effects of inert additives in the explosive formulation were modeled using a 1-D hydrocode with multiphase flow capability using Lagrangian particles. The relative effect of particle impact on the plate compared to the blast wave impulse is determined and modeling is compared to free field pressure results.
A Thoracic Mechanism of Mild Traumatic Brain Injury Due to Blast Pressure Waves
Courtney, Amy; 10.1016/j.mehy.2008.08.015
2008-01-01
The mechanisms by which blast pressure waves cause mild to moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. ...
Energy transfer from a laser pulse to a blast wave in reduced-pressure air atmospheres
International Nuclear Information System (INIS)
Focusing a transversely excited atmospheric CO2 laser beam in air atmospheres induced a blast wave. The kinetic energy of a laser-induced blast wave was determined from shadowgraph images of shock wave expansion. Results showed that the fraction of input laser energy that is converted into the blast wave energy decreased from 0.45 to 0.2 concomitant with the decrease in ambient pressure from 100 to 10 kPa. Also, it was insensitive to input laser energy from 4 to 13 J
Self-similar blast waves incorporating deflagrations of variable speed
Guirguis, R. H.; Kamel, M. M.; Oppenheim, A. K.
1983-01-01
The present investigation is concerned with the development of a systematic approach to the problem of self-similar blast waves incorporating nonsteady flames. The regime covered by the presented solutions is bounded on one side by an adiabatic strong explosion and, on the other, by deflagration propagating at an infinite acceleration. Results for a representative set of accelerations are displayed, taking into account the full range of propagation speeds from zero to velocities corresponding to the Chapman-Jouguet deflagration. It is found that the distribution of stored energy in the undisturbed medium determines the acceleration of the deflagration-shock wave system. The obtained results reveal the existence of a simple relation between the location of the deflagration and its Mach number.
Physics of IED blast shocktube simulations for mTBI research
Directory of Open Access Journals (Sweden)
JesusMediavilla Varas
2011-09-01
Full Text Available Shocktube experiments and simulations are conducted with a spherical gelatin filled skull-brain surrogate, in order to study the mechanisms leading to blast induced mild traumatic brain injury (mTBI. A shocktube including sensor system is optimized to simulate realistic improvised explosive devise (IED blast profiles obtained from full scale field tests. The response of the skull-brain surrogate is monitored using pressure and strain measurements. Fluid-structure interaction (FSI is modeled using a combination of computational fluid dynamics (CFD simulations for the air blast, and finite element (FE model for the structural response. The results help to understand the physics of wave propagation, from air blast into the skull-brain. The presence of openings on the skull and its orientation does have a strong effect on the internal pressure. A parameter study reveals that when there is an opening in the skull, the skull gives little protection and the internal pressure is fairly independent on the skull stiffness; the gelatin shear stiffness has little effect on the internal pressure. Simulations show that the presence of pressure sensors in the gelatin hardly disturbs the pressure field.
Modeling and Simulating Blast Effects on Electric Substations
Energy Technology Data Exchange (ETDEWEB)
Lyle G. Roybal; Robert F. Jeffers; Kent E. McGillivary; Tony D. Paul; Ryan Jacobson
2009-05-01
A software simulation tool was developed at the Idaho National Laboratory to estimate the fragility of electric substation components subject to an explosive blast. Damage caused by explosively driven fragments on a generic electric substation was estimated by using a ray-tracing technique to track and tabulate fragment impacts and penetrations of substation components. This technique is based on methods used for assessing vulnerability of military aircraft and ground vehicles to explosive blasts. An open-source rendering and ray-trace engine was used for geometric modeling and interactions between fragments and substation components. Semi-empirical material interactions models were used to calculate blast parameters and simulate high-velocity material interactions between explosively driven fragments and substation components. Finally, a Monte Carlo simulation was added to model the random nature of fragment generation allowing a skilled analyst to predict failure probabilities of substation components.
Blast wave exposure impairs memory and decreases axon initial segment length.
Baalman, Kelli L; Cotton, R James; Rasband, S Neil; Rasband, Matthew N
2013-05-01
Exposure to a blast wave has been proposed to cause mild traumatic brain injury (mTBI), with symptoms including altered cognition, memory, and behavior. This idea, however, remains controversial, and the mechanisms of blast-induced brain injury remain unknown. To begin to resolve these questions, we constructed a simple compressed air shock tube, placed rats inside the tube, and exposed them to a highly reproducible and controlled blast wave. Consistent with the generation of a mild injury, 2 weeks after exposure to the blast, we found that motor performance was unaffected, and a panel of common injury markers showed little or no significant changes in expression in the cortex, corpus callosum, or hippocampus. Similarly, we were unable to detect elevated spectrin breakdown products in brains collected from blast-exposed rats. Using an object recognition task, however, we found that rats exposed to a blast wave spent significantly less time exploring a novel object when compared with control rats. Intriguingly, we also observed a significant shortening of the axon initial segment (AIS) in both the cortex and hippocampus of blast-exposed rats, suggesting altered neuronal excitability after exposure to a blast. A computational model showed that shortening the AIS increased both threshold and the interspike interval of repetitively firing neurons. These results support the conclusion that exposure to a single blast wave can lead to mTBI with accompanying cognitive impairment and subcellular changes in the molecular organization of neurons. PMID:23025758
Sundaramurthy, Aravind; Chandra, Namas
2014-01-01
Detonation of a high-explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects, even at farther distances. When a pure shock-blast wave encounters the subject, in the absence of shrapnels, fall, or gaseous products the loading is termed as primary blast loading and is the subject of this paper. The wave profile is characterized by blast overpressure, positive time duration, and impulse a...
New exact solution of the blast wave problem in gas dynamics
International Nuclear Information System (INIS)
Various authors have investigated the problem of a propagation and structure of blast wave in gas dynamics during the stage when the symmetrical shock wave is still strong, and some exact or numerical solutions are known. In this paper, we present a new exact solution of the problem with an atmosphere whose the density ahead of the shock front is assumed to vary as a power of the distance from the source of the blast wave
Numerical simulation of armored vehicles subjected to undercarriage landmine blasts
Erdik, A.; Kilic, S. A.; Kilic, N.; Bedir, S.
2015-05-01
Landmine threats play a crucial role in the design of armored personnel carriers. Therefore, a reliable blast simulation methodology is valuable to the vehicle design development process. The first part of this study presents a parametric approach for the quantification of the important factors such as the incident overpressure, the reflected overpressure, the incident impulse, and the reflected impulse for the blast simulations that employ the Arbitrary Lagrangian-Eulerian formulation. The effects of mesh resolution, mesh topology, and fluid-structure interaction (FSI) parameters are discussed. The simulation results are compared with the calculations of the more established CONventional WEaPons (CONWEP ) approach based on the available experimental data. The initial findings show that the spherical topology provides advantages over the Cartesian mesh domains. Furthermore, the FSI parameters play an important role when coarse Lagrangian finite elements are coupled with fine Eulerian elements at the interface. The optimum mesh topology and the mesh resolution of the parametric study are then used in the landmine blast simulation. The second part of the study presents the experimental blast response of an armored vehicle subjected to a landmine explosion under the front left wheel in accordance with the NATO AEP-55 Standard. The results of the simulations show good agreement with the experimental measurements.
Nakagawa, Atsuhiro; Ohtani, Kiyonobu; Goda, Keisuke; Kudo, Daisuke; Arafune, Tatsuhiko; Washio, Toshikatsu; Tominaga, Teiji
2016-01-01
Purpose Primary blast-induced traumatic brain injury (bTBI) is the least understood of the four phases of blast injury. Distant injury induced by the blast wave, on the opposite side from the wave entry, is not well understood. This study investigated the mechanism of distant injury in bTBI. Materials and Methods Eight 8-week-old male Sprague-Dawley rats were divided into two groups: group 1 served as the control group and did not receive any shock wave (SW) exposure; group 2 was exposed to SWs (12.5 ± 2.5 MPa). Propagation of SWs within a brain phantom was evaluated by visualization, pressure measurement, and numerical simulation. Results Intracerebral hemorrhage near the ignition site and elongation of the distant nucleus were observed, despite no apparent damage between the two locations in the animal experiment. Visualization, pressure measurement, and numerical simulation indicated the presence of complex wave dynamics accompanying a sudden increase in pressure, followed by negative pressure in the phantom experiment. Conclusion A local increase in pressure above the threshold caused by interference of reflection and rarefaction waves in the vicinity of the brain-skull surface may cause distant injury in bTBI. PMID:27165867
Bubble merger model for the nonlinear Rayleigh-Taylor instability driven by a strong blast wave
International Nuclear Information System (INIS)
A bubble merger model is presented for the nonlinear evolution of the Rayleigh-Taylor instability driven by a strong blast wave. Single bubble motion is determined by an extension of previous buoyancy-drag models extended to the blast-wave-driven case, and a simple bubble merger law in the spirit of the Sharp-Wheeler model allows for the generation of larger scales. The blast-wave-driven case differs in several respects from the classical case of incompressible fluids in a uniform gravitational field. Because of material decompression in the rarefaction behind the blast front, the asymptotic bubble velocity and the merger time depend on time as well as the transverse scale and the drive. For planar blast waves, this precludes the emergence of a self-similar regime independent of the initial conditions. With higher-dimensional blast waves, divergence restores the properties necessary for the establishment of the self-similar state, but its establishment requires a very high initial characteristic mode number and a high Mach number for the incident blast wave
Convective instability of hollow Sedov-Taylor blast waves
International Nuclear Information System (INIS)
The self-similar solutions by Sedov (1946) and Taylor (1950) for a strong spherical shock in an ideal gas are evacuated at their centers if the preshock density falls as a high power of radius. These solutions could represent an idealized form of a supernova blast wave in the early phase when the shock moves through the stellar envelope. For astrophysically relevant values of the adiabatic index, the hollow solutions are unstable to global convective modes; that is, the compressible generalization of Rayleigh-Taylor modes. For very large spherical harmonic degrees l, the growth rate scales as l exp 1/2 and the eigenfunction is concentrated within a distance proportional to 1/l of the inner edge of the fluid. A condition is also given for local convective instability, which may exist even when unstable global modes to not. 36 refs
International Nuclear Information System (INIS)
In this work I studied the nature and important effects of massive galaxy cluster merger phenomena. Due to inherent complexity of such events analytical solution is impossible, so, numerical simulations are performed using ENZO-2.1 hydrodynamic code. It is noticed that the formation of Mega parsec scale merger shocks in such events substantially change the energy distribution of Inter Cluster Medium. A striking similarity is noticed between expanding intra cluster medium during mergers with the blast wave formation in supernovae explosion. The blast wave meets the void/ accretion shocks when propagated out to the virial radius. Particle acceleration at the meeting point produce a significant amount of synchrotron radio emission through which curved shocks are made visible in radio waves. This study thus also sheds some light on the formation of curved and nearly symmetric radio emission found in Abell 3376, Abell 3667, CIZA J2242.8+5301, plck g287.0+32.9 etc. clusters.
Interaction and coalescence of multiple simultaneous and non-simultaneous blast waves
Qiu, S.; Eliasson, V.
2016-05-01
Interaction of multiple blast waves can be used to direct energy toward a target while simultaneously reducing collateral damage away from the target area. In this paper, simulations of multiple point source explosives were performed and the resulting shock interaction and coalescence behavior were explored. Three to ten munitions were placed concentrically around the target, and conditions at the target area were monitored and compared to those obtained using a single munition. For each simulation, the energy summed over all munitions was kept constant, while the radial distances between target and munitions and the munition initiation times were varied. Each munition was modeled as a point source explosion. The resulting blast wave propagation and shock front coalescence were solved using the inviscid Euler equations of gas dynamics on overlapping grids employing a finite difference scheme. Results show that multiple munitions can be beneficial for creating extreme conditions at the intended target area; over 20 times higher peak pressure is obtained for ten simultaneous munitions compared to a single munition. Moreover, peak pressure at a point away from the target area is reduced by more than a factor of three.
THE BLAST-WAVE-DRIVEN INSTABILITY AS A VEHICLE FOR UNDERSTANDING SUPERNOVA EXPLOSION STRUCTURE
International Nuclear Information System (INIS)
Blast-wave-driven instabilities play a rich and varied role in supernovae (SNe) evolution from explosion to remnant, but interpreting their role is difficult due to the enormous complexity of stellar systems. We consider the simpler idealized problem of an interface between two constant-density fluids perturbed from spherical and driven by a central blast wave. Where valid, the existence of unified solutions suggests that general conclusions can be drawn about the likely asymptotic structure of the mixing zone. To this end, we apply buoyancy-drag and bubble merger models that include effects of divergence and compressibility. In general, these effects preclude the true self-similar evolution of classical Rayleigh-Taylor (RT), but can be incorporated into a quasi-self-similar growth model. Loss of memory of initial conditions (ICs) can occur in the model, but requires pre-explosion mode numbers higher than predicted for Type II SNe, suggesting that their late-time structure is influenced by details of the initial perturbations. Where low modes dominate, as in the Type Ia Tycho remnant, they result from initial perturbations rather than generation from smaller scales. Therefore, the structure observed now contains direct information about the explosion process. When large-amplitude modes exist in the ICs, the contribution from the Richtmyer-Meshkov (RM) instability is significant compared to RT. Such RM growth can yield proximity of the forward shock to the growing spikes and structure that strongly resembles that observed in Tycho. Laser-driven laboratory experiments offer a promising avenue for testing model and simulation descriptions of blast-wave-driven instabilities and making connections to their astrophysical counterparts.
Directory of Open Access Journals (Sweden)
LiyingZhang
2013-08-01
Full Text Available Blast-induced traumatic brain injury has emerged as a “signature injury” in combat casualty care. Present combat helmets are designed primarily to protect against ballistic and blunt impacts, but the current issue with helmets is protection concerning blasts. In order to delineate the blast wave attenuating capability of the Advanced Combat Helmet (ACH, a finite element (FE study was undertaken to evaluate the head response against blast loadings with and without helmet using a partially validated FE model of the human head and ACH. Four levels of overpressures (0.27-0.66 MPa from the Bowen’s lung iso-damage threshold curves were used to simulate blast insults. Effectiveness of the helmet with respect to head orientation was also investigated. The resulting biomechanical responses of the brain to blast threats were compared for human head with and without the helmet. For all Bowen’s cases, the peak intracranial pressures (ICP in the head ranged from 0.68-1.8 MPa in the coup cortical region. ACH was found to mitigate ICP in the head by 10-35%. Helmeted head resulted in 30% lower average peak brain strains and product of strain and strain rate. Among three blast loading directions with ACH, highest reduction in peak ICP (44% was due to backward blasts whereas the lowest reduction in peak ICP and brain strains was due to forward blast (27%. The biomechanical responses of a human head to primary blast insult exhibited directional sensitivity owing to the different geometry contours and coverage of the helmet construction and asymmetric anatomy of the head. Thus, direction-specific tolerances are needed in helmet design in order to offer omni-directional protection for the human head. The blasts of varying peak overpressures and durations that are believed to produce the same level of lung injury produce different levels of mechanical responses in the brain, and hence "iso-damage" curves for brain injury are likely different than the Bowen
Helium blast-wave measurements of laser-heated microshell targets
International Nuclear Information System (INIS)
Measurements of blast waves produced by laser heating of spherical glass-shell targets in an atmosphere of 20 Torr helium are described. These measurements made use of a streak camera, monitoring the self-luminosity of the strong shock, a blast probe detecting the ionization behind the shock front, and a piezoelectric pressure probe recording the pressure pulse of the shock. The time history of the blast wave is used to determine the kinetic energy of target dissembly via a simple model which is applicable in both the strong-shock and acoustic regions. These measurements show that the inferred blast-wave energy increases for larger radius--time-shock coordinates. This anomalous effect is ascribed to ''fast'' ion preheating of the ambient helium gas in front of the shock wave
Computational Study of Thrust Generation from Laser-Driven Blast Wave
International Nuclear Information System (INIS)
We have performed axisymmetric simulations in order to investigate the thrust generation resulting from the interference between the projectile and the blast wave produced by a pulsed laser. The results obtained by our numerical code well agree for the pressure history and the momentum coupling coefficient with the experimental data. In such analysis, it is found that the approximate impulse estimated only by the pressure history at the projectile base is difficult to predict the actual one. Since the shock wave rapidly attenuates in low fill pressure, and the interaction with the projectile almost finishes in the shroud, a high momentum coupling coefficient can be achieved unlike the case of high fill pressure in which the projectile experiences the subsequent negative thrust
A numerical study of the evolution of the blast wave shape in rectangular tunnels
Uystepruyst, David; Monnoyer, François
2015-01-01
When the explosion of condensed materials occurs in square or circular cross-section tunnel, the subsequent blast wave reveals two patterns: three-dimensional close to the explosive charge and one-dimensional far from the explosion. Pressure decays for these two patterns have been thoroughly studied. However, when the explosion occurs in rectangular cross-section tunnel, which is the most regular geometry for underground networks, the blast wave exhibits a third, two-dimensional, patterns. In...
Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects
Courtney, Amy; Andrusiv, Lubov; Courtney, Michael
2011-01-01
This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27 - 79 mm. A range of peak press...
Analytical Solution of the Blast Wave Problem in a Non-Ideal Gas
International Nuclear Information System (INIS)
An analytical approach is used to construct the exact solution of the blast wave problem with generalized geometries in a non-ideal medium. It is assumed that the density ahead of the shock front varies according to a power of distance from the source of the blast wave. Also, an analytical expression for the total energy in a non-ideal medium is derived. (fundamental areas of phenomenology(including applications))
Laboratory observation of secondary shock formation ahead of a strongly radiative blast wave
International Nuclear Information System (INIS)
High Mach number blast waves were created by focusing a laser pulse on a solid pin, surrounded by nitrogen or xenon gas. In xenon, the initial shock is strongly radiative, sending out a supersonic radiative heat wave far ahead of itself. The shock propagates into the heated gas, diminishing in strength as it goes. The radiative heat wave also slows, and when its Mach number drops to two with respect to the downstream plasma, the heat wave drives a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame; the heat wave becomes subsonic behind the second shock. For some time both shocks are observed simultaneously. Eventually the initial shock diminishes in strength so much that it can longer be observed, but the second shock continues to propagate long after this time. This sequence of events is a new phenomenon that has not previously been discussed in the literature. Numerical simulation clarifies the origin of the second shock, and its position is consistent with an analytical estimate
Wang, Chenzhi; Pahk, Jae Bum; Balaban, Carey D.; Miller, Mark C.; Adam R Wood; Jeffrey S Vipperman
2014-01-01
Human exposure to blast waves without any fragment impacts can still result in primary blast-induced traumatic brain injury (bTBI). To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human female. The finite element head model was partially validated and w...
A SEMI-ANALYTIC FORMULATION FOR RELATIVISTIC BLAST WAVES WITH A LONG-LIVED REVERSE SHOCK
International Nuclear Information System (INIS)
This paper performs a semi-analytic study of relativistic blast waves in the context of gamma-ray bursts. Although commonly used in a wide range of analytical and numerical studies, the equation of state (EOS) with a constant adiabatic index is a poor approximation for relativistic hydrodynamics. Adopting a more realistic EOS with a variable adiabatic index, we present a simple form of jump conditions for relativistic hydrodynamical shocks. Then we describe in detail our technique of modeling a very general class of GRB blast waves with a long-lived reverse shock. Our technique admits an arbitrary radial stratification of the ejecta and ambient medium. We use two different methods to find dynamics of the blast wave: (1) customary pressure balance across the blast wave and (2) the 'mechanical model'. Using a simple example model, we demonstrate that the two methods yield significantly different dynamical evolutions of the blast wave. We show that the pressure balance does not satisfy the energy conservation for an adiabatic blast wave while the mechanical model does. We also compare two sets of afterglow light curves obtained with the two different methods.
Blast wave radiation source measurement experiments on the Z Z-pinch facility
International Nuclear Information System (INIS)
The Dynamic Hohlraum (DH) radiation on the Z facility at Sandia National Laboratories [R. B. Spielman, W. A. Stygar, J. F. Seamen et al., Proceeding of the 11th International Pulsed Power Conference, Baltimore, 1997, edited by G. Cooperstein and I. Vitkovitsky (IEEE, Piscataway, NJ, 1997), Vol. 1, p. 709] is a bright source of radiant energy that has proven useful for high energy density physics experiments. But the radiation output from a DH on Z needs to be well known. In this paper, a new method is presented for measuring the radiation fluence deposited in an experiment, specifically, an experiment driven by a Z DH. This technique uses a blast wave produced in a SiO2 foam, which starts as supersonic but transitions to subsonic, producing a shock at the transition point that is observable via radiography. The position of this shock is a sensitive measure of the radiation drive energy from the Z DH. Computer simulations have been used to design and analyze a Z foam blast wave experiment
GAMMA-RAY BURST AFTERGLOW SCALING RELATIONS FOR THE FULL BLAST WAVE EVOLUTION
International Nuclear Information System (INIS)
We demonstrate that gamma-ray burst afterglow spectra and light curves can be calculated for arbitrary explosion and radiation parameters by scaling the peak flux and the critical frequencies connecting different spectral regimes. Only one baseline calculation needs to be done for each jet opening angle and observer angle. These calculations are done numerically using high-resolution relativistic hydrodynamical afterglow blast wave simulations which include the two-dimensional dynamical features of expanding and decelerating afterglow blast waves. Any light curve can then be generated by applying scaling relations to the baseline calculations. As a result, it is now possible to fully fit for the shape of the jet break, e.g., at early-time X-ray and optical frequencies. In addition, late-time radio calorimetry can be improved since the general shape of the transition into the Sedov-Taylor regime is now known for arbitrary explosion parameters so the exact moment when the Sedov-Taylor asymptote is reached in the light curve is no longer relevant. When calculating the baselines, we find that the synchrotron critical frequency νm and the cooling break frequency νc are strongly affected by the jet break. The νm temporal slope quickly drops to the steep late-time Sedov-Taylor slope, while the cooling break νc first steepens and then rises to meet the level of its shallow late-time asymptote.
Awwad, Hibah O; Gonzalez, Larry P; Tompkins, Paul; Lerner, Megan; Brackett, Daniel J; Awasthi, Vibhudutta; Standifer, Kelly M
2015-01-01
Physiological alterations, anxiety, and cognitive disorders are strongly associated with blast-induced traumatic brain injury (blast TBI), and are common symptoms in service personnel exposed to blasts. Since 2006, 25,000-30,000 new TBI cases are diagnosed annually in U.S. Service members; increasing evidence confirms that primary blast exposure causes diffuse axonal injury and is often accompanied by altered behavioral outcomes. Behavioral and acute metabolic effects resulting from blast to the head in the absence of thoracic contributions from the periphery were examined, following a single blast wave directed to the head of male Sprague-Dawley rats protected by a lead shield over the torso. An 80 psi head blast produced cognitive deficits that were detected in working memory. Blast TBI rats displayed increased anxiety as determined by elevated plus maze at day 9 post-blast compared to sham rats; blast TBI rats spent significantly more time than the sham controls in the closed arms (p blast. Instead, blast TBI rats displayed increased rearing behavior at day 48 post-blast compared to sham rats. Blast TBI rats also exhibited suppressed acoustic startle responses, but similar pre-pulse inhibition at day 15 post-blast compared to sham rats. Acute physiological alterations in cerebral glucose metabolism were determined by positron emission tomography 1 and 9 days post-blast using (18)F-fluorodeoxyglucose ((18)F-FDG). Global glucose uptake in blast TBI rat brains increased at day 1 post-blast (p blast injury. Markers for reactive astrogliosis and neuronal damage were noted by immunoblotting motor cortex tissue from day 10 post-blast in blast TBI rats compared to sham controls (p < 0.05; n = 5-6). PMID:26136722
Modeling and simulation of explosion effectiveness as a function of blast and crowd characteristics
Usmani, Zeeshan-Ul-Hassan
Suicide bombing has become one of the most lethal and favorite modus operandi of terrorist organizations around the world. On average, there is a suicide bombing attack every six days somewhere in the world. While various attempts have been made to assess the impact of explosions on structures and military personnel, little has been done on modeling the impact of a blast wave on a crowd in civilian settings. The assessment of an explosion's effect on a crowd can lead to better management of disasters, triage of patients, locating blast victims under the debris, development of protective gear, and safe distance recommendations to reduce the casualties. The overall goal of this work is to predict the magnitude of injuries and lethality on humans from a blast-wave with various explosive and crowd characteristics, and to compare, contrast, and analyze the performance of explosive and injury models against the real-life data of suicide bombing incidents. This thesis introduces BlastSim---a physics based stationary multi-agent simulation platform to model and simulate a suicide bombing event. The agents are constrained by the physical characteristics and mechanics of the blast wave. The BlastSim is programmed to test, analyze, and validate the results of different model combinations under various conditions with different sets of parameters, such as the crowd and explosive characteristics, blockage and human shields, fragmentation and the bomber's position, in 2-dimensional and 3-dimensional environments. The suicide bombing event can be re-created for forensic analysis. The proposed model combinations show a significant performance---the Harold Brode explosive model with Catherine Lee injury model using the blockage stands out consistently to be the best with an overall cumulative accuracy of 87.6%. When comparing against actual data, overall, prediction accuracy can be increased by 71% using this model combination. The J. Clutter with Reflection explosive model using
Challenging Some Contemporary Views of Coronal Mass Ejections. I. The Case for Blast Waves
Howard, T. A.; Pizzo, V. J.
2016-06-01
Since the closure of the “solar flare myth” debate in the mid-1990s, a specific narrative of the nature of coronal mass ejections (CMEs) has been widely accepted by the solar physics community. This narrative describes structured magnetic flux ropes at the CME core that drive the surrounding field plasma away from the Sun. This narrative replaced the “traditional” view that CMEs were blast waves driven by solar flares. While the flux rope CME narrative is supported by a vast quantity of measurements made over five decades, it does not adequately describe every observation of what have been termed CME-related phenomena. In this paper we present evidence that some large-scale coronal eruptions, particularly those associated with EIT waves, exhibit characteristics that are more consistent with a blast wave originating from a localized region (such as a flare site) rather than a large-scale structure driven by an intrinsic flux rope. We present detailed examples of CMEs that are suspected blast waves and flux ropes, and show that of our small sample of 22 EIT-wave-related CMEs, 91% involve a blast wave as at least part of the eruption, and 50% are probably blast waves exclusively. We conclude with a description of possible signatures to look for in determining the difference between the two types of CMEs and with a discussion on modeling efforts to explore this possibility.
Computation of viscous blast wave solutions with an upwind finite volume method
Molvik, Gregory A.
1987-01-01
A fully conservative, viscous, implicit, upwind, finite-volume scheme for the thin-layer Navier-Stokes equations is described with application to blast wave flow fields. In this scheme, shocks are captured without the oscillations typical of central differencing techniques and wave speeds are accurately predicted. The finite volume philosophy ensures conservation and since boundary conditions are also treated conservatively, accurate reflections of waves from surfaces are assured. Viscous terms in the governing equations are treated in a manner consistent with the finite volume philosophy, resulting in very accurate prediction of boundary layer quantities. Numerical results are presented for four viscous problems: a steady boundary layer, a shock-induced boundary layer, a blast wave/cylinder interaction and a blast wave/supersonic missile interaction. Comparisons of the results with an established boundary layer code, similarity solution, and experimental data show excellent agreement.
A geophysical shock and air blast simulator at the National Ignition Facility
International Nuclear Information System (INIS)
The energy partitioning energy coupling experiments at the National Ignition Facility (NIF) have been designed to measure simultaneously the coupling of energy from a laser-driven target into both ground shock and air blast overpressure to nearby media. The source target for the experiment is positioned at a known height above the ground-surface simulant and is heated by four beams from the NIF. The resulting target energy density and specific energy are equal to those of a low-yield nuclear device. The ground-shock stress waves and atmospheric overpressure waveforms that result in our test system are hydrodynamically scaled analogs of full-scale seismic and air blast phenomena. This report summarizes the development of the platform, the simulations, and calculations that underpin the physics measurements that are being made, and finally the data that were measured. Agreement between the data and simulation of the order of a factor of two to three is seen for air blast quantities such as peak overpressure. Historical underground test data for seismic phenomena measured sensor displacements; we measure the stresses generated in our ground-surrogate medium. We find factors-of-a-few agreement between our measured peak stresses and predictions with modern geophysical computer codes
A geophysical shock and air blast simulator at the National Ignition Facility
Energy Technology Data Exchange (ETDEWEB)
Fournier, K. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Brown, C. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); May, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Compton, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Walton, O. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shingleton, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kane, J. O. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Holtmeier, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Loey, H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Mirkarimi, P. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dunlop, W. H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Guyton, R. L. [National Security Technologies, Livermore, CA (United States); Huffman, E. [National Security Technologies, Livermore, CA (United States)
2014-09-01
The energy partitioning energy coupling experiments at the National Ignition Facility (NIF) have been designed to measure simultaneously the coupling of energy from a laser-driven target into both ground shock and air blast overpressure to nearby media. The source target for the experiment is positioned at a known height above the ground-surface simulant and is heated by four beams from the NIF. The resulting target energy density and specific energy are equal to those of a low-yield nuclear device. The ground-shock stress waves and atmospheric overpressure waveforms that result in our test system are hydrodynamically scaled analogs of full-scale seismic and air blast phenomena. This report summarizes the development of the platform, the simulations, and calculations that underpin the physics measurements that are being made, and finally the data that were measured. Agreement between the data and simulation of the order of a factor of two to three is seen for air blast quantities such as peak overpressure. Historical underground test data for seismic phenomena measured sensor displacements; we measure the stresses generated in our ground-surrogate medium. We find factors-of-a-few agreement between our measured peak stresses and predictions with modern geophysical computer codes.
On the conversion of blast wave energy into radiation in active galactic nuclei and gamma-ray bursts
Pohl, Martin; Schlickeiser, Reinhard
1999-01-01
It has been suggested that relativistic blast waves may power the jets of AGN and gamma-ray bursts (GRB). We address the important issue how the kinetic energy of collimated blast waves is converted into radiation. It is shown that swept-up ambient matter is quickly isotropised in the blast wave frame by a relativistic two-stream instability, which provides relativistic particles in the jet without invoking any acceleration process. The fate of the blast wave and the spectral evolution of the...
Numerical Simulation of Response of SRC Columns Subjected to Blast Loading
Institute of Scientific and Technical Information of China (English)
SUN Jianyun; LI Guoqiang; LU Yong
2006-01-01
The dynamic characteristics and failure modes of steel reinforced concrete (SRC) columns subjected to blast loading are complicated because of the transient stress wave in the SRC columns and the interaction between steel and concrete.This paper presents a numerical simulation of the response of SRC columns subjected to blast loading using hydrocode LS-DYNA.In the numerical model,a sophisticate concrete material model (the Concrete Damage Model) is employed with consideration of the strain rate effect and the damage accumulation.An erosion technique is adopted to model the spalling process of concrete.The possible failure modes of SRC columns are evaluated.It is observed that the failure of SRC columns subjected to blast load can generally be classified into three modes,namely,a direct failure in concrete body due to the stress wave,a transverse shear failure near the support sections due to the high shear force,and a flexural failure pertaining to large local and global deformation of the reinforcing steel.
Zhang, Liying; Makwana, Rahul; Sharma, Sumit
2013-01-01
Blast-induced traumatic brain injury has emerged as a “signature injury” in combat casualty care. Present combat helmets are designed primarily to protect against ballistic and blunt impacts, but the current issue with helmets is protection concerning blasts. In order to delineate the blast wave attenuating capability of the Advanced Combat Helmet (ACH), a finite element (FE) study was undertaken to evaluate the head response against blast loadings with and without helmet using a partially va...
Blast Wave Initiation of a Sheet Explosive Covered with Metal Plates.
Directory of Open Access Journals (Sweden)
H. S. Yadav
1996-12-01
Full Text Available Initiationof RDX-based sheetexplosiveby a normalincident blast wavehas been studied. Explosive sheets : (i bare (ii aluminium foil-covered and (iii sandwiched between different thicknesses of aluminium alloy metal plates, were impacted by the blast wave. The blast wave was produced by detonating a cylindrical plastic explosive charge kept symmetrically over the sheet at different stand-off distances in the air for varying the intensity of the blast wave. The values of critical distances, pressures obtained in the case of bare, foil-covered and aluminium alloy metal plates-covered sheet explosives have beenfitted to exponentialcurves.It is observedthat the sheet explosivesandwichedbetweenthe two metal plates having thicknesses between 4 and 12 rom requires initiating pressures higher than those for bare sheet explosives. If the sheet explosive is, however, covered by thin aluminium foil (0.25 mm then it is initiated by blast wave of pressure lower than that for bare or sandwiched sheet explosive. Initiation of sheet explosiveby a blast waveoccurs after a delay of 2 us when it is covered with thin aluminium foil (0.25 mm and about 7 us when it is covered with 4 mm thick aluminium plates.
ON THE AMPLIFICATION OF MAGNETIC FIELD BY A SUPERNOVA BLAST SHOCK WAVE IN A TURBULENT MEDIUM
International Nuclear Information System (INIS)
We have performed extensive two-dimensional magnetohydrodynamic simulations to study the amplification of magnetic fields when a supernova blast wave propagates into a turbulent interstellar plasma. The blast wave is driven by injecting high pressure in the simulation domain. The interstellar magnetic field can be amplified by two different processes, occurring in different regions. One is facilitated by the fluid vorticity generated by the 'rippled' shock front interacting with the background turbulence. The resulting turbulent flow keeps amplifying the magnetic field, consistent with earlier work. The other process is facilitated by the growth of the Rayleigh-Taylor instability at the contact discontinuity between the ejecta and the shocked medium. This can efficiently amplify the magnetic field and tends to produce the highest magnetic field. We investigate the dependence of the amplification on numerical parameters such as grid-cell size and on various physical parameters. We show that the magnetic field has a characteristic radial profile such that the downstream magnetic field gets progressively stronger away from the shock. This is because the downstream magnetic field needs a finite time to reach the efficient amplification, and will get further amplified in the Rayleigh-Taylor region. In our simulation, we do not observe a systematic strong magnetic field within a small distance to the shock. This indicates that if the magnetic-field amplification in supernova remnants indeed occurs near the shock front, other processes such as three-dimensional instabilities, plasma kinetics, and/or cosmic ray effect may need to be considered to explain the strong magnetic field in supernova remnants.
Oscillations in the wake of a flare blast wave
Tothova, D.; Innes, D. E.; Stenborg, G.
2011-04-01
Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes. Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME. Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry. Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave. The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif
Numerical Simulations of Blast Loads from Near-Field Ground Explosions in Air
Dobrociński, Stanisław; Flis, Leszek
2015-12-01
Numerical simulations of air blast loading in the near-field acting on the ground have been performed. A simplified blast model based on empirical blast loading data representing spherical and hemispherical explosive shapes has been simulated. Conwep is an implementation of the empirical blast models presented by Kingery and Bulmash, which is also implemented in the commercial code LS-DYNA based on work done by Rahnders-Pehrson and Bannister. This makes it possible to simulate blast loads acting on structures representing spherical and hemispherical explosive shapes of TNT with reasonable computational effort as an alternative to the SPH and Eulerian model. The CPU time for the simplified blast model is however considerably shorter and may still be useful in time consuming concept studies. Reasonable numerical results using reasonable model sizes can be achieved not only for modelling near-field explosions in air but most areas of geotechnical. Calculation was compared with blast SPH and Eulerian model.
Dry decontamination of simulated test piece by blasting dry ice pellets
International Nuclear Information System (INIS)
Dry decontamination technique is required for maintaining nuclear material handling equipment contaminated with highly radioactive material in a hot cell. In order to determine the optimum blasting conditions of dry decontamination device using the impact of the dry ice pellets, the basic experiments have been conducted on the simulated test specimens of four types of metals. The removal efficiency of test piece was evaluated by the XRF analysis and the change of the surface condition before and after blasting. The removal efficiency of cesium on loose contamination was 100% under blasting pressure; 3kg/cm2, blasting distance; 10 cm, blasting time; 10 sec. In case of fixed contamination, the removal efficiency of cesium was almost 96% under blasting pressure; 4kg/cm2, blasting time; 10 cm, blasting time; 30 sec
Stability of the Primakoff-Sedov blast wave and its generalizations
International Nuclear Information System (INIS)
The linear stability of those Sedov blast wave similarity solutions for which the flow is homologous behind the shock, of which the best-known example is the Primakoff point blast model, along with that of their two-dimensional counterparts, is proved analytically. This conclusion in the three-dimensional case applies to all perturbations, and in the two-dimensional case to flutelike (k/sub Z/=0) modes. Implications for supernova remnant evolution are discussed
Analysis of reflected blast wave pressure profiles in a confined room
Sochet, Isabelle; Sauvan, Pierre-Emmanuel; Trelat, Sophie
2012-01-01
To understand the blast effects of confined explosions, it is necessary to study the characteristic parameters of the blast wave in terms of overpressure, impulse and arrival time. In a previous study, experiments were performed using two different scales of a pyrotechnic workshop. The main purpose of these experiments was to compare the TNT equivalent for solid and gaseous explosives in terms of mass to define a TNT equivalent in a reflection field and to validate the similitude between real...
Revisiting geometrical shock dynamics for blast wave propagation in complex environment
Ridoux, J.; Lardjane, N.; Gomez, T.; Coulouvrat, F.
2015-10-01
A new fast-running model for blast wave propagation in air is described. This model is an extension of Whitham's Geometrical Shock Dynamics with specific closure to non sustained shock waves. The numerical procedure relies on a Cartesian fast-marching like algorithm with immersed boundary method for complex boundaries. Comparison to academic results underline the capacity of this model.
POLYCYCLIC AROMATIC HYDROCARBON PROCESSING IN THE BLAST WAVE OF THE SUPERNOVA REMNANT N132D
International Nuclear Information System (INIS)
We present Spitzer Infrared Spectrograph 14-36 μm mapping observations of the supernova remnant N132D in the Large Magellanic Cloud. This study focuses on the processing of polycyclic aromatic hydrocarbons (PAHs) that we previously identified in the southern blast wave. The mid-infrared spectra show strong continuum emission from shock-heated dust and a unique, nearly featureless plateau in the 15-20 μm region, which we attribute to PAH molecules. The typical PAH emission bands observed in the surrounding interstellar medium ahead of the blast wave disappear, which indicates shock processing of PAH molecules. The PAH plateau appears most strongly at the outer edge of the blast wave and coincides with diffuse X-ray emission that precedes the brightest X-ray and optical filaments. This suggests that PAH molecules in the surrounding medium are swept up and processed in the hot gas of the blast wave shock, where they survive the harsh conditions long enough to be detected. We also observe a broad emission feature at 20 μm appearing with the PAH plateau. We speculate that this feature is either due to FeO dust grains or connected to the processing of PAHs in the supernova blast wave shock.
Gross, Jonathan; Eliasson, Veronica
2015-11-01
Work has been performed to experimentally characterize the interaction of a multiple blast waves. The blast waves were generated using an exploding wire system. This system can store up to 400 J of energy in a high voltage capacitor bank. By discharging the capacitors through wires of a diameter of 150 μm it was possible to produce blast waves with Mach numbers as high as 2.3 at a distance of 40 mm from the center of the blast. A parametric study was performed to measure the behavior of the shocks for a variety of wire thicknesses, voltages, and separation distances. Additionally a background oriented schlieren system was used to quantify the flowfield behind the shocks. The interaction of the shocks featured expected nonlinear phenomena such as the presence of Mach stems, and showed good agreement with results in the shock wave literature. This investigation lays the groundwork for subsequent research that will use exploding wires to experimentally reproduce conditions investigated numerically, in which the effects of multiple converging blast waves on a central target were investigated.
Untangling the Effect of Head Acceleration on Brain Responses to Blast Waves.
Mao, Haojie; Unnikrishnan, Ginu; Rakesh, Vineet; Reifman, Jaques
2015-12-01
Multiple injury-causing mechanisms, such as wave propagation, skull flexure, cavitation, and head acceleration, have been proposed to explain blast-induced traumatic brain injury (bTBI). An accurate, quantitative description of the individual contribution of each of these mechanisms may be necessary to develop preventive strategies against bTBI. However, to date, despite numerous experimental and computational studies of bTBI, this question remains elusive. In this study, using a two-dimensional (2D) rat head model, we quantified the contribution of head acceleration to the biomechanical response of brain tissues when exposed to blast waves in a shock tube. We compared brain pressure at the coup, middle, and contre-coup regions between a 2D rat head model capable of simulating all mechanisms (i.e., the all-effects model) and an acceleration-only model. From our simulations, we determined that head acceleration contributed 36-45% of the maximum brain pressure at the coup region, had a negligible effect on the pressure at the middle region, and was responsible for the low pressure at the contre-coup region. Our findings also demonstrate that the current practice of measuring rat brain pressures close to the center of the brain would record only two-thirds of the maximum pressure observed at the coup region. Therefore, to accurately capture the effects of acceleration in experiments, we recommend placing a pressure sensor near the coup region, especially when investigating the acceleration mechanism using different experimental setups. PMID:26458125
Coke Reactivity in Simulated Blast Furnace Shaft Conditions
Haapakangas, Juho; Suopajärvi, Hannu; Iljana, Mikko; Kemppainen, Antti; Mattila, Olli; Heikkinen, Eetu-Pekka; Samuelsson, Caisa; Fabritius, Timo
2016-08-01
Despite the fact that H2 and H2O are always present in the gas atmosphere of a blast furnace shaft, their role in the solution-loss reactions of coke has not been thoroughly examined. This study focuses on how H2 and H2O affect the reaction behavior and whether a strong correlation can be found between reactivity in the conditions of the CRI test (Coke Reactivity Index) and various simulated blast furnace shaft gas atmospheres. Partial replacement of CO/CO2 with H2/H2O was found to significantly increase the reactivity of all seven coke grades at 1373 K (1100 °C). H2 and H2O, however, did not have a significant effect on the threshold temperature of gasification. The reactivity increasing effect was found to be temperature dependent and clearly at its highest at 1373 K (1100 °C). Mathematical models were used to calculate activation energies for the gasification, which were notably lower for H2O gasification compared to CO2 indicating the higher reactivity of H2O. The reactivity results in gas atmospheres with CO2 as the sole gasifying component did not directly correlate with reactivity results in gases also including H2O, which suggests that the widely used CRI test is not entirely accurate for estimating coke reactivity in the blast furnace.
Courtney, Elya; Summer, Peter David; Courtney, Michael
2014-01-01
Results are presented for lead free primers based on diazodinitrophenol (DDNP)compared with tests on lead styphnate based primers. First, barrel friction measurements in 5.56 mm NATO are presented. Second, shot to shot variations in blast waves are presented as determined by detonating primers in a 7.62x51mm rifle chamber with a firing pin, but without any powder or bullet loaded and measuring the blast wave at the muzzle with a high speed pressure transducer. Third, variations in primer blast waves, muzzle velocities, and ignition delay are presented after environmental conditioning (150 days) for two lead based and two DDNP based primers under cold and dry (-25 deg C,0% relative humidity), ambient (20 deg C, 50% relative humidity), and hot & humid (50 deg C, 100% relative humidity) conditions in 5.56 mm NATO. Taken together, these results indicate that DDNP based primers are not sufficiently reliable for service use.
soft X-ray background as a supernova blast wave viewed from inside: solar abundance models
International Nuclear Information System (INIS)
A model of the soft X-ray background is presented in which the Sun is assumed to be inside an active supernova blast wave. The blast wave evolves in a preexisting cavity. The broad band surface brightnesses is explained by such a blast wave with an explosion energy of E sub approx. 5 x 10 to the 50th power ergs and radius 80 to 100 pc, using solar abundances. An approach to treating the problem of large anisotropies in the ambient medium is also explored, accommodating the observed anticorrelation between the soft X-ray surface brightness and the 21 cm column density. It is found that only for post shock temperatures below 10 6 K a shock propagating into a density enhancement will be dimmer than a similar shock in a lower density region
Blast wave formation of the extended stellar shells surrounding elliptical galaxies
Williams, R. E.; Christiansen, W. A.
1985-01-01
The existence of stellar shells at large distances from isolated elliptical galaxies is explained in terms of a blast wave associated with an active nucleus phase early in the history of the galaxy. The blast wave sweeps the initial interstellar medium out of the galaxy into an expanding shell which radiatively cools behind its leading shock front. Cooling of the shell following turnoff of the nucleus activity, which keeps the shell photoionized, leads to a brief epoch of star formation which is terminated by heating of the shell from supernovae and UV radiation from massive stars. The stars so formed follow similar, highly radial, bound orbits, moving in phase with each other and spending much of their time near apogalacteum, thus taking on the appearance of a shell. Multiple shells may be produced when conditions allow repeated episodes of shell cooling and supernovae heating to occur in the blast wave.
Blast wave formation of the extended stellar shells surrounding elliptical galaxies
International Nuclear Information System (INIS)
The existence of stellar shells at large distances from isolated elliptical galaxies is explained in terms of a blast wave associated with an active nucleus phase early in the history of the galaxy. The blast wave sweeps the initial interstellar medium out of the galaxy into an expanding shell which radiatively cools behind its leading shock front. Cooling of the shell following turnoff of the nucleus activity, which keeps the shell photoionized, leads to a brief epoch of star formation which is terminated by heating of the shell from supernovae and UV radiation from massive stars. The stars so formed follow similar, highly radial, bound orbits, moving in phase with each other and spending much of their time near apogalacteum, thus taking on the appearance of a shell. Multiple shells may be produced when conditions allow repeated episodes of shell cooling and supernovae heating to occur in the blast wave
Isothermal self-similar blast wave theory of supernova remnants driven by relativistic gas pressure
International Nuclear Information System (INIS)
The spherically symmetric, self-similar flow behind a blast wave from a point explosion in a medium whose density varies with distance as rsup(-ω) is investigated with the assumption that the flow is both isothermal and contains a relativistic component of pressure. A self-similar solution is shown to exist only if both the blast wave speed, usub(s), and the local sound speed, w, are constant. If Ω [equivalent to ω(1-w2/c2)] lies in 1 >Ω>0, there exists a critical point in the radial distance-flow velocity plane. To be physically acceptable, the solution must pass through the origin and through the critical point and then through to the blast front; solution branches between these points exist, although a proper connection at the critical point has not been demonstrated. It is concluded that isothermal self-similar blast waves do not provide a valid model for a supernova remnant driven by a relativistic gas pressure. Since the validity of the adiabatic blast wave models has elsewhere been shown to be questionable, it is doubtful whether the self-similar property can be involved at all in the case of supernova remnants. This raises serious questions of interpretation of quantities deduced for supernova remnants on the basis of the use of self-similar models. (Auth.)
Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects
Courtney, Michael
2011-01-01
Instrumentation is needed to produce realistic blast waves in a laboratory setting. This paper describes the development and characterization of oxy-acetylene driven, laboratory scale shock tubes for use in studying blast injury, candidate armor materials, and material properties at blast loading rates. The pressure-time profiles show a true shock front and exponential decay characteristic of blast waves and have relevant durations. The modular design includes shock tube diameters of 27 mm and 41 mm, and a selection of peak pressures from 204 kPa to 920 kPa can be produced by selection of the driver section diameter and placement of the test sample. Characterization studies of several driver/driven section combinations showed consistent results, with peak pressures having 0.8 - 6.9 percent uncertainty in the mean. This shock tube design provides a more realistic blast profile than current air-driven shock tubes. In addition, operation does not require specialized personnel or facilities like most blast-driven...
Effects of internal heat transfer on the structure of self-similar blast waves
Ghoniem, A. F.; Berger, S. A.; Oppenheim, A. K.; Kamel, M. M.
1982-01-01
An analysis of the problem of self-similar, nonadiabatic blast waves, where both conduction and radiation are allowed to take place, show the problem to be reducible to the integration of a system of six coupled nonlinear ordinary differential equations. Consideration of these equations shows that although radiation tends to produce uniform fields through temperature gradient attenuation, all the energy carried by radiation is deposited on the front and the bounding shock becomes increasingly overdriven. When conduction is taken into account, the distribution of gasdynamic parameters in blast waves in the case of Rosseland diffusion radiation is more uniform than in the case of the Planck emission radiation.
Studying radiative shocks using laser driven blast waves in clustered gases
International Nuclear Information System (INIS)
We report on the creation of radiative blast waves by irradiating gases of atomic clusters with intense short pulse laser light. The efficient absorption of the cluster medium leads to high energy deposition and development into a cylindrical shock. These non-equilibrium, optically thin shocks have great potential for hydrodynamic scaling with astrophysical relevance, particularly for supernova remnants. We discuss how cluster blast waves may become susceptible to spatial and temporal instabilities and the application of the RAPCAL atomic physics code to determine our plasma conditions.
International Nuclear Information System (INIS)
An intense ultrafast laser pulse can be very strongly absorbed in a moderate density gas composed of van der Waals bonded clusters. In this paper, the deposition of the energy of intense 30 fs light pulses in a gas of deuterium clusters has been diagnosed using a technique based on analysis of the trajectories of the resulting cylindrically symmetric blast waves. Using the well-known relation between blast wave velocity and energy deposition in gas, the laser energy deposited per unit length as a function of distance in gas jet plume was measured. These measurements were conducted in jets containing either deuterium clusters or simple deuterium molecules
Modeling blast waves, gas and particles dispersion in urban and hilly ground areas.
Hank, S; Saurel, R; Le Métayer, O; Lapébie, E
2014-09-15
The numerical simulation of shock and blast waves as well as particles dispersion in highly heterogeneous media such as cities, urban places, industrial plants and part of countries is addressed. Examples of phenomena under study are chemical gas products dispersion from damaged vessels, gas dispersion in urban places under explosion conditions, shock wave propagation in urban environment. A three-dimensional simulation multiphase flow code (HI2LO) is developed in this aim. To simplify the consideration of complex geometries, a heterogeneous discrete formulation is developed. When dealing with large scale domains, such as countries, the topography is considered with the help of elevation data. Meteorological conditions are also considered, in particular regarding complex temperature and wind profiles. Heat and mass transfers on sub-scale objects, such as buildings, trees and other obstacles are considered as well. Particles motion is addressed through a new turbulence model involving a single parameter to describe accurately plumes. Validations against experiments in basic situations are presented as well as examples of industrial and environmental computations. PMID:25199503
Directory of Open Access Journals (Sweden)
Aravind eSundaramurthy
2014-12-01
Full Text Available Detonation of a high explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects even at farther distances, which is termed as primary blast injury, which is the theme of this work. The shock-blast profile is characterized with blast overpressure, positive time duration, and impulse as shock-blast wave parameters (SWPs. These parameters in turn are a function of field factors, such as the strength of high explosive and the distance of the human subjects from the epicenter. The shape and magnitude of the profile determine the severity of injury to the subjects. As shown in some of our recent works (Chandra et al., 2011;Sundaramurthy et al., 2012;Skotak et al., 2013, the profile not only determines the survival of the animal but also the acute and chronic biomechanical injuries along with the following bio-chemical sequelae. It is extremely important to carefully design and operate the shock tube to produce field relevant SWPs. Furthermore, it is vital to identify and eliminate the artifacts that are inadvertently introduced in the shock-blast profile that may affect the results. In this work, we examine the relationship between shock tube adjustable parameters (SAPs and SWPs that can be used to control the blast profile; the results can be easily applied to many of the laboratory shock tubes. Further, exact replication of shock profile (magnitude and shape can be related to field explosions and can be a standard in comparing results across different laboratories. 40 experiments are carried out by judiciously varying SAPs such as membrane thickness, breech length (66.68 to 1209.68 mm, measurement location, and type of driver gas (nitrogen, helium. The relationships between SAPs and the resulting shock-blast profiles are characterized. Finally, shock-blast profiles of a TNT explosion from ConWep software is compared with the profiles obtained
Extended adiabatic blast waves and a model of the soft X-ray background. [interstellar matter
Cox, D. P.; Anderson, P. R.
1981-01-01
An analytical approximation is generated which follows the development of an adiabatic spherical blast wave in a homogeneous ambient medium of finite pressure. An analytical approximation is also presented for the electron temperature distribution resulting from coulomb collisional heating. The dynamical, thermal, ionization, and spectral structures are calculated for blast waves of energy E sub 0 = 5 x 10 to the 50th power ergs in a hot low-density interstellar environment. A formula is presented for estimating the luminosity evolution of such explosions. The B and C bands of the soft X-ray background, it is shown, are reproduced by such a model explosion if the ambient density is about .000004 cm, the blast radius is roughly 100 pc, and the solar system is located inside the shocked region. Evolution in a pre-existing cavity with a strong density gradient may, it is suggested, remove both the M band and OVI discrepancies.
Directory of Open Access Journals (Sweden)
Jianguo Ning
2016-01-01
Full Text Available Artificial explosions are commonly used to prevent rockburst in deep roadways. However, the dissipation of the impact stress wave within the artificial blasting damage zone (ABDZ of the rocks surrounding a deep roadway has not yet been clarified. The surrounding rocks were divided into the elastic zone, blasting damage zone, plastic zone, and anchorage zone in this research. Meanwhile, the ABDZ was divided into the pulverizing area, fractured area, and cracked area from the inside out. Besides, the model of the normal incidence of the impact stress waves in the ABDZ was established; the attenuation coefficient of the amplitude of the impact stress waves was obtained after it passed through the intact rock mass, and ABDZ, to the anchorage zone. In addition, a numerical simulation was used to study the dynamic response of the vertical stress and impact-induced vibration energy in the surrounding rocks. By doing so, the dissipation of the impact stress waves within the ABDZ of the surrounding rocks was revealed. As demonstrated in the field application, the establishment of the ABDZ in the surrounding rocks reduced the effect of the impact-induced vibration energy on the anchorage support system of the roadway.
International Nuclear Information System (INIS)
The spherically symmetric, self-similar flow behind a blast wave from a point explosion in a medium whose density varies with distance as rsup(-ω) is investigated with the assumption that the flow is isothermal and viscid. If 0<ω<ωsub(c) where ωsub(c)=[13-(160)sup(1/2)]/9 Lerche and Vasyliunas have shown in the inviscid situation that there exist two critical points in the flow speed-radial distance plane, and that all solutions are degenerate in that they pass through the lower critical point with the same slope. The present paper shows that as the viscosity tends to zero, the viscid flow does not tend towards the inviscid flow pattern. Now the validity of adiabatic blast wave models has elsewhere been shown to be questionable for supernova remnants, and the inviscid blast wave models have also been shown to be inappropriate for supernova remnants. Taken together with these previous results, the results of the present calculations strongly suggest that the assumption of isothermal blast wave behaviour of supernova remnants, either viscid or inviscid is not valid. (Auth.)
Skull Flexure from Blast Waves: A New Mechanism for Brain Injury with Implications for Helmet Design
Moss, William C; Blackman, Eric G
2008-01-01
Traumatic brain injury [TBI] has become the signature injury of current military conflicts. The debilitating effects of TBI on society are long-lasting and costly. Although the mechanisms by which impacts cause TBI have been well researched, the mechanisms by which blasts cause TBI are not understood. Various mechanisms, including impacts caused by the blast, have been investigated, but blast-induced deformation of the skull has been neglected. Through the use of hydrodynamical numerical simulations, we have discovered that non-lethal blasts can induce sufficient flexure of the skull to generate potentially damaging loads in the brain, even if no impact occurs. This mechanism has implications for the diagnosis of TBI in soldiers and the design of protective equipment such as helmets.
A Numerical Method for Blast Shock Wave Analysis of Missile Launch from Aircraft
Directory of Open Access Journals (Sweden)
Sebastian Heimbs
2015-01-01
Full Text Available An efficient empirical approach was developed to accurately represent the blast shock wave loading resulting from the launch of a missile from a military aircraft to be used in numerical analyses. Based on experimental test series of missile launches in laboratory environment and from a helicopter, equations were derived to predict the time- and position-dependent overpressure. The method was finally applied and validated in a structural analysis of a helicopter tail boom under missile launch shock wave loading.
Similarity solution of isothermal flows behind a MGD blast wave in an inhomogeneous medium
International Nuclear Information System (INIS)
Self-similar solutions of isothermal flows behind a cylindrical magnetogasdynamic blast wave have been obtained. A strong cylindrical shock wave generated by a sudden line source explosion in an inhomogeneous medium of electrically conducting gas has been studied. Numerical and analytical treatments have been presented and a uniformly valid distribution of pressure, density and velocity profiles has been determined and the magnetic-field effects on the flow distributions have been investigated
An Analytic Solution to the Propagation of Cylindrical Blast Waves in a Radiative Gas
Directory of Open Access Journals (Sweden)
B.G Verma
1977-01-01
Full Text Available In this paper, we have obtained a set of non-similarity in closed forms for the propagation of a cylindrical blast wave in a radiative gas. An explosion in a gas of constant density and pressure has been considered by assuming the existence of an initial uniform magnetic field in the axial direction. The disturbance is supposed to be headed by a shock surface of variable strength and the total energy of the wave varies with time.
International Nuclear Information System (INIS)
The problem of blast wave propagation and attenuation have always been of considerable basic and practical interest. Due to diffraction effects, reflections and possible focusing, blast wave intensity may vary considerably even at the same distance from the explosion center. From the computational point of view, these problems deal typically with computational domains of complex geometry, often requiring the resolution of gas dynamics phenomena having characteristic scales much smaller than the scale of a computational domain. This paper presents experiences and capabilities in applying the above techniques to various practical problems involving blast wave propagation and attenuation
Sevagan, Gopinath; Zhu, Feng; Jiang, Binhui; Yang, King H
2013-07-01
This article presents the results of a finite element simulation on the occupant head response in an infantry vehicle under two separated loading conditions: (1) blunt impact and (2) blast loading conditions. A Hybrid-III dummy body integrated with a previously validated human head model was used as the surrogate. The biomechanical response of the head was studied in terms of head acceleration due to the impact by a projectile on the vehicle and intracranial pressure caused by blast wave. A series of parametric studies were conducted on the numerical model to analyze the effect of some key parameters, such as seat configuration, impact velocity, and boundary conditions. The simulation results indicate that a properly designed seat and internal surface of the infantry vehicle can play a vital role in reducing the risk of head injury in the current scenarios. Comparison of the kinematic responses under the blunt impact and blast loading conditions reveals that under the current loading conditions, the acceleration pulse in the blast scenario has much higher peak values and frequency than blunt impact case, which may reflect different head response characteristics. PMID:23636759
Blast event simulation for a structure subjected to a landmine explosion
Sun, J.; Vlahopoulos, N.; Stabryla, T.J.; Goetz, R.; Velde, R. van de
2006-01-01
One of the main threats to military vehicles originates from landmine blasts. In order to improve the survivability of the occupants it is important to design a military vehicle for increased occupant safety. Simulation technology that combines modeling of the blast loads from the landmine explosion
International Nuclear Information System (INIS)
This paper describes experiments exploring the three-dimensional (3D) Rayleigh-Taylor instability at a blast-wave-driven interface. This experiment is well scaled to the He/H interface during the explosion phase of SN1987A. In the experiments, ∼5 kJ of energy from the Omega laser was used to create a planar blast wave in a plastic disk, which is accelerated into a lower-density foam. These circumstances induce the Richtmyer-Meshkov instability and, after the shock passes the interface, the system quickly becomes dominated by the Rayleigh-Taylor instability. The plastic disk has an intentional pattern machined at the plastic/foam interface. This perturbation is 3D with a basic structure of two orthogonal sine waves with a wavelength of 71 μm and an amplitude of 2.5 μm. Additional long-wavelength modes with a wavelength of either 212 or 424 μm are added onto the single-mode pattern. The addition of the long-wavelength modes was motivated by the results of previous experiments where material penetrated unexpectedly to the shock front, perhaps due to an unintended structure. The current experiments and simulations were performed to explore the effects of this unintended structure; however, we were unable to reproduce the previous results.
Field of infrasound wave on the earth from blast wave, produced by supersonic flight of a rocket
International Nuclear Information System (INIS)
It was developed a physical model, which allowed calculating a field of infrasound wave on the earth from blast wave, produced by supersonic flight of a rocket. For space launching site Baikonur it is shown that the nearest horizontal distance from launching site of rocket up to which arrive infrasound waves, produced by supersonic flight of a rocket, is 56 km. Amplitude of acoustic impulse decreases in 5 times on distance of 600 km. Duration of acoustic impulse increases from 1.5 to 3 s on the same distance. Values of acoustic field parameters on the earth surface, practically, do not depend from season of launching of rocket. (author)
Simulation of the Response of Glass Window Under Blast Load
Institute of Scientific and Technical Information of China (English)
WANG Zhongqi; GONG Guangdong; ZHANG Yanchun; BAI Chunhua
2008-01-01
In the investigation of accidental explosion scene,the damage on the glass is one of the typical traces which can be used to decide the characteristic of the explosion source.To analyze the response of glass under the blast load,a numerical model was developed.In the model,the brittleness glass model was adopted.A 'node release' method,which had some special merits compared with the erosion method was used to simulate the rupture of the glass In the calculation,several problems which play major role in the response of the glass were discussed.The velocity and the displacement of the glass fragment were two major factors.The numerical results are very helpful for the design and hazard assessment.
Trans-Relativistic Blast Waves in Supernovae as Gamma-Ray Burst Progenitors
Tan, J C; McKee, C F; Tan, Jonathan C.; Matzner, Christopher D.; Kee, Christopher F. Mc
2000-01-01
We investigate the acceleration of shock waves to relativistic velocities in the outer layers of exploding stars. By concentrating the explosion energy in the outermost ejecta, such trans-relativistic blast waves can serve as the progenitors of gamma-ray bursts (GRBs); in particular, the ``baryon-loading'' problem that plagues many models of GRBs is circumvented. We present physically motivated and numerically validated analytic expressions to describe trans-relativistic blast waves in supernovae. We find that relativistic ejecta are enhanced in more centrally condensed envelopes, e.g., for radiative envelopes, when the luminosity approaches the Eddington limit. Convenient formulae are presented with which to estimate the production of relativistic ejecta from a given progenitor. We apply our analytic and numerical methods to a model of SN 1998bw, finding significantly enhanced relativistic ejecta compared to previous studies. We propose that GRB 980425 is associated with SN 1998bw and resulted from a spheric...
Simard, J. Marc; Pampori, Adam; Keledjian, Kaspar; Tosun, Cigdem; Schwartzbauer, Gary; Ivanova, Svetlana; Gerzanich, Volodymyr
2014-01-01
Traumatic brain injury (TBI) caused by an explosive blast (blast-TBI) is postulated to result, in part, from transvascular transmission to the brain of a hydrodynamic pulse (a.k.a., volumetric blood surge, ballistic pressure wave, hydrostatic shock, or hydraulic shock) induced in major intrathoracic blood vessels. This mechanism of blast-TBI has not been demonstrated directly. We tested the hypothesis that a blast wave impacting the thorax would induce a hydrodynamic pulse that would cause pa...
Marscher, A. P.
1978-01-01
A relativistic blast-wave version of a signal-screen model is developed which can adequately explain the details of the flux-density and structural variations of compact extragalactic radio sources. The relativistic motion implied by flux variations is analyzed with respect to the synchrotron spectrum of the BL Lac object AO 0235+164 observed during outbursts, and a signal-screen model for rapidly expanding shells produced by ultrarelativistic blast waves is examined. The approximate observed structure of the blast wave at three stages in its evolution is illustrated, each stage is described, and the model is applied to the flux density outburst in AO 0235+164 observed in late 1975. The results show that a relativistic blast-wave model can in general reproduce the main features of the observed flux variations in compact sources. Some problems with the proposed model are briefly discussed.
Kane, Michael J; Angoa-Pérez, Mariana; Francescutti, Dina M.; Sykes, Catherine E.; Briggs, Denise I.; Leung, Lai Yee; VandeVord, Pamela J.; Kuhn, Donald M.
2012-01-01
Blast overpressure has long been known to cause barotrauma to air-filled organs such as lung and middle ear. However, experience in Iraq and Afghanistan is revealing that individuals exposed to explosive munitions can also suffer traumatic brain injury (TBI) even in the absence of obvious external injury. The interaction of a blast shock wave with the brain in the intact cranial vault is extremely complex making it difficult to conclude that a blast wave interacts in a direct manner with the ...
International Nuclear Information System (INIS)
Understanding the dynamics of laser-produced plasma is essentially important for increasing available thrust force in a gas-driven laser propulsion system such as laser-driven in-tube accelerator. A computer code is developed to explore the formation of expanding nonequilibrium plasma produced by laser irradiation. Various properties of the blast wave driven by the nonequilibrium plasma are examined. It is found that the blast wave propagation is substantially affected by radiative cooling effect for lower density case
Simulation for the powder movement and accumulation in the lower part of blast furnace
Energy Technology Data Exchange (ETDEWEB)
Sugiyama, Takashi [Mineral Resources Research Center, Nippon Steel Technoresearch, Futtsu-shi Chiba (Japan)
1997-12-31
The behavior of unburnt char and coke powder in the blast furnace becomes material for discussion with the increase in injection rate of pulverized coal into the blast furnace. An analysis was made as to the simulation of powder accumulation at the deadman and dripping zone of blast furnace by using a powder/gas two-phases flow experimental data. When an excessive powder has penetrated at a low gas velocity, it brings an increment in holdup and the controlling factors are powder/gas ratio and gas velocity. An empirical formula used for estimating the powder hold-up in the blast furnace internal conditions has proposed based on similarity. The controlling {pi} numbers are Floude number, powder/gas ratio and particle diameter ratio of powder/lump. This empirical formular was connected with Blast Furnace Total Model `BRIGHT` for the simulation of powder amount distribution in the lower part of blast furnace. When Powder diameter Dk exceeds 100 {mu} and gas velocity becomes lower than 0.7m/s at PC1OOkg/T, the powder tends to accumulate in the deadman. These results was available for the decision of optimum blast conditions and optimum powder diameter in the high amount of pulverized coal injection to the blast furnace. (author) 10 refs.
International Nuclear Information System (INIS)
We investigate the dynamics and afterglow light curves of gamma-ray burst blast waves that encounter various density structures (such as bumps, voids, or steps) in the surrounding ambient medium. We present and explain the characteristic response features that each type of density structure in the medium leaves on the forward shock (FS) and reverse shock (RS) dynamics for blast waves with either a long-lived or short-lived RS. We show that when the ambient medium density drops, the blast waves exhibit in some cases a period of an actual acceleration (even during their deceleration stage) due to adiabatic cooling of blast waves. Comparing numerical examples that have different shapes of bumps or voids, we propose a number of consistency tests that must be satisfied by correct modeling of blast waves. Our model results successfully pass these tests. Employing a Lagrangian description of blast waves, we perform a sophisticated calculation of afterglow emission. We show that as a response to density structures in the ambient medium, the RS light curves produce more significant variations than the FS light curves. Some observed features (such as rebrightenings, dips, or slow wiggles) can be more easily explained within the RS model. We also discuss the origin of these different features imprinted on the FS and RS light curves.
Radiant Image Simulation of Pulverized Coal Combustion in Blast Furnace Raceway
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The relationship between two-dimensional radiant image and three-dimensional radiant energy in blast furnace raceway was studied by numerical simulation of combustion process. Taking radiant image as radiant boundary for numerical simulation of combustion process, the uneven radiation parameter can be calculated. A method to examine three-dimensional temperature distribution in blast furnace raceway was put forward by radiant image processing. The numeral temperature field matching the real combustion can be obtained by proposed numeric image processing technique.
Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design
Energy Technology Data Exchange (ETDEWEB)
Moss, W C; King, M J; Blackman, E G
2009-04-30
Traumatic brain injury [TBI] has become a signature injury of current military conflicts, with debilitating, costly, and long-lasting effects. Although mechanisms by which head impacts cause TBI have been well-researched, the mechanisms by which blasts cause TBI are not understood. From numerical hydrodynamic simulations, we have discovered that non-lethal blasts can induce sufficient skull flexure to generate potentially damaging loads in the brain, even without a head impact. The possibility that this mechanism may contribute to TBI has implications for injury diagnosis and armor design.
Kinematics of ICMEs/shocks: blast wave reconstruction using type II emissions
Corona-Romero, P; Aguilar-Rodriguez, E; de-la-Luz, V; Mejia-Ambriz, J C
2015-01-01
We present a physical methodology to reconstruct the trajectory of interplanetary shocks using type II radio emission data. This technique calculates the shock trajectory assuming that the disturbance propagates as a blast wave in the interplanetary medium. We applied this Blast Wave Reconstruction (BWR) technique to analyze eight fast Earth-directed ICMEs/shocks associated with type II emissions. The technique deduces a shock trajectory that reproduces the type II frequency drifts, and calculates shock onset speed, shock transit time and shock speed at 1~AU. There were good agreements comparing the BWR results with the type II spectra, with data from coronagraph images, {\\it in situ} measurements, and interplanetary scintillation (IPS) observations. Perturbations on the type II data affect the accuracy of the BWR technique. This methodology could be applied to track interplanetary shocks causing TII emissions in real-time, to predict the shock arrival time and shock speed at 1~AU.
Impulsive dispersion of a granular layer by a weak blast wave
Rodriguez, V.; Saurel, R.; Jourdan, G.; Houas, L.
2016-04-01
The dispersion of particles by blast or shock waves induces the formation of coherent structures taking the shape of particle jets. In the present study, a blast wave, issued from an open shock tube, is generated at the center of a granular ring initially confined in a Hele-Shaw cell. With the present experimental setup, solid particle jet formation is clearly observed in a quasi-two-dimensional configuration. In all instances, the jets are initially generated inside the particle ring and thereafter expelled outward. Furthermore, thanks to the two-dimensional experimental configuration, a general study of the main parameters involved in these types of flows can be performed. Among them, the particle diameter, the density of the particles, the initial size of the ring, the shape of the overpressure generated and the surface friction of the Hele-Shaw cell are investigated. Empirical relationships are deduced from experimental results.
A viscous blast-wave model for relativistic heavy-ion collisions
Jaiswal, Amaresh
2015-01-01
Using a viscosity-based survival scale for geometrical perturbations formed in the early stages of relativistic heavy-ion collisions, we model the radial flow velocity during freeze-out. Subsequently, we employ the Cooper-Frye freeze-out prescription, with first-order viscous corrections to the distribution function, to obtain the transverse momentum distribution of particle yields and flow harmonics. For initial eccentricities, we use the results of Monte Carlo Glauber model. We fix the blast-wave model parameters by fitting the transverse momentum spectra of identified particles at the Large Hadron Collider (LHC) and demonstrate that this leads to a fairly good agreement with transverse momentum distribution of elliptic and triangular flow for various centralities. Within this viscous blast-wave model, we estimate the shear viscosity to entropy density ratio $\\eta/s\\simeq 0.24$ at the LHC.
Beam energy dependence of Hanbury-Brown-Twiss radii from a blast-wave model
Zhang, S; Chen, J H; Zhong, C
2016-01-01
Beam energy dependence of correlation lengths (Hanbury-Brown-Twiss radii) is calculated by using a blast-wave model and the results are comparable with those from RHIC-STAR beam energy scan data as well as the LHC-ALICE measurements. The parameters for the blast-wave model as a function of beam energy are configured by fitting Hanbury-Brown-Twiss radii at each energy point. Transverse momentum dependence of Hanbury-Brown-Twiss radii are presented with the extracted parameters for $\\sqrt{s_{NN}} = $ 200 GeV and 2.76 TeV. From the results it can be found that particle emission duration can not be ignored while calculating Hanbury-Brown-Twiss radii with the same parameters. And tuning kinetic freeze-out temperature in a range will result in system lifetime changing in reverse direction as that in RHIC-STAR measurements.
Nonlinear growth of dynamical overstabilities in blast waves. [effects on supernova remnants
Mac Low, Mordecai-Mark; Norman, Michael L.
1993-01-01
The numerical gasdynamics code ZEUS-2D is used to directly model the dynamical overstabilities in blast waves. The linear analysis is confirmed by perturbing a blast wave with a low-amplitude eigenfunction of the overstability. The amplitude of the perturbations is increased in order to determine the nonlinear behavior of the overstabilities. The overstability is found to saturate due to weak transverse shocks in the shell. Transverse velocities in the dense shell reach the postshock sound speed, and high-density regions with sizes of the order of the shell thickness form. Transverse oscillations continue even after saturation. This confirms and explains the damping of the overstability experimentally discovered by Grun et al. (1991).
On self-similar blast waves headed by the Chapman-Jouguet detonation.
Oppenheim, A. K.; Kuhl, A. L.; Kamel, M. M.
1972-01-01
Consideration of the whole class of self-similar solutions for blast waves bounded by Chapman-Jouguet detonations that propagate into a uniform, quiescent, zero counterpressure atmosphere of a perfect gas with constant specific heats. Since such conditions can be approached quite closely by some actual chemical systems at NTP, this raises the interesting possibility of the existence of Chapman-Jouguet detonations of variable velocity. The principal virtue of the results presented is, however, more of theoretical significance. They represent the limiting case for all the self-similar blast waves headed by gasdynamic discontinuities associated with a deposition of finite amounts of energy, and they exhibit some unique features owing to the singular nature of the Chapman-Jouguet condition.
Kinematics of ICMEs/Shocks: Blast Wave Reconstruction Using Type-II Emissions
Corona-Romero, P.; Gonzalez-Esparza, J. A.; Aguilar-Rodriguez, E.; De-la-Luz, V.; Mejia-Ambriz, J. C.
2015-09-01
We present a physical methodology for reconstructing the trajectory of interplanetary shocks using Type-II radio emission data. This technique calculates the shock trajectory assuming that the disturbance propagates as a blast wave in the interplanetary medium. We applied this blast-wave reconstruction (BWR) technique to analyze eight fast Earth-directed ICMEs/shocks associated with Type-II emissions. The technique deduces a shock trajectory that reproduces the Type-II frequency drifts and calculates shock onset speed, shock travel time, and shock speed at 1 AU. The BWR results agreed well with the Type-II spectra, with data from coronagraph images, in-situ measurements, and interplanetary scintillation observations. Perturbations in the Type-II data affect the accuracy of the BWR technique. This methodology could be applied to track interplanetary shocks causing Type-II emissions in real-time and to predict the shock arrival time and shock speed at 1 AU.
The numerical study of interaction between spherical blast-wave and explosion product and fireball
International Nuclear Information System (INIS)
To understand the flow structure of spherical blast-wave and the interaction between the shock and the gaseous product or fireball of explosion, 3rd-order TVD Runge-Kutta time integration and 5th-order WENO spatial discretization scheme was used to solve the Navier-stokes equations with buoyant source term in the environment of real gas. It was found that peaks and valleys of pressure and density coexisted in the field of explosion, and the underside of the interface between the product or fireball and the environment became irregular. Secondly, vortex structure formed on the under surface of the product as a result of entrainment and upward movement. Moreover, the reflective blast-wave propagating through the secondary shock induced by the main shock resulted in the compression of product and changed the profile and thermodynamic parameters of the product. (authors)
PARTICLE ACCELERATION IN THE EXPANDING BLAST WAVE OF η CARINA'S GREAT ERUPTION OF 1843
International Nuclear Information System (INIS)
Non-thermal hard X-ray and high-energy (HE; 1 MeV ≤ E ≤ 100 GeV) γ-ray emission in the direction of η Carina has been recently detected using the INTEGRAL, AGILE, and Fermi satellites. So far this emission has been interpreted in the framework of particle acceleration in the colliding wind region between the two massive stars. However, the existence of a very fast moving blast wave which originates in the historical 1843 'Great Eruption' provides an alternative particle acceleration site in this system. Here, we explore an alternate scenario and find that inverse Compton emission from electrons accelerated in the blast wave can naturally explain both the flux and spectral shape of the measured hard X-ray and HE γ-ray emission. This scenario is further supported by the lack of significant variability in the INTEGRAL and Fermi measured fluxes.
On the propagation of a cylindrical MHD blast wave
International Nuclear Information System (INIS)
The propagation of a cylindrical MHD shock wave, during the staqe when the wave is still strong (in the hydrodynamical sense) has been studied. The variations of the flow and field parameters at the rear of the wave are determined in terms of its radius R and the time derivatives of R. The dependence of the speed of propagation on the explosive energy, the radius of the wave and the magnetic field is determined and some interesting inferences are drawn. The law of propagation obtained by Lin (1954) has been recovered in the limit of vanishing magnetic field. (auth.)
Skull flexure from blast waves: a mechanism for brain injury with implications for helmet design
Energy Technology Data Exchange (ETDEWEB)
Moss, W C; King, M J; Blackman, E G
2009-04-14
Traumatic brain injury [TBI] has become a signature injury of current military conflicts. The debilitating effects of TBI are long-lasting and costly. Although the mechanisms by which impacts cause TBI have been well researched, the mechanisms by which blasts cause TBI are not understood. Various possibilities have been investigated, but blast-induced deformation of the skull has been neglected. From numerical hydrodynamic simulations, we have discovered that nonlethal blasts can induce sufficient flexure of the skull to generate potentially damaging loads in the brain, even if no impact occurs. The possibility that this mechanism may contribute to TBI has implications for the diagnosis of soldiers and the design of protective equipment such as helmets.
THE CALCULATION OF INITIAL SHOCK WAVE IN ROCK WITH UNCOUPLING CHARGE BLASTING
Institute of Scientific and Technical Information of China (English)
李玉民; 倪芝芳; 黄忆龙
1997-01-01
According to the structure of explosive charge in rock blasting, a physical model has been set up in this paper. Based on the model, a methodology for calculating initial shock wave of uncoupling charge has been given. The pressure P3 has been calculated when high explosives act on granite, limestone, marble and shale respectively. Some important conclusions are also gained by the analysis of results.
Calculation of wing response to gusts and blast waves with vortex lift effect
Chao, D. C.; Lan, C. E.
1983-01-01
A numerical study of the response of aircraft wings to atmospheric gusts and to nuclear explosions when flying at subsonic speeds is presented. The method is based upon unsteady quasi-vortex lattice method, unsteady suction analogy and Pade approximant. The calculated results, showing vortex lag effect, yield reasonable agreement with experimental data for incremental lift on wings in gust penetration and due to nuclear blast waves.
The time development of a blast wave with shock-heated electrons
Edgar, R. J.; Cox, D. P.
1984-01-01
Accurate approximations are presented for the time development of both edge conditions and internal structures of a blast wave with shock heated electrons, and equal ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform ambient density case) and have negligible external pressure. Account is taken of possible saturation of the thermal conduction flux. The structures evolve smoothly to the adiabatic structures.
A Semi-analytic Formulation for Relativistic Blast Waves with a Long-lived Reverse Shock
Uhm, Z. Lucas
2010-01-01
This paper performs a semi-analytic study of relativistic blast waves in the context of gamma-ray bursts (GRBs). Although commonly used in a wide range of analytical and numerical studies, the equation of state (EOS) with a constant adiabatic index is a poor approximation for relativistic hydrodynamics. Adopting a more realistic EOS with a variable adiabatic index, we present a simple form of jump conditions for relativistic hydrodynamical shocks. Then we describe in detail our technique of m...
The time development of a blast wave with shock heated electrons
Edgar, R. J.; Cox, D. P.
1983-01-01
Accurate approximations are presented for the time development of both edge conditions and internal structures of a blast wave with shock heated electrons, and equal ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform ambient density case) and have negligible external pressure. Account is taken of possible saturation of the thermal conduction flux. The structures evolve smoothly to the adiabatic structures.
A Numerical Method for Blast Shock Wave Analysis of Missile Launch from Aircraft
Sebastian Heimbs; Josef Ritzer; Johannes Markmiller
2015-01-01
An efficient empirical approach was developed to accurately represent the blast shock wave loading resulting from the launch of a missile from a military aircraft to be used in numerical analyses. Based on experimental test series of missile launches in laboratory environment and from a helicopter, equations were derived to predict the time- and position-dependent overpressure. The method was finally applied and validated in a structural analysis of a helicopter tail boom under missile launch...
Dynamics and Afterglow Light Curves of GRB Blast Waves with a Long-lived Reverse Shock
Uhm, Z Lucas; Hascoet, Romain; Daigne, Frederic; Mochkovitch, Robert; Park, Il H
2012-01-01
We perform a detailed study on the dynamics of a relativistic blast wave with the presence of a long-lived reverse shock (RS). Although a short-lived RS has been widely considered, the RS is believed to be long-lived as a consequence of a stratification expected on the ejecta Lorentz factors. The existence of a long-lived RS makes the forward shock (FS) dynamics to deviate from a self-similar Blandford-McKee solution. Employing the "mechanical model" that correctly incorporates the energy conservation for such blast waves with a long-lived RS, we present an accurate solution for both the FS and RS dynamics. We conduct a sophisticated calculation of the afterglow emission. Adopting a Lagrangian description of the blast wave, we keep track of an adiabatic evolution of numerous shells between the FS and RS. An evolution of the electron spectrum is also followed individually for every shell. We then find the FS and RS light curves by integrating over the entire FS and RS shocked regions, respectively. In particul...
Influence of ambient air pressure on the energy conversion of laser-breakdown induced blast waves
International Nuclear Information System (INIS)
Influence of ambient pressure on energy conversion efficiency from a Nd : glass laser pulse (λ = 1.053 µm) to a laser-induced blast wave was investigated at reduced pressure. Temporal incident and transmission power histories were measured using sets of energy meters and photodetectors. A half-shadowgraph half-self-emission method was applied to visualize laser absorption waves. Results show that the blast energy conversion efficiency ηbw decreased monotonically with the decrease in ambient pressure. The decrease was small, from 40% to 38%, for the pressure change from 101 kPa to 50 kPa, but the decrease was considerable, to 24%, when the pressure was reduced to 30 kPa. Compared with a TEA-CO2-laser-induced blast wave (λ = 10.6 µm), higher fraction absorption in the laser supported detonation regime ηLSD of 90% was observed, which is influenced slightly by the reduction of ambient pressure. The conversion fraction ηbw/ηLSD≈90% was achieved at pressure >50 kPa, which is significantly higher than that in a CO2 laser case. (paper)
Soft x-ray background as a blast wave viewed from inside
International Nuclear Information System (INIS)
A model of the soft x-ray background is presented in which the Sun is assumed to be inside an active supernova blast wave. The broad-band surface brightnesses can be explained by such a blast wave with an explosion energy of E0 greater than or equal to 5 x 1050 ergs and radius 80 to 100 pc, using solar abundances. The dynamical model used includes the effects of thermal conduction, as the electrons are assumed to be heated by non-Coulomb processes in the shock front. At early times these effects are important, but as the temperature drops with time, they fade away and the structure approaches that of an adiabatic blast wave. An approach to treating the problem of large anisotropies in the ambient medium is also explored, accommodating the observed anticorrelation between the soft x-ray surface brightness and the column density of neutral hydrogen. It is found that only for post shock temperatures below 106 K will a shock propagating into a density enhancement be dimmer than a shock of similar pressure in a medium of lower density
Extended adiabatic blast waves and a model of the soft X-ray background
Cox, D. P.; Anderson, P. R.
1982-01-01
The suggestion has been made that much of the soft X-ray background observed in X-ray astronomy might arise from being inside a very large supernova blast wave propagating in the hot, low-density component of the interstellar (ISM) medium. An investigation is conducted to study this possibility. An analytic approximation is presented for the nonsimilar time evolution of the dynamic structure of an adiabatic blast wave generated by a point explosion in a homogeneous ambient medium. A scheme is provided for evaluating the electron-temperature distribution for the evolving structure, and a procedure is presented for following the state of a given fluid element through the evolving dynamical and thermal structures. The results of the investigation show that, if the solar system were located within a blast wave, the Wisconsin soft X-ray rocket payload would measure the B and C band count rates that it does measure, provided conditions correspond to the values calculated in the investigation.
The Production of Strong Blast Waves through Intense Laser Irradiation of Atomic Clusters
International Nuclear Information System (INIS)
An understanding of radiation effects on the evolution of shock waves is of great importance to many problems in astrophysics. Shock waves driven by a laser-heated plasma are attractive for laboratory investigation of these phenomena. Recent studies of intense short-pulse laser interactions with gases of atomic clusters indicate a potential avenue to access this regime of radiative hydrodynamics. We have measured the energy absorption efficiency of high-intensity, picosecond laser pulses in low-density gases composed of large atomic clusters and find that the energy absorption can be very high (>95%), producing a high-temperature plasma filament which consequently produces a strong blast wave. Interferometric characterization of these shock waves indicates that in high-Z gases such as Xe, radiation transport plays an important role in the evolution of the shock wave. (c) 2000 The American Astronomical Society
Sundaramurthy, Aravind; Chandra, Namas
2014-01-01
Detonation of a high-explosive produces shock-blast wave, shrapnel, and gaseous products. While direct exposure to blast is a concern near the epicenter, shock-blast can affect subjects, even at farther distances. When a pure shock-blast wave encounters the subject, in the absence of shrapnels, fall, or gaseous products the loading is termed as primary blast loading and is the subject of this paper. The wave profile is characterized by blast overpressure, positive time duration, and impulse and called herein as shock-blast wave parameters (SWPs). These parameters in turn are uniquely determined by the strength of high explosive and the distance of the human subjects from the epicenter. The shape and magnitude of the profile determine the severity of injury to the subjects. As shown in some of our recent works (1-3), the profile not only determines the survival of the subjects (e.g., animals) but also the acute and chronic biomechanical injuries along with the following bio-chemical sequelae. It is extremely important to carefully design and operate the shock tube to produce field-relevant SWPs. Furthermore, it is vital to identify and eliminate the artifacts that are inadvertently introduced in the shock-blast profile that may affect the results. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs that can be used to control the blast profile; the results can be easily applied to many of the laboratory shock tubes. Further, replication of shock profile (magnitude and shape) can be related to field explosions and can be a standard in comparing results across different laboratories. Forty experiments are carried out by judiciously varying SAPs such as membrane thickness, breech length (66.68-1209.68 mm), measurement location, and type of driver gas (nitrogen, helium). The effects SAPs have on the resulting shock-blast profiles are shown. Also, the shock-blast profiles of a TNT explosion from ConWep software is compared
Battery Lifetime Analysis and Simulation Tool (BLAST) Documentation
Energy Technology Data Exchange (ETDEWEB)
Neubauer, J.
2014-12-01
The deployment and use of lithium-ion batteries in automotive and stationary energy storage applications must be optimized to justify their high up-front costs. Given that batteries degrade with use and storage, such optimizations must evaluate many years of operation. As the degradation mechanisms are sensitive to temperature, state-of-charge histories, current levels, and cycle depth and frequency, it is important to model both the battery and the application to a high level of detail to ensure battery response is accurately predicted. To address these issues, the National Renewable Energy Laboratory has developed the Battery Lifetime Analysis and Simulation Tool (BLAST) suite of tools. This suite of tools pairs NREL's high-fidelity battery degradation model with a battery electrical and thermal performance model, application-specific electrical and thermal performance models of the larger system (e.g., an electric vehicle), application-specific system use data (e.g., vehicle travel patterns and driving data), and historic climate data from cities across the United States. This provides highly realistic, long-term predictions of battery response and thereby enables quantitative comparisons of varied battery use strategies.
Afterglow emission from pair-loaded blast waves in gamma-ray bursts
Beloborodov, A M
2005-01-01
The MeV radiation front of gamma-ray bursts creates copious e+- pairs as it propagates through an ambient medium. The created pairs enrich the leptonic component of the medium by a large factor at distances R < R_load ~ 10^{16} cm from the burst center. The following blast wave sweeps up the pair-rich medium and then emits the observed afterglow radiation. We find that the afterglow has a "memory" of e+- loading outside R_load. The e+- pairs remain in the swept-up material and slowly cool down by emitting synchrotron radiation. They are likely to dominate the blast-wave emission in IR, optical, and UV bands during the first minutes of the observed afterglow. The expected e+- radiation is described by a simple formula, which is derived analytically and checked by numerical integration of synchrotron emission over the blast material; a suitable Lagrangian formalism is developed for such calculations. The main signature of e+- radiation is its flat ("white") spectrum in a broad range of frequencies from IR to...
Kinetics of blast waves in one-dimensional conservative and dissipative gases
Barbier, Matthieu
2015-11-01
Blast waves caused by a localized release of energy in a gas have become a textbook hydrodynamics problem since the seminal works of Taylor, von Neumann and Sedov. However, the topic has received very little attention at the kinetic level, which can provide a complementary range of insights: notably, transient regimes and the microscopic structure of the shock front, reduced to a singular boundary in continuum equations. As a first step, we study blast waves in a one-dimensional gas of hard particles. This simple limit helps develop important intuitions pertaining to any type of blast, and it is amenable to kinetic analysis—even with the addition of energy dissipation leading to ‘snowplow’ dynamics, or an inhomogeneous mass repartition (as found in astrophysical systems and granular materials). Furthermore, the conservative case proves to be of remarkable interest in demonstrating subtle aspects of dimensional analysis and their resolution through microscopic insights. We show that it can effectively behave like a zero-dimensional system, reduced to the shock front, depending on whether a length scale appears in the initial mass distribution.
Application of blast wave theory to explosive propulsion. [system performance analysis
Back, L. H.
1975-01-01
An analysis was carried out by using blast wave theory to delineate the important aspects of detonating explosives in nozzles, such as flow and wave phenomena, characteristic length and time scales, and the parameters on which the specific impulse is dependent. The propulsive system utilizes the momentum of the ambient gas set into motion in the nozzle by the explosion. A somewhat simplified model was considered for the situation where the mass of ambient gas in the nozzle is much greater than the mass of gas produced in the explosion, a condition of interest for dense atmospheres, e.g., near the surface of Venus. Instantaneous detonation and energy release was presumed to occur at the apex of a conical nozzle, and the shock wave generated by the explosion was taken to propagate as a spherical wave, thereby setting the ambient gas in the nozzle into one-dimensional radially outward motion.
Kabu, Shushi; Jaffer, Hayder; Petro, Marianne; Dudzinski, Dave; Stewart, Desiree; Courtney, Amy; Courtney, Michael; Labhasetwar, Vinod
2015-01-01
Blast-associated shock wave-induced traumatic brain injury (bTBI) remains a persistent risk for armed forces worldwide, yet its detailed pathophysiology remains to be fully investigated. In this study, we have designed and characterized a laboratory-scale shock tube to develop a rodent model of bTBI. Our blast tube, driven by a mixture of oxygen and acetylene, effectively generates blast overpressures of 20-130 psi, with pressure-time profiles similar to those of free-field blast waves. We tested our shock tube for brain injury response to various blast wave conditions in rats. The results show that blast waves cause diffuse vascular brain damage, as determined using a sensitive optical imaging method based on the fluorescence signal of Evans Blue dye extravasation developed in our laboratory. Vascular leakage increased with increasing blast overpressures and mapping of the brain slices for optical signal intensity indicated nonhomogeneous damage to the cerebral vasculature. We confirmed vascular leakage due to disruption in the blood-brain barrier (BBB) integrity following blast exposure. Reactive oxygen species (ROS) levels in the brain also increased with increasing blast pressures and with time post-blast wave exposure. Immunohistochemical analysis of the brain sections analyzed at different time points post blast exposure demonstrated astrocytosis and cell apoptosis, confirming sustained neuronal injury response. The main advantages of our shock-tube design are minimal jet effect and no requirement for specialized equipment or facilities, and effectively generate blast-associated shock waves that are relevant to battle-field conditions. Overall data suggest that increased oxidative stress and BBB disruption could be the crucial factors in the propagation and spread of neuronal degeneration following blast injury. Further studies are required to determine the interplay between increased ROS activity and BBB disruption to develop effective therapeutic strategies
"BLAST": A compilation of codes for the numerical simulation of the gas dynamics of explosions
Berg, A.C. van den
2009-01-01
The availability of powerful computers these days increasingly enables the use of CFD for the numerical simulation of explosion phenomena. The BLAST software consists of a compilation of codes for the numerical simulation of the gas dynamics of explosions. Each individual code has been tailored to a
Cosmic ray acceleration at blast waves from type Ia supernovae
Kang, H
2007-01-01
We have calculated the cosmic ray (CR) acceleration at young remnants from Type Ia supernovae expanding into a uniform interstellar medium (ISM). Adopting quasi-parallel magnetic fields, gasdynamic equations and the diffusion convection equation for the particle distribution function are solved in a comoving spherical grid which expands with the shock. Bohm-type diffusion due to self-excited Alfven waves, drift and dissipation of these waves in the precursor and thermal leakage injection were included. With magnetic fields amplified by the CR streaming instability, the particle energy can reach up to 10^{16}Z eV at young supernova remnants (SNRs) of several thousand years old. The fraction of the explosion energy transferred to the CR component asymptotes to 40-50 % by that time. For a typical SNR in a warm ISM, the accelerated CR energy spectrum should exhibit a concave curvature with the power-law slope flattening from 2 to 1.6 at E>0.1 TeV.
Relativistic blast-wave model for superlight motion in compact double radio sources
International Nuclear Information System (INIS)
We explore the observational characteristics of a relativistic blast wave which is propagating through an external medium which is confined to a thin disk and whose density and magnetic field decrease with radius. We find that the blast wave appears as a double or triple radio source to an observer viewing the system within 200 of edge-on. The components of the source appear to separate with a velocity exceeding 2c. The dependence of flux density on the observer's inclination angle provides a strong selection effect against sources which do not exhibit the well-separated double or triple structure.The characteristics of the model are favorably compared with observations of the sources 3C 120 and 3C 345. Furthermore, the expected brightness distribution, frequency spectrum, and polarization properties of the model lead to observational predictions which may be subject to future tests. If the external medium lies along the orbital plane of the nuclear region of the galaxy or quasar, then any extended outer lobes produced by massive objects ejected from the nucleus via the ''slingshot'' mechanism have roughly an 80% probability of alignment with the compact components to within 200.In a subsequent paper it is shown that the nature of the flux density variations of the blast-wave model are generally consistent with the observations of Altschuler and Wardle. According to the model, the difference between sources exhibiting superlight motion and those which do not show such tendencies but whose flux density is variable lies in the various recovery times of the external media and elapsed times between outbursts
The soft X-ray background as a supernova blast wave viewed from inside - Solar abundance models
Edgar, R. J.
1986-01-01
A model of the soft X-ray background is presented in which the sun is assumed to be inside an active supernova blast wave. The blast wave evolves in a preexisting cavity. The broad band surface brightnesses is explained by such a blast wave with an explosion energy of E sub approximately 5 x 10 to the 50th power ergs and radius 80 to 100 pc, using solar abundances. An approach to treating the problem of large anisotropies in the ambient medium is also explored, accommodating the observed anticorrelation between the soft X-ray surface brightness and the 21 cm column density. It is found that only for post shock temperatures below 10 to the 6 power K a shock propagating into a density enhancement will be dimmer than a similar shock in a lower density region.
The soft X-ray background as a supernova blast wave viewed from inside: Solar abundance models
Edgar, R. J.
1984-01-01
A model of the soft X-ray background is presented in which the Sun is assumed to be inside an active supernova blast wave. The blast wave evolves in a preexisting cavity. The broad band surface brightnesses is explained by such a blast wave with an explosion energy of E sub approx. 5 x 10 to the 50th power ergs and radius 80 to 100 pc, using solar abundances. An approach to treating the problem of large anisotropies in the ambient medium is also explored, accommodating the observed anticorrelation between the soft X-ray surface brightness and the 21 cm column density. It is found that only for post shock temperatures below 10 6 K a shock propagating into a density enhancement will be dimmer than a similar shock in a lower density region.
An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi.
Sokoloski, J L; Luna, G J M; Mukai, K; Kenyon, Scott J
2006-07-20
Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. The onset of a nova is well understood as driven by runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system; but the structure, dynamics and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion, and the explosion products plough through the nebula and produce X-ray emission. Here we report X-ray observations of such an event, from the eruption of the recurrent nova RS Ophiuchi. The hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated owing to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell structure. The early onset of deceleration indicates that the ejected shell had a low mass, the white dwarf has a high mass, and that RS Ophiuchi is therefore a progenitor of the type of supernova (type Ia) integral to studies of the expansion of the Universe. PMID:16855584
X-Ray Emitting Blast Wave from the Recurrent Nova RS Ophiuchi
Sokoloski, J L; Mukai, K; Kenyon, S J; Kenyon, Scott J.
2006-01-01
Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. Although the onset of novae from runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system is understood[1], the structure, dynamics, and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion; the explosion products plow through the nebula and produce X-ray emission. Early this year, an eruption of the recurrent nova RS Ophiuchi[2,3] provided the first opportunity to perform comprehensive X-ray observations of such an event and diagnose conditions within the ejecta. Here we show that the hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated due to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell...
Numerical Simulation of Fluid Flow in Blast Furnace Hearth
Institute of Scientific and Technical Information of China (English)
ZHAO Min-ge; SUN Tian-liang; CHENG Su-sen; GAO Zheng-kai
2005-01-01
The liquid flow in blast furnace hearth can result in the erosion of hearth. To prolong the campaign life of blast furnace, the effects of coke bed structure, coke porosity and deepness of taphole on liquid flow in hearth were studied by κ-ε model under different conditions. The results show that with the decrease of coke porosity, the peripheral flow is enhanced. Moreover, the existence of narrow coke free zone and the deepness reduction of taphole can increase the flowability on the bottom of hearth.
Early GRB Afterglows from Relativistic Blast Waves in General Radiative Regimes
Böttcher, M
1999-01-01
We present simple analytical expressions for the predicted spectral and temporal behavior of the early afterglow radiation from gamma-ray bursts in radiative regimes intermediate between the adiabatic and the fully radiative solutions of the blastwave hydrodynamic equations. Our expressions are valid as long as the relativistic electrons responsible for the observed synchrotron emission are in the fast cooling regime and the blast wave is relativistic. We show that even a slight deviation from a perfectly adiabatic evolution results in significant changes of the temporal characteristics of the afterglow emission.
Afterglow emission from pair-loaded blast waves in gamma-ray bursts
Beloborodov, Andrei M.
2005-01-01
The MeV radiation front of gamma-ray bursts creates copious e+- pairs as it propagates through an ambient medium. The created pairs enrich the leptonic component of the medium by a large factor at distances R < R_load ~ 10^{16} cm from the burst center. The following blast wave sweeps up the pair-rich medium and then emits the observed afterglow radiation. We find that the afterglow has a "memory" of e+- loading outside R_load. The e+- pairs remain in the swept-up material and slowly cool dow...
Blast wave in a nozzle for propulsive applications
Varsi, G.; Back, L. H.; Kim, K.
1976-01-01
The reported investigation has been conducted in connection with studies concerning the development of a propulsion system based on the use of a detonating fluid propellant. Measurements have been made of the pressure and shock wave velocity in a conical nozzle at various ambient pressures and at an ambient temperature of 25 C. In the experiments a small amount of explosive was placed at the end wall of a conical aluminum nozzle and detonated by a microdetonator inside the nozzle. Differences regarding the characteristics of conventional chemical propulsion and detonation propulsion are illustrated with the aid of a graph. One- and two-dimensional numerical flow calculations were performed and compared with the experimental data.
Simulation analyses of vibration tests on pile-group effects using blast-induced ground motions
International Nuclear Information System (INIS)
Extensive vibration tests have been performed on pile-supported structures at a large-scale mining site to promote better understanding of the dynamic behavior of pile-supported structures, especially pile-group effects. Two test structures were constructed in an excavated pit. One structure was supported on 25 tubular steel piles and the other on 4. The test pit was backfilled with sand of an appropriate grain size distribution to ensure good compaction. Ground motions induced by large-scale blasting operations were used as excitation forces for the tests. The 3D Finite Element Method (3D FEM)and a Genetic Algorithm (GA) were employed to identify the shear wave velocities and damping factors of the compacted sand, especially of the surface layer. A beam-interaction spring model was employed to simulate the test results of the piles and the pile-supported structures. The superstructure and pile foundation were modeled by a one-stick model comprising lumped masses and beam elements. The pile foundations were modeled just as they were, with lumped masses and beam elements to simulate the test results showing that, for the 25-pile structure, piles at different locations showed different responses. It was confirmed that the analysis methods employed were very useful for evaluating the nonlinear behavior of the soil-pile-structure system, even under severe ground motions. (authors)
Lerche, I.
1981-01-01
An analysis is conducted regarding the properties of cylindrically symmetric self-similar blast waves propagating away from a line source into a medium whose density and magnetic field (with components in both the phi and z directions) both vary as r to the -(omega) power (with omega less than 1) ahead of the blast wave. The main results of the analysis can be divided into two classes, related to a zero azimuthal field and a zero longitudinal field. In the case of the zero longitudinal field it is found that there are no physically acceptable solutions with continuous postshock variations of flow speed and gas density.
Roh, Soonyoung; Inutsuka, Shu-ichiro; Inoue, Tsuyoshi
2016-01-01
Supernova remnants (SNRs) are one of the most energetic astrophysical events and are thought to be the dominant source of Galactic cosmic rays (CRs). A recent report on observations from the Fermi satellite has shown a signature of pion decay in the gamma-ray spectra of SNRs. This provides strong evidence that high-energy protons are accelerated in SNRs. The actual gamma-ray emission from pion decay should depend on the diffusion of CRs in the interstellar medium. In order to quantitatively analyse the diffusion of high-energy CRs from acceleration sites, we have performed test particle numerical simulations of CR protons using a three-dimensional magnetohydrodynamics (MHD) simulation of an interstellar medium swept-up by a blast wave. We analyse the diffusion of CRs at a length scale of order a few pc in our simulated SNR, and find the diffusion of CRs is precisely described by a Bohm diffusion, which is required for efficient acceleration at least for particles with energies above 30 TeV for a realistic interstellar medium. Although we find the possibility of a superdiffusive process (travel distance ∝ t0.75) in our simulations, its effect on CR diffusion at the length scale of the turbulence in the SNR is limited.
Extended adiabatic blast waves and a model of the soft x-ray background
International Nuclear Information System (INIS)
An analytical approximation is generated which follows the development of an adiabatic spherical blast wave in a homogeneous ambient medium of finite pressure. At early times when the external pressure is negligible, the structure is that of the usual self-similar solution. At later times, the structure evolves smoothly as the shock weakens, the postshock compression declines, and the gradients in pressure and density become less severe within the shocked region. The complete structure should be reliable down to a postshock compression of about 2, with conditions close inside the shock remaining well described somewhat longer. An analytical approximation is also presented for the electron-temperature distribution resulting from Coulomb collisional heating. It is shown that thermal conduction, limited by saturation at early times, fades in importance just as Coulomb collisional heating becomes significant. An estimate is made of the nonequilibrium cooling coefficient and the degree of ionization equilibrium expected by the time significant cooling sets in. From the estimates of the end point of the adiabatic era, based on the collisional equilibrium emissivity, are shown to be reasonably accurate. The dynamical, thermal, ionization, and spectral structures are calculated for blast waves of energy E0 = 5 x 1050 ergs in a hot, low-density interstellar environment. A formulais presented for estimating the luminosity evolution of such explosions, including the effects of nonequilibrium ionization. It is shown that the B and C bands of the soft x-ray background are reproduced by such a model explosion if the ambient density is about 0.004 cm(sup -3), the blast radius is roughly 100 pc, and the solar system is located inside the shocked region. The age of such an explosion is roughly 10(sup 5) years. This result is almost independent of whether there is apprecialy non-Coulomb heating of the electrons
Kabu, Shushi; Jaffer, Hayder; Petro, Marianne; Dudzinski, Dave; Stewart, Desiree; Courtney, Amy; Courtney, Michael; Labhasetwar, Vinod
2015-01-01
Blast-associated shock wave-induced traumatic brain injury (bTBI) remains a persistent risk for armed forces worldwide, yet its detailed pathophysiology remains to be fully investigated. In this study, we have designed and characterized a laboratory-scale shock tube to develop a rodent model of bTBI. Our blast tube, driven by a mixture of oxygen and acetylene, effectively generates blast overpressures of 20–130 psi, with pressure-time profiles similar to those of free-field blast waves. We te...
Spatially-resolved x-ray scattering measurements of a planar blast wave
Gamboa, E. J.; Montgomery, D. S.; Benage, J. F.; Falk, K.; Kuranz, C. C.; Keiter, P. A.; Drake, R. P.
2012-10-01
In many laboratory astrophysics experiments, intense laser irradiation creates novel material conditions with large, one-dimensional gradients in the temperature, density, and ionization state. X-ray Thomson scattering is a powerful technique for measuring these plasma parameters. However, the scattered signal is typically measured with little or no spatial resolution, which limits the ability to diagnose inhomogeneous plasmas. We report on the development of a new imaging x-ray Thomson spectrometer (IXTS) for the Omega laser facility. The diffraction of x-rays from a toroidally curved crystal creates high-resolution images that are spatially resolved along a one-dimensional profile while spectrally dispersing the radiation. An experiment is described in which we used the IXTS to measure the spatial temperature profile of a novel system. A low-density carbon foam was irradiated with intensities on the order of 10^15 W/cm^2, launching a planar blast wave. After a delay of several nanoseconds, x-rays created from irradiation of a nickel foil, scattered at 90 and were recorded by the IXTS. The resulting spatially resolved scattering spectra were analyzed to extract the temperature profile across the blast wave.
The Half Wave Plate Rotator for the BLAST-TNG Balloon-Borne Telescope
Setiawan, Hananiel; Ashton, Peter; Novak, Giles; Angilè, Francesco E.; Devlin, Mark J.; Galitzki, Nicholas; Ade, Peter; Doyle, Simon; Pascale, Enzo; Pisano, Giampaolo; Tucker, Carole E.
2016-01-01
The Next Generation Balloon-borne Large Aperture Submillimeter Telescope (BLAST-TNG) is an experiment designed to map magnetic fields in molecular clouds in order to study their role in the star formation process. The telescope will be launched aboard a high-altitude balloon in December 2016 for a 4-week flight from McMurdo station in Antarctica. BLAST-TNG will measure the polarization of submillimeter thermal emission from magnetically aligned interstellar dust grains, using large format arrays of kinetic inductance detectors operating in three bands centered at 250, 350, and 500 microns, with sub-arcminute angular resolution. The optical system includes an achromatic Half Wave Plate (HWP), mounted in a Half Wave Plate rotator (HWPr). The HWP and HWPr will operate at 4 K temperature to reduce thermal noise in our measurements, so it was crucial to account for the effects of thermal contraction at low temperature in the HWPr design. It was also equally important for the design to meet torque requirements while minimizing the power from friction and conduction dissipated at the 4 K stage. We also discuss our plan for cold testing the HWPr using a repurposed cryostat with a Silicon Diode thermometer read out by an EDAS-CE Ethernet data acquisition system.
Institute of Scientific and Technical Information of China (English)
Yi-kai FAN; Zu-yu CHEN; Xiang-qian LIANG; Xue-dong ZHANG; Xin HUANG
2012-01-01
This paper presents the explosion cratering effects and their propagation laws of blast waves in dry standard sands using a 450 g-t geotechnical centrifuge apparatus.Ten centrifuge model tests were completed with various ranges of explosive mass,burial depth and centrifuge accelerations.Eleven accelerometers were installed to record the acceleration response in sand.The dimensions of the explosion craters were measured after the tests.The results demonstrated that the relationship between the dimensionless parameters of cratering efficiency and gravity scaled yield is a power regression function.Three specific function equations were obtained.The results are in general agreement with those obtained by other studies.A scaling law based on the combination of the r terms was used to fit the results of the ten model tests with a correlation coefficient of 0.931.The relationship can be conveniently used to predict the cratering effects in sand.The results also showed that the peak acceleration is a power increasing function of the acceleration level.An empirical exponent relation between the proportional peak acceleration and distance is proposed.The propagation velocity of blast waves is found to be ranged between 200 and 714 m/s.
Collimation and asymmetry of the hot blast wave from the recurrent nova V745 Scorpii
Drake, Jeremy J; Laming, J Martin; Starrfield, Sumner; Kashyap, Vinay; Orlando, Salvatore; Page, Kim L; Hernanz, M; Ness, J-U; Gehrz, R D; van Rossum, Daan; Woodward, Charles E
2016-01-01
The recurrent symbiotic nova V745 Sco exploded on 2014 February 6 and was observed on February 22 and 23 by the Chandra X-ray Observatory Transmission Grating Spectrometers. By that time the supersoft source phase had already ended and Chandra spectra are consistent with emission from a hot, shock-heated circumstellar medium with temperatures exceeding 10^7K. X-ray line profiles are more sharply peaked than expected for a spherically-symmetric blast wave, with a full width at zero intensity of approximately 2400 km/s, a full width at half maximum of 1200 +/- 30 km/s and an average net blueshift of 165 +/- 10 km/s. The red wings of lines are increasingly absorbed toward longer wavelengths by material within the remnant. We conclude that the blast wave was sculpted by an aspherical circumstellar medium in which an equatorial density enhancement plays a role, as in earlier symbiotic nova explosions. Expansion of the dominant X-ray emitting material is aligned close to the plane of the sky and most consistent wit...
Numerical Simulation of Innovative Operation of Blast Furnace Based on Multi-Fluid Model
Institute of Scientific and Technical Information of China (English)
CHU Man-sheng; YANG Xue-feng; SHEN Feng-man; YAGI Jun-ichiro; NOGAMI Hiroshi
2006-01-01
A multi-fluid blast furnace model was simply introduced and was used to simulate several innovative iron-making operations. The simulation results show that injecting hydrogen bearing materials, especially injecting natural gas and plastics, the hydrogen reduction is enhanced, and the furnace performance is improved simultaneously. Total heat input shows obvious decrease due to the decrease of heat consumption in direct reduction, solution loss and silicon transfer reactions. If carbon composite agglomerates are charged into the furnace, the temperature of thermal reserve zone will obviously decrease, and the reduction of iron-bearing burden materials will be retarded. However, the efficiency of blast furnace is improved just due to the decrease in heat requirements for solution loss, sinter reduction, and silicon transfer reactions, and less heat loss through top gas and furnace wall. Finally, the model is used to investigate the performance of blast furnace under the condition of top gas recycling together with plastics injection, cold oxygen blasting and carbon composite agglomerate charging. The lower furnace temperature, extremely accelerated reduction rate, drastically decreased CO2 emission and remarkably enhanced heat efficiency were obtained by using the innovative operations, and the blast furnace operation with superhigh efficiency can be realized.
LARGE EDDY SIMULATION FOR PLUNGING BREAKER WAVE
Institute of Scientific and Technical Information of China (English)
Bai Yu-chuan; Wang Zhao-yin
2003-01-01
As wave propagates into shallow water, the shoaling effect leads to increase of wave height, and at a certain position, the wave will be breaking. The breaking wave is powerful agents for generating turbulence, which plays an important role in most of the fluid dynamical processes in the surf zone, so a proper numerical model for describing the turbulent effect is needed urgently. A numerical model is set up to simulate the wave breaking process, which consists of a free surface model using the surface marker method and the vertical two-dimensional model that solves the flow equations. The turbulence is described by Large Eddy Simulation (LES) method where the larger turbulent features are simulated by solving the flow equations, and the small-scale turbulence that is represented by a sub-grid model. A dynamic eddy viscosity sub-grid scale stress model has been used for the present simulation. The large eddy simulation model, which we presented in this paper, can be used to study the propagation of a solitary wave in constant water depth and the shoaling of a non-breaking solitary wave on a beach. To track free-surface movements, The TUMMAC method is employed. By applying the model to wave breaking problem in the surf zone, we found that these model results compared very well with experimental data. In addition, this model is able to reproduce the complicated flow phenomena, especially the plunging breaker.
Experimental characterization of energetic material dynamics for multiphase blast simulation.
Energy Technology Data Exchange (ETDEWEB)
Beresh, Steven Jay; Wagner, Justin L.; Kearney, Sean Patrick; Wright, Elton K.; Baer, Melvin R.; Pruett, Brian Owen Matthew
2011-09-01
Currently there is a substantial lack of data for interactions of shock waves with particle fields having volume fractions residing between the dilute and granular regimes, which creates one of the largest sources of uncertainty in the simulation of energetic material detonation. To close this gap, a novel Multiphase Shock Tube has been constructed to drive a planar shock wave into a dense gas-solid field of particles. A nearly spatially isotropic field of particles is generated in the test section by a gravity-fed method that results in a spanwise curtain of spherical 100-micron particles having a volume fraction of about 19%. Interactions with incident shock Mach numbers of 1.66, 1.92, and 2.02 were achieved. High-speed schlieren imaging simultaneous with high-frequency wall pressure measurements are used to reveal the complex wave structure associated with the interaction. Following incident shock impingement, transmitted and reflected shocks are observed, which lead to differences in particle drag across the streamwise dimension of the curtain. Shortly thereafter, the particle field begins to propagate downstream and spread. For all three Mach numbers tested, the energy and momentum fluxes in the induced flow far downstream are reduced about 30-40% by the presence of the particle field. X-Ray diagnostics have been developed to penetrate the opacity of the flow, revealing the concentrations throughout the particle field as it expands and spreads downstream with time. Furthermore, an X-Ray particle tracking velocimetry diagnostic has been demonstrated to be feasible for this flow, which can be used to follow the trajectory of tracer particles seeded into the curtain. Additional experiments on single spherical particles accelerated behind an incident shock wave have shown that elevated particle drag coefficients can be attributed to increased compressibility rather than flow unsteadiness, clarifying confusing results from the historical database of shock tube
Roh, Soonyoung; Inoue, Tsuyoshi
2015-01-01
Supernova remnants (SNRs) are one of the most energetic astrophysical events and are thought to be the dominant source of Galactic cosmic rays (CRs). A recent report on observations from the Fermi satellite has shown a signature of pion decay in the gamma-ray spectra of SNRs. This provides strong evidence that high-energy protons are accelerated in SNRs. The actual gamma-ray emission from pion decay should depend on the diffusion of CRs in the interstellar medium. In order to quantitatively analyse the diffusion of high-energy CRs from acceleration sites, we have performed test particle numerical simulations of CR protons using a three-dimensional magnetohydrodynamics (MHD) simulation of an interstellar medium swept-up by a blast wave. We analyse the diffusion of CRs at a length scale of order a few pc in our simulated SNR, and find the diffusion of CRs is precisely described by a Bohm diffusion, which is required for efficient acceleration at least for particles with energies above 30 TeV for a realistic int...
Large eddy simulation of breaking waves
DEFF Research Database (Denmark)
Christensen, Erik Damgaard; Deigaard, Rolf
2001-01-01
A numerical model is used to simulate wave breaking, the large scale water motions and turbulence induced by the breaking process. The model consists of a free surface model using the surface markers method combined with a three-dimensional model that solves the flow equations. The turbulence is...... incoming waves are specified by a flux boundary condition. The waves are approaching in the shore-normal direction and are breaking on a plane, constant slope beach. The first few wave periods are simulated by a two-dimensional model in the vertical plane normal to the beach line. The model describes the...... steepening and the overturning of the wave. At a given instant, the model domain is extended to three dimensions, and the two-dimensional flow field develops spontaneously three-dimensional flow features with turbulent eddies. After a few wave periods, stationary (periodic) conditions are achieved. The...
Grujicic, M.; Bell, W. C.; Pandurangan, B.; Glomski, P. S.
2011-08-01
To combat the problem of traumatic brain injury (TBI), a signature injury of the current military conflicts, there is an urgent need to design head protection systems with superior blast/ballistic impact mitigation capabilities. Toward that end, the blast impact mitigation performance of an advanced combat helmet (ACH) head protection system equipped with polyurea suspension pads and subjected to two different blast peak pressure loadings has been investigated computationally. A fairly detailed (Lagrangian) finite-element model of a helmet/skull/brain assembly is first constructed and placed into an Eulerian air domain through which a single planar blast wave propagates. A combined Eulerian/Lagrangian transient nonlinear dynamics computational fluid/solid interaction analysis is next conducted in order to assess the extent of reduction in intra-cranial shock-wave ingress (responsible for TBI). This was done by comparing temporal evolutions of intra-cranial normal and shear stresses for the cases of an unprotected head and the helmet-protected head and by correlating these quantities with the three most common types of mild traumatic brain injury (mTBI), i.e., axonal damage, contusion, and subdural hemorrhage. The results obtained show that the ACH provides some level of protection against all investigated types of mTBI and that the level of protection increases somewhat with an increase in blast peak pressure. In order to rationalize the aforementioned findings, a shockwave propagation/reflection analysis is carried out for the unprotected head and helmet-protected head cases. The analysis qualitatively corroborated the results pertaining to the blast-mitigation efficacy of an ACH, but also suggested that there are additional shockwave energy dissipation phenomena which play an important role in the mechanical response of the unprotected/protected head to blast impact.
Eerden, F.J.M. van der; Berg, F.
2010-01-01
In the densely populated area of the Netherlands, the objective of the Netherlands Ministry of Defence is to find an optimal balance between military training and the impact on the surrounding civilian community. A special case concerns large weapons, such as artillery or demolitions, which create high-energy blast waves. These waves have a low frequency content, typically between 15 and 125 Hz, and can propagate over large distances. As a result it is a relative important cause for annoyance...
Institute of Scientific and Technical Information of China (English)
SONG Yanze; LI Zhiqiang; ZHAO Longmao; ZHENG Jinyang
2006-01-01
In order to constitute engineering design methods of the flat ribbon wound explosion containment vessels,the dynamic response of such vessels subjected to internal explosion loading is simulated using LS-DYNA3D.Three winding angles,10°,15°and 20°,are considered.It is shown that among ribbon vessels investigated,the center displacement of outermost ribbons of the vessel with 10°winding angle is the smallest under the same blast loading.The response of vessels loaded in inner core is local.From the center of the cylindrical shell to the bottom cover,the maximum strain gradually decreases.The ribbons are subjected to tension in the length direction and compression in the width direction.Blasting shock energy concentrates on where is close to center section of blasting.For comparison,numerical simulation of a monobloc thick-walled explosion containment vessel is also investigated.It can be found that the biggest deformation of the flat ribbon wound explosion containment vessels is bigger than that of the monobloc thick-walled explosion containment vessel in the center section of blasting under the same TNT.Numerical results are approximately in agreement with experimental ones.It is proved that the ribbon vessels have the valuable properties of "leak before burst at worst" compared with the monobloc vessels through numerical simulation.
Mathematical theory of cylindrical isothermal blast waves in a magnetic field
International Nuclear Information System (INIS)
An investigation is made of the self-similar flow behind a cylindrical blast wave from a line explosion (situated on r=0, using conventional cylindrical coordinates r, phi, z) in a medium whose density and magnetic field both vary as rsup(-ω) ahead of the blast front, with the assumption that the flow is isothermal. The magnetic field can have components in both the azimuthal Bsub(phi) and longitudinal Bsub(z) directions. It is found that: (i) For Bsub(phi) and Bsub(z) not 0 a continuous single-valued solution with a velocity field representing outflow of material away from the line of explosion only exists for ω >=0. (ii) For Bsub(z) = 0, but Bsub(phi) not 0, there is no continuous single-valued solution with a velocity field representing outflow of material away from the line of the explosion for any ω value. (iii) For Bsub(phi) = 0, but Bsub(z) not 0, the behaviour is as follows: (a) for ω ω > 0 the governing equation posseses a set of movable critical points. In this case it is shown that the fluid flow velocity is bracketed between two curves and that the asymptotes of the velocity curve on the shock are intersected by, or are tangent to, the two curves
Supernovae and their expanding blast waves during the early evolution of Galactic globular clusters
Tenorio-Tagle, Guillermo; Silich, Sergiy; Cassisi, Santi
2015-01-01
Our arguments deal with the early evolution of Galactic globular clusters and show why only a few of the supernovae products were retained within globular clusters and only in the most massive cases ($M \\ge 10^6$ Msol), while less massive clusters were not contaminated at all by supernovae. Here we show that supernova blast waves evolving in a steep density gradient undergo blowout and end up discharging their energy and metals into the medium surrounding the clusters. This inhibits the dispersal and the contamination of the gas left over from a first stellar generation. Only the ejecta from well centered supernovae, that evolve into a high density medium available for a second stellar generation in the most massive clusters would be retained. These are likely to mix their products with the remaining gas, leading in these cases eventually to an Fe contaminated second stellar generation.
Study of radiative blast waves generated on the Z-beamlet laser.
Energy Technology Data Exchange (ETDEWEB)
Edens, Aaron D.; Schwarz, Jens
2012-02-01
This document describes the original goals of the project to study the Vishniac Overstability on blast waves produced using the Z-Beamlet laser facility as well as the actual results. The proposed work was to build on earlier work on the facility and result in the best characterized set of data for such phenomena in the laboratory. To accomplish the goals it was necessary to modify the existing probe laser at the facility so that it could take multiple images over the course of 1-2 microseconds. Troubles with modifying the probe laser are detailed as well as the work that went into said modifications. The probe laser modification ended up taking the entire length of the project and were the major accomplishment of the research.
A viscous blast-wave model for high energy heavy-ion collisions
Jaiswal, Amaresh; Koch, Volker
2016-07-01
Employing a viscosity-based survival scale for initial geometrical perturbations formed in relativistic heavy-ion collisions, we model the radial flow velocity at freeze-out. Subsequently, we use the Cooper-Frye freeze-out prescription, with viscous corrections to the distribution function, to extract the transverse momentum dependence of particle yields and flow harmonics. We fit the model parameters for central collisions, by fitting the spectra of identified particles at the Large Hadron Collider (LHC), and estimate them for other centralities using simple hydrodynamic relations. We use the results of Monte Carlo Glauber model for initial eccentricities. We demonstrate that this improved viscous blast-wave model leads to good agreement with transverse momentum distribution of elliptic and triangular flow for all centralities and estimate the shear viscosity to entropy density ratio η/s ≃ 0.24 at the LHC.
Supernovae and Their Expanding Blast Waves during the Early Evolution of Galactic Globular Clusters
Tenorio-Tagle, Guillermo; Muñoz-Tuñón, Casiana; Silich, Sergiy; Cassisi, Santi
2015-11-01
Our arguments deal with the early evolution of Galactic globular clusters and show why only a few of the supernovae (SNe) products were retained within globular clusters and only in the most massive cases (M ≥ 106 M⊙), while less massive clusters were not contaminated at all by SNe. Here, we show that SN blast waves evolving in a steep density gradient undergo blowout and end up discharging their energy and metals into the medium surrounding the clusters. This inhibits the dispersal and the contamination of the gas left over from a first stellar generation. Only the ejecta from well-centered SNe that evolve into a high-density medium available for a second stellar generation (2SG) in the most massive clusters would be retained. These are likely to mix their products with the remaining gas, eventually leading in these cases to an Fe-contaminated 2SG.
Self-generated magnetic fields in blast-wave driven Rayleigh-Taylor experiments
Flaig, Markus; Plewa, Tomasz
2015-12-01
We study the effect of self-generated magnetic fields in two-dimensional computer models of blast-wave driven high-energy density Rayleigh-Taylor instability (RTI) experiments. Previous works [1,2] suggested that such fields have the potential to influence the RTI morphology and mixing. When neglecting the friction force between electrons and ions, we do indeed find that dynamically important (β≲103) magnetic fields are generated. However, in the more realistic case where the friction force is accounted for, the resulting fields are much weaker, β≳105 , and can no longer influence the dynamics of the system. Although we find no evidence for dynamically important magnetic fields being created in the two-dimensional case studied here, the situation might be different in a three-dimensional setup, which will be addressed in a future study.
Hydromagnetic cylindrical variable energy blast wave through self-gravitating gas
International Nuclear Information System (INIS)
Propagation of hydromagnetic cylindrical variable energy blast wave through a self-gravitating gas has been studied by modified similarity method. For an energy input Esub(α)=E0tsup(β) (1+e1 w+e2w2+...), where Esub(α) is the energy released upto time t, E0 is a functional constant, β, e1 and e2 etc. are constants and w is non-dimensional time, it is seen that the effects of non-uniformity caused by selfgravitation of the gas are essentially of third order. Dependence of flow variables on (i) the non-uniformity of the medium and (ii) the strength of energy input characterised respectively by the parameters A2 and various e-values has been discussed for both magnetic and non-magnetic cases. It is observed that an increase in magnetic field leads to an increase in shock velocity. (author)
Gamma-ray burst afterglows from decelerating material: Blast waves and plasmoids
International Nuclear Information System (INIS)
We examine the dynamics and emitted radiation from material with a large initial bulk Lorentz factor which decelerates as it sweeps up ambient matter. The bulk kinetic energy of the material is converted into non-thermal energy of electrons which radiate isotropically in the locally co-moving frame. Self-consistent solutions for the dynamics of the material are computed which account for changes in its bulk relativistic inertia due to accretion and the emitted radiation. Fully radiative and non-radiative solutions are shown to be limiting cases agreeing with standard solutions for spherically expanding blast waves. We have calculated the afterglow synchrotron emission for a variety of parameters and geometries, and we compare a fiducial example to the afterglow behavior observed from recent gamma-ray burst X-ray and optical counterparts
Numerical Calculation of Concrete Slab Response to Blast Loading
Institute of Scientific and Technical Information of China (English)
ZHOU Xiaoqing; HAO Hong; KUZNETSOV Valerian A; WASCHL John
2006-01-01
In the present paper,a dynamic plastic damage model for concrete has been employed to estimate responses of a reinforced concrete slab subjected to blast loading.The interaction between the blast wave and the concrete slab is considered in 3D simulation.In the first stage,the initial detonation and blast wave propagation is modelled in 2D simulation before the blast wave reaches the concrete slab,then the results obtained from 2D calculation are remapped to a 3D model.The calculated blast load is compared with that obtained from TM5-1300.Numerical results of the concrete slab response are compared with the explosive test carried out in the Weapons System Division,Defence Science and Technology Organisation,Department of Defence,Australia.
Simulation of Stress Wave Propagation
Czech Academy of Sciences Publication Activity Database
Pelikán, Vladimír; Hora, Petr; Machová, Anna; Červená, Olga
Prague : CESNET, 2010 - (Křenková, I.; Antoš, D.; Matyska, L.), s. 105-114 ISBN 978-80-904173-7-3 R&D Projects: GA AV ČR KJB200760802; GA ČR(CZ) GA101/07/0789 Institutional research plan: CEZ:AV0Z20760514 Keywords : molecular dynamics * wave propagation Subject RIV: BI - Acoustics http://meta.cesnet.cz/cs/about/MetaCentrum_Yearbook9_web.pdf
Kuriakose, Matthew; Skotak, Maciej; Misistia, Anthony; Kahali, Sudeepto; Sundaramurthy, Aravind; Chandra, Namas
2016-01-01
The end plate mounted at the mouth of the shock tube is a versatile and effective implement to control and mitigate the end effects. We have performed a series of measurements of incident shock wave velocities and overpressures followed by quantification of impulse values (integral of pressure in time domain) for four different end plate configurations (0.625, 2, 4 inches, and an open end). Shock wave characteristics were monitored by high response rate pressure sensors allocated in six positions along the length of 6 meters long 229 mm square cross section shock tube. Tests were performed at three shock wave intensities, which was controlled by varying the Mylar membrane thickness (0.02, 0.04 and 0.06 inch). The end reflector plate installed at the exit of the shock tube allows precise control over the intensity of reflected waves penetrating into the shock tube. At the optimized distance of the tube to end plate gap the secondary waves were entirely eliminated from the test section, which was confirmed by pressure sensor at T4 location. This is pronounced finding for implementation of pure primary blast wave animal model. These data also suggest only deep in the shock tube experimental conditions allow exposure to a single shock wave free of artifacts. Our results provide detailed insight into spatiotemporal dynamics of shock waves with Friedlander waveform generated using helium as a driver gas and propagating in the air inside medium sized tube. Diffusion of driver gas (helium) inside the shock tube was responsible for velocity increase of reflected shock waves. Numerical simulations combined with experimental data suggest the shock wave attenuation mechanism is simply the expansion of the internal pressure. In the absence of any other postulated shock wave decay mechanisms, which were not implemented in the model the agreement between theory and experimental data is excellent. PMID:27603017
Numerical simulation of electrostatic waves in plasmas
International Nuclear Information System (INIS)
In this paper the propagation of electrostatic waves in plasmas and the non-linear interactions, which occur in the case of large wave amplitudes, are studied using a new numerical method for plasma simulation. This mathematical description is based on the Vlasov-model. Changes in the distribution-function are taken into account and thus plasma kinetic effects can be treated. (orig./HT)
Institute of Scientific and Technical Information of China (English)
WU Jun; LIU Jingbo; YAN Qiushi
2008-01-01
The loads of shock wave effect on fabricated anti-blast wall and distribution law around the wall were investigated by using near surface explosion test method and FEM.The pressure-time histories and variety law on the foreside and backside of the anti-blast wall were adopted in the tests of variety of different explosion distances and dynamites,as well as in the comparison between the test and numerical calculation.The test results show that the loads of shock wave effect on the anti-blast wall were essen-tially consistent with calculation results using criterion under surface explosion when explosion distances exceed 2 m,the distribution of overpressure behind wall was gained according to variety law based on small-large-small.It is also demonstrated that the peak overpressure behind wall had commonly appeared in wall height by 1.5--2.5 multiples,and the peak overpressures of protective building behind wall could be reduced effectively by using the fabricated anti-blast wall.
Numerical simulation of lower hybrid wave propagation
International Nuclear Information System (INIS)
Concerning the LHRH (Lower Hybrid Resonance Heating) in a tokamak, a numerical simulation is made of the propagation of a lower hybrid wave. By solving the system of two-fluid equations and Poisson's equation, ray trajectories of the lower hybrid waves are traced. The cases of cold plasma approximation, linear approximation and nonlinear two-fluid model are examined. The effect of density fluctuation due to the presence of a drift wave on the conical ray trajectories is also studied. Only the preliminary results are presented in this report. (auth.)
Simard, J Marc; Pampori, Adam; Keledjian, Kaspar; Tosun, Cigdem; Schwartzbauer, Gary; Ivanova, Svetlana; Gerzanich, Volodymyr
2014-07-15
Traumatic brain injury (TBI) caused by an explosive blast (blast-TBI) is postulated to result, in part, from transvascular transmission to the brain of a hydrodynamic pulse (a.k.a., volumetric blood surge, ballistic pressure wave, hydrostatic shock, or hydraulic shock) induced in major intrathoracic blood vessels. This mechanism of blast-TBI has not been demonstrated directly. We tested the hypothesis that a blast wave impacting the thorax would induce a hydrodynamic pulse that would cause pathological changes in the brain. We constructed a Thorax-Only Blast Injury Apparatus (TOBIA) and a Jugular-Only Blast Injury Apparatus (JOBIA). TOBIA delivered a collimated blast wave to the right lateral thorax of a rat, precluding direct impact on the cranium. JOBIA delivered a blast wave to the fluid-filled port of an extracorporeal intravenous infusion device whose catheter was inserted retrograde into the jugular vein, precluding lung injury. Long Evans rats were subjected to sublethal injury by TOBIA or JOBIA. Blast injury induced by TOBIA was characterized by apnea and diffuse bilateral hemorrhagic injury to the lungs associated with a transient reduction in pulse oximetry signals. Immunolabeling 24 h after injury by TOBIA showed up-regulation of tumor necrosis factor alpha, ED-1, sulfonylurea receptor 1 (Sur1), and glial fibrillary acidic protein in veins or perivenular tissues and microvessels throughout the brain. The perivenular inflammatory effects induced by TOBIA were prevented by ligating the jugular vein and were reproduced using JOBIA. We conclude that blast injury to the thorax leads to perivenular inflammation, Sur1 up-regulation, and reactive astrocytosis resulting from the induction of a hydrodynamic pulse in the vasculature. PMID:24673157
International Nuclear Information System (INIS)
In this work, we examine the hydrodynamics of high-energy-density (HED) shear flows. Experiments, consisting of two materials of differing density, use the OMEGA-60 laser to drive a blast wave at a pressure of ∼50 Mbar into one of the media, creating a shear flow in the resulting shocked system. The interface between the two materials is Kelvin-Helmholtz unstable, and a mixing layer of growing width develops due to the shear. To theoretically analyze the instability's behavior, we rely on two sources of information. First, the interface spectrum is well-characterized, which allows us to identify how the shock front and the subsequent shear in the post-shock flow interact with the interface. These observations provide direct evidence that vortex merger dominates the evolution of the interface structure. Second, simulations calibrated to the experiment allow us to estimate the time-dependent evolution of the deposition of vorticity at the interface. The overall result is that we are able to choose a hydrodynamic model for the system, and consequently examine how well the flow in this HED system corresponds to a classical hydrodynamic description
Heggelund, Solveig
2014-01-01
The main objective in this thesis is to further investigate the accuracy of the accumulated blast impulse and plate response employing this method, and comparing the results with performed experiments. Experiments were performed at \\O st\\o ya, Norway, where quadratic 0.8 mm thick Docol 600 DL steel plates were subjected to free air explosion. The experimental results have been compared with numerical simulations employing the discrete particle method implemented in Impetus-Afea. A pure Lagr...
Simulation of Blast and Fragment Loading Usinga Coupled Multi-Solver Approach
Institute of Scientific and Technical Information of China (English)
QUAN Xiangyang; GERBER Bence; COWLER Malcolm; BIRNBAUM Naury
2006-01-01
Simulating blast and fragment loading simultaneously in a single computation requires the combined use of multiple states of the art solvers.A pipe bomb is an example of simple improvised explosive device (IED) that consists of a piece of pipe filled with explosive material and capped at both ends.To simulate the explosion of a pipe bomb and the damage it causes,a coupled multisolver approach based upon finite element and finite volume methods is applied.The numerical calculation presented demonstrates the ability of ANSYS AUTODYN(R) to correctly simulate the threats of IEDs and provides insight into how the most significant physical phenomena affect the results.
Numerical simulation of blast wave interaction with structure columns
Shi, Yanchao; Hao, Hong; Li, Zhong-Xian
2007-08-01
Buckling of slender structures under compressive loading is a failure of infinitesimal stability due to a confluence of two factors: the energy density non-convexity and the smallness of Korn’s constant. The problem has been well understood only for bodies with simple geometries when the slenderness parameter is well defined. In this paper, we present the first rigorous analysis of buckling for bodies with complex geometry. By limiting our analysis to the “near-flip” instability, we address the universal features of the buckling phenomenon that depend on neither the shape of the domain nor the degree of constitutive nonlinearity of the elastic material.
A theoretical analysis of stress wave propagation in the head under primary blast loading.
Zhu, Feng; Chou, Clifford C; Yang, King H; King, Albert I
2014-04-01
Traumatic brain injury due to primary blast loading has become a signature injury in recent military conflicts. Efforts have been made to study the stress wave propagation in the head. However, the relationship of incident pressure, reflected pressure and intracranial pressure is still not clear, and the experimental findings reported in the literature are contradictory. In this article, an analytical model is developed to calculate the stress wave transfer through a multiple-layered structure which is used to mimic the head. The model predicts stress at the scalp-skull and skull-brain interfaces as the functions of reflected pressure, which is further dependent on incident pressure. A numerical model is used to corroborate the theoretical predictions. It is concluded that scalp has an amplification effect on intracranial pressure. If scalp is absent, there exists a critical incident pressure, defined as P cr at approximately 16 kPa. When peak incident pressure σ in is higher than 16 kPa, the pressure at the skull-brain interface is greater than σ in; otherwise, it is lower than σ in. PMID:24718865
Assessment of dynamic mechanical behaviour of reinforced concrete beams using a blast simulator
Peroni, Marco; Solomos, George; Caverzan, Alessio; Larcher, Martin; Valsamos, Georgios
2015-09-01
Critical infrastructures may become the target of terrorist bombing attacks or may have to withstand explosive loads due to accidents. The impulsive load connected to explosions is delivered to the structure in a few milliseconds forcing it to respond or fail in a peculiar mode. With reference to the above scientific framework this work presents an innovative apparatus designed and developed at the European Laboratory for Structural Assessment to reproduce a blast pressure history without using explosives. This apparatus is practically a hybrid nitrogen-spring-driven actuator that accelerates masses of up to 100 kg to a maximum velocity of about 25 m/s that impact against the tested structure. The pressure-load history applied to the structure is modulated and reshaped using appropriate layers of elastic soft materials (such as polymeric foams) placed between the specimen and the impacting masses. Specific instrumentation has extensively been utilised to investigate the blast simulator performance and to precisely measure the pressure loads applied to the specimen. A series of tests on real scale reinforced concrete beams/columns (250 × 250 × 2200 mm) has been performed to efficiently assess the performance and potentiality of the new blast simulator. Results are under evaluation. In addition to the experimental work, a series of numerical simulations by means of the explicit FEM code EUROPLEXUS have been carried out to support and improve the equipment design.
Simulation of wave interactions with MHD
International Nuclear Information System (INIS)
The broad scientific objectives of the SWIM (Simulation of Wave Interaction with MHD) project are twofold: (1) improve our understanding of interactions that both radio frequency (RF) wave and particle sources have on extended-MHD phenomena, and to substantially improve our capability for predicting and optimizing the performance of burning plasmas in devices such as ITER: and (2) develop an integrated computational system for treating multiphysics phenomena with the required flexibility and extensibility to serve as a prototype for the Fusion Simulation Project. The Integrated Plasma Simulator (IPS) has been implemented. Presented here are initial physics results on RF effects on MHD instabilities in tokamaks as well as simulation results for tokamak discharge evolution using the IPS.
Stochastic Simulations on the Cellular Wave Computers
Ercsey-Ravasz, M.; Roska, T.; Néda, Z.
2006-01-01
The computational paradigm represented by Cellular Neural/nonlinear Networks (CNN) and the CNN Universal Machine (CNN-UM) as a Cellular Wave Computer, gives new perspectives for computational physics. Many numerical problems and simulations can be elegantly addressed on this fully parallelized and analogic architecture. Here we study the possibility of performing stochastic simulations on this chip. First a realistic random number generator is implemented on the CNN-UM, and then as an example...
Blast-wave analysis of strange particle $m_T$ spectra in Pb-Pb collisions at the SPS
Bruno, G. E.
2004-01-01
The transverse mass spectra of high statistics, high purity samples of K0s, Lambda, Xi and Omega particles produced in Pb-Pb collisions at SPS energy have been studied in the framework of the blast-wave model. The dependence of the freeze-out parameters on particle species and event centrality is discussed. Results at 40 A GeV/c are presented here for the first time.
Cox, D. P.; Edgar, R. J.
1982-01-01
Accurate approximations are presented for the self-similar structures of nonradiating blast waves with adiabatic ions, isothermal electrons, and equation ion and electron temperatures at the shock. The cases considered evolve in cavities with power law ambient densities (including the uniform density case) and have negligible external pressure. The results provide the early time asymptote for systems with shock heating of electrons and strong thermal conduction. In addition, they provide analytical results against which two fluid numerical hydrodynamic codes can be checked.
Reflection and diffraction phenomena of blast wave propagation in nuclear fuel cycle facility
International Nuclear Information System (INIS)
This paper presents the results of an optical experiment which is carried out to measure the pressure and to observe the wave propagations when an explosion occurs in a model of a nuclear facility for preventing and mitigating the serious damage of nuclear facility. Numerical simulation is also performed to compare the phenomena in a model of nuclear facility. Nuclear facility is simulated as the several closed rooms in these experiments and simulations, because the nuclear facility is composed of many closed rooms. As a result, typical tendencies of pressure history are obtained, and it is confirmed that the explosion which occurs in a closed space is reflected in the complexity at the walls and interfered mutually with progressing waves. Finally, experimental results are compared with a numerical simulation. It is confirmed that the results of a numerical simulation show a good agreement with experimental results. (author)
Numerical simulations of convectively excited gravity waves
International Nuclear Information System (INIS)
Magneto-convection and gravity waves are numerically simulated with a nonlinear, three-dimensional, time-dependent model of a stratified, rotating, spherical fluid shell heated from below. A Solar-like reference state is specified while global velocity, magnetic field, and thermodynamic perturbations are computed from the anelastic magnetohydrodynamic equations. Convective overshooting from the upper (superadiabatic) part of the shell excites gravity waves in the lower (subadiabatic) part. Due to differential rotation and Coriolis forces, convective cell patterns propagate eastward with a latitudinally dependent phase velocity. The structure of the excited wave motions in the stable region is more time-dependent than that of the convective motions above. The magnetic field tends to be concentrated over giant-cell downdrafts in the convective zone but is affected very little by the wave motion in the stable region
Blast Wave Exposure to the Extremities Causes Endothelial Activation and Damage
Spear, Abigail M.; Davies, Emma M.; Taylor, Christopher; Whiting, Rachel; Macildowie, Sara; Kirkman, Emrys; Midwinter, Mark; Watts, Sarah A.
2015-01-01
ABSTRACT Extremity injury is a significant burden to those injured in explosive incidents and local ischaemia can result in poor functionality in salvaged limbs. This study examined whether blast injury to a limb resulted in a change in endothelial phenotype leading to changes to the surrounding tissue. The hind limbs of terminally anaesthetized rabbits were subjected to one of four blast exposures (high, medium, low, or no blast). Blood samples were analyzed for circulating endothelial cells...
Numerical simulation of flow in the raceway of blast furnace with heavy oil combustion
Energy Technology Data Exchange (ETDEWEB)
Xia, Jiliang; Ahokainen, T.; Jokilaakso, A.; Mannila, P.; Haerkki, J.
1998-12-31
The present study is to simulate the flow and combustion in the raceway of an industrial blast furnace with heavy oil as an injection fuel. The raceway shape is estimated from the force balance. Different geometry models have been used in order to find a suitable model which allows appropriate solution for the flow. The velocity vector plot, pressure, turbulent kinetic energy, and temperature distributions have been given. Predictions provide some insight into the flow mechanisms in the blast furnace and some useful information of engineering interests. Results show that there appear a recirculation zone located in the up-left region outside the raceway and a vortex below the raceway, and that the main flow moves upwards to the outlet. The flame penetrates into the raceway about two-fifth of its depth. (orig.) 15 refs.
Shetty, Ashok K.
2014-01-01
Mild traumatic brain injury (mTBI) resulting from exposure to blast shock waves (BSWs) is one of the most predominant causes of illnesses among veterans who served in the recent Iraq and Afghanistan wars. Such mTBI can also happen to civilians if exposed to shock waves of bomb attacks by terrorists. While cognitive problems, memory dysfunction, depression, anxiety and diffuse white matter injury have been observed at both early and/or delayed time-points, an initial brain pathology resulting ...
Yoo, Jin-Hyeong; Murugan, Muthuvel; Wereley, Norman M.
2013-04-01
This study investigates a lumped-parameter human body model which includes lower leg in seated posture within a quarter-car model for blast injury assessment simulation. To simulate the shock acceleration of the vehicle, mine blast analysis was conducted on a generic land vehicle crew compartment (sand box) structure. For the purpose of simulating human body dynamics with non-linear parameters, a physical model of a lumped-parameter human body within a quarter car model was implemented using multi-body dynamic simulation software. For implementing the control scheme, a skyhook algorithm was made to work with the multi-body dynamic model by running a co-simulation with the control scheme software plug-in. The injury criteria and tolerance levels for the biomechanical effects are discussed for each of the identified vulnerable body regions, such as the relative head displacement and the neck bending moment. The desired objective of this analytical model development is to study the performance of adaptive semi-active magnetorheological damper that can be used for vehicle-occupant protection technology enhancements to the seat design in a mine-resistant military vehicle.
Evidence of a blast shock wave formation in a "CME-streamer" interaction
Eselevich, V. G.; Eselevich, M. V.; Sadykov, V. M.; Zimovets, I. V.
2015-12-01
Analysis of the solar event on 16 February 2011 (SOL2011-02-16T14:19) allows to classify it as an "impulsive" coronal mass ejection (CME) event. It is argued that the observed deviation of a streamer ray from its pre-event state and generation of a metric type II radio burst in this event was a result of a "CME-streamer" interaction in the lower corona (r≲ 1.5R⊙). Most probably, it was a consequence of an impulsive action of a compressed magnetic field to the streamer. This compression of the coronal magnetic field was due to a moving and expanding magnetic flux rope, which was a core of the CME. The estimated radial speed of the type II burst sources was significantly (≈2-;8 times) larger than the radial speed of the erupting flux rope, and it decreased rapidly with time. This indicates that during the "CME-streamer" interaction a blast shock wave could be excited and propagated along the streamer.
Spectral properties of blast-wave models of gamma-ray burst sources
Meszaros, P.; Rees, M. J.; Papathanassiou, H.
1994-01-01
We calculate the spectrum of blast-wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find that the radiation efficiency is high and leads to nonthermal spectra with breaks at various energies comparable to those observed in the gamma-ray range. Radiation is also predicted at other wavebands, in particular at X-ray, optical/UV, and GeV/TeV energies. We discuss the spectra as a function of duration for three basic types of models, and for cosmological, halo, and galactic disk distances. We also evaluate the gamma-ray fluences and the spectral characteristics for a range of external densities. Impulsive burst models at cosmological distances can satisfy the conventional X-ray paucity constraint S(sub x)/S(sub gamma)less than a few percent over a wide range of durations, but galactic models can do so only for bursts shorter than a few seconds, unless additional assumptions are made. The emissivity is generally larger for bursts in a denser external environment, with the efficiency increasing up to the point where all the energy input is radiated away.
A study on impulsive sound attenuation for a high-pressure blast flow field
International Nuclear Information System (INIS)
The present work addresses a numerical study on impulsive sound attenuation for a complex high-pressure blast flow field; these characteristics are generated by a supersonic propellant gas flow through a shock tube into an ambient environment. A numerical solver for analyzing the high pressure blast flow field is developed in this study. From numerical simulations, wave dynamic processes (which include a first precursor shock wave, a second main propellant shock wave, and interactions in the muzzle blasts) are simulated and discussed. The pressure variation of the blast flow field is analyzed to evaluate the effect of a silencer. A live firing test is also performed to evaluate four different silencers. The results of this study will be helpful in understanding blast wave and in designing silencers
Slamming Simulations in a Conditional Wave
DEFF Research Database (Denmark)
Seng, Sopheak; Jensen, Jørgen Juncher
2012-01-01
surface NS/VOF CFD simulations under the same wave conditions. In moderate seas and no occurrence of slamming the structural responses predicted by the methods agree well. When slamming occurs the strip theory overpredicts VBM but the peak values of VBM occurs at approximately the same time as predicted...... by the CFD method implying the possibility to use the more accurate CFD results to improve the estimation of slamming loads in the strip theory through a rational correction coefficient....
Simulation of dust-acoustic waves
International Nuclear Information System (INIS)
The authors use molecular dynamics (MD) and particle-in-cell (PIC) simulation methods to investigate the dispersion relation of dust-acoustic waves in a one-dimensional, strongly coupled (Coulomb coupling parameter Λ = ratio of the Coulomb energy to the thermal energy = 120) dusty plasma. They study both cases where the dust is represented by a small number of simulation particles that form into a regular array structure (crystal limit) as well as where the dust is represented by a much larger number of particles (fluid limit)
Model Simulations of Waves in Hurricane Juan
Perrie, W.; Toulany, B.; Padilla-Hernandez, R.; Hu, Y.; Smith, P.; Zhang, W.; Zou, Q.; Ren, X.
2004-05-01
Hurricane Juan made landfall at 0300 UTC near Halifax Nova Scotia. This was a category 2 hurricane with winds of 44 m/s, the largest storm to pass over these coastal areas in several decades. Associated high ocean waves were experienced in coastal waters, from Peggy's Cove to Sheet Harbour, growing to epic proportions on the Scotian Shelf, and exceeding the 100-year return wave based on the present climatology. As part of the GoMOOS program (Gulf of Maine Ocean Observing System, www.gomoos.org), winds from the USA Navy COAMPS (Coupled Ocean Atmosphere Model Prediction System) were used to evaluate and compare three widely-used third generation numerical wave models, SWAN, WAM and WaveWatch-III (hereafter WW3) for accuracy, with in situ measurements. Model comparisons consist of a set of composite model systems, respectively nesting WAM, WW3 and SWAN in WAM and WW3. We report results from the intermediate-resolution grid for Hurricane Juan. Wave measurements were made using four operational deep-water buoys (C44258, C44142, C44137, 44005), by a conventional directional wave rider (DWR) moored offshore from Lunenburg Bay, and also by two acoustic Doppler current profiler (ADCP) located (1) near an oil rig on Sable Island Bank, in relatively shallow water, and (2) near the outer boundary of Lunenburg Bay. We discuss the reliability of DWR wave data compared to ADCP wave data. We show that all models provide reliable hindcasts for significant wave height (Hs) and for peak period (Tp) for Juan, although a clear under-estimation of Hs at the peak of the storm is evident, compared to observations. A feature in the COAMPS storm simulation is that the storm track appears to be slightly to the east of that of Quikscat scatterometer data. Comparisons between models and 2-dimensional wave spectra are presented. Preliminary results suggest that the recently released upgrade to the WW3 model shows slightly enhanced skill compared to the other models.
Combustion of waste oils simulating their injection in blast furnace tuyeres
Cores, A.; Ferreira, S.; Isidro, A; Muñiz, M
2009-01-01
A study has been made of the combustion of different waste oils produced in an iron and steel works. Combustion is achieved by injecting the waste oil at flows of 10-20 kg/h in a combustion chamber that simulates the conditions of the blast furnace tuyere zone. The waste oil is preheated to 65-90 °C in order to achieve conditions of fluidity and is injected by spraying into the combustion chamber. During combustion the temperatures and the CO_{2}, O_{2}...
Bailey, Ann Marie; Christopher, John J; Salzar, Robert S; Brozoski, Frederick
2015-05-01
Response of the human body to high-rate vertical loading, such as military vehicle underbody blast (UBB), is not well understood because of the chaotic nature of such events. The purpose of this research was to compare the response of postmortem human surrogates (PMHS) and the Hybrid-III anthropomorphic test device (ATD) to simulated UBB loading ranging from 100 to 860 g seat and floor acceleration. Data from 13 whole body PMHS tests were used to create response corridors for vertical loading conditions for the pelvis, T1, head, femur, and tibia; these responses were compared to Hybrid-III responses under matched loading conditions. PMID:25751733
Blast Wave Exposure to the Extremities Causes Endothelial Activation and Damage.
Spear, Abigail M; Davies, Emma M; Taylor, Christopher; Whiting, Rachel; Macildowie, Sara; Kirkman, Emrys; Midwinter, Mark; Watts, Sarah A
2015-11-01
Extremity injury is a significant burden to those injured in explosive incidents and local ischaemia can result in poor functionality in salvaged limbs. This study examined whether blast injury to a limb resulted in a change in endothelial phenotype leading to changes to the surrounding tissue.The hind limbs of terminally anaesthetized rabbits were subjected to one of four blast exposures (high, medium, low, or no blast). Blood samples were analyzed for circulating endothelial cells pre-injury and at 1, 6, and 11 h postinjury as well as analysis for endothelial activation pre-injury and at 1, 6, and 12 h postinjury. Post-mortem tissue (12 h post-injury) was analysed for both protein and mRNA expression and also for histopathology. The high blast group had significantly elevated levels of circulating endothelial cells 6 h postinjury. This group also had significantly elevated tissue mRNA expression of IL-6, E-selection, TNF-α, HIF-1, thrombomodulin, and PDGF. There was a significant correlation between blast dose and the degree of tissue pathology (hemorrhage, neutrophil infiltrate, and oedema) with the worst scores in the high blast group. This study has demonstrated that blast injury can activate the endothelium and in some cases cause damage that in turn leads to pathological changes in the surrounding tissue. For the casualty injured by an explosion the damaging effects of hemorrhage and shock could be exacerbated by blast injury and vice versa so that even low levels of blast become damaging, all of which could affect tissue functionality and long-term outcomes. PMID:26418548
Stochastic Simulations on the Cellular Wave Computers
Ercsey-Ravasz, M; Neda, Z
2006-01-01
The computational paradigm represented by Cellular Neural/nonlinear Networks (CNN) and the CNN Universal Machine (CNN-UM) as a Cellular Wave Computer, gives new perspectives for computational physics. Many numerical problems and simulations can be elegantly addressed on this fully parallelized and analogic architecture. Here we study the possibility of performing stochastic simulations on this chip. First a realistic random number generator is implemented on the CNN-UM, and then as an example the two-dimensional Ising model is studied by Monte Carlo type simulations. The results obtained on an experimental version of the CNN-UM with 128 * 128 cells are in good agreement with the results obtained on digital computers. Computational time measurements suggests that the developing trend of the CNN-UM chips - increasing the lattice size and the number of local logic memories - will assure an important advantage for the CNN-UM in the near future.
Modelling and Dynamic Response of Steel Reticulated Shell under Blast Loading
Ximei Zhai; Yonghui Wang
2013-01-01
Explicit finite element programme LS-DYNA was used to simulate a long-span steel reticulated shell under blast loading to investigate the structural dynamic responses in this paper. The elaborate finite element model of the Kiewitt-8 single-layer reticulated shell with span of 40 m subjected to central blast loading was established and all the process from the detonation of the explosive charge to the demolition, including the propagation of the blast wave and its interaction with structure w...
DYNAMICS AND AFTERGLOW LIGHT CURVES OF GAMMA-RAY BURST BLAST WAVES WITH A LONG-LIVED REVERSE SHOCK
International Nuclear Information System (INIS)
We perform a detailed study on the dynamics of a relativistic blast wave with the presence of a long-lived reverse shock (RS). Although a short-lived RS has been widely considered, the RS is believed to be long-lived as a consequence of a stratification expected on the ejecta Lorentz factors. The existence of a long-lived RS causes the forward shock (FS) dynamics to deviate from a self-similar Blandford-McKee solution. Employing the ''mechanical model'' that correctly incorporates the energy conservation, we present an accurate solution for both the FS and RS dynamics. We conduct a sophisticated calculation of the afterglow emission. Adopting a Lagrangian description of the blast wave, we keep track of an adiabatic evolution of numerous shells between the FS and RS. An evolution of the electron spectrum is also followed individually for every shell. We then find the FS and RS light curves by integrating over the entire FS and RS shocked regions, respectively. Exploring a total of 20 different ejecta stratifications, we explain in detail how a stratified ejecta affects its blast wave dynamics and afterglow light curves. We show that, while the FS light curves are not sensitive to the ejecta stratifications, the RS light curves exhibit much richer features, including steep declines, plateaus, bumps, re-brightenings, and a variety of temporal decay indices. These distinctive RS features may be observable if the RS has higher values of the microphysics parameters than the FS. We discuss possible applications of our results in understanding the gamma-ray burst afterglow data.
Characteristics of rocky massif in aspect of intensity from seismic waves associated with blasting
Dambov, Risto; Mircovski, Vojo
2014-01-01
In previous studies carried out on a large number of scientists and experts in these area that connects the physical laws of oscillation of the ground and blasting as the mining operation, it was found that the oscillation of the ground and the intensity of seismic tremors caused by blasting series depend of the physical – mechanical characteristics of the rock massif. This physical – mechanical characteristics are related to their geological structure and the secondary deforma...
International Nuclear Information System (INIS)
The propagation of a blast wave inside the Darlington Nuclear Generating Station NGS) powerhouse following an accidental explosion at a nearby railway line has been studied numerically using two different computer codes. Pressurization of the building interior at various locations in the powerhouse are computed with an Ontario Hydro in-house finite-difference containment code called PATRIC, and in one benchmark case with an Institute for Aerospace Studies code based on the random-choice method, both of which solve unsteady one-dimensional flow problems. Some pertinent results of both codes are presented, and they are also shown to be in good agreement
Energy Technology Data Exchange (ETDEWEB)
Miles, A
2004-04-27
In core-collapse supernovae, strong blast waves drive interfaces susceptible to Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities. In addition, perturbation growth can result from material expansion in large-scale velocity gradients behind the shock front. Laser-driven experiments are designed to produce a strongly shocked interface whose evolution is a scaled version of the unstable hydrogen-helium interface in core-collapse supernovae such as SN 1987A. The ultimate goal of this research is to develop an understanding of the effect of hydrodynamic instabilities and the resulting transition to turbulence on supernovae observables that remain as yet unexplained. In this dissertation, we present a computational study of unstable systems driven by high Mach number shock and blast waves. Using multi-physics radiation hydrodynamics codes and theoretical models, we consider the late nonlinear instability evolution of single mode, few mode, and multimode interfaces. We rely primarily on 2D calculations but present recent 3D results as well. For planar multimode systems, we show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions (IC's) by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Aspects of the IC's are shown to have a strong effect on the time to transition to the quasi-self-similar regime. With higher-dimensional blast waves, divergence restores the properties necessary for establishment of the self-similar state, but achieving it requires very high initial characteristic mode number and high Mach number for the incident blast wave. We point to recent stellar calculations that predict IC's we find incompatible with self-similarity, and
Blast Wave Fits to Elliptic Flow Data at $\\sqrt{s_{\\rm NN}} =$ 7.7--2760 GeV
Sun, X; Poskanzer, A M; Schmah, A
2014-01-01
We present blast wave fits to elliptic flow ($v_{2}(p_{\\rm T})$) data in minimum bias collisions from the $\\sqrt{s_{\\rm NN}} =$ 7.7--200 GeV at RHIC, and 2.76 TeV at LHC. The fits are performed separately for particles and corresponding anti-particles. The mean transverse velocity parameter $\\beta$ shows an energy dependent difference between particles and corresponding anti-particles, which increases as the beam energy decreases. Possible effects of feed down, baryon stopping, anti-particle absorption, and early production times for anti-particles are discussed.
Blast-wave model description of the Hanbury-Brown--Twiss radii in pp collisions at LHC energies
Bialas, Andrzej; Florkowski, Wojciech; Zalewski, Kacper
2014-01-01
The blast wave model is applied to the recent data on HBT radii in pp collisions, measured by the ALICE collaboration. A reasonable description of data is obtained for a rather low temperature of the kinetic freeze-out, T ~ 100 MeV, and the transverse profile corresponding to the emission from a shell of a fairly small width 2 d ~ 1.5 fm. The size and the life-time of the produced system are determined for various multiplicities of the produced particles.
Blast-wave model description of the Hanbury-Brown--Twiss radii in pp collisions at LHC energies
Bialas, Andrzej; Zalewski, Kacper
2014-01-01
The blast wave model is applied to the recent data on HBT radii in $pp$ collisions, measured by the ALICE collaboration. A reasonable description of data is obtained for a rather low temperature of the system, $T\\leq$ 120 MeV and the transverse profile corresponding to the emission from a shell of a fairly small width $2 \\delta \\sim 1.5$ fm. The size and the life-time of the produced system are determined for various multiplicities of the produced particles.
International Nuclear Information System (INIS)
A spherically symmetric model incorporating a self-consistent magnetic field is constructed to describe a blast wave in the solar wind caused by the explosive energy release of a solar flare. The shock is assumed to advance into a conducting gas of spatially decreasing density and pervaded by an idealised spatially decreasing magnetic field. The limitations of the self-similar model constructed are considered, and as a result of the approximations made it is suggested that the model can have only limited applicability to real flare-produced shocks. (orig./BY)
International Nuclear Information System (INIS)
In core-collapse supernovae, strong blast waves drive interfaces susceptible to Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities. In addition, perturbation growth can result from material expansion in large-scale velocity gradients behind the shock front. Laser-driven experiments are designed to produce a strongly shocked interface whose evolution is a scaled version of the unstable hydrogen-helium interface in core-collapse supernovae such as SN 1987A. The ultimate goal of this research is to develop an understanding of the effect of hydrodynamic instabilities and the resulting transition to turbulence on supernovae observables that remain as yet unexplained. In this dissertation, we present a computational study of unstable systems driven by high Mach number shock and blast waves. Using multi-physics radiation hydrodynamics codes and theoretical models, we consider the late nonlinear instability evolution of single mode, few mode, and multimode interfaces. We rely primarily on 2D calculations but present recent 3D results as well. For planar multimode systems, we show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions (IC's) by allowing for memory of the initial conditions to be retained in the mix-width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Aspects of the IC's are shown to have a strong effect on the time to transition to the quasi-self-similar regime. With higher-dimensional blast waves, divergence restores the properties necessary for establishment of the self-similar state, but achieving it requires very high initial characteristic mode number and high Mach number for the incident blast wave. We point to recent stellar calculations that predict IC's we find incompatible with self-similarity, and emphasize the
Yang, Jianhua; Lu, Wenbo; Hu, Yingguo; Chen, Ming; Yan, Peng
2015-09-01
Presence of an excavation damage zone (EDZ) around a tunnel perimeter is of significant concern with regard to safety, stability, costs and overall performance of the tunnel. For deep-buried tunnel excavation by drill and blast, it is generally accepted that a combination of effects of stress redistribution and blasting is mainly responsible for development of the EDZ. However, few open literatures can be found to use numerical methods to investigate the behavior of rock damage induced by the combined effects, and it is still far from full understanding how, when and to what degree the blasting affects the behavior of the EDZ during excavation. By implementing a statistical damage evolution law based on stress criterion into the commercial software LS-DYNA through its user-subroutines, this paper presents a 3D numerical simulation of the rock damage evolution of a deep-buried tunnel excavation, with a special emphasis on the combined effects of the stress redistribution of surrounding rock masses and the blasting-induced damage. Influence of repeated blast loadings on the damage extension for practical millisecond delay blasting is investigated in the present analysis. Accompanying explosive detonation and secession of rock fragments from their initial locations, in situ stress in the immediate vicinity of the excavation face is suddenly released. The transient characteristics of the in situ stress release and induced dynamic responses in the surrounding rock masses are also highlighted. From the simulation results, some instructive conclusions are drawn with respect to the rock damage mechanism and evolution during deep-buried tunnel excavation by drill and blast.
Passive millimeter wave simulation in blender
Murakowski, Maciej
Imaging in the millimeter wave (mmW) frequency range is being explored for applications where visible or infrared (IR) imaging fails, such as through atmospheric obscurants. However, mmW imaging is still in its infancy and imager systems are still bulky, expensive, and fragile, so experiments on imaging in real-world scenarios are difficult or impossible to perform. Therefore, a simulation system capable of predicting mmW phenomenology would be valuable in determining the requirements (e.g. resolution or noise floor) of an imaging system for a particular scenario and aid in the design of such an imager. Producing simulation software for this purpose is the objective of the work described in this thesis. The 3D software package Blender was modified to simulate the images produced by a passive mmW imager, based on a Geometrical Optics approach. Simulated imagery was validated against experimental data and the software was applied to novel imaging scenarios. Additionally, a database of material properties for use in the simulation was collected.
Design of wave breaking experiments and A-Posteriori Simulations
Kurnia, R.; Groesen, van, M.
2014-01-01
This report presents results of 30 wave breaking experiments conducted in the long wave tank of TU Delft, Department of Maritime and Transport Technology (6,7 and 10-12 March 2014), together with simulations performed before the experiment to determine the required wave maker motion and a-posteriori simulations that use a measured time trace as influx for calculation further downstream.
Simulating acoustic waves in spotted stars
Papini, Emanuele; Gizon, Laurent; Hanasoge, Shravan M
2015-01-01
Acoustic modes of oscillation are affected by stellar activity, however it is unclear how starspots contribute to these changes. Here we investigate the non-magnetic effects of starspots on global modes with angular degree $\\ell \\leq 2$ in highly active stars, and characterize the spot seismic signature on synthetic light curves. We perform 3D time-domain simulations of linear acoustic waves to study their interaction with a model starspot. We model the spot as a 3D change in the sound speed stratification with respect to a convectively stable stellar background, built from solar Model S. We perform a parametric study by considering different depths and perturbation amplitudes. Exact numerical simulations allow investigation of the wavefield-spot interaction beyond first order perturbation theory. The interaction of the axisymmetric modes with the starspot is strongly nonlinear. As mode frequency increases, the frequency shifts for radial modes exceed the value predicted by linear theory, while the shifts for...
Directory of Open Access Journals (Sweden)
Zhou Fei
2015-05-01
Full Text Available In current military conflicts and civilian terrorism, blast-induced traumatic brain injury (bTBI is the primary cause of neurotrauma. However, the effects and mechanisms of bTBI are poorly understood. Although previous researchers have made significant contributions to establishing animal models for the simulation of bTBI, the precision and controllability of blast-induced injury in animal models must be improved. Therefore, we established a novel rat model to simulate blast-wave injury to the brain. To simulate different extents of bTBI injury, the animals were divided into moderate and severe injury groups. The miniature spherical explosives (PETN used in each group were of different sizes (2.5 mm diameter in the moderate injury group and 3.0 mm diameter in the severe injury group. A specially designed apparatus was able to precisely adjust the positions of the miniature explosives and create eight rats with bTBI simultaneously, using a single electric detonator. Neurological functions, gross pathologies, histopathological changes and the expression levels of various biomarkers were examined after the explosion. Compared with the moderate injury group, there were significantly more neurological dysfunctions, cortical contusions, intraparenchymal hemorrhages, cortical expression of S-100β, MBP, NSE, IL-8, IL-10, iNOS and HIF-1α in the severe injury group. These results demonstrate that we have created a reliable and reproducible bTBI model in rats. This model will be helpful for studying the mechanisms of bTBI and developing strategies for clinical bTBI treatment.
Blast-Induced Damage on Millisecond Blasting Model Test with Multicircle Vertical Blastholes
Qin-yong Ma; Pu Yuan; Jing-shuang Zhang; Rui-qiu Ma; Bo Han
2015-01-01
To investigate the blast-induced damage effect on surrounding rock in vertical shaft excavation, 4 kinds of millisecond blasting model tests with three-circle blastholes were designed and carried out with excavation blasting in vertical shaft as the background. The longitudinal wave velocity on the side of concrete model was also measured before and after blasting. Then blast damage factor was then calculated by measuring longitudinal wave velocity before and after blasting. The test results ...
Tubman, Eleanor; Crowston, R.; Lam, G.; Dimoline, G.; Alraddadi, R.; Doyle, H.; Meinecke, J.; Cross, J.; Bolis, R.; Lamb, D.; Tzeferacos, P.; Doria, D.; Reville, B.; Ahmed, H.; Borghesi, M.; Gregori, G.; Woolsey, N.
2015-11-01
The ability to recreate scaled conditions of a supernova remnant within a laboratory environment is of great interest for informing the understanding of the evolution of galactic magnetic fields. The experiments rely on a near point explosion driven by one sided laser illumination producing a plasma, surrounded by a background gas. The subsequent shock and blast waves emerge following an initial ballistic phase into a self-similar expansion. Studies have been undertaken into the evolution of shock asymmetries which lead to magnetic field generation via the Biermann battery mechanism. Here we use the Vulcan laser facility, with targets such as carbon rods and plastic spheres placed in ambient gases of argon, helium or hydrogen, to produce the blast waves. These conditions allow us to study the asymmetries of the shocks using multi-frame imaging cameras, interferometry, and spectroscopy, while measuring the resulting magnetic fields with B-dot probes. The velocity of the shock and the temporal resolution of the asymmetries can be acquired on a single shot by the multi-framing cameras, and comparison with the measured B-dot fields allow for detailed inferences to be made.
Conversion of piston-driven shocks from powerful solar flares to blast wave shocks in the solar wind
International Nuclear Information System (INIS)
It was suggested by Smart and Shea (1985) that the time of arrival of solar-flare-generated shock waves at any point in space may be predicted by assuming that they are first driven from the Sun after which they decay into blast shocks. Their study was extended by using the duration of the Type IV radio emission as a phenomenological symptom of the piston-driven phase of these shocks. Using a sample of 39 cases of combined Type II/Type IV observations from 1972 to 1982 solar flares, it was found that the average predicted times-of-arrival of these shocks to Earth (and elsewhere) deviate from the actual times by 1.40 hr with a standard deviation of 1.25 hr. On the average, a representative shock from this sample is emitted from a powerful flare with a velocity of 1,560 km sec-1; moves at a constant inertial velocity to a distance of 0.12 AU after which it begins to decelerate as a classical (Sedov-type) blast shock that is convected by the ambient solar wind as suggested by Smart and Shea; and arrives to Earth 45.8 hr after its initiation in the Sun. Shocks that appear to deviate from this phenomenological scenario by virtue of lack of detection on Earth are assumed to decay into fast mode MHD waves. (author). 7 figs., 1 tab., 53 refs
Bailey, Ann M; Christopher, John J; Brozoski, Frederick; Salzar, Robert S
2015-08-01
Military vehicle underbody blast (UBB) is the cause of many serious injuries in theatre today; however, the effects of these chaotic events on the human body are not well understood. The purpose of this research was to replicate both UBB loading conditions and investigate occupant response in a controlled laboratory setting. In addition to better understanding the response of the human to high rate vertical loading, this test series also aimed to identify high rate injury thresholds. Ten whole body post mortem human surrogate (PMHS) tests were completed using the University of Virginia's ODYSSEY simulated blast rig under a range of loading conditions. Seat pan accelerations ranged from 291 to 738 g's over 3 ms of positive phase duration, and foot pan accelerations from 234 to 858 g's over 3 ms of positive phase duration. Post-test computed tomography (CT) scans and necropsies were performed to determine injuries, and revealed a combination of pelvic, lumbar, thoracic, and lower extremity injuries. The research in this paper discusses pelvis and lower extremity injuries under high rate vertical loads. PMID:25503737
Pulverized coal burnout in blast furnace simulated by a drop tube furnace
Energy Technology Data Exchange (ETDEWEB)
Du, Shan-Wen [Steel and Aluminum Research and Development Department, China Steel Corporation, Kaohsiung 812 (China); Chen, Wei-Hsin [Department of Greenergy, National University of Tainan, Tainan 700 (China); Lucas, John A. [School of Engineering of the University of Newcastle, Callaghan, NSW 2308 (Australia)
2010-02-15
Reactions of pulverized coal injection (PCI) in a blast furnace were simulated using a drop tube furnace (DTF) to investigate the burnout behavior of a number of coals and coal blends. For the coals with the fuel ratio ranging from 1.36 to 6.22, the experimental results indicated that the burnout increased with decreasing the fuel ratio, except for certain coals departing from the general trend. One of the coals with the fuel ratio of 6.22 has shown its merit in combustion, implying that the blending ratio of the coal in PCI operation can be raised for a higher coke replacement ratio. The experiments also suggested that increasing blast temperature was an efficient countermeasure for promoting the combustibility of the injected coals. Higher fuel burnout could be achieved when the particle size of coal was reduced from 60-100 to 100-200 mesh. However, once the size of the tested coals was in the range of 200 and 325 mesh, the burnout could not be improved further, resulting from the agglomeration of fine particles. Considering coal blend reactions, the blending ratio of coals in PCI may be adjusted by the individual coal burnout rather than by the fuel ratio. (author)
Directory of Open Access Journals (Sweden)
Bruno Orlando de Almeida Santos
2014-04-01
Full Text Available The Injection of powdered materials in blast furnaces is a great option for reducing costs, increasing productivity and satisfy the environmental norms. Thus, this paper presents a study on the use of a flame stabilization system with rotation, designed to promote greater coal injection in the combustion zone, reducing losses and increasing the efficiency of the equipment. A physical model was used to evaluate scattering of pulverized fuel and is compared with numerical results in the same scale. In the second step, a combustion model was added to the numerical simulation, using dimensions of a real blast furnace. Fields like temperature, velocity and behavior of chemical reactions were analyzed. The results showed that double lances promote better particle injection when compared with simple lance for reduced material injection. The new injection system proposed, with swirl numbers of 0.12 and 0.24, promoted a better injection of both reduced material and temperature in the raceway zone. The swirl 0.24 showed superior performance when compared to other injection systems.
Awwad, Hibah O.; Gonzalez, Larry P.; Tompkins, Paul; Lerner, Megan; Brackett, Daniel J.; Awasthi, Vibhudutta; Standifer, Kelly M
2015-01-01
Physiological alterations, anxiety, and cognitive disorders are strongly associated with blast-induced traumatic brain injury (blast TBI), and are common symptoms in service personnel exposed to blasts. Since 2006, 25,000–30,000 new TBI cases are diagnosed annually in U.S. Service members; increasing evidence confirms that primary blast exposure causes diffuse axonal injury and is often accompanied by altered behavioral outcomes. Behavioral and acute metabolic effects resulting from blast to ...
Modelling and Dynamic Response of Steel Reticulated Shell under Blast Loading
Directory of Open Access Journals (Sweden)
Ximei Zhai
2013-01-01
Full Text Available Explicit finite element programme LS-DYNA was used to simulate a long-span steel reticulated shell under blast loading to investigate the structural dynamic responses in this paper. The elaborate finite element model of the Kiewitt-8 single-layer reticulated shell with span of 40 m subjected to central blast loading was established and all the process from the detonation of the explosive charge to the demolition, including the propagation of the blast wave and its interaction with structure was reproduced. The peak overpressure from the numerical analysis was compared with empirical formulas to verify the credibility and applicability of numerical simulation for blast loading. The dynamic responses of the structure under blast loading with different TNT equivalent weights of explosive and rise-span ratios were obtained. In addition, the response types of Kiewitt-8 single-layer reticulated shell subjected to central explosive blast loading were defined.
McLaughlin, Keith L.; Bonner, Jessie L.; Barker, Terrance
2004-01-01
A theoretical understanding of the mechanisms by which quarry blasts excite seismic waves is useful in understanding how quarry blast discriminants may be transported from one region to another. An experiment in Texas with well-placed seismic stations and a cooperative blasting engineer has shed light on some of the physical mechanisms of seismic excitation at short periods (0.1-3 Hz). Azimuthal radiation patterns of the 0.2-3 Hz Rayleigh and Love waves are diagnostic of two proposed mechanisms for non-isotropic radiation from quarry blasts. Observations show that the Love and Rayleigh wave radiation patterns depend upon the orientation of the quarry benches. Two possible mechanisms for non-isotropic radiation are (1) the lateral throw of spalled material and (2) the presence of the topographic bench in the quarry. The spall of material can be modelled by vertical and horizontal forces applied to the free surface with time functions proportional to the derivative of the momentum of the spalled material. We use wavenumber integration synthetics to model the explosion plus spall represented by seismic moment tensor sources plus point forces. The resulting synthetics demonstrate that the magnitude of the SH (Love) compared with the SV (fundamental Rayleigh or Rg) in the short period band (0.5-3 Hz) may be explained by the spall mechanism. Nearly all of the available mass must participate in the spall with an average velocity of 2-5 m s-1 to provide sufficient impulse to generate the observed Love waves. Love wave radiation patterns from such a mechanism are consistent with the spall mechanism. We modelled the effects of the topographic bench using 3-D linear finite-difference calculations to compute progressive elastic wavefields from explosion sources behind the quarry bench. These 3-D calculations show SH radiation patterns consistent with observations while the SV radiation patterns are not consistent with observations. We find that the radiation patterns from the
Detonation wave problems : modeling, numerical simulations and linear stability
Carvalho, Filipe; Soares, A. J.
2012-01-01
Traveling waves arising in detonation physics are described by the reactive Euler equations obtained in the fluid dynamical limit of the Boltzmann equation for a binary reactive mixture. The hydrodynamic linear stability of the detonation wave solution is investigated with a normal mode analysis. Numerical simulations are performed for both the detonation wave solution and its linear stability.
Numerical simulation and mechanism analysis of freak waves
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A numerical wave model based on the modified fourth-order nonlinear Schroe dinger equation (mNLSE) in deep water was developed to simulate the formation of freak waves and a standard split-step, pseudo-spectral method was used to solve the equation. The validation of the model is firstly verified, then the simulation of freak waves was performed by changing sideband conditions, and the variation of wave energy was also analyzed in the evolution. The results indicate that Benjamin-Feir instability (sideband instability) is an important mechanism for freak wave formation.
Three-Dimensional Simulations of Deep-Water Breaking Waves
Brucker, Kyle A; Dommermuth, Douglas G; Adams, Paul
2014-01-01
The formulation of a canonical deep-water breaking wave problem is introduced, and the results of a set of three-dimensional numerical simulations for deep-water breaking waves are presented. In this paper fully nonlinear progressive waves are generated by applying a normal stress to the free surface. Precise control of the forcing allows for a systematic study of four types of deep-water breaking waves, characterized herein as weak plunging, plunging, strong plunging, and very strong plunging.
International Nuclear Information System (INIS)
Highlights: • An integrated system of coal gasification with slag waste heat recovery was proposed. • The goal of BF slag heat saving and emission reduction was achieved by this system. • The optimal parameters were obtained and the waste heat recovery rate reached 83.08%. • About 6.64 kmol/min syngas was produced when using one ton BF slag to provide energy. - Abstract: This article presented a model for the system of coal gasification with steam and blast furnace slag waste heat recovery by using the ASPEN Plus as the simulating and modeling tool. Constrained by mass and energy balance for the entire system, the model included the gasifier used to product syngas at the chemical equilibrium based on the Gibbs free energy minimization approach and the boiler used to recover the heat of the blast furnace slag (BF slag) and syngas. Two parameters of temperature and steam to coal ratio (S/C) were considered to account for their impacts on the Datong coal (DT coal) gasification process. The carbon gasification efficiency (CE), cold gasification efficiency (CGE), syngas product efficiency (PE) and the heating value of syngas produced by 1 kg pulverized coal (HV) were adopted as the indicators to examine the gasification performance. The optimal operating temperature and S/C were 800 °C and 1.5, respectively. At this condition, CE reached above 90% and the maximum values of the CGE, PE and HV were all obtained. Under the optimal operating conditions, 1000 kg/min BF slag, about 40.41 kg/min DT pulverized coal and 77.94 kg/min steam were fed into the gasifier and approximate 6.64 kmol/min syngas could be generated. Overall, the coal was converted to clean syngas by gasification reaction and the BF slag waste heat was also recovered effectively (reached up to 83.08%) in this system, achieving the objective of energy saving and emission reduction
Multiscale Simulation of Breaking Wave Impacts
DEFF Research Database (Denmark)
Lindberg, Ole
compare reasonably well. The incompressible and inviscid ALE-WLS model is coupled with the potential flow model of Engsig-Karup et al. [2009], to perform multiscale calculation of breaking wave impacts on a vertical breakwater. The potential flow model provides accurate calculation of the wave...... potential flow model to provide multiscale calculation of forces from breaking wave impacts on structures....
Zhang, Song; Chen, Jin-Hui; Zhong, Chen
2014-01-01
The particle production of Kaon and $\\Lambda$ are studied in nucleus-nucleus collisions at relativistic energy based on a chemical equilibrium blast-wave model. The transverse momentum spectra of Kaon and $\\Lambda$ at the kinetic freeze-out stage from our model are in good agreement with the experimental results. The kinetic freeze-out parameters of temperature ($T_{kin}$) and radial flow parameter $\\rho_{0}$ are presented for the FOPI, RHIC and LHC energies. And the resonance decay effect is also discussed. The systematic study for beam energy dependence of the strangeness particle production will help us to better understand the properties of the matter created in heavy-ion collisions at the kinetic freeze-out stage.
Global Simulation of Electromagnetic Ion Cyclotron Waves
Khazanov, George V.; Gallagher, D. L.; Kozyra, J. U.
2007-01-01
It is very well known that the effects of electromagnetic ion cyclotron (EMIC) waves on ring current (RC) ion and radiation belt (RB) electron dynamics strongly depend on such particle/wave characteristics as the phase-space distribution function, frequency, wave-normal angle, wave energy, and the form of wave spectral energy density. The consequence is that accurate modeling of EMIC waves and RC particles requires robust inclusion of the interdependent dynamics of wave growth/damping, wave propagation, and particles. Such a self-consistent model is being progressively developed by Khazanov et al. This model is based on a system of coupled kinetic equations for the RC and EMIC wave power spectral density along with the ray tracing equations. We will discuss the recent progress in understanding EMIC waves formation mechanisms in the inner magnetosphere. This problem remains unsettled in spite of many years of experimental and theoretical studies. Modern satellite observations by CRRES, Polar and Cluster still do not reveal the whole picture experimentally since they do not stay long enough in the generation region to give a full account of all the spatio-temporal structure of EMIC waves. The complete self-consistent theory taking into account all factors significant for EMIC waves generation remains to be developed. Several mechanisms are discussed with respect to formation of EMIC waves, among them are nonlinear modification of the ionospheric reflection by precipitating energetic protons, modulation of ion-cyclotron instability by long-period (Pc3/4) pulsations, reflection of waves from layers of heavy-ion gyroresonances, and nonlinearities of wave generation process. We show that each of these mechanisms have their attractive features and explains certain part experimental data but any of them, if taken alone, meets some difficulties when compared to observations. We conclude that development of a refined nonlinear theory and further correlated analysis of modern
Numerical Simulation of the Submarine Pipeline under Wave Action
Directory of Open Access Journals (Sweden)
Zhi-Yong Zhang
2013-06-01
Full Text Available A two-dimensional viscous numerical wave flume is established in this study. The Navier-Stokes equations are discretized by Finite Difference Method (FDM. The turbulence is considered by using the standard k-ε turbulence model. Volume of Fluid (VOF method is adopted to capture the free surface of water wave. A virtual inclined porous structure is devised to absorb the wave energy near the end of computational domain. The numerical wave flume was validated by the comparisons with analytical result. Based on the numerical wave flume, the wave field around submarine pipeline was simulated and the numerical results were compared with experimental data. The comparison results show that the present numerical model works well. The maximum horizontal wave force and vertical wave force increase with the wave height.
Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A
Dwek, Eliahu; Arendt, Richard G.; Bouchet, Patrice; Burrows, David N.; Challis, Peter; Danziger, John; DeBuizer James M.; Gehrz, Robert D.; Kirshner, Robert P.; McCray, Richard; Park, Sangwok; Polomski, Elisha; Woodward, Charles
2007-01-01
Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring, produced by mass loss from the progenitor star. The observed infrared (IR) radiation arises from the interaction of dust grains that formed in mass outflow with the soft X-ray emitting plasma component of the shocked gas. Spitzer IRS spectra at 5 - 30 microns taken on day 6190 since the explosion show that the emission arises from approx. 1.1 x 10(exp -6) solar mass of silicate grains radiating at a temperature of approx. 180+/-(15-20) K. Subsequent observations on day 7137 show that the IR flux had increased by a factor of 2 while maintaining an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX) is consistent with that of a dusty plasma with standard LMC dust abundances. This flux ratio has decreased by a factor of approx. 2 between days 6190 and 7137, providing the first direct observation of the ongoing destruction of dust in an expanding SN blast wave on dynamic time scales. Detailed models consistent with the observed dust temperature, the ionization fluence of the soft X-ray emission component, and the evolution of IRX suggest that the radiating si1icate grains are immersed in a 3.5 x 10(exp 6) K plasma with a density of (0.3 - 1) x 10(exp 4)/cu cm, and have a size distribution that is confined to a narrow range of radii between 0.02 and 0.2 microns. Smaller grains may have been evaporated by the initial UV flash from the supernova.
International Nuclear Information System (INIS)
A relativisitc blast-wave model is developed which can adequately explain the observed features of flux and structural variations in compact extragalactic radio sources. The model employs a pulse of energy E/sub sig/ (a ''signal'') which strikes a ring of gas (a ''screen'') of inner radius R/sub scr/ and thickness L/sub scr/. The interaction of the signal with the gas in the screen causes a relativistically expanding blast wave to be formed, with particle acceleration and magnetic field amplification occurring near the shock front. The evolution of the resulting synchrotron emission is calculated and is shown to agree with observations of the late 1975 radio burst in the BL Lacertae object AO 0235+164 and with the observed nature of the majority of other highly variable radio sources. The combined effects of relativistic bulk motions with Lorentz factors GAMMA> or approx. =10, expansion and radiation losses of the high-energy electrons, and confinement of the screen to a thin ring result in the appearance of two distinct radio components which separate with superluminal relative velocities, v/sub sep/approx. =2GAMMAc, consistent with VLBI observations. More highly relativistic bulk motions (GAMMA> or approx. =10) cause a rapidly expanding (v/sub exp/approx. =GAMMAc) ring of emission to appear.The model overcomes the well known problems of excessive implied brightness temperatures and lack of observable inverse Compton X-ray emission, while explaining the commonly observed rapid flux and structural changes of many compact radio sources. However, the required mass and energy production rates of the central region are approximately two orders of magnitude greater than those provided by current theory
Making Waves: A Simulation and Modeling Computer-Tool for Studying Wave Phenomena.
Snir, Joseph
1989-01-01
Examines the use of a computer simulation program as a tool to help in the understanding of wave phenomena. After analyzing some of the main difficulties and common misconceptions about waves, features of the "Making Waves" software package are described. Figures showing a typical monitor display are presented. (YP)
Numerical Simulation of Wave Height and Wave Set-Up in Nearshore Regions
Institute of Scientific and Technical Information of China (English)
郑永红; 沈永明; 邱大洪
2001-01-01
Based on the time dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation, and then a practical method for the simulation of wave height and wave set-up in nearshore regions is presented. The variation of the complex wave amplitude is numerically simulated by use of the parabolic mild slope equation including the effect of wave energy dissipation due to wave breaking. The components of wave radiation stress are calculated subsequently by new expressions for them according to the obtained complex wave amplitude, and then the depth-averaged equation is applied to the calculation of wave set-up due to wave breaking. Numerical results are in good agreement with experimental data,showing that the expression for the energy dissipation factor is reasonable and that the new method is effective for the simulation of wave set-up due to wave breaking in nearshore regions.
Obergaulinger, M.; Iyudin, A. F.; Muller, E.; Smoot, G. F.
2014-01-01
Observations in all electromagnetic bands show that many supernova remnants (SNRs) have a very aspherical shape. This can be the result of asymmetries in the supernova explosion or a clumpy circumstellar medium. We study the generation of inhomogeneities and the mixing of elements arising from these two sources in multidimensional hydrodynamic simulations of the propagation of a supernova blast wave into a cloudy environment. We model a specific SNR, Vela Jr (RX J0852.0-4622). By comparing ou...
International Nuclear Information System (INIS)
This book introduces gunpowder blasting, which consists of ten chapters. It deals with conception of gunpowder on the history of gunpowder, difference between gunpowder and general materials and classification of gunpowder, reaction of gunpowder, shock wave and detonation, on properties, material velocity and structure, test method on gunpowder and an article processed with heat, gunpowder such as igniter charge, carlit and slurry gunpowder, propellant and an article processed with heat, blasting on basics and Bench cut, blasting operations and security blasting construction and using of gunpowder.
Numerical simulations of internal wave generation by convection in water
Lecoanet, Daniel; Le Bars, Michael; Burns, Keaton J.; Vasil, Geoffrey M.; Brown, Benjamin P.; Quataert, Eliot; Oishi, Jeffrey S.
2015-06-01
Water's density maximum at 4 ∘C makes it well suited to study internal gravity wave excitation by convection: an increasing temperature profile is unstable to convection below 4 ∘C,but stably stratified above 4 ∘C . We present numerical simulations of a waterlike fluid near its density maximum in a two-dimensional domain. We successfully model the damping of waves in the simulations using linear theory, provided we do not take the weak damping limit typically used in the literature. To isolate the physical mechanism exciting internal waves, we use the spectral code dedalus to run several simplified model simulations of our more detailed simulation. We use data from the full simulation as source terms in two simplified models of internal-wave excitation by convection: bulk excitation by convective Reynolds stresses, and interface forcing via the mechanical oscillator effect. We find excellent agreement between the waves generated in the full simulation and the simplified simulation implementing the bulk excitation mechanism. The interface forcing simulations overexcite high-frequency waves because they assume the excitation is by the "impulsive" penetration of plumes, which spreads energy to high frequencies. However, we find that the real excitation is instead by the "sweeping" motion of plumes parallel to the interface. Our results imply that the bulk excitation mechanism is a very accurate heuristic for internal-wave generation by convection.
A Methodology for Wave-to-Wire WEC Simulations
Bailey, Helen; Ortiz, Juan P.; Robertson, Bryson; Buckham, Bradley J.; Nicoll, Ryan S.
2014-01-01
This paper looks at the methodology of building a full wave-to-wire WEC (Wave Energy Convertor) simulation and presents examples of its use for a variety of different types of WEC. Wave resource information from the West Coast of Vancouver Island is considered. A detailed wave-body interaction model is generated using ProteusDS software. This model is linked to Simulink, which allows a detailed PTO (Power Take Off) model to be simulated, which will feedback into the motions of the WEC. Three ...
Esparaza, E. D.; Baker, W. E.
1977-01-01
Incident overpressure data from frangible spheres pressurized with a flash-evaporating fluid in liquid and vapor form were obtained in laboratory experiments. Glass spheres under higher than ambient internal pressure of Freon-12 were purposely burst to obtain time histories of overpressure. Nondimensional peak pressures, arrival and duration times, and impulses are presented, and whenever possible plotted and compared with compiled data for Pentolite high-explosive. The data are generally quite repeatable and show differences from blast data produced by condensed high-explosives.
Non-linear interaction of a blasting electron beam with a surface plasma wave
International Nuclear Information System (INIS)
Numerical methods are applied to solve the problem on nonlinear dynamics of a surface wave excited by an electron beam which blows round cylindrical or plane surfaces of a plasma. The mechanism of instability saturation consists in the particle beam capture by the wave field. The time behaviour and the maximum value of the wave amplitude, the fraction of the beam energy transferred to the field are determined in dependence on the beam and plasma thicknesses. It is shown that owing to the phase mixing of captured particles caused by strong space inhomogeneity of the wave field, the wave amplitude can reach monotonously the maximum steady-state value
NUMERICAL SIMULATIONS OF NONLINEAR WAVE TRANSFORMATION AROUND WAVE-PERMEABLE STRUCTURE
Institute of Scientific and Technical Information of China (English)
Li Xi; YAN Yi-xin
2005-01-01
The problem of wave partial/full reflection and transmission by wave-permeable structure is approached by solving the shape-related function with focus on the understanding of wave attenuation.2D depth-averaged Boussinesq type wave equations are given with new damping item in simulating the nonlinear wave transmission through wave-permeable structure.1D wave equation is examined to give the analytical expression of the absorbing coefficient, and is compared with laboratory data in flume to calibrate the coefficients, and the expression is applied directly in modified Boussinesq type equations.Compared with wave basin data for various incident wave conditions,the accurate predictions of combined diffraction-refraction effects in simulating nonlinear wave going through wave-permeable breakwater in the engineering application can be obtained.It shows that wave-permeable breakwaters with proper absorbing effects can be used as an effective alternative to massive gravity breakwaters in reduction of wave transmission in shallow water.
Numerical Simulation of Waves Generated by Seafloor Movements
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Waves generated by vertical seafloor movements are simulated by use of a fully nonlinear two-dimensional numerical wave tank. In the source region, the seafloor lifts to a designated height by a generation function. The numerical tests show that the linear theory is only valid for estimating the wave behaviors induced by the seafloor movements with a small amplitude, and the fully nonlinear numerical model should be adopted in the simulation of the wave generation by the large amplitude seafloor movements. Without the background surface waves, many numerical tests on the stable maximum elevations ηmax0 are carried out by both the linear theory and the fully nonlinear model. The results of two models are compared and analyzed. For the fully nonlinear model, the influences of the amplitudes and the horizontal lengths on ηmax0 are stronger than that of the characteristic duration times. Furthermore, results reveal that there are significant differences between the linear theory and the fully nonlinear model. When the influences of the background surface waves are considered, the corresponding numerical analyses reveal that with the fully nonlinear model the ηmax0 near-linearly varies with the wave amplitudes of the surface waves, and the ηmax0 has significant depndences on the wave lengths and the wave phases of the surface waves. In addition, the differences between the linear theory and the fully nonlinear model are still obvious, and these differences are significantly affected by the wave parameters of the background surface waves, such as the wave amplitude, the wave length and the wave phase.
Simulation Study on SAR Images of the Oceanic Internal Waves
Institute of Scientific and Technical Information of China (English)
Jin-song CHONG; Fei LI; Yue OUYANG
2010-01-01
Based on the research of Lynett and Liu,the horizontal fully two-dimensional,depth-integrated model for the internal wave propagation is re-deduced.By combining this model with the M4S model,the propagation process of the internal waves is simulated in Synthetic Aperture Radar (SAR) images.The simulation results clearly show the bottom effects during the propagation such as fission and isobaths-parallelized propagation direction.This simulation procedure can lay the foundation for the quantitative interaretation of internal waves from fully two-dimensional SAR images.
Energy Technology Data Exchange (ETDEWEB)
Moss, W C; King, M J; Blackman, E G
2011-01-21
In their Contributed Article, Nyein et al. (1,2) present numerical simulations of blast waves interacting with a helmeted head and conclude that a face shield may significantly mitigate blast induced traumatic brain injury (TBI). A face shield may indeed be important for future military helmets, but the authors derive their conclusions from a much smaller explosion than typically experienced on the battlefield. The blast from the 3.16 gm TNT charge of (1) has the following approximate peak overpressures, positive phase durations, and incident impulses (3): 10 atm, 0.25 ms, and 3.9 psi-ms at the front of the head (14 cm from charge), and 1.4 atm, 0.32 ms, and 1.7 psi-ms at the back of a typical 20 cm head (34 cm from charge). The peak pressure of the wave decreases by a factor of 7 as it traverses the head. The blast conditions are at the threshold for injury at the front of the head, but well below threshold at the back of the head (4). The blast traverses the head in 0.3 ms, roughly equal to the positive phase duration of the blast. Therefore, when the blast reaches the back of the head, near ambient conditions exist at the front. Because the headform is so close to the charge, it experiences a wave with significant curvature. By contrast, a realistic blast from a 2.2 kg TNT charge ({approx} an uncased 105 mm artillery round) is fatal at an overpressure of 10 atm (4). For an injury level (4) similar to (1), a 2.2 kg charge has the following approximate peak overpressures, positive phase durations, and incident impulses (3): 2.1 atm, 2.3 ms, and 18 psi-ms at the front of the head (250 cm from charge), and 1.8 atm, 2.5 ms, and 16.8 psi-ms at the back of the head (270 cm from charge). The peak pressure decreases by only a factor of 1.2 as it traverses the head. Because the 0.36 ms traversal time is much smaller than the positive phase duration, pressures on the head become relatively uniform when the blast reaches the back of the head. The larger standoff implies
Blast effects of external explosions
Sochet, Isabelle
2010-01-01
International audience Security considerations for industrial production and storage require characterization of the mechanical effects caused by blast waves resulting from a detonation or deflagration. This paper evaluates current analytical methods to determine the characteristic parameters of a blast wave with respect to the pressure, impulse and duration of the positive phase of the blast. In the case of a detonation, the trinitrotoluene (TNT) equivalent-based method determines the mas...
Effectiveness of eye armor during blast loading.
Bailoor, Shantanu; Bhardwaj, Rajneesh; Nguyen, Thao D
2015-11-01
Ocular trauma is one of the most common types of combat injuries resulting from the interaction of military personnel with improvised explosive devices. Ocular blast injury mechanisms are complex, and trauma may occur through various injury mechanisms. However, primary blast injuries (PBI) are an important cause of ocular trauma that may go unnoticed and result in significant damage to internal ocular tissues and visual impairment. Further, the effectiveness of commonly employed eye armor, designed for ballistic and laser protection, in lessening the severity of adverse blast overpressures (BOP) is unknown. In this paper, we employed a three-dimensional (3D) fluid-structure interaction computational model for assessing effectiveness of the eye armor during blast loading on human eyes and validated results against free field blast measurements by Bentz and Grimm (2013). Numerical simulations show that the blast waves focused on the ocular region because of reflections from surrounding facial features and resulted in considerable increase in BOP. We evaluated the effectiveness of spectacles and goggles in mitigating the pressure loading using the computational model. Our results corroborate experimental measurements showing that the goggles were more effective than spectacles in mitigating BOP loading on the eye. Numerical results confirmed that the goggles significantly reduced blast wave penetration in the space between the armor and the eyes and provided larger clearance space for blast wave expansion after penetration than the spectacles. The spectacles as well as the goggles were more effective in reducing reflected BOP at higher charge mass because of the larger decrease in dynamic pressures after the impact. The goggles provided greater benefit of reducing the peak pressure than the spectacles for lower charge mass. However, the goggles resulted in moderate, sustained elevated pressure loading on the eye, that became 50-100% larger than the pressure loading
Numerical simulation of air-blast atomization of a liquid layer
Agbaglah, G. Gilou; McCaslin, Jeremy; Desjardins, Olivier
2015-11-01
Numerical simulations of a planar co-flowing air/water airblast atomization is performed using an in-house multiphase Navier-Stokes solver based on a semi-lagrangian geometric Volume of Fluid (VOF) method to track the position of the interface. This solver conserves mass and momentum exactly within each phase. Excellent agreement with recent experiments is obtained when comparing physical quantities, such as the liquid cone length, the maximum wave frequency and the spatial growth rate of the primary instability. A full three dimensional simulation is used to analyze the turbulence in the gas phase. The gas layer is laminar close to the injector and becomes turbulent at downstream positions. The transition to the turbulence is shown to increase first as an exponential function of the downstream positions and then reach a statistically stable regime where the liquid wave crests expand in a thin sheet which breaks into secondary droplets.
BOMB BLAST: PATTERN AND NATURE OF INJURIES
Brahmaji Master; Chandra Sekhar; Rangaiah
2015-01-01
Bomb blast cause injury on large groups of people by multiple mechanisms. Bomb blast injuries differ from the conventional description of trauma complexity. Primary injuries are caused by blast wave and over pressure. Secondary injuries are caused by flyin g debris and cause shrapnel wounds. Tertiary injuries are caused by blast wind due to forceful impact and quaternary injuries are caused by other vectors like heat, radiation etc. Combined injuries, especially blast and...
Lerche, I.
1978-01-01
One-dimensional self-similar isothermal flow behind a blast wave propagating in a medium whose density varies with distance is investigated for the cases of one-dimensional and two-dimensional flow. The isothermal flow model is adopted as an alternative to adiabatic models of self-similar flow, which neglect heat flux. The topology of the one-dimensional flow solutions, the singularities, and the influence of boundary conditions are discussed; the instability of the isothermal blast waves against nonself-similar perturbations is also considered. The number of critical points in the two-dimensional solutions is found to vary from the number in the one-dimensional problem.
Numerical simulation of the resonantly excited capillary-gravity waves
Hanazaki, Hideshi; Hirata, Motonori; Okino, Shinya
2015-11-01
Capillary gravity waves excited by an obstacle are investigated by a direct numerical simulation. In the flow without capillary effects, it is well known that large-amplitude upstream advancing solitary waves are generated periodically under the resonant condition, i.e., when the phase velocity of the long surface waves and the mean flow velocity agrees. With capillary effects, solutions of the Euler equations show the generation of very short waves further upstream of the solitary waves and also in the depression region downstream of the obstacle. The overall characteristics of these waves agree with the solutions of the forced fifth-order KdV equation, while the weakly nonlinear theory generally overestimates the wavelength of the short waves.
Hot metal temperature prediction and simulation by fuzzy logic in a blast furnace
International Nuclear Information System (INIS)
This work describes the development and further validation of a model devoted to blast furnace hot metal temperature forecast, based on Fuzzy logic principles. The model employs as input variables, the control variables of an actual blast furnace: Blast volume, moisture, coal injection, oxygen addition, etc. and it yields as a result the hot metal temperature with a forecast horizon of forty minutes. As far as the variables used to develop the model have been obtained from data supplied by an actual blast furnaces sensors, it is necessary to properly analyse and handle such data. Especial attention was paid to data temporal correlation, fitting by interpolation the different sampling rates. In the training stage of the model the ANFIS (Adaptive Neuro-Fuzzy Inference System) and the Subtractive Clustering algorithms have been used. (Author) 9 refs
Design of a nuclear facility against earthquake, airplane crash and blast wave
International Nuclear Information System (INIS)
An integral 3D shell model for the vitrification plant is developed at which all global static and dynamic results as displacements, accelerations, reinforcement, floor response spectra are determined. For the design of the outer walls, dominated by the direct impacts of airplane crash, a non-linear 2-mass-model is used. The results are verified by a finite element model with non-linear material laws for the reinforced concrete inducing cracking, tension stiffening and membrane effects. The floor response spectra of the load cases APC envelop the load case earthquake which again covers the load case blast. The equipment in the cells requires a coupled 3-D beam model of steel structure, vessels and piping. The report shows the state of the art in the design of a nuclear facility against extreme internal and external load cases
The synchrotron-self-Compton spectrum of relativistic blast waves at large Y
Lemoine, M
2015-01-01
Recent analyses of multiwavelength light curves of gamma-ray bursts afterglows point to values of the magnetic turbulence well below the canonical $\\sim1\\,$\\% of equipartition, in agreement with theoretical expectations of a micro-turbulence generated in the shock precursor, which then decays downstream of the shock front through collisionless damping. As a direct consequence, the Compton parameter $Y$ can take large values in the blast. In the presence of decaying micro-turbulence and/or as a result of the Klein-Nishina suppression of inverse Compton cooling, the $Y$ parameter carries a non-trivial dependence on the electron Lorentz factor, which modifies the spectral shape of the synchrotron and inverse Compton components. This paper provides detailed calculations of this synchrotron-self-Compton spectrum in this large $Y$ regime, accounting for the possibility of decaying micro-turbulence. It calculates the expected temporal and spectral indices $\\alpha$ and $\\beta$ customarily defined by $F_\
Starling, R. L. C.; vanderHorst, A. J.; Rol, E.; Wijers, R. A. M. J.; Kouveliotou, C.; Wiersema, K.; Curran, P. A.; Weltervrede, P.
2008-01-01
We constrain blast wave parameters and the circumburst media ofa subsample of 10 BeppoSAX gamma-ray bursts (GRBs). For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral fits to their X-ray, optical, and NIR afterglow data. The spectral fits have been done in count space and include the effects ofmetallicity, and are compared with the previously reported optical and X-ray temporal behavior. Using the blast wave model and some assumptions which include on-axis viewing and standard jet structure, constant blast wave energy, and no evolution of the microphysical parameters, we find a mean value ofp for the sample as a whole of 9.... oa -0.003.0" 2 a_ statistical analysis of the distribution demonstrates that the p-values in this sample are inconsistent with a single universal value forp at the 3 _ level or greater, which has significant implications for particle acceleration models. This approach provides us with a measured distribution ofcircumburst density structures rather than considering only the cases of k ----0 (homogeneous) and k - 2 (windlike). We find five GRBs for which k can be well constrained, and in four of these cases the circumburst medium is clearly windlike. The fifth source has a value of 0 medium.
Starling, R. L. C.; vanderHorst, A. J.; Rol, E.; Wijers, R. A. M. J.; Kouveliotou, C.; Wiersema, K.; Curran, P. A.; Weltervrede, P.
2008-01-01
We constrain blast wave parameters and the circumburst media ofa subsample of 10 BeppoSAX gamma-ray bursts (GRBs). For this sample we derive the values of the injected electron energy distribution index, p, and the density structure index of the circumburst medium, k, from simultaneous spectral fits to their X-ray, optical, and NIR afterglow data. The spectral fits have been done in count space and include the effects ofmetallicity, and are compared with the previously reported optical and X-ray temporal behavior. Using the blast wave model and some assumptions which include on-axis viewing and standard jet structure, constant blast wave energy, and no evolution of the microphysical parameters, we find a mean value ofp for the sample as a whole of 9.... oa -0.003.0" 2 a_ statistical analysis of the distribution demonstrates that the p-values in this sample are inconsistent with a single universal value forp at the 3 _ level or greater, which has significant implications for particle acceleration models. This approach provides us with a measured distribution ofcircumburst density structures rather than considering only the cases of k ----0 (homogeneous) and k - 2 (windlike). We find five GRBs for which k can be well constrained, and in four of these cases the circumburst medium is clearly windlike. The fifth source has a value of 0 < k < 1, consistent with a homogeneous circumburst medium.
Hybrid S2/Carbon Epoxy Composite Armours Under Blast Loads
Dolce, F.; Meo, Michele; Wright, A.; French, M.; Bernabei, M.
2012-06-01
Civil and military structures, such as helicopters, aircrafts, naval ships, tanks or buildings are susceptible to blast loads as terroristic attacks increases, therefore there is the need to design blast resistant structures. During an explosion the peak pressure produced by shock wave is much greater than the static collapse pressure. Metallic structures usually undergo large plastic deformations absorbing blast energy before reaching equilibrium. Due to their high specific properties, fibre-reinforced polymers are being considered for energy absorption applications in blast resistant armours. A deep insight into the relationship between explosion loads, composite architecture and deformation/fracture behaviour will offer the possibility to design structures with significantly enhanced energy absorption and blast resistance performance. This study presents the results of a numerical investigation aimed at understanding the performance of a hybrid composite (glass/carbon fibre) plate subjected to blast loads using commercial LS-DYNA software. In particular, the paper deals with numerical 3D simulations of damages caused by air blast waves generated by C4 charges on two fully clamped rectangular plates made of steel and hybrid (S2/Carbon) composite, respectively. A Multi Materials Arbitrary Lagrangian Eulerian (MMALE) formulation was used to simulate the shock phenomenon. For the steel plates, the Johnson-Cook material model was employed. For the composite plates both in-plane and out-of-plane failure criteria were employed. In particular, a contact tiebreak formulation with a mixed mode failure criteria was employed to simulate delamination failure. As for the steel plates the results showed that excellent correlation with the experimental data for the two blast load conditions in terms of dynamic and residual deflection for two different C4 charges. For the composite plates the numerical results showed that, as expected, a wider delamination damage was observed
Large Eddy Simulation for Wave Breaking in the Surf Zone
Institute of Scientific and Technical Information of China (English)
白玉川; 蒋昌波; 沈焕庭
2001-01-01
In this paper, the large eddy simulation method is used combined with the marker and cell method to study the wave propagation or shoaling and breaking process. As wave propagates into shallow water, the shoaling leads to the increase of wave height, and then at a certain position, the wave will be breaking. The breaking wave is a powerful agent for generating turbulence, which plays an important role in most of the fluid dynamic processes throughout the sarf zone, such as transformation of wave energy, generation of near-shore current and diffusion of materials. So a proper numerical model for describing the turbulence effect is needed. In this paper, a revised Smagorinsky subgrid-scale model is used to describe the turbulence effect. The present study reveals that the coefficient of the Smagorinsky model for wave propagation or breaking simulation may be taken as a varying function of the water depth and distance away from the wave breaking point. The large eddy simulation model presented in this paper has been used to study the propagation of the solitary wave in constant water depth and the shoaling of the non-breaking solitary wave on a beach. The model is based on large eddy simulation, and to track free-surface movements, the Tokyo University Modified Marker and Cell (TUMMAC) method is employed. In order to ensure the accuracy of each component of this wave mathematical model,several steps have been taken to verify calculated solutions with either analytical solutions or experimental data. For non-breaking waves, very accurate results are obtained for a solitary wave propagating over a constant depth and on a beach. Application of the model to cnoidal wave breaking in the surf zone shows that the model results are in good agreement with analytical solution and experimental data. From the present model results, it can be seen that the turbulent eddy viscosity increases from the bottom to the water surface in surf zone. In the eddy viscosity curve, there is a
The spherical pinch experiment: Generation of laser driven converging blast wave
International Nuclear Information System (INIS)
The interaction of laser radiation with matter has been studied extensively due to its wide variety of applications. Laser fluid interaction implies remarkable phenomena such as energy deposition, cavity formation, bubble formation etc. On the other hand optical break-down of the gas under the action of intense laser pulse precede many interesting processes like plasma expansion, formation of shock wave, detachment of shock wave from the plasma and others. In the latter case, shock wave propagation assumes central importance in plasma fusion scheme like Spherical Pinch. In Spherical Pinch the preformed hot plasma produced at the center of a spherical vessel is confined and compressed by imploding shock wave fired from the cell periphery, in such a way, in principle, that the plasma breakeven condition may be satisfied. With out laser facility of energy up to 20 Joules (7 ns FWHM) at 1.06 μm wavelength in each of the two beams, the authors are performing some experiments on converging motion of the shock wave launched from the periphery of the spherical glass cell. These laser beams from axially opposite directions irradiate a glass cell over a wide solid angle in such a way so that quasi-spherically symmetric convergent shock wave is generated from the evaporation of aluminium layer coated over the internal surface of the glass cell. The authors plan to present the experimental results on the temporal evolution of inwardly converging shock wave consistently followed by frame camera Imacon 792/LC and interference holographic technique, and its comparison with the theoretical results. Apart from this, some experimental results on the dynamics of converging shock wave generated in the same way in water would also be presented
Simulation Of Attenuation Regularity Of Detonation Wave In Pmma
Lan, Wei; Xiaomian, Hu
2012-03-01
Polymethyl methacrylate (PMMA) is often used as clapboard or protective medium in the parameter measurement of detonation wave propagation. Theoretical and experimental researches show that the pressure of shock wave in condensed material has the regularity of exponential attenuation with the distance of propagation. Simulation of detonation produced shock wave propagation in PMMA was conducted using a two-dimensional Lagrangian computational fluid dynamics program, and results were compared with the experimental data. Different charge diameters and different angles between the direction of detonation wave propagation and the normal direction of confined boundary were considered during the calculation. Results show that the detonation produced shock wave propagation in PMMA accords with the exponential regularity of shock wave attenuation in condensed material, and several factors are relevant to the attenuation coefficient, such as charge diameter and interface angle.
Numerical Simulation of Wave Loading on a SPAR Platform
Kleefsman, K.M.T.; Veldman, A.E.P.
2003-01-01
This paper describes a study of simulation of wave loading on a SPAR platform. The method used for the simulations is based on the Navier-Stokes equations, discretised using a finite volume method. The free-surface displacement is described by the VOF-method combined with a local height function. Th
Yoganandan, Narayan; Pintar, Frank A; Schlick, Michael; Humm, John R; Voo, Liming; Merkle, Andrew; Kleinberger, Michael
2015-09-18
The objective of the study was to develop a simple device, Vertical accelerator (Vertac), to apply vertical impact loads to Post Mortem Human Subject (PMHS) or dummy surrogates because injuries sustained in military conflicts are associated with this vector; example, under-body blasts from explosive devices/events. The two-part mechanically controlled device consisted of load-application and load-receiving sections connected by a lever arm. The former section incorporated a falling weight to impact one end of the lever arm inducing a reaction at the other/load-receiving end. The "launch-plate" on this end of the arm applied the vertical impact load/acceleration pulse under different initial conditions to biological/physical surrogates, attached to second section. It is possible to induce different acceleration pulses by using varying energy absorbing materials and controlling drop height and weight. The second section of Vertac had the flexibility to accommodate different body regions for vertical loading experiments. The device is simple and inexpensive. It has the ability to control pulses and flexibility to accommodate different sub-systems/components of human surrogates. It has the capability to incorporate preloads and military personal protective equipment (e.g., combat helmet). It can simulate vehicle roofs. The device allows for intermittent specimen evaluations (x-ray and palpation, without changing specimen alignment). The two free but interconnected sections can be used to advance safety to military personnel. Examples demonstrating feasibilities of the Vertac device to apply vertical impact accelerations using PMHS head-neck preparations with helmet and booted Hybrid III dummy lower leg preparations under in-contact and launch-type impact experiments are presented. PMID:26159057
The synchrotron self-Compton spectrum of relativistic blast waves at large Y
Lemoine, Martin
2015-11-01
Recent analyses of multiwavelength light curves of gamma-ray bursts afterglows point to values of the magnetic turbulence well below the canonical ˜1 per cent of equipartition, in agreement with theoretical expectations of a microturbulence generated in the shock precursor, which then decays downstream of the shock front through collisionless damping. As a direct consequence, the Compton parameter Y can take large values in the blast. In the presence of decaying microturbulence and/or as a result of the Klein-Nishina suppression of inverse Compton cooling, the Y parameter carries a non-trivial dependence on the electron Lorentz factor, which modifies the spectral shape of the synchrotron and inverse Compton components. This paper provides detailed calculations of this synchrotron self-Compton spectrum in this large Y regime, accounting for the possibility of decaying microturbulence. It calculates the expected temporal and spectral indices α and β customarily defined by F_ν ∝ t_obs^{-α }ν ^{-β } in various spectral domains. This paper also makes predictions for the very high energy photon flux; in particular, it shows that the large Y regime would imply a detection rate of gamma-ray bursts at >10 GeV several times larger than currently anticipated.
Numerical simulations of waves in a magnetically structured atmosphere
Espinola, Thomas Peter
A physical model for simulating waves in a stellar atmosphere was developed from a combination of basic fluid mechanics, plasma physics, and electrodynamics. The model was three dimensional and included the effects of gravity, magnetic fields, and viscosity. An algorithm was developed to numerically implement this model. The resulting program used an explicit time integration scheme based on Runge-Kutta and a combination of finite difference and spectral methods to evaluate the spatial derivatives. A number of numerical boundary conditions were developed—the most successful used a modified Sommerfeld radiation condition. The program was written and coded in Fortran on a Vax computer. Additional routines were written to evaluate the required fast fourier transforms and to graph and display the data. The program was tested on a large number of one and two dimensional problems for which the solutions were known. These problems included acoustic waves, Alfvén waves, magnetoacoustic waves, shocks, rarefactions, and contact discontinuities. The numerical results agreed with the analytic solutions of the physical problems to within the precision requested of the simulation. The program proved to be stable and robust for all the problems attempted. This program was then used to simulate three problems for which analytic solutions are not known. All three simulations concerned the propagation of waves in magnetically structured atmospheres and may be applied to outstanding problems in solar physics. First, the interactions of non-linear waves and a flux slab were studied. From the result it is apparent that sources of shocks and rarefactions, such as the solar convection zone, do not concentrate the magnetic field in flux sheaths. Next I used the program to simulate the interaction of non-linear waves with a flux tube. The results suggest that the magnetic fields in flux tubes are also not concentrated by pairs of passing shocks and rarefactions; however, a complete
Numerical simulation of 3D breaking waves
Fraunie, Philippe; Golay, Frederic
2015-04-01
Numerical methods dealing with two phase flows basically can be classified in two ways : the "interface tracking" methods when the two phases are resolved separately including boundary conditions fixed at the interface and the "interface capturing" methods when a single flow is considered with variable density. Physical and numerical properties of the two approaches are discussed, based on some numerical experiments performed concerning 3D breaking waves. Acknowledgements : This research was supported by the Modtercom program of Region PACA.
Full-wave simulations of lower hybrid wave propagation in the EAST tokamak
Bonoli, P. T.; Lee, J. P.; Shiraiwa, S.; Wright, J. C.; Ding, B.; Yang, C.
2015-11-01
Studies of lower hybrid (LH) wave propagation have been conducted in the EAST tokamak where electron Landau damping (ELD) of the wave is typically weak, resulting in multiple passes of the wave front prior to its being absorbed in the plasma core. Under these conditions it is interesting to investigate full-wave effects that can become important at the plasma cut-off where the wave is reflected at the edge, as well as full-wave effects such as caustic formation in the core. High fidelity LH full-wave simulations were performed for EAST using the TORLH field solver. These simulations used sufficient poloidal mode resolution to resolve the perpendicular wavelengths associated with electron Landau damping of the LH wave at the plasma periphery, thus achieving fully converged electric field solutions at all radii of the plasma. Comparison of these results with ray tracing simulations will also be presented. Work supported by the US DOE under Contract No. DE-SC0010492 and DE-FC02-01ER54648.
Blast Valve Design and Related Studies : A Review
Sharma, P. K.; Patel, B. P.; Harbans Lal
2016-01-01
The protective structures required for performing critical operations are vulnerable to the blast and shock loads of advanced weapons. A blast valve is an important component of such structures for ventilation during normal conditions and for protection from blast/ shock during explosion. In this paper, various aspects of blast valve design and related studies are briefly reviewed. The concept and effects of blast wave, blast impact, numerical modelling and deformation of circular plate (one ...
Numerical Simulation of Wave Interaction with Moving Net Structures
DEFF Research Database (Denmark)
Chen, Hao; Christensen, Erik Damgaard
2015-01-01
Fluid structure interaction is an important issue in designof many engineering systems including offshore fish cages. As a first step to develop a coupled CFD/FEM model, in the present study a moving porous media model has been developed in the open source library Open FOAM. The net structure was...... described as a sheet of porous media with prescribed rigid body motion and mesh motion was incorporated to conform the motion of the net. Free surface wave generation and absorption framework was also introduced to simulate wave interaction with moving net structures. The results showed that mesh motion...... solver was coupled with free surface wave generation and absorption framework and porous media model flawlessly, and the deformed mesh remained acceptable. It was concluded that Laplace mesh motionsolver with inversed quadratic diffusivity model was an appropriate option for simulating wave interaction...
Nonlinear particle simulation of ion cyclotron waves in toroidal geometry
Energy Technology Data Exchange (ETDEWEB)
Kuley, A., E-mail: akuley@uci.edu; Lin, Z. [Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Bao, J. [Fusion Simulation Center, Peking University, Beijing (China); Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Wei, X. S.; Xiao, Y. [Institute of Fusion Theory and Simulation, Zhejiang University, Hangzhou (China)
2015-12-10
Global particle simulation model has been developed in this work to provide a first-principles tool for studying the nonlinear interactions of radio frequency (RF) waves with plasmas in tokamak. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation with realistic electron-to-ion mass ratio. Boris push scheme for the ion motion has been developed in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron and ion Bernstein waves in global gyrokinetic toroidal code (GTC). The nonlinear simulation capability is applied to study the parametric decay instability of a pump wave into an ion Bernstein wave side band and a low frequency ion cyclotron quasi mode.
Underwater blast wave pressure sensor based on polymer film fiber Fabry-Perot cavity.
Wang, Junjie; Wang, Meng; Xu, Jian; Peng, Li; Yang, Minghong; Xia, Minghe; Jiang, Desheng
2014-10-01
This paper describes the theoretical and experimental aspects of an optical underwater shock wave sensor based on a polymer film optical fiber Fabry-Perot cavity manufactured by vacuum deposition technology. The transduction mechanism of the sensor involves a normally incident acoustic stress wave that changes the thickness of the polymer film, thereby giving rise to a phase shift. This transient interferometric phase is interrogated by a three-phase-step algorithm. Theoretically, the sensor-acoustic-field interaction principle is analyzed, and the phase modulation sensitivity based on the theory of waves in the layered media is calculated. Experimentally, a static calibration test and a dynamic calibration test are conducted using a piston-type pressure calibration machine and a focusing-type electromagnetic shock wave. Results indicate that the repeatability, hysteresis, nonlinearity, and the overall measurement accuracy of the sensor within the full pressure range of 55 MPa are 1.82%, 0.86%, 1.81%, and 4.49%, respectively. The dynamic response time is less than 0.767 μs. Finally, three aspects that need further study for practical use are pointed out. PMID:25322237
Seismic Wave Simulation for Complex Rheologies on Unstructured Meshes
de la Puente, Josep
2008-01-01
The possibility of using accurate numerical methods to simulate seismic wavefields on unstructured meshes for complex rheologies is explored. In particular, the Discontinuous Galerkin (DG) finite element method for seismic wave propagation is extended to the rheological types of viscoelasticity, anisotropy and poroelasticity. First is presented the DG method for the elastic isotropic case on tetrahedral unstructured meshes. Then an extension to viscoelastic wave propagation based upon a Gener...
Simulation of Fully Nonlinear 3-D Numerical Wave Tank
Institute of Scientific and Technical Information of China (English)
张晓兔; 滕斌; 宁德志
2004-01-01
A fully nonlinear numerical wave tank (NWT) has been simulated by use of a three-dimensional higher order boundary element method (HOBEM) in the time domain. Within the frame of potential flow and the adoption of simply Rankine source, the resulting boundary integral equation is repeatedly solved at each time step and the fully nonlinear free surface boundary conditions are integrated with time to update its position and boundary values. A smooth technique is also adopted in order to eliminate the possible saw-tooth numerical instabilities. The incident wave at the uptank is given as theoretical wave in this paper. The outgoing waves are absorbed inside a damping zone by spatially varying artificial damping on the free surface at the wave tank end. The numerical results show that the NWT developed by these approaches has a high accuracy and good numerical stability.
International Nuclear Information System (INIS)
The results of sintered iron and of blast-furnace slag examination obtained by X-ray fluorescent analyses of energy and of wave dispersion are compared. They show that the methods are comparable for such elements as Ca and Fe, whereas for Mn (in sinter) the X-ray fluorescent analysis of wave dispersion is less precise. (author)
Effects of Primary Blast Overpressure on Retina and Optic Tract in Rats
DeMar, James; Sharrow, Keith; Hill, Miya; Berman, Jonathan; Oliver, Thomas; Long, Joseph
2016-01-01
Blast has been the leading cause of injury, particularly traumatic brain injury and visual system injury, in combat operations in Iraq and Afghanistan. We determined the effect of shock tube-generated primary blast on retinal electrophysiology and on retinal and brain optic tract histopathology in a rat model. The amplitude of a- and b-waves on the electroretinogram (ERG) for both right and left eyes were measured prior to a battlefield simulation Friedlander-type blast wave and on 1, 7, and 14 days thereafter. Histopathologic findings of the right and left retina and the right and left optic tracts (2.8 mm postoptic chiasm) were evaluated 14 days after the blast. For two experiments in which the right eye was oriented to the blast, the amplitude of ERG a- and b-waves at 7 days post blast on the right side but not on the left side was diminished compared to that of sham animals (P = 0.005–0.01) Histopathologic injury scores at 14 days post blast for the right retina but not the left retina were higher than for sham animals (P = 0.01), and histopathologic injury scores at 14 days for both optic tracts were markedly higher than for shams (P blast wave, comparable to that causing human injury, produced injury to the retina as determined by ERG and histopathology, and to both postchiasmatic optic tracts as determined by histopathology. This model may be useful for analyzing the effect of therapeutic interventions on retinal damage due to primary blast waves. PMID:27199884
Effects of Primary Blast Overpressure on Retina and Optic Tract in Rats.
DeMar, James; Sharrow, Keith; Hill, Miya; Berman, Jonathan; Oliver, Thomas; Long, Joseph
2016-01-01
Blast has been the leading cause of injury, particularly traumatic brain injury and visual system injury, in combat operations in Iraq and Afghanistan. We determined the effect of shock tube-generated primary blast on retinal electrophysiology and on retinal and brain optic tract histopathology in a rat model. The amplitude of a- and b-waves on the electroretinogram (ERG) for both right and left eyes were measured prior to a battlefield simulation Friedlander-type blast wave and on 1, 7, and 14 days thereafter. Histopathologic findings of the right and left retina and the right and left optic tracts (2.8 mm postoptic chiasm) were evaluated 14 days after the blast. For two experiments in which the right eye was oriented to the blast, the amplitude of ERG a- and b-waves at 7 days post blast on the right side but not on the left side was diminished compared to that of sham animals (P = 0.005-0.01) Histopathologic injury scores at 14 days post blast for the right retina but not the left retina were higher than for sham animals (P = 0.01), and histopathologic injury scores at 14 days for both optic tracts were markedly higher than for shams (P blast wave, comparable to that causing human injury, produced injury to the retina as determined by ERG and histopathology, and to both postchiasmatic optic tracts as determined by histopathology. This model may be useful for analyzing the effect of therapeutic interventions on retinal damage due to primary blast waves. PMID:27199884
A Coupled Atmospheric and Wave Modeling System for Storm Simulations
DEFF Research Database (Denmark)
Du, Jianting; Larsén, Xiaoli Guo; Bolanos, R.
2015-01-01
This study aims at improving the simulation of wind and waves during storms in connection with wind turbine design and operations in coastal areas. For this particular purpose, we investigated the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System which couples the Weather...... for the coastal condition. With the current model setup, using high spatial resolution gives better results for strong winds both for the open ocean and coastal sites. The signicant wave height (Hm0) is very sensitive to the model resolution and bathymetry data for the coastal zone. In addition, using...
A Numerical Simulation of a Plunging Breaking Wave
Adams, Paul; Stephens, Mike; Brucker, Kyle A; O'Shea, Thomas; Dommermuth, Douglas
2009-01-01
This article describes the fluid dynamics video, "A Numerical Simulation of a Plunging Breaking Wave", which was submitted to the gallery of fluid motion at the 2009 APS/DFD conference. The simulation was of a deep-water plunging breaking wave. It was a two-phase calculation which used a Volume of Fluid (VOF) method to simulate the interface between the two immiscible fluids. Surface tension and viscous effects were not considered. The initial wave was generated by applying a spatio-temporal pressure forcing on the free surface. The video shows the 50% isocontour of the volume fraction from several different perspectives. Significant air entrainment is observed as well as the presence of stream-wise vortex structures.
Nonlinear time-dependent simulation of helix traveling wave tubes
International Nuclear Information System (INIS)
A one-dimensional nonlinear time-dependent theory for helix traveling wave tubes is studied. A generalized electromagnetic field is applied to the expression of the radio frequency field. To simulate the variations of the high frequency structure, such as the pitch taper and the effect of harmonics, the spatial average over a wavelength is substituted by a time average over a wave period in the equation of the radio frequency field. Under this assumption, the space charge field of the electron beam can be treated by a space charge wave model along with the space charge coefficient. The effects of the radio frequency and the space charge fields on the electrons are presented by the equations of the electron energy and the electron phase. The time-dependent simulation is compared with the frequency-domain simulation for a helix TWT, which validates the availability of this theory. (interdisciplinary physics and related areas of science and technology)
Internal waves generated by unsteady impulsive forcing - numerical simulations
Paoletti, Matthew; Shipley, Kara; Brandt, Alan
2014-11-01
Numerical simulations of the generation of internal waves by an unsteady impulse are presented. While extensive work has examined the generation of internal waves by steady flow, such as winds over mountains, or periodic flow, an example being tidal flow over bathymetry, internal waves can also be generated by transient events like those produced by local instabilities. The studies presented here focus on the generation of internal waves by the release of a patch of miscible fluid of constant density into a stably stratified water column. The fluid descends owing to its initial momentum, spreads in the lateral direction, and vertically displaces the isopycnals, leading to the generation of internal waves. The transfer of energy from the impulse to the internal wave field is characterized by the energy flux of the radiated internal waves. While the impulse is initially axisymmetric, the effects of the three-dimensional nature of the turbulent evolution are examined by comparing the results of two-dimensional and three-dimensional numerical simulations. Supported by the Office of Navel Research.
A Simulation Study of TRT Control System of the Blast Furnace%高炉TRT控制系统模型仿真研究
Institute of Scientific and Technical Information of China (English)
刘志刚
2014-01-01
The author of this paper constructs a mathematical model of blast furnace top pressure TRT system based on the blast furnace process,the factors affecting the stability of the top pres-sure of the blast furnace and the pipeline analysis of the blast furnace TRT system.Matlab is em-ployed to carry out simulation to test the mathematical model of the adj ustment system of blast furnace top pressure with a static blade,constituting a theoretical basis for further improve the stability of the blast furnace top pressure.%根据高炉TRT工艺和影响高炉顶压稳定的因素，以及对高炉 TRT系统的管路分析，建立高炉顶压TRT系统数学模型。应用Matlab 对静叶单独调节高炉顶压时系统的数学模型进行仿真验证，为进一步改善高炉顶压的稳定提供理论依据。
Dambov, Risto; Karanakova Stefanovska, Radmila; Dambov, Ilija
2015-01-01
In blasting performance for any purpose and in any location to implement these safeguards is necessary first to determine (calculated) safety distances in terms of the effect of the explosion from some explosive quantity. Calculation of distance safety in blasting performance are refers to: calculation of safety distances from the influence of air - shock waves, calculation of safety distances (zones) of spraying pieces (fragments action) and calculation of safety distances in action of seis...
Non-linear collisionless damping of Weibel turbulence in relativistic blast waves
Lemoine, Martin
2014-01-01
The Weibel/filamentation instability is known to play a key role in the physics of weakly magnetized collisionless shock waves. From the point of view of high energy astrophysics, this instability also plays a crucial role because its development in the shock precursor populates the downstream with a small-scale magneto-static turbulence which shapes the acceleration and radiative processes of suprathermal particles. The present work discusses the physics of the dissipation of this Weibel-generated turbulence downstream of relativistic collisionless shock waves. It calculates explicitly the first-order non-linear terms associated to the diffusive nature of the particle trajectories. These corrections are found to systematically increase the damping rate, assuming that the scattering length remains larger than the coherence length of the magnetic fluctuations. The relevance of such corrections is discussed in a broader astrophysical perspective, in particular regarding the physics of the external relativistic ...
VictorPrima; StanislavI.Svetlov; DanielKirk; KennethCurley; VictorSerebruany
2012-01-01
A number of experimental models of blast brain injury have been implemented in rodents and larger animals. However, the variety of blast sources and the complexity of blast wave biophysics have made data on injury mechanisms and biomarkers difficult to analyze and compare. Recently, we showed the importance of rat position towards blast generated by an external shock tube. In this study, we further characterized blast producing moderate TBI and defined ‘composite’ blast and primary blast...
Reliable Damping of Free Surface Waves in Numerical Simulations
Peric, Robinson
2015-01-01
This paper generalizes existing approaches for free-surface wave damping via momentum sinks for flow simulations based on the Navier-Stokes equations. It is shown in 2D flow simulations that, to obtain reliable wave damping, the coefficients in the damping functions must be adjusted to the wave parameters. A scaling law for selecting these damping coefficients is presented, which enables similarity of the damping in model- and full-scale. The influence of the thickness of the damping layer, the wave steepness, the mesh fineness and the choice of the damping coefficients are examined. An efficient approach for estimating the optimal damping setup is presented. Results of 3D ship resistance computations show that the scaling laws apply to such simulations as well, so the damping coefficients should be adjusted for every simulation to ensure convergence of the solution in both model and full scale. Finally, practical recommendations for the setup of reliable damping in flow simulations with regular and irregular...
Analysis of structural response under blast loads using the coupled SPH-FEM approach
Institute of Scientific and Technical Information of China (English)
Jun-xiang XU; Xi-la LIU
2008-01-01
A numerical model using the coupled smoothed particle hydrodynamics-finite element method(SPH-FEM)approach is presented for analysis of structures under blast loads.The analyses on two numerical cases,one for free field explosive and the other for structural response under blast loads,are performed to model the whole processes from the propagation of the pressure wave to the response of structures.Based on the simulation,it is concluded that this model can be used for reasonably accurte explosive analysis of structures.The resulting information would be valuable for protecting structures under blast loads.
A Phased Array Approach to Rock Blasting
Energy Technology Data Exchange (ETDEWEB)
Leslie Gertsch; Jason Baird
2006-07-01
A series of laboratory-scale simultaneous two-hole shots was performed in a rock simulant (mortar) to record the shock wave interference patterns produced in the material. The purpose of the project as a whole was to evaluate the usefulness of phased array techniques of blast design, using new high-precision delay technology. Despite high-speed photography, however, we were unable to detect the passage of the shock waves through the samples to determine how well they matched the expected interaction geometry. The follow-up mine-scale tests were therefore not conducted. Nevertheless, pattern analysis of the vectors that would be formed by positive interference of the shockwaves from multiple charges in an ideal continuous, homogeneous, isotropic medium indicate the potential for powerful control of blast design, given precise characterization of the target rock mass.
Characterization of blasts in medium and low thermosphere from infrasonic wave observations
International Nuclear Information System (INIS)
The International Monitoring System (IMS) designed to monitor compliance with the Comprehensive Nuclear Test-Ban Treaty (CTBT) uses four complementary verification methods: seismic, hydro-acoustic, radionuclide and micro-barometric stations spanning the entire globe. Micro-barometric stations record continuously infrasonic waves in the frequency band 0.02-4 Hz. These waves propagate at long-ranges through atmospheric ducts resulting from the natural stratification of atmospheric properties (temperature, density, winds,...) and represent a valuable information to understand atmospheric dynamic until the lower thermosphere. In this thesis, we seek to determine the possible contribution of infra-sound observations for improving current atmospheric specifications. We describe the atmospheric media and its circulation mechanisms as well as the conventional observations used in the development of atmospheric models. A description of the interaction between infrasonic waves and the atmosphere help to understand the interest of micro-barometric measurement compared with conventional observations. To highlight this potential we develop an inverse algorithm in order to estimate atmospheric parameters from infrasonic observations. The forward problem is handled by a ray-tracing algorithm. First-order perturbation equation resulting from perturbation of atmospheric properties, and especially wind parameters, are developed and numerically validated. We then analyse the inverse problem through several numerical experiments in order to show the capabilities and limitations of our algorithm. Results show the suitability of our approach and indicate that infrasonic observations can significantly improve current atmospheric specification at the altitudes of acoustic energy refraction, i.e. around 50 km and between 100 and 120 km. (author)
Interaction of a strong blast wave with a free surface. [at ocean surface
Falade, A.; Holt, M.
1978-01-01
When a point source explosion is initiated at the ocean surface, the shock propagated into the water is reflected at the surface as a centered expansion wave. The solution in the neighborhood of the interaction point is obtained by writing the equations of motion in the appropriate similarity variables and then changing the independent variables to polar coordinates based at the interaction point. From the zero-order solution of the resulting equations the slopes of boundaries at the interaction point are obtained. A first-order perturbation of this solution provides more accurate representation of the flow variables and the curvature of the shock surface near the interaction point.
Characteristics of gravity waves generated in a baroclinic instability simulation
Directory of Open Access Journals (Sweden)
Y.-H. Kim
2015-11-01
Full Text Available An idealized baroclinic instability case is simulated using a ~ 10 km resolution global model to investigate the characteristics of gravity waves (GWs generated in the baroclinic life cycle. Three groups of GWs (W1–W3 appear around the high-latitude surface trough at the mature stage of the baroclinic wave. They have horizontal and vertical wavelengths of 40–400 and 2.9–9.8 km, respectively, in the upper troposphere. The two-dimensional phase-velocity spectrum of the waves is arc-shaped with a peak at 17 m s−1 eastward, which is difficult for the waves to propagate upward through the tropospheric westerly jet. At the breaking stage of the baroclinic wave, a midlatitude surface low is isolated from the higher-latitude trough, and two groups of quasi-stationary GWs (W4 and W5 appear near the surface low. These waves have horizontal and vertical wavelengths of 60–400 and 4.9–14 km, respectively, and are able to propagate vertically for long distances. The generation mechanism of the simulated GWs is discussed.
BOMB BLAST: PATTERN AND NATURE OF INJURIES
Directory of Open Access Journals (Sweden)
Brahmaji Master
2015-01-01
Full Text Available Bomb blast cause injury on large groups of people by multiple mechanisms. Bomb blast injuries differ from the conventional description of trauma complexity. Primary injuries are caused by blast wave and over pressure. Secondary injuries are caused by flyin g debris and cause shrapnel wounds. Tertiary injuries are caused by blast wind due to forceful impact and quaternary injuries are caused by other vectors like heat, radiation etc. Combined injuries, especially blast and burn injury or blast and crush injur y, are common during an explosive event. Knowledge about nature of injuries is essential for medicolegal and postmortem reports.
Full-wave Electromagnetic Field Simulations of Lower Hybrid Waves in Tokamaks
International Nuclear Information System (INIS)
The most common method for treating wave propagation in tokamaks in the lower hybrid range of frequencies (LHRF) has been toroidal ray tracing, owing to the short wavelengths (relative to the system size) found in this regime. Although this technique provides an accurate description of 2D and 3D plasma inhomogeneity effects on wave propagation, the approach neglects important effects related to focusing, diffraction, and finite extent of the RF launcher. Also, the method breaks down at plasma cutoffs and caustics. Recent adaptation of full-wave electromagnetic field solvers to massively parallel computers has made it possible to accurately resolve wave phenomena in the LHRF. One such solver, the TORIC code, has been modified to simulate LH waves by implementing boundary conditions appropriate for coupling the fast electromagnetic and the slow electrostatic waves in the LHRF. In this frequency regime the plasma conductivity operator can be formulated in the limits of unmagnetized ions and strongly magnetized electrons, resulting in a relatively simple and explicit form. Simulations have been done for parameters typical of the planned LHRF experiments on Alcator C-Mod, demonstrating fully resolved fast and slow LH wave fields using a Maxwellian non-relativistic plasma dielectric. Significant spectral broadening of the injected wave spectrum and focusing of the wave fields have been found, especially at caustic surfaces. Comparisons with toroidal ray tracing have also been done and differences between the approaches have been found, especially for cases where wave caustics form. The possible role of this diffraction-induced spectral broadening in filling the spectral gap in LH heating and current drive will be discussed
Continuous wave approach for simulating Ferromagnetic Resonance in nanosized elements
Wagner, K; Farle, M
2015-01-01
We present a numerical approach to simulate the Ferromagnetic Resonance (FMR) of micron and nanosized magnetic elements by a micromagnetic finite di?erence method. In addition to a static magnetic field a linearly polarized oscillating magnetic field is utilized to excite and analyze the spin wave excitations observed by Ferromagnetic Resonance in the space- and time-domain. Our continuous wave approach (CW) provides an alternative to the common simulation method, which uses a pulsed excitation of the magnetic system. It directly models conventional FMR-experiments and permits the determination of the real and imaginary part of the complex dynamic susceptibility without the need of post-processing. Furthermore not only the resonance fields, but also linewidths, ellipticity, phase relations and relative intensities of the excited spin wave modes in a spectrum can be determined and compared to experimental data. The magnetic responses can be plotted as a function of spatial dimensions yielding a detailed visual...
Numerical Simulation of Cylindrical Solitary Waves in Periodic Media
Quezada de Luna, Manuel
2013-07-14
We study the behavior of nonlinear waves in a two-dimensional medium with density and stress relation that vary periodically in space. Efficient approximate Riemann solvers are developed for the corresponding variable-coefficient first-order hyperbolic system. We present direct numerical simulations of this multiscale problem, focused on the propagation of a single localized perturbation in media with strongly varying impedance. For the conditions studied, we find little evidence of shock formation. Instead, solutions consist primarily of solitary waves. These solitary waves are observed to be stable over long times and to interact in a manner approximately like solitons. The system considered has no dispersive terms; these solitary waves arise due to the material heterogeneity, which leads to strong reflections and effective dispersion.
Numerical simulations of Klein-Gordon solitary-wave interactions
International Nuclear Information System (INIS)
Solitons of a non-linear Klein-Gordon equation are studied numerically using a cubic B-spline finite-element method. Test results indicate that, when solitary waves interact, the final state obtained depends on their relative velocity.The simulations confirm existing observations and produce new results. The numerical algorithm developed is efficient with an undemanding stability criterion
Design and Control of Full Scale Wave Energy Simulator System
DEFF Research Database (Denmark)
Pedersen, Henrik C.; Hansen, Anders Hedegaard; Hansen, Rico Hjerm;
2012-01-01
-float interaction, the inertia of the float and the added inertia of the water. Based on this simulation results are presented, which show that the system is able to emulate waves more than three meters in height and with a resulting force of more than 800 kN, while interacting with a general PTO-system....
Oesterle, Michael G.
2009-01-01
Loads generated in explosions that result from terrorist attacks and industrial accidents create devastating hazards for buildings and their occupants. The objective of this dissertation is to develop design guidelines and methodologies for protective/hardening strategies used to mitigate blast hazards in reinforced concrete and concrete masonry walls. Commonly, guidelines and methodologies are developed from experimental data. Field testing with live explosive is a reliable experimental meth...
International Nuclear Information System (INIS)
The results of two works on the topic 'propagation and effect of nuclear pressure waves in the ground and in rocks' are given in this report. The first part deals with fundamentals and preliminary results of a numerical computer programme to calculate the spherically symmetrical pressure wave propagation in viscoelastic and elastoplastic media. The second part deals with the application of existing programmes to calculate the building stress in the subseismic region of air-blast induced ground pressure waves. (orig./LH)
Institute of Scientific and Technical Information of China (English)
张宗良; 孟嘉乐; 郭占成
2015-01-01
为研究不同氧气高炉操作流程及操作参数对高炉内部过程产生的影响，预测氧气高炉流程各参数的变化规律，基于多流体理论、冶金传输原理、冶金反应动力学与热力学理论以及计算流体力学建立了普通高炉多流体模型，并在此基础上修改边界条件及内部相关参数，建立氧气高炉多流体数学模型。通过建立的模型分别对普通高炉和气化炉氧气高炉（GF-FOBF）流程中的氧气高炉进行了模拟计算，得到两种工艺流程下高炉内温度场、浓度场和速度场等典型参数的分布情况。通过对计算结果的对比，分析了氧气高炉操作条件下炉内状态的主要特征和相对于普通高炉发生的变化，发现氧气高炉内部速度场、温度场均发生变化，特别是气相组分的均匀分布问题明显。本模型可为氧气高炉流程试验及流程开发提供参考。%To study the effects of different oxygen blast furnace operating procedures and their operating parameters on blast furnace process,and to predict the variation of each parameter of oxygen blast furnace process,a multi-fluid blast furnace model is built based on multi-fluid theory,metallurgical transport theory,metallurgical thermodynamics and kinetics,and computational fluid dynamics.By modifying its boundary conditions and internal parameters,the establishment of multi-fluid model of oxygen blast furnace is achieved.Numerical simulation of the normal blast furnace and gasification furnace-oxygen blast furnace (GF-FOBF)is carried out with this model and the fields of typical parameters,such as temperature field,are obtained.By comparing the calculation results,the main features of the furnace under oxygen blast furnace operating conditions and changes relative to the traditional blast furnace are analyzed.It can be found that the oxygen blast furnace internal velocity field and temperature field change,especially the distribution of gas
Nakagawa, A.; Ohtani, K.; Arafune, T.; Washio, T.; Iwasaki, M.; Endo, T.; Ogawa, Y.; Kumabe, T.; Takayama, K.; Tominaga, T.
1. Investigation of shock wave-induced phenomenon: blast-induced traumatic brain injury Blast wave (BW) is generated by explosion and is comprised of lead shock wave (SE) followed by subsequent supersonic flow.
Institute of Scientific and Technical Information of China (English)
HU Qiuyun; YU Haitao; YUAN Yong
2008-01-01
In order to design and retrofit a subway station to resist an internal blast,the distribution of blast loading and its effects on structures should be investigated firstly.In this paper,the behavior of a typical subway station subjected to different internal blast Ioadings was analyzed.It briefly introduced the geometric characteristics and material constitutive model of an existing two-layer and three-span frame subway station.Then three cases of different explosive charges were considered to analyze the dynamic responses of the structure.Finally,the maximum principal stress,displacement and velocity of the columns in the three cases were obtained and discussed.It concluded that the responses of the columns are sensitive to the charge of explosive and the distance from the detonation.It's also found that the stairs between the two layers have significant effects on the distribution of the maximum principal stress of the columns in the upper layer.The explicit dynamic nonlinear finite element software-ANSYS/LS-DYNA was used in this study.
Ion acoustic wave collapse via two-ion wave decay: 2D Vlasov simulation and theory
Chapman, Thomas; Berger, Richard; Banks, Jeffrey; Brunner, Stephan
2015-11-01
The decay of ion acoustic waves (IAWs) via two-ion wave decay may transfer energy from the electric field of the IAWs to the particles, resulting in a significant heating of resonant particles. This process has previously been shown in numerical simulations to decrease the plasma reflectivity due to stimulated Brillouin scattering. Two-ion wave decay is a fundamental property of ion acoustic waves that occurs over most if not all of the parameter space of relevance to inertial confinement fusion experiments, and can lead to a sudden collapse of IAWs. The treatment of all species kinetically, and in particular the electrons, is required to describe the decay process correctly. We present fully kinetic 2D+2V Vlasov simulations of IAWs undergoing decay to a highly nonlinear turbulent state using the code LOKI. The scaling of the decay rate with characteristic plasma parameters and wave amplitude is shown. A new theory describing two-ion wave decay in 2D, that incorporates key kinetic properties of the electrons, is presented and used to explain quantitatively for the first time the observed decay of IAWs. Work performed under auspices of U.S. DoE by LLNL, Contract DE-AC52-07NA2734. Funded by LDRD 15-ERD-038 and supported by LLNL Grand Challenge allocation.
Compressive spectral method for the simulation of the water waves
Bayindir, Cihan
2015-01-01
In this paper an approach for decreasing the computational effort required for the spectral simulations of the water waves is introduced. Signals with majority of the components zero, are known as the sparse signals. Like majority of the signals in the nature it can be realized that water waves are sparse either in time or in the frequency domain. Using the sparsity property of the water waves in the time or in the frequency domain, the compressive sampling algorithm can be used as a tool for improving the performance of the spectral simulation of the water waves. The methodology offered in this paper depends on the idea of using a smaller number of spectral components compared to the classical spectral method with a high number of components. After performing the time integration with a smaller number of spectral components and using the compressive sampling technique, it is shown that the water wave field can be reconstructed with a significantly better efficiency compared to the classical spectral method w...
Exit from Inflation with a First-Order Phase Transition and a Gravitational Wave Blast
Ashoorioon, Amjad
2015-01-01
In double-field inflation, which exploits two scalar fields, one of the fields rolls slowly during inflation whereas the other field is trapped in a meta-stable vacuum. The nucleation rate from the false vacuum to the true one becomes substantial enough that triggers a first order phase transition and ends inflation. We revisit the question of first order phase transition in an "extended" model of hybrid inflation, realizing the double-field inflationary scenario, and correctly identify the parameter space that leads to a first order phase transition at the end of inflation. We compute the gravitational wave profile which is generated during this first order phase transition. Assuming instant reheating, the peak frequency falls in the $1$ GHz to $10$ GHz frequency band and the amplitude varies in the range $10^{-8}\\lesssim \\Omega_{\\rm GW} h^2 \\lesssim 10^{-11}$, depending on the value of the cosmological constant in the false vacuum. The signature could be observed by the planned Chongqing high frequency grav...
Hypersonic collision of a blast wave on a low-mass star
García Senz, Domingo; Serichol Augué, Núria; Bravo Guil, Eduardo
2001-01-01
When a neutron star is born as a result of the accretion-induced collapse (AIC) of a white dwarf, a small but signi_cant fraction of its mass can be simultaneously expelled at a velocity of around 104 kms −1. In this paper we study the collision between the gas ejected during the AIC of a white dwarf and a 0.3 M_ mainsequence star by using numerical simulation techniques. We found that, for a plausible combination of the orbital parameters and impact energy, the low-mass star is completely...
FEM Simulations of Leaky Lamb Wave in Ultrasonic Waveguide Sensor
International Nuclear Information System (INIS)
As the sodium coolant of a sodium-cooled fast reactor (SFR) is opaque to light, a conventional visual inspection cannot be used for carrying out an in-service inspection of the internal structures under a sodium level. An ultrasonic wave should be applied for an under-sodium viewing of the internal structures in a reactor vessel. Recently, a noble plate-type ultrasonic waveguide sensor has been developed for versatile applications in an under-sodium viewing application. The beam profile of a A0-mode leaky Lamb wave of the waveguide sensor affects the resolution of visualization image in under-sodium viewing. In the design and manufacture of the waveguide sensor, the finite element method (FEM) modeling and simulation of the propagation of a leaky Lamb wave is required for the estimation and optimization of the waveguide sensor design parameters. In the previous research, the simple 2D modeling and simulation of the waveguide sensor had been carried out. In this work, FEM simulation of the propagation and radiation of the leaky Lamb wave in the waveguide sensor is performed for the vertical and lateral beam profile analysis using the pseudo 3D modeling including the wedge
Simulation of seismic wave propagation for reconnaissance in machined tunnelling
Lambrecht, L.; Friederich, W.
2012-04-01
During machined tunnelling, there is a complex interaction chain of the involved components. For example, on one hand the machine influences the surrounding ground during excavation, on the other hand supporting measures are needed acting on the ground. Furthermore, the different soil conditions are influencing the wearing of tools, the speed of the excavation and the safety of the construction site. In order to get information about the ground along the tunnel track, one can use seismic imaging. To get a better understanding of seismic wave propagation for a tunnel environment, we want to perform numerical simulations. For that, we use the spectral element method (SEM) and the nodal discontinuous galerkin method (NDG). In both methods, elements are the basis to discretize the domain of interest for performing high order elastodynamic simulations. The SEM is a fast and widely used method but the biggest drawback is it's limitation to hexahedral elements. For complex heterogeneous models with a tunnel included, it is a better choice to use the NDG, which needs more computation time but can be adapted to tetrahedral elements. Using this technique, we can perform high resolution simulations of waves initialized by a single force acting either on the front face or the side face of the tunnel. The aim is to produce waves that travel mainly in the direction of the tunnel track and to get as much information as possible from the backscattered part of the wave field.
Xiao, Jianyuan; Liu, Jian; Qin, Hong; Yu, Zhi; Xiang, Nong
2015-01-01
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonli...
Numerical simulation for explosion wave propagation of combustible mixture gas
Institute of Scientific and Technical Information of China (English)
WANG Cheng; NING Jian-guo; MA Tian-bao
2008-01-01
A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code, Young's technique was employed to track the interface between the explosion products and air, and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct, for point initiation, the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall, multi-peak values appear on pressure-time curve, and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct, explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products, and indicate that the ignition model and multi-material interface treatment method are feasible.
Simulation of nonlinear surface waves generated by submarine landslides
Tjandra, S. S.; Pudjaprasetya, S. R.
2016-02-01
In this work, we study about nonlinear surface wave generated by submarine landslides. The landslide is modeled as a rigid block sliding down along a sloping bottom. We implement a numerical scheme based on the staggered finite volume method to simulate surface wave. We enhance the conservative scheme for nonlinear shallow water equation (SWE) to include this bottom motion. Our numerical result show a good agreement with previous results of the nonlinear boundary integral equation model (BIEM) by Lynett and Liu and central-upwind scheme by Kurganov and Petrova.
Advances in numerical simulation of nonlinear water waves
Ma, Qingwei
2014-01-01
Most of the Earth's surface is covered by water. Our everyday lives and activities are affected by water waves in oceans, such as the tsunami that occurred in the Indian Ocean on 26 December 2004. This indicates how important it is for us to fully understand water waves, in particular the very large ones. One way to do so is to perform numerical simulation based on the nonlinear theory. Considerable research advances have been made in this area over the past decade by developing various numerical methods and applying them to emerging problems; however, until now there has been no comprehensive
Wide-band slow-wave systems simulation and applications
Staras, Stanislovas
2012-01-01
The field of electromagnetics has seen considerable advances in recent years, based on the wide applications of numerical methods for investigating electromagnetic fields, microwaves, and other devices. Wide-Band Slow-Wave Systems: Simulation and Applications presents new technical solutions and research results for the analysis, synthesis, and design of slow-wave structures for modern electronic devices with super-wide pass-bands. It makes available, for the first time in English, significant research from the past 20 years that was previously published only in Russian and Lithuanian. The aut
Self-Destructing Spiral Waves: Global Simulations of a Spiral Wave Instability in Accretion Disks
Bae, Jaehan; Hartmann, Lee; Richard, Samuel
2016-01-01
We present results from a suite of three-dimensional global hydrodynamic simulations which show that spiral density waves propagating in circumstellar disks are unstable to the growth of a parametric instability that leads to break-down of the flow into turbulence. This spiral wave instability (SWI) arises from a resonant interaction between pairs of inertial waves, or inertial-gravity waves, and the background spiral wave. The development of the instability in the linear regime involves the growth of a broad spectrum of inertial modes, with growth rates on the order of the orbital time, and results in a nonlinear saturated state in which turbulent velocity perturbations are of a similar magnitude to those induced by the spiral wave. The turbulence induces angular momentum transport, and vertical mixing, at a rate that depends locally on the amplitude of the spiral wave (we obtain a stress parameter $\\alpha \\sim 5 \\times 10^{-4}$ in our reference model). The instability is found to operate in a wide-range of ...
Richter, Matthew Joseph
1995-01-01
Shock waves in molecular clouds heat, compress, accelerate, and chemically alter the gas they encounter. Despite their crucial role in determining the physical state of the dense interstellar medium and despite their making possible direct observations of H_2, molecular shocks are still poorly understood, as evidenced by the many discrepancies between theory and observations. In my dissertation, I use the supernova remnant IC 443 as a laboratory to test our understanding of shock -excited H_2 emission. By examining roughly 20 separate 2-4 μm Ha transitions, I find the non-uniform temperature structure essentially reproduces that found in Orion Peak 1, and so is consistent with the partially dissociating J-shock model presented by Brand and collaborators. Subsequent mid-infrared observations of the pure rotational S(2) transition at 12 mu m strengthens these conclusions. Velocity resolved line profiles of the strong 1-0 S(1) transition uncover a relationship between the remnant's large-scale geometry and the line profile's full-width at 10% intensity, centroid, and shape. The relationship contradicts any model requiring local bow geometries to explain broad H_2 line widths. Comparing the 1-0 S(1) data with similar observations of the 2-1 S(1) line, I demonstrate that the excitation temperature in the shocked gas depends primarily on position, not velocity. Taken together, the identical velocity extent of the 1-0 S(1) and the 2-1 S(1) lines and their upper state energy separation of E/k ~ 6000 K proves the H_2 -emitting gas reaches its full velocity dispersion prior to cooling below roughly 1500 K. Finally, I compare, with similar spatial and spectral resolution, H_2 and HCO^+ J = 1 - 0 and find evidence for temperature gradients as a result of both preshock density inhomogeneities and postshock cooling.
Exit from inflation with a first-order phase transition and a gravitational wave blast
Directory of Open Access Journals (Sweden)
Amjad Ashoorioon
2015-07-01
Full Text Available In double-field inflation, which exploits two scalar fields, one of the fields rolls slowly during inflation whereas the other field is trapped in a meta-stable vacuum. The nucleation rate from the false vacuum to the true one becomes substantial enough that triggers a first order phase transition and ends inflation. We revisit the question of first order phase transition in an “extended” model of hybrid inflation, realizing the double-field inflationary scenario, and correctly identify the parameter space that leads to a first order phase transition at the end of inflation. We compute the gravitational wave profile which is generated during this first order phase transition. Assuming instant reheating, the peak frequency falls in the 1 GHz to 10 GHz frequency band and the amplitude varies in the range 10−11≲ΩGWh2≲10−8, depending on the value of the cosmological constant in the false vacuum. For a narrow band of vacuum energies, the first order phase transition can happen after the end of inflation via the violation of slow-roll, with a peak frequency that varies from 1 THz to 100 THz. For smaller values of cosmological constant, even though inflation can end via slow-roll violation, the universe gets trapped in a false vacuum whose energy drives a second phase of eternal inflation. This range of vacuum energies do not lead to viable inflationary models, unless the value of the cosmological constant is compatible with the observed value, M∼10−3 eV.
Simulations of Magnetohydrodynamic Waves Driven by Photospheric Motions
Mumford, Stuart
2016-04-01
This thesis investigates the properties of various modelled photospheric motions as generation mechanisms for magnetohydrodynamic (MHD) waves in the low solar atmosphere. The solar atmosphere is heated to million-degree temperatures, yet there is no fully understood heating mechanism which can provide the ≈ 300 W/m^2) required to keep the quiet corona at its observed temperatures. MHD waves are one mechanism by which this energy could be provided to the upper solar atmosphere, however, these waves need to be excited. The excitation of these waves, in or below the photosphere is a complex interaction between the plasma and the magnetic field embedded within it. This thesis studies a model of a small-scale magnetic flux tube based upon a magnetic bright point (MBP). These features are very common in the photosphere and have been observed to be affected by the plasma motions. The modelled flux tube has a foot point magnetic field strength of 120 mT and a FWHM of 90 km, and is embedded in a realistic, stratified solar atmosphere based upon the VALIIIc model. To better understand the excitation of MHD waves in this type of magnetic structures, a selection of velocity profiles are implemented to excite waves. Initially a study of five different driving profiles was performed. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers which mimic observed torsional motions in the solar photosphere, along with vertical and horizontal drivers to mimic different motions caused by convection in the photosphere. The results are then analysed using a novel method for extracting the parallel, perpendicular and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated, to enable
Spectroscopic Characterization of Post-Cluster Argon Plasmas During the Blast Wave Expansion
International Nuclear Information System (INIS)
In this work we present temperature diagnostics of an expanding laser-produced argon plasma. A short-pulse (35fs) laser with an intensity of I = 1017W/cm2 deposits ∼ 100 mJ of energy into argon clusters. This generates a hot plasma filament that develops into a cylindrically expanding shock. We develop spectral diagnostics for the temperatures of the argon plasma in the shock region and the preionized region ahead of the shock. A collisional-radiative model is applied to explore line intensity ratios derived from Ar II - Ar IV spectra that are sensitive to temperatures in a few eV range. The results of hydrodynamic simulations are employed to derive a time dependent radiative transport calculation that generates the theoretical emission spectra from the expanding plasma
Water temperature and concentration measurements within the expanding blast wave of a high explosive
International Nuclear Information System (INIS)
We present an application of absorption spectroscopy to directly measure temperature and concentration histories of water vapor within the expansion of a high explosive detonation. While the approach of absorption spectroscopy is well established, the combination of a fast, near-infrared array, broadband light source, and rigid gauge allow the first application of time-resolved absorption measurements in an explosive environment. The instrument is demonstrated using pentaerythritol tetranitrate with a sampling rate of 20 kHz for 20 ms following detonation. Absorption by water vapor is measured between 1335 and 1380 nm. Water temperatures are determined by fitting experimental transmission spectra to a simulated database. Water mole fractions are deduced following the temperature assignment. The sources of uncertainty and their impact on the results are discussed. These measurements will aid the development of chemical-specific reaction models and the predictive capability in technical fields including combustion and detonation science
Institute of Scientific and Technical Information of China (English)
赵根; 季荣; 郑晓宁; 王文辉; 吴从清
2011-01-01
In the process of underwater blasting, the adobe blasting method was usually used to cut and demolish underwater metallic structure, sympathatic detonation of suspicious explosive object, etc. When blast area near by the culture area and protection of aquatic wildlife, it needs to consider the factor of water wave. In this paper, the propagation empirical formula of water wave is discussed. Through the blast test and arialysis on the monitored data, the propagation rules of water wave by high-energy and common emulsion explosives underwater blasting are obtained.%在水下工程爆破中,通常采用裸露药包爆破法,进行水下金属构件的切割与拆除、水下可疑爆炸物的诱爆等,当爆破区域附近有养殖区、野生保护水生物时,就需考虑炸药爆炸产生的水中冲击波影响问题.对水中冲击波传播规律的公式形式进行了探讨,通过爆破试验以及对监测资料的分析,得到了高能、普通乳化炸药的水中爆炸冲击波传播规律.
Study on Smooth-Blasting Results in Jointed and Fractured Rock
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Factors that affect blasting results may be grouped into those factors that can be controlled and those that cannot be controlled. The controllable factors include explosive properties, initiation timing, and blast geometry. The uncontrollable factors comprise the rock’s natural structures, such as joints and fractures, and the properties, such as elastic constants, density and strength. Among these, the influence of rock structural planes often contributes a high degree of variability to blasting results. This paper presents a theoretical analysis of rock structural plane influences on smooth-blasting results based on elasticity and stress wave propagation theory with an emphasis on smooth blasting techniques. Two types of simulated experiments in lab (using strain and acoustic emission measurements) are used to verify the theoretical analysis. The results show that it is difficult to achieve smooth-blasting results when the angle between the natural rock structural planes and the blast-induced fracture planes ranges from 10° to 60°. Among these angles, 30° is the least desirable angle to produce a smooth wall. For angles less than 10° and greater than 60°, the influence of rock structural planes on blasting results can be ignored.
Isentropic 'shock waves' in numerical simulations of astrophysical bodies
Bisnovatyi-Kogan, G S
2016-01-01
Strong discontinuities in solutions of the gas dynamic equations under isentropic conditions, i.e., with continuity of entropy at the discontinuity, are examined. Solutions for a standard shock wave with continuity of energy at the discontinuity are compared with those for an isentropic 'shock wave'. It is shown that numerical simulation of astrophysical problems in which high-amplitude shock waves are encountered (supernova explosions, modelling of jets) with conservation of entropy, rather than of energy, leads to large errors in the shock calculations. The isentropic equations of gas dynamics can be used only when there are no strong discontinuities in the solution or when the intensity of the shocks is not high and they do not significantly affect the flow.
Multiscale simulation of 2D elastic wave propagation
Zhang, Wensheng; Zheng, Hui
2016-06-01
In this paper, we develop the multiscale method for simulation of elastic wave propagation. Based on the first-order velocity-stress hyperbolic form of 2D elastic wave equation, the particle velocities are solved first ona coarse grid by the finite volume method. Then the stress tensor is solved by using the multiscale basis functions which can represent the fine-scale variation of the wavefield on the coarse grid. The basis functions are computed by solving a local problem with the finite element method. The theoretical formulae and description of the multiscale method for elastic wave equation are given in more detail. The numerical computations for an inhomogeneous model with random scatter are completed. The results show the effectiveness of the multiscale method.
Transport and mixing of r-process elements in neutron star binary merger blast waves
Montes, Gabriela; Naiman, Jill; Shen, Sijing; Lee, William H
2016-01-01
The r-process nuclei are robustly synthesized in the material ejected during a neutron star binary merger (NSBM), as tidal torques transport angular momentum and energy through the outer Lagrange point in the form of a vast tidal tail. If NSBM are indeed solely responsible for the solar system r- process abundances, a galaxy like our own would require to host a few NSBM per million years, with each event ejecting, on average, about 5x10^{-2} M_sun of r-process material. Because the ejecta velocities in the tidal tail are significantly larger than in ordinary supernovae, NSBM deposit a comparable amount of energy into the interstellar medium (ISM). In contrast to extensive efforts studying spherical models for supernova remnant evolution, calculations quantifying the impact of NSBM ejecta in the ISM have been lacking. To better understand their evolution in a cosmological context, we perform a suite of three-dimensional hydrodynamic simulations with optically-thin radiative cooling of isolated NSBM ejecta expa...
Simulation of wind wave growth with reference source functions
Badulin, Sergei I.; Zakharov, Vladimir E.; Pushkarev, Andrei N.
2013-04-01
We present results of extensive simulations of wind wave growth with the so-called reference source function in the right-hand side of the Hasselmann equation written as follows First, we use Webb's algorithm [8] for calculating the exact nonlinear transfer function Snl. Second, we consider a family of wind input functions in accordance with recent consideration [9] ( )s S = ?(k)N , ?(k) = ? ? ?- f (?). in k 0 ?0 in (2) Function fin(?) describes dependence on angle ?. Parameters in (2) are tunable and determine magnitude (parameters ?0, ?0) and wave growth rate s [9]. Exponent s plays a key role in this study being responsible for reference scenarios of wave growth: s = 4-3 gives linear growth of wave momentum, s = 2 - linear growth of wave energy and s = 8-3 - constant rate of wave action growth. Note, the values are close to ones of conventional parameterizations of wave growth rates (e.g. s = 1 for [7] and s = 2 for [5]). Dissipation function Sdiss is chosen as one providing the Phillips spectrum E(?) ~ ?5 at high frequency range [3] (parameter ?diss fixes a dissipation scale of wind waves) Sdiss = Cdissμ4w?N (k)θ(? - ?diss) (3) Here frequency-dependent wave steepness μ2w = E(?,?)?5-g2 makes this function to be heavily nonlinear and provides a remarkable property of stationary solutions at high frequencies: the dissipation coefficient Cdiss should keep certain value to provide the observed power-law tails close to the Phillips spectrum E(?) ~ ?-5. Our recent estimates [3] give Cdiss ? 2.0. The Hasselmann equation (1) with the new functions Sin, Sdiss (2,3) has a family of self-similar solutions of the same form as previously studied models [1,3,9] and proposes a solid basis for further theoretical and numerical study of wave evolution under action of all the physical mechanisms: wind input, wave dissipation and nonlinear transfer. Simulations of duration- and fetch-limited wind wave growth have been carried out within the above model setup to check its
Ghasemi, Amirmahdi; Pathak, Ashish; Chiodi, Robert; Raessi, Mehdi
2013-11-01
Ocean waves represent a vast renewable energy resource, which is mostly untapped. We present a computational tool for simulation of the interactions between waves and two-dimensional oscillating solid bodies representing simple wave energy converters (WECs). The computational tool includes a multiphase flow solver, in which the two-step projection method with GPU acceleration is used to solve the Navier-Stokes equations. The fictitious domain method is used to capture the interactions of a moving rigid solid body with the two-fluid flow. The solid and liquid volumes are tracked using the volume-of-fluid (VOF) method, while the triple points and phase interfaces in three-phase cells are resolved. A consistent mass and momentum transport scheme is used to handle the large density ratio. We present results of two wave generation mechanisms with a piston or flap wave maker, where the theoretical and experimental results were used for validation. Then, simulation results of several simple devices representative of distinct WECs, including a bottom-hinged flap device as well as cylindrical or rectangular terminators are presented. The results are in good agreement with the available experimental data.
Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks
DEFF Research Database (Denmark)
Wright, J.C.; Bonoli, P.T.; Brambilla, M.;
2004-01-01
Fast wave (FW) studies of mode conversion (MC) processes at the ion-ion hybrid layer in toroidal plasmas must capture the disparate scales of the FW and mode converted ion Bernstein and ion cyclotron waves. Correct modeling of the MC layer requires resolving wavelengths on the order of k......). Two full wave codes, a massively-parallel-processor (MPP) version of the TORIC-2D finite Larmor radius code [M. Brambilla, Plasma Phys. Controlled Fusion 41, 1 (1999)] and also an all orders spectral code AORSA2D [E. F. Jaeger , Phys. Plasmas 9, 1873 (2002)], have been developed which for the first...... time are capable of achieving the resolution and speed necessary to address mode conversion phenomena in full two-dimensional (2-D) toroidal geometry. These codes have been used in conjunction with theory and experimental data from the Alcator C-Mod [I. H. Hutchinson , Phys. Plasmas 1, 1511 (1994)] to...
The Mediterranean surface wave climate inferred from future scenario simulations
Lionello, P.; Cogo, S.; Galati, M. B.; Sanna, A.
2008-09-01
This study is based on 30-year long simulations of the wind-wave field in the Mediterranean Sea carried out with the WAM model. Wave fields have been computed for the 2071-2100 period of the A2, B2 emission scenarios and for the 1961-1990 period of the present climate (REF). The wave model has been forced by the wind field computed by a regional climate model with 50 km resolution. The mean SWH (Significant Wave Height) field over large fraction of the Mediterranean sea is lower for the A2 scenario than for the present climate during winter, spring and autumn. During summer the A2 mean SWH field is also lower everywhere, except for two areas, those between Greece and Northern Africa and between Spain and Algeria, where it is significantly higher. All these changes are similar, though smaller and less significant, in the B2 scenario, except during winter in the north-western Mediterranean Sea, when the B2 mean SWH field is higher than in the REF simulation. Also extreme SWH values are smaller in future scenarios than in the present climate and such SWH change is larger for the A2 than for the B2 scenario. The only exception is the presence of higher SWH extremes in the central Mediterranean during summer for the A2 scenario. In general, changes of SWH, wind speed and atmospheric circulation are consistent, and results show milder marine storms in future scenarios than in the present climate.
Full wave simulation of waves in ECRIS plasmas based on the finite element method
Energy Technology Data Exchange (ETDEWEB)
Torrisi, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania, Italy and Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell' Informazione, delle Infrastrutture e dell' Energia Sostenibile (DIIES), Via Graziella, I (Italy); Mascali, D.; Neri, L.; Castro, G.; Patti, G.; Celona, L.; Gammino, S.; Ciavola, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania (Italy); Di Donato, L. [Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica (DIEEI), Viale Andrea Doria 6, 95125 Catania (Italy); Sorbello, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania, Italy and Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica (DIEEI), Viale Andrea Doria 6, 95125 Catania (Italy); Isernia, T. [Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell' Informazione, delle Infrastrutture e dell' Energia Sostenibile (DIIES), Via Graziella, I-89100 Reggio Calabria (Italy)
2014-02-12
This paper describes the modeling and the full wave numerical simulation of electromagnetic waves propagation and absorption in an anisotropic magnetized plasma filling the resonant cavity of an electron cyclotron resonance ion source (ECRIS). The model assumes inhomogeneous, dispersive and tensorial constitutive relations. Maxwell's equations are solved by the finite element method (FEM), using the COMSOL Multiphysics{sup ®} suite. All the relevant details have been considered in the model, including the non uniform external magnetostatic field used for plasma confinement, the local electron density profile resulting in the full-3D non uniform magnetized plasma complex dielectric tensor. The more accurate plasma simulations clearly show the importance of cavity effect on wave propagation and the effects of a resonant surface. These studies are the pillars for an improved ECRIS plasma modeling, that is mandatory to optimize the ion source output (beam intensity distribution and charge state, especially). Any new project concerning the advanced ECRIS design will take benefit by an adequate modeling of self-consistent wave absorption simulations.
Kinetic Simulations of Ladder Climbing and Autoresonance of Plasma Waves
Kaminski, Erez; Barth, Ido; Fisch, Nat; Dodin, Ilya
2015-11-01
Quantum like Ladder Climbing and Autoresonance of classical Langmuir waves in bounded plasmas are numerically studied within a kinetic model and compared with earlier fluid model simulations. Both dynamical solutions are excited and controlled via chirped modulations of the background density that preserve the plasma wave quanta. Landau damping determines the system's maximal stable level, imposing a kinetic limit on the maximal level of the Ladder Climbing or Autoresonance dynamics. Vlasov simulations are employed to test the kinetic stability of both dynamics and to find the kinetic limit for different system's parameters. This work was Supported by NNSA grant DE274-FG52-08NA28553, DOE contract DE-AC02-09CH11466, and DTRA grant HDTRA1-11-1-0037.
Simulation and Analysis of Converging Shock Wave Test Problems
Energy Technology Data Exchange (ETDEWEB)
Ramsey, Scott D. [Los Alamos National Laboratory; Shashkov, Mikhail J. [Los Alamos National Laboratory
2012-06-21
Results and analysis pertaining to the simulation of the Guderley converging shock wave test problem (and associated code verification hydrodynamics test problems involving converging shock waves) in the LANL ASC radiation-hydrodynamics code xRAGE are presented. One-dimensional (1D) spherical and two-dimensional (2D) axi-symmetric geometric setups are utilized and evaluated in this study, as is an instantiation of the xRAGE adaptive mesh refinement capability. For the 2D simulations, a 'Surrogate Guderley' test problem is developed and used to obviate subtleties inherent to the true Guderley solution's initialization on a square grid, while still maintaining a high degree of fidelity to the original problem, and minimally straining the general credibility of associated analysis and conclusions.
Energy Technology Data Exchange (ETDEWEB)
Xiao, Jianyuan; Liu, Jian, E-mail: jliuphy@ustc.edu.cn [Department of Modern Physics and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Key Laboratory of Geospace Environment, CAS, Hefei, Anhui 230026 (China); Qin, Hong [Department of Modern Physics and School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Yu, Zhi; Xiang, Nong [Theory and Simulation Division, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China)
2015-09-15
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments.
International Nuclear Information System (INIS)
In this paper, the nonlinear mode conversion of extraordinary waves in nonuniform magnetized plasmas is studied using the variational symplectic particle-in-cell simulation. The accuracy of the nonlinear simulation is guaranteed by the long-term accuracy and conservativeness of the symplectic algorithm. The spectra of the electromagnetic wave, the evolution of the wave reflectivity, the energy deposition profile, and the parameter-dependent properties of radio-frequency waves during the nonlinear mode conversion are investigated. It is illustrated that nonlinear effects significantly modify the physics of the radio-frequency injection in magnetized plasmas. The evolutions of the radio-frequency wave reflectivity and the energy deposition are observed, as well as the self-interaction of the Bernstein waves and mode excitations. Even for waves with small magnitude, nonlinear effects can also become important after continuous wave injections, which are common in the realistic radio-frequency wave heating and current drive experiments
Numerical simulation methods for wave propagation through optical waveguides
International Nuclear Information System (INIS)
The simulation of the field propagation through waveguides requires numerical solutions of the Helmholtz equation. For this purpose a method based on the principle of orthogonal collocation was recently developed. The method is also applicable to nonlinear pulse propagation through optical fibers. Some of the salient features of this method and its application to both linear and nonlinear wave propagation through optical waveguides are discussed in this report. 51 refs, 8 figs, 2 tabs
Influence Mechanism of Lamella Joints on Tunnel Blasting Effect
Shiwei Shen; Lei Nie; Shulin Dai; Yan Xu
2013-01-01
In this study, we have a research of the influence mechanism of lamella joints on tunnel blasting effect. During the process of the tunnel blasting construction, primary structural planes make an important role for the effect of smooth blasting. Especially, it is difficult to attain the perfect blasting effect when the lamella joints intersect with the designed contour line. Coupled effect of the explosive stress waves and the explosive gas is deemed to the basic theory, analysis the blasting...
Whistler Observations on DEMETER Compared with Full Electromagnetic Wave Simulations
Compston, A. J.; Cohen, M.; Lehtinen, N. G.; Inan, U.; Linscott, I.; Said, R.; Parrot, M.
2014-12-01
Terrestrial Very Low Frequency (VLF) electromagnetic radiation, which strongly impacts the Van Allen radiation belt electron dynamics, is injected across the ionosphere into the Earth's plasmasphere from two primary sources: man-made VLF transmitters and lightning discharges. Numerical models of trans-ionospheric propagation of such waves remain unvalidated, and early models may have overestimated the absorption, hindering a comprehensive understanding of the global impact of VLF waves in the loss of radiation belt electrons. In an attempt to remedy the problem of a lack of accurate trans-ionospheric propagation models, we have used a full electromagnetic wave method (FWM) numerical code to simulate the propagation of lightning-generated whistlers into the magnetosphere and compared the results with whistlers observed on the DEMETER satellite and paired with lightning stroke data from the National Lightning Detection Network (NLDN). We have identified over 20,000 whistlers occuring in 14 different passes of DEMETER over the central United States during the summer of 2009, and 14,000 of those occured within the 2000 km x 2000 km simulation grid we used. As shown in the attached figure, which shows a histogram of the ratio of the simulated whistler energy to the measured whistler energy for the 14,000 whistlers we compared, the simulation tends to slightly underestimate the total whistler energy injected by about 5 dB. However, the simulation underestimates the DEMETER measurements more as one gets further from the source lightning stroke, so since the signal to noise ratio of more distant whistlers will be smaller, possibly additive noise in the DEMETER measurements (which of course is not accounted for in the model) may explain some of the observed discrepancy.
Numerical simulation of wave propagation in a realistic model of the human external ear.
Fadaei, Mohaddeseh; Abouali, Omid; Emdad, Homayoun; Faramarzi, Mohammad; Ahmadi, Goodarz
2015-01-01
In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the '4-kHz notch' in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study. PMID
Discrete event simulation of Maglev transport considering traffic waves
Directory of Open Access Journals (Sweden)
Moo Hyun Cha
2014-10-01
Full Text Available A magnetically levitated vehicle (Maglev system is under commercialization as a new transportation system in Korea. The Maglev is operated by an unmanned automatic control system. Therefore, the plan of train operation should be carefully established and validated in advance. In general, when making a train operation plan, statistically predicted traffic data is used. However, a traffic wave often occurs in real train service, and demand-driven simulation technology is required to review a train operation plan and service quality considering traffic waves. We propose a method and model to simulate Maglev operation considering continuous demand changes. For this purpose, we employed a discrete event model that is suitable for modeling the behavior of railway passenger transportation. We modeled the system hierarchically using discrete event system specification (DEVS formalism. In addition, through implementation and an experiment using the DEVSim++ simulation environment, we tested the feasibility of the proposed model. Our experimental results also verified that our demand-driven simulation technology can be used for a priori review of train operation plans and strategies.
爆破地震的数值模拟及爆破振动规律分析%Numerical Simulation of Blast-induced Earthquake and Blast Vibration Analysis
Institute of Scientific and Technical Information of China (English)
张智超; 刘汉龙; 陈育民; 王维国
2012-01-01
In the frame of LS-DYNA, the constitutive model which can well describe the dynamic property of soil under blast loading was proposed, meanwhile, certain blast-induced earthquake in-situ test was simulated, with the calculated acceleration time histories approximate to the recorded data, which indicates the numerical method can provide useful instructions for the in-situ blasting tests in advance and well predicts the blasting results ; based on it, the blasting vibration law through the stratums was analyzed, which reveals that up from the plane where explosive charges lay, the amplitude of horizontal acceleration and velocity minish continuously with the decrease of the burial depth ( or the increase of blast center distance) , while the amplitude of vertical acceleration and velocity increase first, then decrease and at last remain relatively stable when approaching the free surface on the ground surface. The numerical endeavour enriches the research on the blast-induced ground motion and supplies a simple, effective and economic method for the simulation of natural earthquake by millisecond blasting test as well as for the study of seismic response of soil based on it.%在LS - DYNA软件框架内,建立了适合土体爆炸动力分析的实用模型,对某利用微差爆破诱发人工地震的原位试验进行了数值模拟,结果表明,计算得到的地表加速度时程与实测值比较吻合.因此,可预先利用数值手段对为爆破试验方案提供指导,对爆破地震结果进行预测.在此基础上,分析了地层中的爆破振动规律,表明自炸药的埋深向上,随着深度的减小、爆心距的增加,爆破水平向加速度幅值和速度幅值逐渐减小,而竖直向加速度幅值和速度幅值则呈现先增大,后减小,到了近地表自由面又基本维持稳定的趋势.数值结果丰富了爆破地震的研究,为微差爆破模拟天然地震、并以此来研究土体地震动力响应提供了经济、简便而实用的方法.
Svetlov, Stanislav I.; Prima, Victor; Glushakova, Olena; Svetlov, Artem; Kirk, Daniel R.; Gutierrez, Hector; Serebruany, Victor L.; Curley, Kenneth C.; Wang, Kevin K. W.; Hayes, Ronald L.
2012-01-01
A number of experimental models of blast brain injury have been implemented in rodents and larger animals. However, the variety of blast sources and the complexity of blast wave biophysics have made data on injury mechanisms and biomarkers difficult to analyze and compare. Recently, we showed the importance of rat position toward blast generated by an external shock tube. In this study, we further characterized blast producing moderate traumatic brain injury and defined “composite” blast and ...
Blast-Induced Damage on Millisecond Blasting Model Test with Multicircle Vertical Blastholes
Directory of Open Access Journals (Sweden)
Qin-yong Ma
2015-01-01
Full Text Available To investigate the blast-induced damage effect on surrounding rock in vertical shaft excavation, 4 kinds of millisecond blasting model tests with three-circle blastholes were designed and carried out with excavation blasting in vertical shaft as the background. The longitudinal wave velocity on the side of concrete model was also measured before and after blasting. Then blast damage factor was then calculated by measuring longitudinal wave velocity before and after blasting. The test results show that the blast-induced damage factor attenuated gradually with the centre of three-circle blastholes as centre. With the threshold value of 0.19 for blast-induced damage factor, blast-induced damage zones for 4 kinds of model tests are described and there is an inverted cone blast-induced damage zone in concrete model. And analyses of cutting effect and blast-induced damage zone indicate that in order to minimize the blast-induced damage effect and ensure the cutting effect the reasonable blasting scheme for three-circle blastholes is the inner two-circle blastholes initiated simultaneously and the outer third circle blastholes initiated in a 25 ms delay.
Binary black hole late inspiral: Simulations for gravitational wave observations
Baker, J G; Choi, D I; Kelly, B J; Koppitz, M; McWilliams, S T; Van Meter, J R; Baker, John G.; Centrella, Joan; Choi, Dae-Il; Kelly, Bernard J.; Koppitz, Michael; Meter, James R. van; Williams, Sean T. Mc
2006-01-01
Coalescing binary black hole mergers are expected to be the strongest gravitational wave sources for ground-based interferometers, such as the LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Until recently it has been impossible to reliably derive the predictions of General Relativity for the final merger stage, which takes place in the strong-field regime. Recent progress in numerical relativity simulations is, however, revolutionizing our understanding of these systems. We examine here the specific case of merging equal-mass Schwarzschild black holes in detail, presenting new simulations in which the black holes start in the late inspiral stage on orbits with very low eccentricity and evolve for ~1200M through ~7 orbits before merging. We study the accuracy and consistency of our simulations and the resulting gravitational waveforms, which encompass ~14 cycles before merger, and highlight the importance of using frequency (rather than time) to set the physical reference when compari...
Hybrid Simulation of the Shock Wave Trailing the Moon
Israelevich, P.; Ofman, Leon
2012-01-01
A standing shock wave behind the Moon was predicted by Michel (1967) but never observed nor simulated. We use 1D hybrid code in order to simulate the collapse of the plasma-free cavity behind the Moon and for the first time to model the formation of this shock. Starting immediately downstream of the obstacle we consider the evolution of plasma expansion into the cavity in the frame of reference moving along with the solar wind. Well-known effects as electric charging of the cavity affecting the plasma flow and counterstreaming ion beams in the wake are reproduced. Near the apex of the inner Mach cone where the plasma flows from the opposite sides of the obstacle meet, a shock wave arises. We expect the shock to be produced at periods of high electron temperature solar wind streams (T(sub i) much less than T(sub e) approximately 100 eV). The shock is produced by the interaction of oppositely directed proton beams in the plane containing solar wind velocity and interplanetary magnetic field vectors. In the direction across the magnetic field and the solar wind velocity, the shock results from the interaction of the plasma flow with the region of the enhanced magnetic field inside the cavity that plays the role of the magnetic barrier. The appearance of the standing shock wave is expected at the distance of approximately 7R(sub M) downstream of the Moon.
Molecular dynamics simulation of complex plasmas: interaction of nonlinear waves
Durniak, Celine; Samsonov, Dmitry
2008-11-01
Complex plasmas consist of micron sized microspheres immersed into ordinary ion-electron plasmas. They exist in solid, liquid, gaseous states and exhibit a range of dynamic phenomena such as waves, solitons, phase transitions, heat transfer. These phenomena can be modelled in complex plasmas at the microscopic or ``molecular'' scale, which is almost impossible in ordinary solids and liquids. We simulate a monolayer complex plasma consisting of 3000 negatively-charged particles (or grains) with the help of molecular dynamics computer simulations. The equations of grain motion are solved using a 5^th order Runge Kutta method taking into account interaction of every grain with each other via a Yukawa potential. The grains are confined more strongly in the vertical direction than in the horizontal. After seeding the grains randomly the code is run until the equilibrium is reached as the grain kinetics energy reduces due to damping force equal to the neutral friction in the experiments and a monolayer crystal lattice is formed. Then we investigate interactions between nonlinear waves in a monolayer strongly coupled complex plasma moving in three dimensions. Different excitations are applied during a short time symmetrically on both sides of the lattice. Structural properties and nonlinear waves characteristics are examined as the pulses propagate across the complex plasma in opposite directions.
Blast Dynamics in a Dissipative Gas.
Barbier, M; Villamaina, D; Trizac, E
2015-11-20
The blast caused by an intense explosion has been extensively studied in conservative fluids, where the Taylor-von Neumann-Sedov hydrodynamic solution is a prototypical example of self-similarity driven by conservation laws. In dissipative media, however, energy conservation is violated, yet a distinctive self-similar solution appears. It hinges on the decoupling of random and coherent motion permitted by a broad class of dissipative mechanisms. This enforces a peculiar layered structure in the shock, for which we derive the full hydrodynamic solution, validated by a microscopic approach based on molecular dynamics simulations. We predict and evidence a succession of temporal regimes, as well as a long-time corrugation instability, also self-similar, which disrupts the blast boundary. These generic results may apply from astrophysical systems to granular gases, and invite further cross-fertilization between microscopic and hydrodynamic approaches of shock waves. PMID:26636851
Blast Dynamics in a Dissipative Gas
Barbier, M.; Villamaina, D.; Trizac, E.
2015-11-01
The blast caused by an intense explosion has been extensively studied in conservative fluids, where the Taylor-von Neumann-Sedov hydrodynamic solution is a prototypical example of self-similarity driven by conservation laws. In dissipative media, however, energy conservation is violated, yet a distinctive self-similar solution appears. It hinges on the decoupling of random and coherent motion permitted by a broad class of dissipative mechanisms. This enforces a peculiar layered structure in the shock, for which we derive the full hydrodynamic solution, validated by a microscopic approach based on molecular dynamics simulations. We predict and evidence a succession of temporal regimes, as well as a long-time corrugation instability, also self-similar, which disrupts the blast boundary. These generic results may apply from astrophysical systems to granular gases, and invite further cross-fertilization between microscopic and hydrodynamic approaches of shock waves.
International Nuclear Information System (INIS)
We have used the Spitzer satellite to monitor the mid-IR evolution of SN 1987A over a five year period spanning the epochs between days ∼6000 and 8000 since the explosion. The supernova (SN) has evolved into a supernova remnant and its radiative output is dominated by the interaction of the SN blast wave with the pre-existing equatorial ring (ER). The mid-IR spectrum is dominated by emission from ∼180 K silicate dust, collisionally heated by the hot X-ray emitting gas with a temperature and density of ∼5 x 106 K and ∼3 x 104 cm-3, respectively. The mass of the radiating dust is ∼1.2 x 10-6 Msun on day 7554 and scales linearly with IR flux. Comparison of the IR data with the soft X-ray flux derived from Chandra observations shows that the IR-to-X-ray flux ratio, IRX, is roughly constant with a value of 2.5. Gas-grain collisions therefore dominate the cooling of the shocked gas. The constancy of IRX is most consistent with the scenario that very little grain processing or gas cooling has occurred throughout this epoch. The shape of the dust spectrum remained unchanged during the observations while the total flux increased by a factor of ∼5 with a time dependence of t'0.87±0.20, t' being the time since the first encounter between the blast wave and the ER. These observations are consistent with the transitioning of the blast wave from free expansion to a Sedov phase as it propagates into the main body of the ER, as also suggested by X-ray observations. The constant spectral shape of the IR emission provides strong constraints on the density and temperature of the shocked gas in which the interaction takes place. Silicate grains, with radii of ∼0.2 μm and temperature of T ∼ 180 K, best fit the spectral and temporal evolution of the ∼8-30 μm data. The IR spectra also show the presence of a secondary population of very small, hot (T ∼> 350 K), featureless dust. If these grains spatially coexist with the silicates, then they must have shorter
Dwek, Eli; Arendt, Richard G.; Bouchet, Patrice; Burrows, David N.; Challis, Peter; Danziger, I. John; De Buizer, James M.; Gehrz, Robert D.; Park, Sangwook; Polomski, Elisha F.; Slavin, Jonathan D.; Woodward, Charles E.
2010-01-01
We have used the Spitzer satellite to monitor the laid-IR evolution of SN 1987A over a 5 year period spanning the epochs between days 6000 and 8000 since the explosion. The supernova (SN) has evolved into a supernova remnant (SNR) and its radiative output, is dominated by the interaction of the SN blast wave with the pre-existing equatorial ring (ER). The mid-IR spectrum is dominated by emission from approximately 180 K silicate dust, collisionally-heated by the hot X-ray emitting gas with a temperature and density of 5 x 10(exp 6) K and approximately 3 x 10(exp 4) per cubic centimeter, respectively. The mass of the radiating dust is approximately 1.2 x 10(exp -6) solar mass on day 7554, and scales linearly with IR flux. Comparison of the IR data with the soft X-ray flux derived from Chandra observations shows that the IR-to-X-ray flux ratio, IRX, is roughly constant with a value of 2.5. Gas-grain collisions therefore dominate the cooling of the shocked gas. The constancy of IRX is most consistent with the scenario that very little grain processing or gas cooling have occurred throughout this epoch. The shape of the dust spectrum remained unchanged during the observations while the total flux increased by a factor of approximately 5 with a time dependence of t(sup '0.87 plus or minus 0.20), t' being the time since the first encounter between the blast wave and the ER. These observations are consistent with the transitioning of the blast wave from free expansion to a Sedov phase as it propagates into the main body of the ER, as also suggested by X-ray observations. The constant spectral shape of they IR, emission provides strong constraints on the density and temperature of the shocked gas in which the interaction takes place. The IR spectra also suggest the presence of a secondary population of very small, hot (T greater than or equal to 350 K), featureless dust. If these grains spatially coexists with the silicates, then they must have shorter lifetimes. The data
Beniamini, Paz; Nava, Lara; Duran, Rodolfo Barniol; Piran, Tsvi
2015-11-01
We consider a sample of 10 gamma-ray bursts with long-lasting ( ≳ 102 s) emission detected by Fermi/Large Area Telescope and for which X-ray data around 1 d are also available. We assume that both the X-rays and the GeV emission are produced by electrons accelerated at the external forward shock, and show that the X-ray and the GeV fluxes lead to very different estimates of the initial kinetic energy of the blast wave. The energy estimated from GeV is on average ˜50 times larger than the one estimated from X-rays. We model the data (accounting also for optical detections around 1 d, if available) to unveil the reason for this discrepancy and find that good modelling within the forward shock model is always possible and leads to two possibilities: (i) either the X-ray emitting electrons (unlike the GeV emitting electrons) are in the slow-cooling regime or (ii) the X-ray synchrotron flux is strongly suppressed by Compton cooling, whereas, due to the Klein-Nishina suppression, this effect is much smaller at GeV energies. In both cases the X-ray flux is no longer a robust proxy for the blast wave kinetic energy. On average, both cases require weak magnetic fields (10-6 ≲ ɛB ≲ 10-3) and relatively large isotropic kinetic blast wave energies 10^{53} erg<{E}_{0,kin}<10^{55} erg corresponding to large lower limits on the collimated energies, in the range 10^{52} erg<{E}_{θ ,kin}<5× 10^{52} erg for an ISM (interstellar medium) environment with n ˜ 1 cm-3 and 10^{52} erg<{E}_{θ ,kin}<10^{53} erg for a wind environment with A* ˜ 1. These energies are larger than those estimated from the X-ray flux alone, and imply smaller inferred values of the prompt efficiency mechanism, reducing the efficiency requirements on the still uncertain mechanism responsible for prompt emission.
A Table-top Blast Driven Shock Tube
Courtney, Michael; Courtney, Amy
2011-01-01
The prevalence of blast-induced traumatic brain injury in conflicts in Iraq and Afghanistan has motivated laboratory scale experiments on biomedical effects of blast waves and studies of blast wave transmission properties of various materials in hopes of improving armor design to mitigate these injuries. This paper describes the design and performance of a table-top shock tube that is more convenient and widely accessible than traditional compression driven and blast driven shock tubes. The d...
A coupling of empirical explosive blast loads to ALE air domains in LS-DYNA (registered)
International Nuclear Information System (INIS)
A coupling method recently implemented in LS-DYNA (registered) allows empirical explosive blast loads to be applied to air domains treated with the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation. Previously, when simulating structures subjected to blast loads, two methods of analysis were available: a purely Lagrangian approach or one involving the ALE and Lagrangian formulations coupled with a fluid-structure interaction (FSI) algorithm. In the former, air blast pressure is computed with empirical equations and directly applied to Lagrangian elements of the structure. In the latter approach, the explosive as well as the air are explicitly modeled and the blast wave propagating through the ALE air domain impinges on the Lagrangian structure through FSI. Since the purely Lagrangian approach avoids modeling the air between the explosive and structure, a significant computational cost savings can be realized - especially so when large standoff distances are considered. The shortcoming of the empirical blast equations is their inability to account for focusing or shadowing of the blast waves due to their interaction with structures which may intervene between the explosive and primary structure of interest. The new method presented here obviates modeling the explosive and air leading up the structure. Instead, only the air immediately surrounding the Lagrangian structures need be modeled with ALE, while effects of the far-field blast are applied to the outer face of that ALE air domain with the empirical blast equations; thus, focusing and shadowing effects can be accommodated yet computational costs are kept to a minimum. Comparison of the efficiency and accuracy of this new method with other approaches shows that the ability of LS-DYNA (registered) to model a variety of new blast scenarios has been greatly extended.
Krzystała, Edyta; Mężyk, Arkadiusz; Kciuk, Sławomir
2016-06-01
The aim of this study was to elaborate identification method of crew overload as a result of trinitrotoluene charge explosion under the military wheeled vehicle. During the study, an experimental military ground research was carried out. The aim of this research was to verify the mine blast resistance of the prototype wheeled vehicle according to STANG 4569 as well as the anti-explosive seat. Within the work, the original methodology was elaborated along with a prototype research statement. This article presents some results of the experimental research, thanks to which there is a possibility to estimate the crew's lives being endangered in an explosion through the measurement of acceleration as well as the pressure on the chest, head and internal organs. On the basis of our acceleration results, both effectiveness and infallibility of crew protective elements along with a blast mitigation seat were verified. PMID:25307173
TNT-blast-equivalence for bursting of pressurized-gas conventional vessels
International Nuclear Information System (INIS)
A simple procedure is given for roughly simulating the positive phase of a blast wave arising from the sudden rupture of a conventional pressurized-gas vessel. The procedure differs somewhat from the usual TNT-energy-equivalence method. It is based on equating a bursting-gas-vessel blast to that of a high explosive charge of energy higher than the stored gas energy, and detonating farther away than the vessel considered. In conjunction with blast damage curves or formulas known from military technology, the present method can be used in roughly and quickly assessing the damage hazards that are due to a hypothetical vessel burst, or in designing protective structures. It can also be used in performing model-scale tests on structures that are potentially subject to blast loads. (orig.)
Hybrid simulation codes with application to shocks and upstream waves
Winske, D.
1985-01-01
Hybrid codes in which part of the plasma is represented as particles and the rest as a fluid are discussed. In the past few years such codes with particle ions and massless, fluid electrons have been applied to space plasmas, especially to collisionless shocks. All of these simulation codes are one-dimensional and similar in structure, except for how the field equations are solved. The various approaches that are used (resistive Ohm's law, predictor-corrector, Hamiltonian) are described in detail and results from the various codes are compared with examples taken from collisionless shocks and low frequency wave phenomena upstream of shocks.
Numerical simulation of tsunami-scale wave boundary layers
DEFF Research Database (Denmark)
Williams, Isaac A.; Fuhrman, David R.
2016-01-01
, boundary layer thickness, turbulence, and bed shear stresses induced are systematically monitored and parameterised, under both hydraulically smooth and roughbed conditions. The results generally support a notion that the boundary layers induced by tsunami-scalewaves are both current-like, due...... layer properties beneath wind-waves maintain reasonable accuracy when extrapolated to full tsunami scales. Boundary layers driven by actual field-measured tsunami signals are likewise simulated, stemming from both the 2004 Indian Ocean as well as the 2011 Tohoku events. These results are reconciled...
NUMERICAL SIMULATION OF SEA SURFACE DIRECTIONAL WAVE SPECTRA UNDER TYPHOON WIND FORCING
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Numercial simulation of sea surface directional wave spectra under typhoon wind forcing in the South China Sea (SCS) was carreid out using the WAVEWATCH-III wave model. The simulation was run for 210 h until the Typhoon Damrey (2005) approached Vietnam. The simulated data were compared with buoy observations, which were obtained in the northwest sea area of Hainan Island. The results show that the significant wave height, wave direction, wave length and frequency spetra agree well with buoy observations. The spatial characteristics of the signifciant wave height, mean wave period, mean wave length, wave age and directional spectra depend on the relative position from the typhoon center. Also, the misalignment between local wind and wave directions were investigated.
Numerical Simulation of Breaking Wave Based on Higher-Order Mild Slope Equation
Institute of Scientific and Technical Information of China (English)
陶建华; 韩光
2001-01-01
The "surface roller" to simulate wave energy dissipation of wave breaking is introduced into the random wave model based on approximate parabolic mild slope equation in this paper to simulate the random wave transportation including diffraction, refraction and breaking in nearshore areas. The roller breaking random wave higher-order approximate parabolic equation model has been verified by the existing experimental data for a plane slope beach and a circularshoal, and the numerical results of random wave breaking model agree with the experimental data very well. This modelcan be applied to calculate random wave propagation from deep to shallow water in large areas near the shore over natural topography.
Influence of nut coke on iron ore sinter reducibility under simulated blast furnace conditions
Energy Technology Data Exchange (ETDEWEB)
Mousa, E.A.; Senk, D.; Babich, A.; Gudenau, H.W.
2010-04-15
One of the most important factors to increase the economic efficiency of the blast furnace process is to reduced coke losses (undersieve product known as nut coke). In recent years there has been increased interest in mixing nut coke in the sinter layers. In order to clarify the influence of nut coke on sinter reducibility, sinter and sinter-nut coke mixtures were isothermally reduced with 30%CO-70%N{sub 2} at 1173-1523 K using a muffle furnace supported by an on-line gas analyser. Reflected light microscopy, scanning electron microscopy and X-ray technique were used to characterise the microstructure and the different phases developed in the original and reduced sinter. Sinter reduced without nut coke participation exhibited reduction retardation at elevated temperatures (>1373 K) while the presence of nut coke prevented such phenomena. The rate controlling mechanism of sinter and sinter-nut coke mixture was predicted from the correlation between apparent activation energy calculations, mathematical modelling derived from gas-solid reaction model and microstructure examination.
Numerical Simulation of Impulse Waves Generated by Sliding Masses
Suleimani, E.; Vollmoeller, P.
2006-12-01
Landslide-generated impulse waves are a significant hazard in coastal areas. They could be generated by a number of natural mass-movement processes including landslides, avalanches, debris and lava flows. One example is the famous 1958 tsunami in Lituya Bay, Alaska, that had an amplitude of more than 500 meters and was generated by a huge rock avalanche. These impulse waves are the result of a dynamic interplay of several highly unstable processes where three interacting phases (air, fluid and solid material) are involved. The sliding solid material has complicated rheological behavior characterized by the interaction between solid and fluid phases. In addition, there is the overall three-dimensional turbulent flow behavior and the interfacial flow structure. Recent modeling activities operate in the frame of depth-averaged Navier-Stokes equations and hence are restricted to applications where the relation between horizontal (H) and the vertical length scales (V) is V/Hflow behavior, we use the large-eddy simulation approach. Together with standard numerical methods like the Chorin type scheme, which solves these equations in the finite volume context, the model realizes a level-set algorithm for tracking the interface between the ambient air and the two other phases. As a first test case, we numerically modeled the interaction of water with a solid, sliding wedge as a simplified subaerial landslide and investigated the characteristics of the induced water waves.
Simulations of a Detonation Wave in Transverse Magnetic Fields
Cole, Lord; Karagozian, Ann; Cambier, Jean-Luc
2010-11-01
Numerical simulations of magneto-hydrodynamic (MHD) effects on detonation wave structures are performed, with applications to flow control and MHD power extraction in Pulse Detonation Engines (PDE) and their design variations. In contrast to prior studies of MHD interactions in PDEs,ootnotetextCambier, et al., AIAA-2008-4688 the effects of the finite relaxation length scale for ionization on the stability of the detonation wave are examined. Depending on the coupling parameters, the magnetic field can quench the detonation and effectively act as a barrier to its propagation. Conversely, an applied transient magnetic field can exert a force on a pre-ionized gas and accelerate it. The dynamics are subject to non-linear effects; a propagating transverse magnetic field will initially exert a small force if the gas has a low conductivity and the magnetic Reynolds number (Rem) is low. Nevertheless, the gas accelerated by the "piston" action of the field can pre-heat the ambient gas and increase its conductivity. As the wave progresses, Rem increases and the magnetic field becomes increasingly effective. The dynamics of this process are examined in detail with a high-order shock-capturing method and full kinetics of combustion and ionization. The complex chemical kinetics calculations are ported onto a GPU using the CUDA language, and computational performance is compared with standard CPU-based computations.
Finite Element and Experimental Analyses of an Armoured Vehicle Subjected to Landmine Blast
Directory of Open Access Journals (Sweden)
Atıl Erdik
2015-11-01
Full Text Available Landmines severely threaten the armoured vehicles. The principal objective is to present a methodology for blast simulations of vehicles subjected to landmine explosions. First, free field blast experiment of 2 kg TNT charge in a steel pot is carried out to validate the blast parameters used in the numerical simulation. Overpressure-time history collected in the free field blast experiment is compared to the numerical simulation results. Numerical simulations are performed in LS-DYNA hydrocode that employs Arbitrary Lagrangian Eulerian formulation enabling a fully coupled interaction between the blast wave, the detonation gases, and the vehicle. Second, the full-scale field test of an armoured vehicle exposed to 6 kg of TNT charge in a steel pot underneath the rear end of the vehicle is conducted. Maximum dynamic deformations measured inside the vehicle are compared to the results calculated in the numerical simulation. Results show that the numerical simulation is in good agreement with the full-scale field test.
Simulations of drift waves in 3D magnetic configurations
International Nuclear Information System (INIS)
Drift waves are commonly held responsible for anomalous transport in tokamak configurations and in particular for the anomalously high heat loss. The next generation of stellarators on the other hand are hoped to be characterized by a much smaller neo-classical transport and by particle confinement close to that of tokamaks. There is nevertheless a strong interest in the stellarator community to study the properties of drift waves in 3D magnetic configurations. To serve this interest we have developed the first global gyrokinetic code, EUTERPE, aimed at the investigation of linear drift wave stability in general toroidal geometry. The physical model assumes electrostatic waves and adiabatic electrons. EUTERPE is a particle-in-cell (PIC) code in which the gyrokinetic Poisson equation is discretized with the finite element method defined in the PEST -1 system of magnetic coordinates. The magnetic geometry is provided by the magnetohydrodynamic (MHD) equilibrium code VMEC. The complete 3D model has been successfully validated in toroidal axisymmetric and straight helical geometries and has permitted the first simulation of unstable global ITG driven modes in non-axisymmetric toroidal configurations. As a first application, two configurations have been studied, the Quasi-Axially symmetric Stellarator with three fields periods (QAS3) currently one system under consideration at the Princeton Plasma Physics Laboratory and the Helically Symmetric experiment (HSX) which has recently started operation at the University of Wisconsin. QAS3 is characterized by a tokamak-Iike field in the outer part of the torus. In this structure the drift waves are mainly affected by the magnetic shear and barely by the shape of the plasma. Also, the results are very close to those obtained for a tokamak. On the other hand, results for the HSX configuration, which is characterized by a dominant helical magnetic field, show a clear 3D effect, namely a strong toroidal variation of the drift wave
Simulate the volcanic radiation features in medium wave infrared channels
Gong, Cailan; Jiang, Shan; Liu, Fengyi; Hu, Yong
2015-10-01
There are different scales and intensities of the volcanic eruption in the world every year. Existing medium wave infrared (MWI) remote sensing channels are often at atmospheric window in 3-5μm, lack of water vapor and carbon dioxide(CO2) absorption channels data, such as 2.2μm, 2.7μm and so on, however the 2.7μm absorption bands can be used as volcanoes, forest fires and other hot target identification. In order to obtain the high-temperature targets (HTT)radiation features, such as volcanic eruptions and forest fires in the water vapor absorption channels, Firstly, the HTT should be identified from the existing bands based on the temperature differences between the objects and the surrounding environment. Then, the HTT radiation features were simulated, and the correlation between the radiations of different bands were established with statistical analysis method. The HTT reorganization from remote sensing data, radiation characteristics simulation in different atmospheric models were described, then the bands transformed models were set up. The volcanic HTT radiation characteristics were simulated in wavelength 2.7μm and 4.433-4.498μm (band 24 of MODIS) based on the known bands of 3.55 -3.93μm (band 3 of FengYun-3 Visible and Infrared Scanning Radiometer (VIRR)). The simulated results were tested by the volcanic HTT radiation characteristics with 4.433-4.498μm by known bands of MODIS image and the simulated 4.433-4.498μm image. The causes of errors generated were analyzed. The study methods were useful to the new remote sensor bands imaging characteristics simulation analysis.
Incorporating information from source simulations into searches for gravitational-wave bursts
Brady, P R; Brady, Patrick R; Ray-Majumder, Saikat
2004-01-01
The detection of gravitational waves from astrophysical sources of gravitational waves is a realistic goal for the current generation of interferometric gravitational-wave detectors. Short duration bursts of gravitational waves from core-collapse supernovae or mergers of binary black holes may bring a wealth of astronomical and astrophysical information. The weakness of the waves and the rarity of the events urges the development of optimal methods to detect the waves. The waves from these sources are not generally known well enough to use matched filtering however; this drives the need to develop new ways to exploit source simulation information in both detections and information extraction. We present an algorithmic approach to using catalogs of gravitational-wave signals developed through numerical simulation, or otherwise, to enhance our ability to detect these waves. As more detailed simulations become available, it is straightforward to incorporate the new information into the search method. This approa...
A new type numerical model foraction balance equation in simulating nearshore waves
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Several current used wave numerical models are briefly described, the computing techniques of the source terms, numerical wave generation and boundary conditions in the action balance equation model are discussed. Not only the quadruplet wave-wave interactions, but also the triad wave-wave interactions are included in the model, so that nearshore waves could be simulated reasonably. The model is compared with the Boussinesq equation and the mild slope equation. The model is applied to calculating the distribu-tions of wave height and wave period field in the Haian Bay area and to simulating the influences of the unsteady current and water level variation on the wave field. Finally, the de-veloping tendency of the model is discussed.
Investigation on Radio Wave Propagation in Shallow Seawater: Simulations and Measurements
Jimenez, Eugenio; Mena, Pablo; Dorta, Pablo; Perez-Alvarez, Ivan; Zazo, Santiago; Perez, Marina; Quevedo, Eduardo
2016-01-01
The authors present full wave simulations and experimental results of propagation of electromagnetic waves in shallow seawaters. Transmitter and receiver antennas are ten-turns loops placed on the seabed. Some propagation frameworks are presented and simulated. Finally, simulation results are compared with experimental ones.
Simulations of jet formation and blast wave collision in laboratory plasmas
Czech Academy of Sciences Publication Activity Database
Velarde, P.; Gonzalez, M.; Fernandez, C.G.; Oliva, E.; Kasperczuk, A.; Pisarczyk, T.; Ullschmied, Jiří; Colombier, J.P.; Ciardi, A.; Stehle, Ch.; Busquet, M.; Rus, Bedřich; Senz, D.G.; Relano, A.
Bristol: IoP Publishing Bristol, UK, 2008, ThO2.4-ThO2.4. (Journal of Physics: Conference Series (IOP)). [The Fifth International Conference on Inertial Fusion Sciences and Applications (IFSA2007). Kobe (JP), 09.09.2007-14.09.2007] R&D Projects: GA MŠk(CZ) LC528 Grant ostatní: HPC EUROPA(XE) RII3-CT-2003-506350 Institutional research plan: CEZ:AV0Z20430508; CEZ:AV0Z10100523 Source of funding: R - rámcový projekt EK Keywords : plasma jet * astrophysical jets Subject RIV: BL - Plasma and Gas Discharge Physics
NUMERICAL SIMULATION OF TYPHOON WAVE UNDER THE INFLUENCE OF WINNIE (NO.9711)
Institute of Scientific and Technical Information of China (English)
JIANG Xiao-ping; ZHONG Zhong; ZHANG Jin-shan; LU Wen-feng
2007-01-01
In this paper, the wind field provided by a meso-scale atmospheric model is employed. When main physical processes, including wave-current interactions, are considered, the latest version of the third generation wave model SWAN is applied to simulate the typhoon wave generated by Typhoon Winnie. The model results are compared with the TOPEX/POSEIDON and ERS-2 satellite altimeter data and analyzed in details. Then the distribution of wave fields are analyzed, with the results showing that applying SWAN to simulate large-scale domain can also fairly reproduce the observed features of waves and realistically reflect the distribution of typhoon waves.
Validation of recent shear wave velocity models in the United States with full-wave simulation
Gao, Haiying; Shen, Yang
2015-01-01
Interpretations of dynamic processes and the thermal and chemical structure of the Earth depend on the accuracy of Earth models. With the growing number of velocity models constructed with different tomographic methods and seismic data sets, there is an increasing need for a systematic way to validate model accuracy and resolution. This study selects five shear wave velocity models in the U.S. and simulates full-wave propagation within the 3-D structures. Surface-wave signals extracted from ambient seismic noise and regional earthquakes are compared with synthetic waveforms at multiple-frequency bands. Phase delays and cross-correlation coefficients between observed and synthetic waveforms allow us to compare and validate these models quantitatively. In general, measurements from regional earthquakes are consistent with ambient noise results, but appear more scattered, which may result from uncertainty of the earthquake source location, origin time, and moment tensor. Our results show the improvement of model prediction with the increase of seismic data sets and implement of advanced methods. There exists a positive linear trend between phase delay and interstation distance for three models, indicating that on average, these models are faster than the real Earth structure. The phase delays from the jointly inverted model of ambient noise and receiver function have negative means at all periods while without obvious dependence on the interstation distance. The full-wave ambient noise tomographic model predicts more accurate phase arrivals compared to other models. This study suggests a need for an integrated model constructed with multiple seismic waveforms and consideration of anisotropy and attenuation.
Implicit finite-difference simulations of seismic wave propagation
Chu, Chunlei
2012-03-01
We propose a new finite-difference modeling method, implicit both in space and in time, for the scalar wave equation. We use a three-level implicit splitting time integration method for the temporal derivative and implicit finite-difference operators of arbitrary order for the spatial derivatives. Both the implicit splitting time integration method and the implicit spatial finite-difference operators require solving systems of linear equations. We show that it is possible to merge these two sets of linear systems, one from implicit temporal discretizations and the other from implicit spatial discretizations, to reduce the amount of computations to develop a highly efficient and accurate seismic modeling algorithm. We give the complete derivations of the implicit splitting time integration method and the implicit spatial finite-difference operators, and present the resulting discretized formulas for the scalar wave equation. We conduct a thorough numerical analysis on grid dispersions of this new implicit modeling method. We show that implicit spatial finite-difference operators greatly improve the accuracy of the implicit splitting time integration simulation results with only a slight increase in computational time, compared with explicit spatial finite-difference operators. We further verify this conclusion by both 2D and 3D numerical examples. © 2012 Society of Exploration Geophysicists.
ALFVÉN WAVES IN SIMULATIONS OF SOLAR PHOTOSPHERIC VORTICES
Energy Technology Data Exchange (ETDEWEB)
Shelyag, S.; Cally, P. S. [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Victoria 3800 (Australia); Reid, A.; Mathioudakis, M. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast BT7 1NN (United Kingdom)
2013-10-10
Using advanced numerical magneto-hydrodynamic simulations of the magnetized solar photosphere, including non-gray radiative transport and a non-ideal equation of state, we analyze plasma motions in photospheric magnetic vortices. We demonstrate that apparent vortex-like motions in photospheric magnetic field concentrations do not exhibit 'tornado'-like behavior or a 'bath-tub' effect. While at each time instance the velocity field lines in the upper layers of the solar photosphere show swirls, the test particles moving with the time-dependent velocity field do not demonstrate such structures. Instead, they move in a wave-like fashion with rapidly changing and oscillating velocity field, determined mainly by magnetic tension in the magnetized intergranular downflows. Using time-distance diagrams, we identify horizontal motions in the magnetic flux tubes as torsional Alfvén perturbations propagating along the nearly vertical magnetic field lines with local Alfvén speed.
Alfv\\'en waves in simulations of solar photospheric vortices
Shelyag, S; Reid, A; Mathioudakis, M
2013-01-01
Using advanced numerical magneto-hydrodynamic simulations of the magnetised solar photosphere, including non-grey radiative transport and a non-ideal equation of state, we analyse plasma motions in photospheric magnetic vortices. We demonstrate that apparent vortex-like motions in photospheric magnetic field concentrations do not exhibit "tornado"-like behaviour or a "bath-tub" effect. While at each time instance the velocity field lines in the upper layers of the solar photosphere show swirls, the test particles moving with the time-dependent velocity field do not demonstrate such structures. Instead, they move in a wave-like fashion with rapidly changing and oscillating velocity field, determined mainly by magnetic tension in the magnetised intergranular downflows. Using time-distance diagrams, we identify horizontal motions in the magnetic flux tubes as torsional Alfv\\'en perturbations propagating along the nearly vertical magnetic field lines with local Alfv\\'en speed.
Large Eddy Simulation of the ventilated wave boundary layer
DEFF Research Database (Denmark)
Lohmann, Iris P.; Fredsøe, Jørgen; Sumer, B. Mutlu; Christensen, Erik Damgaard
2006-01-01
A Large Eddy Simulation (LES) of (1) a fully developed turbulent wave boundary layer and (2) case 1 subject to ventilation (i.e., suction and injection varying alternately in phase) has been performed, using the Smagorinsky subgrid-scale model to express the subgrid viscosity. The model was found...... overall (local) grid size. The results indicate that the large eddies develop in the resolved scale, corresponding to fluid with an effective viscosity decided by the sum of the kinematic and subgrid viscosity. Regarding case 2, the results are qualitatively in accordance with experimental findings....... Injection generally slows down the flow in the full vertical extent of the boundary layer, destabilizes the flow and decreases the mean bed shear stress significantly; whereas suction generally speeds up the flow in the full vertical extent of the boundary layer, stabilizes the flow and increases the mean...
Gravitational Wave Extraction in Simulations of Rotating Stellar Core Collapse
Reisswig, Christian; Sperhake, Ulrich; Schnetter, Erik
2010-01-01
We perform simulations of general relativistic rotating stellar core collapse and compute the gravitational waves (GWs) emitted in the core bounce phase of three representative models via multiple techniques. The simplest technique, the quadrupole formula (QF), estimates the GW content in the spacetime from the mass quadrupole tensor. It is strictly valid only in the weak-field and slow-motion approximation. For the first time, we apply GW extraction methods in core collapse that are fully curvature-based and valid for strongly radiating and highly relativistic sources. We employ three extraction methods computing (i) the Newman-Penrose (NP) scalar Psi_4, (ii) Regge-Wheeler-Zerilli-Moncrief (RWZM) master functions, and (iii) Cauchy-Characteristic Extraction (CCE) allowing for the extraction of GWs at future null infinity, where the spacetime is asymptotically flat and the GW content is unambiguously defined. The latter technique is the only one not suffering from residual gauge and finite-radius effects. All ...
Tümer, Nihal; Svetlov, Stanislav; Whidden, Melissa; Kirichenko, Nataliya; Prima, Victor; Erdos, Benedek; Sherman, Alexandra; Kobeissy, Firas; Yezierski, Robert; Scarpace, Philip J; Vierck, Charles; Wang, Kevin K W
2013-06-01
Explosive overpressure brain injury (OBI) impacts the lives of both military and civilian population. We hypothesize that a single exposure to OBI results in increased hypothalamic expression of oxidative stress and activation of the sympatho-adrenal medullary axis. Since a key component of blast-induced organ injury is the primary overpressure wave, we assessed selective biochemical markers of autonomic function and oxidative stress in male Sprague Dawley rats subjected to head-directed overpressure insult. Rats were subjected to single head-directed OBI with a 358kPa peak overpressure at the target. Control rats were exposed to just noise signal being placed at ~2m distance from the shock tube nozzle. Sympathetic nervous system activation of the adrenal medullae (AM) was evaluated at 6h following blast injury by assessing the expression of catecholamine biosynthesizing enzymes, tyrosine hydroxylase (TH), dopamine-β hydroxylase (DβH), neuropeptide Y (NPY) along with plasma norepinephrine (NE). TH, DβH and NPY expression increased 20%, 25%, and 91% respectively, following OBI (P<0.05). Plasma NE was also significantly elevated by 23% (P<0.05) following OBI. OBI significantly elevated TH (49%, P<0.05) in the nucleus tractus solitarius (NTS) of the brain stem while AT1 receptor expression and NADPH oxidase activity, a marker of oxidative stress, was elevated in the hypothalamus following OBI. Collectively, the increased levels of TH, DβH and NPY expression in the rat AM, elevated TH in NTS along with increased plasma NE suggest that single OBI exposure results in increased sympathoexcitation. The mechanism may involve the elevated AT1 receptor expression and NADPH oxidase levels in the hypothalamus. Taken together, such effects may be important factors contributing to pathology of brain injury and autonomic dysfunction associated with the clinical profile of patients following OBI. PMID:23570732
Wave propagation simulation of radio occultations based on ECMWF refractivity profiles
DEFF Research Database (Denmark)
von Benzon, Hans-Henrik; Høeg, Per
2015-01-01
This paper describes a complete radio occultation simulation environment, including realistic refractivity profiles, wave propagation modeling, instrument modeling, and bending angle retrieval. The wave propagator is used to simulate radio occultation measurements. The radio waves are propagated...... radio occultations. The output from the wave propagator simulator is used as input to a Full Spectrum Inversion retrieval module which calculates geophysical parameters. These parameters can be compared to the ECMWF atmospheric profiles. The comparison can be used to reveal system errors and get a...... better understanding of the physics. The wave propagation simulations will in this paper also be compared to real measurements. These radio occultations have been exposed to the same atmospheric conditions as the radio occultations simulated by the wave propagator. This comparison reveals that precise...