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.
Evolution of blast wave profiles in simulated air blasts: experiment and computational modeling
Chandra, N.; Ganpule, S.; Kleinschmit, N. N.; Feng, R.; Holmberg, A. D.; Sundaramurthy, A.; Selvan, V.; Alai, A.
2012-09-01
Shock tubes have been extensively used in the study of blast traumatic brain injury due to increased incidence of blast-induced neurotrauma in Iraq and Afghanistan conflicts. One of the important aspects in these studies is how to best replicate the field conditions in the laboratory which relies on reproducing blast wave profiles. Evolution of the blast wave profiles along the length of the compression-driven air shock tube is studied using experiments and numerical simulations with emphasis on the shape and magnitude of pressure time profiles. In order to measure dynamic pressures of the blast, a series of sensors are mounted on a cylindrical specimen normal to the flow direction. Our results indicate that the blast wave loading is significantly different for locations inside and outside of the shock tube. Pressure profiles inside the shock tube follow the Friedlander waveform fairly well. Upon approaching exit of the shock tube, an expansion wave released from the shock tube edges significantly degrades the pressure profiles. For tests outside the shock tube, peak pressure and total impulse reduce drastically as we move away from the exit and majority of loading is in the form of subsonic jet wind. In addition, the planarity of the blast wave degrades as blast wave evolves three dimensionally. Numerical results visually and quantitatively confirm the presence of vortices, jet wind and three-dimensional expansion of the planar blast wave near the exit. Pressure profiles at 90° orientation show flow separation. When cylinder is placed inside, this flow separation is not sustained, but when placed outside the shock tube this flow separation is sustained which causes tensile loading on the sides of the cylinder. Friedlander waves formed due to field explosives in the intermediate-to far-field ranges are replicated in a narrow test region located deep inside the shock tube.
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...
Simulation of the Reflected Blast Wave froma C-4 Charge
Energy Technology Data Exchange (ETDEWEB)
Howard, W M; Kuhl, A L; Tringe, J W
2011-08-01
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 {micro}m 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 8 ranges (GR = 0, 2, 4, 8, 10, and 12 inches) along the reflecting surface. Computed and measured waveforms and positive-phase impulses were similar, except at close-in ranges (GR < 2 inches), which were dominated by jetting effects.
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...
Mesh Size Effect in Numerical Simulation of Blast Wave Propagation and Interaction with Structures
Institute of Scientific and Technical Information of China (English)
SHI Yanchao; LI Zhongxian; HAO Hong
2008-01-01
Numerical method is popular in analysing the blast wave propagation and interaction with structures.However, because of the extremely short duration of blast wave and energy transmission between different grids, the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case, even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accurate numerical results.Therefore, both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test results and the design charts in TM5-1300, a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accuracy of the numerical results of blast wave propagation and blast loads on structures.
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.
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.
Numerical simulations of blast wave characteristics with a two-dimensional axisymmetric room model
Sugiyama, Y.; Homae, T.; Wakabayashi, K.; Matsumura, T.; Nakayama, Y.
2017-01-01
This paper numerically visualizes explosion phenomena in order to discuss blast wave characteristics with a two-dimensional axisymmetric room model. After the shock wave exits via an opening, the blast wave propagates into open space. In the present study, a parametric study was conducted to determine the blast wave characteristics from the room exit by changing the room shape and the mass of the high explosive. Our results show that the blast wave characteristics can be correctly estimated using a scaling factor proposed in the present paper that includes the above parameters. We conducted normalization of the peak overpressure curve using the shock overpressure at the exit and the length scale of the room volume. In the case where the scaling factor has the same value, the normalized peak overpressure curve does not depend on the calculation conditions, and the scaling factor describes the blast wave characteristics emerging from the current room model.
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.
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.
Laboratory blast wave driven instabilities
Kuranz, Carolyn
2008-11-01
This presentation discusses experiments involving the evolution of hydrodynamic instabilities in the laboratory under high-energy-density (HED) conditions. These instabilities are driven by blast waves, which occur following a sudden, finite release of energy, and consist of a shock front followed by a rarefaction wave. When a blast wave crosses an interface with a decrease in density, hydrodynamic instabilities will develop. Instabilities evolving under HED conditions are relevant to astrophysics. These experiments include target materials scaled in density to the He/H layer in SN1987A. About 5 kJ of laser energy from the Omega Laser facility irradiates a 150 μm plastic layer that is followed by a low-density foam layer. A blast wave structure similar to those in supernovae is created in the plastic layer. The blast wave crosses an interface having a 2D or 3D sinusoidal structure that serves as a seed perturbation for hydrodynamic instabilities. This produces unstable growth dominated by the Rayleigh-Taylor (RT) instability in the nonlinear regime. We have detected the interface structure under these conditions using x-ray backlighting. Recent advances in our diagnostic techniques have greatly improved the resolution of our x-ray radiographic images. Under certain conditions, the improved images show some mass extending beyond the RT spike and penetrating further than previously observed or predicted by current simulations. The observed effect is potentially of great importance as a source of mass transport to places not anticipated by current theory and simulation. I will discuss the amount of mass in these spike extensions, the associated uncertainties, and hypotheses regarding their origin We also plan to show comparisons of experiments using single mode and multimode as well as 2D and 3D initial conditions. This work is sponsored by DOE/NNSA Research Grants DE-FG52-07NA28058 (Stewardship Sciences Academic Alliances) and DE-FG52-04NA00064 (National Laser User
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.
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.
Blast Wave Characteristics and Equivalency
Sochet, Isabelle; Schneider, Helmut
2010-01-01
ISBN 978-5-94588-079-5; 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 over...
Numerical simulation of long-duration blast wave evolution in confined facilities
Togashi, F.; Baum, J. D.; Mestreau, E.; Löhner, R.; Sunshine, D.
2010-10-01
The objective of this research effort was to investigate the quasi-steady flow field produced by explosives in confined facilities. In this effort we modeled tests in which a high explosive (HE) cylindrical charge was hung in the center of a room and detonated. The HEs used for the tests were C-4 and AFX 757. While C-4 is just slightly under-oxidized and is typically modeled as an ideal explosive, AFX 757 includes a significant percentage of aluminum particles, so long-time afterburning and energy release must be considered. The Lawrence Livermore National Laboratory (LLNL)-produced thermo-chemical equilibrium algorithm, “Cheetah”, was used to estimate the remaining burnable detonation products. From these remaining species, the afterburning energy was computed and added to the flow field. Computations of the detonation and afterburn of two HEs in the confined multi-room facility were performed. The results demonstrate excellent agreement with available experimental data in terms of blast wave time of arrival, peak shock amplitude, reverberation, and total impulse (and hence, total energy release, via either the detonation or afterburn processes.
Numerical simulation of muzzle blast
Tyler-Street, M.
2014-01-01
Structural design methods for naval ships include environmental, operational and military load cases. One of the operational loads acting on a typical naval vessel is the muzzle blast from a gun. Simulating the muzzle blast load acting on a ship structure with CFD and ALE methods leads to large nume
2007-06-01
radiation flows upward, it passes though a 1.7-mm high, tapered, 25-μm thick gold wall cone that is filled 20 ± 3 mg/cm3 silica aerogel (SiO2). Above...this cone is a 20 ± 3 mg/cm3 silica aerogel filled, 1-mm high, 2.4-mm inner diameter, 25-μm thick gold wall cylinder. On the cylinder rests a 4-mm...diameter gold platform that supports a higher density (40-60 mg/cm3) silica aerogel . This aerogel is the region where the blast wave forms after
Improved blasting results with precise initiation:Numerical simulation of sublevel caving blasting
Yi, Changping
2013-01-01
A series of numerical simulations of rock blasting using LS-DYNA software havebeen conducted to investigate the effect of short delay time on the fragmentation inunderground mines. The purpose was to test the hypothesis proposed by Rossmaniththat stress wave interaction could result in finer fragmentation by controlling theinitiation times. The blasted rock was simulated with RHT material model. After thecalculation, the elements with damage level above 0.6 were removed to simulate thefractur...
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
Triple-layer Absorptive Structures for Shock Wave Blast Protection
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Triple-layer absorptive structure is designed to reinforce a missile silo against shock wave blasts. An energy-absorbing layer and a cushion layer overlay the circular silo cover made of reinforced concrete. The dynamic stress analysis is performed by ABAQUS/Explicit. The mesoscopic structure of the energy absorbing layer is designed as an assembly of ductile tubes containing crushable cellular ceramics. Combined mesoscopic and macroscopic simulations indicate that the structure can enhance the survivability of a missile silo against blast waves.
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 Heat of 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.
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.
Numerical simulation of parallel hole cut blasting with uncharged holes
Institute of Scientific and Technical Information of China (English)
Shijie Qu; Xiangbin Zheng; Lihua Fan; Ying Wang
2008-01-01
The cavity formation and propagation process of stress wave from parallel hole cut blasting was simulated with AN-SYS/LS-DYNA 3D nonlinear dynamic finite element software. The distribution of element plastic strain, node velocity, node time-acceleration history and the blasting cartridge volume ratio during the process were analyzed. It was found that the detonation of charged holes would cause the interaction of stress wave with the wall of uncharged holes. Initial rock cracking and displacement to neighboring uncharged holes become the main mechanism of cavity formation in early stage.
Moon, C.; Fan, X.; Ha, K.; Kim, D.
2017-01-01
We have generated planar blast waves over the large area using carbon nanotubes(CNT)-poly-dimethylsiloxane(PDMS) optoacoustic transducer. Pulse laser is absorbed by CNT and converted to heat, and the heat is transferred to PDMS inducing its thermal expansion and blast wave generation. To theoretically describe the planar blast wave generation, we build one-dimensional simulation model and find analytical solutions for temperature and pressure distributions. The analytical solution validated by the experimental data sheds light on how to improve the performance of the new transducer. Resonance of acoustic waves inside the transducer is also discussed. The new optoacoustic transducer optimized based on the fundamental understandings will be useful in generating high quality blast waves for research and industrial applications.
Numerical simulation of stress for the blasting of foundation pit
Institute of Scientific and Technical Information of China (English)
FEI Hong-lu; ZHAO Xin-pu
2008-01-01
Through the simulation of explicit dynamic analysis software LS-DYNA, made an analysis to the particle velocity and the stress distribution of surrounding rock when the explosives blasting. Explicated the mechanical character of surrounding rock in the foun-dation pit blasting, provided a basis to set of blasting parameters and optimized the blast-ing construction.
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].
Numerical simulation of stress for the blasting of foundation pit
Institute of Scientific and Technical Information of China (English)
FEI Hong-lu; ZHAO Xin-pu
2008-01-01
Through the simulation of explicit dynamic analysis software LS-DYNA,made an analysis to the particle velocity and the stress distribution of surrounding rock when the explosives blasting.Explicated the mechanical character of surrounding rock in the foundation pit blasting,provided a basis to set of blasting parameters and optimized the blasting construction.
Experimental Investigation of a Novel Blast Wave Mitigation Device
Directory of Open Access Journals (Sweden)
Zhenbi Su
2009-01-01
Full Text Available 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 maximum pressure over an order of magnitude. Two types of experiments were carried out to study the blast wave mitigation device. The first type of experiments was done with honeycomb structures protected by the blast wave mitigation device. Experimental results show that the device can adequately protect the honeycomb structure. A second type of experiments was done using a Hopkinson bar to measure the pressure transmitted through the blast wave mitigation device. The experimental results agree well with results from a theoretical model.
High-speed measurement of firearm primer blast waves
Courtney, Michael; 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 pressure of 8.2-25.0%. 3) Combined with smaller blast waves, these large variations in peak blast pressure of DDNP-based primers led to delayed ignition and failure to fire in brief field tests.
2013-11-01
coarse-grained (CG) simulation techniques, including inverse Monte Carlo schemes, force-matching approaches, and calibrated techniques based on...accessed on 10/30/2013). NO. OF COPIES ORGANIZATION 17 1 DEFENSE TECHNICAL (PDF) INFORMATION CTR DTIC OCA 1 DIRECTOR (PDF) US
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.
Li, X. D.; Hu, Z. M.; Jiang, Z. L.
2017-03-01
Bio-shock tubes (BSTs) can approximately simulate the typical blast waves produced by nuclear or chemical charge explosions for use in biological damage studies. The profile of an ideal blast wave in air is characterized by the overpressure, the negative pressure, and the positive pressure duration, which are determined by the geometric configurations of BSTs. Numerical experiments are carried out using the Eulerian equations by the dispersion-controlled dissipative scheme to investigate the effect of different structural components on ideal blast waveforms. The results show that cylindrical and conical frustum driver sections with an appropriate length can produce typical blast wave profiles, but a flattened peak pressure may appear when using a tube of a longer length. Neither a double-expansion tube nor a shrinkage tube set in BSTs is practical for the production of an ideal blast waveform. In addition, negative pressure recovery will occur, exceeding the ambient pressure with an increase in pressure in the vacuum section.
Effect of Foam Cladding for Blast Mitigation: Numerical Simulation
Institute of Scientific and Technical Information of China (English)
MA Guowei; YE Ziqing; ZHANG Xingui
2006-01-01
Two numerical simulations were performed to investigate the protective effect of the foam cladding.One simulation is based on a previous experimental study,which is a ballistic pendulum with and without a foam cladding subjected to close-range blast loading.The other model is a steel beam with and without a foam cladding under blast loading.The overpressure due to the blast event can be calculated by the empirical function ConWep or by an arbitrary Lagrangian-Eulerian (ALE)coupling model.The first approach is relatively simple and widely used.The second approach can model the propagation of the blast wave in the air and the interaction between the air and the solid.Itis found that the pendulum with the foam cladding always swings to a larger rotation angel compared to a bare pendulum.However,the steel beam with an appropriate foam cladding has a smaller deflection compared to the bare beam without a foam cladding.It is concluded that the protective effect of the foam cladding depends on the properties of the foam and the protected structure.
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...
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.
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...
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...
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.
Blast wave injury prediction models for complex scenarios
Teland, J.A.; Doormaal, J.C.A.M. van
2012-01-01
Blast waves from explosions can cause lethal injuries to humans. Development of injury criteria has been ongoing for many years, but with the main focus on free field conditions. However, with terrorist actions as a new threat, explosions in urban areas have become of much more interest. Urban areas
Miles, Aaron
2004-11-01
In this talk we discuss the nature of late-time, broad-banded instability development at an interface when a strong blast wave travels from a heavier to lighter fluid, as is the case in a supernova explosion. After a short period of Richtmyer-Meshkov growth, the interface is unstable via the Rayleigh-Taylor mechanism, which rapidly becomes the dominant energy source for growth. This situation is distinct from the classical case in two important ways, both of which can be understood in terms of a bubble merger model we have developed for blast-wave-driven systems. Rather than the constant acceleration feeding the instability to spawn ever larger scales and accelerate the growth, the decaying acceleration in the blast-wave case leads to a decay in the RT growth rate, and a freezing in of a preferred largest scale, which is dependent on the precise details of the system. In the language of bubble-merger models, this can be understood in terms of the time for the generation of the next largest scale being longer than the lifetime of the blast wave. Secondly, the continual expansion behind the blast front precludes the emergence of a self-similar regime, independent of the initial conditions, in the planar case. Self-similarity may be recovered in diverging systems but may be difficult to observe in reality because of rather restrictive conditions that must be met. These observations are borne out by hi-resolution numerical simulations using the higher order Godunov AMR hydrocode Raptor in 2 and 3D, and explain other simulations of instability growth in supernovae explosions; the initial "interfacial" structure is likely very important in determining the late-time growth. The model predictions are also consistent with numerous images of natural and manmade explosions.
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.
Blast event simulation for a vehicle subjected to an explosion
Zhang, G.; Vlahopoulos, N.; Goetz, R.; Velde, R. van de
2007-01-01
One of the main threats to military vehicles originates from 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 an explosion, the response of t
GRB Afterglow Blast Wave Encountering Sudden Circumburst Density Change Produces No Flares
Gat, Ilana; MacFadyen, Andrew
2013-01-01
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 spreadin...
No flares from GRB afterglow blast waves encountering sudden circumburst density change
Gat, Ilana; MacFadyen, Andrew
2013-01-01
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 spreadin...
Frequency-Dependent Attenuation of Blasting Vibration Waves
Zhou, Junru; Lu, Wenbo; Yan, Peng; Chen, Ming; Wang, Gaohui
2016-10-01
The dominant frequency, in addition to the peak particle velocity, is a critical factor for assessing adverse effects of the blasting vibration on surrounding structures; however, it has not been fully considered in blasting design. Therefore, the dominant frequency-dependent attenuation mechanism of blast-induced vibration is investigated in the present research. Starting with blasting vibration induced by a spherical charge propagating in an infinite viscoelastic medium, a modified expression of the vibration amplitude spectrum was derived to reveal the frequency dependency of attenuation. Then, ground vibration induced by more complex and more commonly used cylindrical charge that propagates in a semi-infinite viscoelastic medium was analyzed by numerical simulation. Results demonstrate that the absorptive property of the medium results in the frequency attenuation versus distance, whereas a rapid drop or fluctuation occurs during the attenuation of ground vibration. Fluctuation usually appears at moderate to far field, and the dominant frequency generally decreases to half the original value when rapid drop occurs. The decay rate discrepancy between different frequency components and the multimodal structure of vibration spectrum lead to the unsmooth frequency-dependent attenuation. The above research is verified by two field experiments. Furthermore, according to frequency-based vibration standards, frequency drop and fluctuation should be considered when evaluating blast safety. An optimized piecewise assessment is proposed for more accurate evaluation: With the frequency drop point as the breakpoint, the assessment is divided into two independent sections along the propagating path.
Head Kinematics Resulting from Simulated Blast Loading Scenarios
2012-09-17
pressure wave and the body which commonly damages air-filled organs such as the lungs , gastrointestinal tract, and ears. Secondary blast injury...subsequent impact with surrounding obstacles or the ground. Quaternary injury is the result of other factors including burns or inhalation of dust and gas... Woods , W., Feldman, S., Cummings, T., et al. (2011). Survival Risk Assessment for Primary Blast Exposures to the Head. Journal of neurotrauma, 2328
Blast wave attenuation by lightly destructable granular materials
Golub, V. V.; Lu, F. K.; Medin, S. A.; Mirova, O. A.; Parshikov, A. N.; Petukhov, V. A.; Volodin, V. V.
Terrorist bombings are a dismal reality nowadays. One of the most effective ways for protection against blast overpressure is the use of lightly compacted materials such as sand [1] and aqueous foam [2] as a protective envelope or barrier. According to [1], shock wave attenuation in a mine tunnel (one-dimensional case) behind a destroyed object is given by q_e ≈ q {1}/{1 + 4(S/q)^{1/6} bρ _{mat} /L^{1/3} }where qe — effective charge, S — exposed area of the obstacle, q — TNT equivalent (grams), L — distance between charge and obstacle, b — obstacle thickness and ρ mat — material density. This empirical equation is applicable only in a one-dimensional case but not for a less confined environment. Another way of protecting a structure against blast is to coat the surface with a sacrificial layer. In [3] full-scale experiments were carried out to investigate the behaviour of a covering of aluminum foam under the effect of a blast wave.
Model for small arms fire muzzle blast wave propagation in air
Aguilar, Juan R.; Desai, Sachi V.
2011-11-01
Accurate modeling of small firearms muzzle blast wave propagation in the far field is critical to predict sound pressure levels, impulse durations and rise times, as functions of propagation distance. Such a task being relevant to a number of military applications including the determination of human response to blast noise, gunfire detection and localization, and gun suppressor design. Herein, a time domain model to predict small arms fire muzzle blast wave propagation is introduced. The model implements a Friedlander wave with finite rise time which diverges spherically from the gun muzzle. Additionally, the effects in blast wave form of thermoviscous and molecular relaxational processes, which are associated with atmospheric absorption of sound were also incorporated in the model. Atmospheric absorption of blast waves is implemented using a time domain recursive formula obtained from numerical integration of corresponding differential equations using a Crank-Nicholson finite difference scheme. Theoretical predictions from our model were compared to previously recorded real world data of muzzle blast wave signatures obtained by shooting a set different sniper weapons of varying calibers. Recordings containing gunfire acoustical signatures were taken at distances between 100 and 600 meters from the gun muzzle. Results shows that predicted blast wave slope and exponential decay agrees well with measured data. Analysis also reveals the persistency of an oscillatory phenomenon after blast overpressure in the recorded wave forms.
Numerical simulations of blast-impact problems using the direct simulation Monte Carlo method
Sharma, Anupam
There is an increasing need to design protective structures that can withstand or mitigate the impulsive loading due to the impact of a blast or a shock wave. A preliminary step in designing such structures is the prediction of the pressure loading on the structure. This is called the "load definition." This thesis is focused on a numerical approach to predict the load definition on arbitrary geometries for a given strength of the incident blast/shock wave. A particle approach, namely the Direct Simulation Monte Carlo (DSMC) method, is used as the numerical model. A three-dimensional, time-accurate DSMC flow solver is developed as a part of this study. Embedded surfaces, modeled as triangulations, are used to represent arbitrary-shaped structures. Several techniques to improve the computational efficiency of the algorithm of particle-structure interaction are presented. The code is designed using the Object Oriented Programming (OOP) paradigm. Domain decomposition with message passing is used to solve large problems in parallel. The solver is extensively validated against analytical results and against experiments. Two kinds of geometries, a box and an I-shaped beam are investigated for blast impact. These simulations are performed in both two- and three-dimensions. A major portion of the thesis is dedicated to studying the uncoupled fluid dynamics problem where the structure is assumed to remain stationary and intact during the simulation. A coupled, fluid-structure dynamics problem is solved in one spatial dimension using a simple, spring-mass-damper system to model the dynamics of the structure. A parametric study, by varying the mass, spring constant, and the damping coefficient, to study their effect on the loading and the displacement of the structure is also performed. Finally, the parallel performance of the solver is reported for three sample-size problems on two Beowulf clusters.
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.
Heating of X-Ray Hot Gas in Groups by Blast Waves
Fujita, Y
2001-01-01
In order to find the conditions which determine whether X-Ray hot gas in galaxy groups (intragroup gas; IGG) is heated externally or internally, we investigate the evolution of blast waves in galaxy groups growing on a hierarchical clustering scenario. We find that the blast waves driven by quasars are confined in groups and heat the IGG internally at z~ 1, they expel the IGG from groups; the expelled gas may fall back into the groups later as externally heated gas. Moreover, this may explain the observed low metal abundance of IGG. For blast waves driven by strong starbursts, the shift of the fate of blast waves occurs at z~ 3. On the other hand, although blast waves driven by weak starbursts do not expel IGG from groups, the heating efficiency decreases at z>~ 3 because of radiative cooling. It will be useful to compare these results with XMM-Newton observations.
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. ...
Institute of Scientific and Technical Information of China (English)
杜欣新; 毛毳
2013-01-01
使用 ANSYS/LS-DYNA 建立了 TNT 炸药在空气中爆炸传播的二维计算模型，比较了相同网格划分比例时，三种不同当量 TNT 爆炸后在各自比例距离上测得的超压峰值．结果表明：各峰值基本相同，差别小于104,Pa．在此基础上，改变网格划分比例，模拟计算5,kg 当量 TNT的超压峰值，并与美国常规武器防护设计规范(TM5-855-1)进行对比，提出了与不同比例距离区间相适应的网格划分比例．%A 2-D calculating model of blast wave spreading in the air is established by ANSYS/LS-DYNA, and the peak overpressure measured on several scale distances of three different kinds of equivalent weight are compared under the same mesh size. The result indicates that the differences of the peak overpressures are less than 104 Pa, which means they are basi-cally the same. Based on the above analysis, the authors changes the mesh size to simulate the peak overpressure of 5.00 kg equivalent weight of TNT, and compares it with the result of the code for design of the U.S.A. conventional weapons protec-tion (TM5-855-1), the fundamentals of protective design for conventional weapons, and proposes different mesh generation methods to suit different scale distance zones.
Physics of IED Blast Shock Tube Simulations for mTBI Research.
Mediavilla Varas, Jesus; Philippens, M; Meijer, S R; van den Berg, A C; Sibma, P C; van Bree, J L M J; de Vries, D V W M
2011-01-01
Shock tube 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. A shock tube including sensor system is optimized to simulate realistic improvised explosive device 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 is modeled using a combination of computational fluid dynamics (CFD) simulations for the air blast, and a finite element 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.
Antiknock Performance of Interlayered High-Damping-Rubber Blast Door under Thermobaric Shock Wave
Directory of Open Access Journals (Sweden)
Xiudi Li
2016-01-01
Full Text Available The long duration and high impulse shock wave of thermobaric bomb threatens the security of underground structures. To obtain high resistance blast door against thermobaric shock wave, firstly, the dynamic mechanic property of high damping rubber was studied by split Hopkinson pressure bar (SHPB equipment and the stress-strain relationship of high damping rubber under average strain rate of 5200/s was obtained. Secondly, the numerical model of interlayered high-damping-rubber blast door was established with ANSYS/LS-DYNA code based on test results, and the antiknock performance of interlayered high-damping-rubber blast door under thermobaric shock wave was analyzed by contrast with ordinary blast door. The results showed that the midspan displacement of the blast door decreased firstly and then increased with the increase of thickness of the high-damping-rubber interlayer, and the optimal thickness of the high-damping-rubber interlayer for energy consuming was 150 mm in the calculation condition of this paper. With the increase of the distance between the interlayer and the front surface of the door, the midspan displacement of the blast door decreased continually. The midspan maximum displacement of interlayered high-damping-rubber blast door decreased 74.5% in comparison to ordinary blast door. It showed that the high-damping-rubber structure can effectively improve the antiknock performance of blast door under thermobaric shock wave.
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.
The Blast-Wave-Driven Instability as a Vehicle for Understanding Supernova Explosion Structure
Energy Technology Data Exchange (ETDEWEB)
Miles, A R
2008-05-27
Blast-wave-driven instabilities play a rich and varied role throughout the evolution of supernovae from explosion to remnant, but interpreting their role is difficult due to the enormous complexity of the stellar systems. We consider the simpler and fundamental hydrodynamic instability problem of a material interface between two constant-density fluids perturbed from spherical and driven by a divergent central Taylor-Sedov blast wave. The existence of unified solutions at high Mach number and small density ratio 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 modified to include the effects of divergence and radial velocity gradients. In general, these effects preclude the true self-similar evolution of classical Raleigh-Taylor, but can be incorporated into a quasi-self-similar growth picture. Loss of memory of initial conditions can occur in the quasi-self-similar model, but requires initial mode numbers higher than those predicted for pre-explosion interfaces in Type II SNe, suggesting that their late-time structure is likely strongly influenced by details of the initial perturbations. Where low-modes are dominant, as in the Type Ia Tycho remnant, they result from initial perturbations rather than generation from smaller scales. Therefore, structure observed now contains direct information about the explosion process. When large-amplitude modes are present in the initial conditions, the contribution to the perturbation growth from the Richtmyer-Meshkov instability is significant or dominant compared to Rayleigh-Taylor. Such Richtmyer-Meshkov growth can yield proximity of the forward shock to the growing spikes and structure that strongly resembles that observed in the Tycho. Laser-driven high-energy-density laboratory experiments offer a promising avenue for testing model and simulation descriptions of blast-wave-driven instabilities and making
Numerical Simulation for Blast Analysis of Insulating Glass in a Curtain Wall
Deng, Rong-bing; Jin, Xian-long
2010-04-01
This article presents a three-dimensional numerical simulation method for blast response calculation of insulating glass in a curtain wall based on multi-material arbitrary Lagrangian-Eulerian (ALE) formulation and high-performance computer. The whole analytical model consists of explosion, air, curtain wall system, and ground. In particular, detailed components including insulating glass panels, aluminum column, silicone sealant, and other parts in the curtain wall are set up in terms of actual size and actual assembly. This model takes account of the coupling between blast and structure, nonlinear material behavior, brittle failure of glass material, and non-reflecting boundary definition. Final calculation has been performed on the Dawning 4000A supercomputer using the finite-element code LS-DYNA 971 MPP. The propagation of shock wave in air and blast-structure interaction is quite well estimated by numerical calculation. The damage regions of outer and inner glass are reproduced in the numerical simulations, which are in agreement with the experimental observations. The result provides a global understanding of insulating glass panels under blast loading in the curtain wall system. It may be generated to supplement experimental studies for developing appropriate design guidelines for curtain wall systems as well.
Numerical simulation of armored vehicles subjected to undercarriage landmine blasts
Erdik, A.; Kilic, S. A.; Kilic, N.; Bedir, S.
2016-07-01
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.
On the magnetisation of gamma-ray burst blast waves
Lemoine, Martin; Wang, Xiang-Yu
2013-01-01
The origin of magnetic fields that permeate the blast waves of gamma-ray bursts is a long-standing problem. The present paper argues that in four GRBs revealing extended emission at >100 MeV, with follow-up in the radio, optical and X-ray domains at later times, this magnetisation can be described as the partial decay of the microturbulence that is generated in the shock precursor. Assuming that the extended high energy emission can be interpreted as synchrotron emission of shock accelerated electrons, we model the multi-wavelength light curves of GRB 090902B, GRB 090323, GRB 090328 and GRB 110731A, using a simplified then a full synchrotron calculation with power law decaying microturbulence \\epsilon_B \\propto t^{\\alpha_t} (t denotes the time since injection through the shock, in the comoving blast frame). We find that these models point to a consistent value of the decay exponent -0.5 < \\alpha_t < -0.4.
Current Status of Blast Wave Theory and Computations. Volume 2. The Quasi-Similar Solution
1984-03-01
0.02 0.04 y Fig. IV.4.17 - 260 - SIV.5. ANALYSIS OF REACTIVE BLAST WAVES PROPAGATING THROUGH GASEOUS MIXTURES WITH A SPATIALLY VARYING HEAT OF DETONATION * i...a Spatially Varying Heat of Detonation " Paper Presented at the 8th International Colloquium on Gasdynamics of Ex- plosions and Reactive Systems... of Detonation 260 6. Blast Waves in a Detonating Medium with Transport Properties Taken into Account 287 REFERENCES 326 iii CHAPTER I NON-SELF-SIMILAR
Circulation in blast driven instabilities
Henry de Frahan, Marc; Johnsen, Eric
2016-11-01
Mixing in many natural phenomena (e.g. supernova collapse) and engineering applications (e.g. inertial confinement fusion) is often initiated through hydrodynamic instabilities. Explosions in these systems give rise to blast waves which can interact with perturbations at interfaces between different fluids. Blast waves are formed by a shock followed by a rarefaction. This wave profile leads to complex time histories of interface acceleration. In addition to the instabilities induced by the acceleration field, the rarefaction from the blast wave decompresses the material at the interface, further increasing the perturbation growth. After the passage of the wave, circulation circulation generated by the blast wave through baroclinic vorticity continues to act upon the interface. In this talk, we provide scaling laws for the circulation and amplitude growth induced by the blast wave. Numerical simulations of the multifluid Euler equations solved using a high-order accurate Discontinuous Galerkin method are used to validate the theoretical results.
Ainalis, Daniel; Kaufmann, Olivier; Tshibangu, Jean-Pierre; Verlinden, Olivier; Kouroussis, Georges
2017-01-01
The mining and construction industries have long been faced with considerable attention and criticism in regard to the effects of blasting. The generation of ground vibrations is one of the most significant factors associated with blasting and is becoming increasingly important as mining sites are now regularly located near urban areas. This is of concern to not only the operators of the mine but also residents. Mining sites are subjected to an inevitable compromise: a production blast is designed to fragment the utmost amount of rock possible; however, any increase in the blast can generate ground vibrations which can propagate great distances and cause structural damage or discomfort to residents in surrounding urban areas. To accurately predict the propagation of ground vibrations near these sensitive areas, the blasting process and surrounding environment must be characterised and understood. As an initial step, an accurate model of the source of blast-induced vibrations is required. This paper presents a comprehensive review of the approaches to model the blasting source in order to critically evaluate developments in the field. An overview of the blasting process and description of the various factors which influence the blast performance and subsequent ground vibrations are also presented. Several approaches to analytically model explosives are discussed. Ground vibration prediction methods focused on seed waveform and charge weight scaling techniques are presented. Finally, numerical simulations of the blasting source are discussed, including methods to estimate blasthole wall pressure time-history, and hydrodynamic codes.
Analytical Solution of the Blast Wave Problem in a Non-Ideal Gas
Institute of Scientific and Technical Information of China (English)
L. P. Singh; S. D. Ram; D. B. Singh
2011-01-01
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.%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.Blast waves are common occurrences in the Earth's atmosphere.They result from a sudden release of a relatively large amount of energy.Typical examples are lightening and chemical or nuclear explosions.Assume that we have an explosion,following which there may exist a very small region filled with hot matter at high pressure in a duration,which starts to expand outwards with its front headed by a strong shock.The process generally takes place in a very short time after which a forward-moving shock wave develops,which continuously assimilates the ambient air into the blast wave.Although some of the explosive material may still remain near the center,the amount of the air absorbed increases with time,and the later behavior of the blast wave may well be represented by the model of the shock wave at the front and a purely gasdynamic treatment for the motion of the air inside,which may be assumed to have ideal and non-viscous adiabatic heat exponent.
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 openings. The samples of the specifically designed body armor in which the liquid-filled plastic tubings were installed vertically as the outer layer of the body armor were tested. The blast test results demonstrated that blast overpressure behind the body armor samples was remarkably reduced by 97% in 0.2 msec after the liquid flowed out of its appropriate volume through the openings. The results also suggested that a volumetric liquid surge might be created when kinetic energy of blast shock wave was transferred into hydraulic energy to cause a rapid physical movement or displacement of the liquid. The volumetric liquid surge has a strong destructive power, and can cause a noncontact, remote injury in humans (such as blast-induced traumatic brain injury and post-traumatic stress disorder) if it is created in cardiovascular system. The hydraulic energy redirection and release technology can successfully mitigate blast shock waves from the outer surface of the body armor. It should be further explored as an innovative approach to effectively protect against blast threats to civilian and military personnel.
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.
A geophysical shock and air blast simulator at the National Ignition Facility
Energy Technology Data Exchange (ETDEWEB)
Fournier, K. B.; Brown, C. G.; May, M. J.; Compton, S.; Walton, O. R.; Shingleton, N.; Kane, J. O.; Holtmeier, G.; Loey, H.; Mirkarimi, P. B.; Dunlop, W. H. [Lawrence Livermore National Laboratory, P.O. Box 808, L-481, Livermore, California 94550 (United States); Guyton, R. L.; Huffman, E. [National Securities Technologies, Vasco Rd., Livermore, California 94551 (United States)
2014-09-15
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.
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.
Numerical Simulations of Blast Loads from Near-Field Ground Explosions in Air
Directory of Open Access Journals (Sweden)
Dobrociński Stanisław
2015-12-01
Full Text Available 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.
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.
Analysis of reflected blast wave pressure profiles in a confined room
Sauvan, P. E.; Sochet, I.; Trélat, S.
2012-05-01
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 and small scales. To study the interactions and propagations of the reflected shock waves, the present study was conducted by progressively building a confined volume around the charge. In this way, the influence of each wall and the origins of the reflected shock waves can be determined. The purpose of this paper is to report the blast wave interactions that resulted from the detonation of a stoichiometric propane-oxygen mixture in a confined room.
Prospects for studying how high-intensity compression waves cause damage in human blast injuries
Brown, Katherine; Bo, Chiara; Ramaswamy, Arul; Masouros, Spiros; Newell, Nicolas; Hill, Adam; Clasper, Jon; Bull, Anthony; Proud, William
2011-06-01
Blast injuries arising from improvised explosive devices are often complex leading to long-term disability in survivors. There is an urgent need to mitigate against the effects of blast that lead to these injuries, and to also improve post-traumatic therapeutic treatments related to problems associated with damage and healing processes and infections. We have initiated multidisciplinary studies to develop experimental facilities and strategies for analyzing the effects blast waves upon the human body, from cellular through to skeletal functions. This work is supported by the Atomic Weapons Establishment and the Defence Science and Technology Laboratory, UK.
Analysis of reflected blast wave pressure profiles in a confined room
Sochet, Isabelle; Sauvan, Pierre-Emmanuel; Trelat, Sophie
2012-01-01
International audience; 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...
POLYCYCLIC AROMATIC HYDROCARBON PROCESSING IN THE BLAST WAVE OF THE SUPERNOVA REMNANT N132D
Energy Technology Data Exchange (ETDEWEB)
Tappe, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-72, Cambridge, MA 02138 (United States); Rho, J. [SOFIA Science Mission Operations/USRA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035 (United States); Boersma, C. [NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States); Micelotta, E. R., E-mail: atappe@cfa.harvard.edu [Department of Physics and Astronomy, Western University, 1151 Richmond Street, London, Ontario N6A 3K7 (Canada)
2012-08-01
We present Spitzer Infrared Spectrograph 14-36 {mu}m 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 {mu}m 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 {mu}m 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.
Energy spectrum analysis of blast waves based on an improved Hilbert-Huang transform
Li, L.; Wang, F.; Shang, F.; Jia, Y.; Zhao, C.; Kong, D.
2016-07-01
Using the improved Hilbert-Huang transform (HHT), this paper investigates the problems of analysis and interpretation of the energy spectrum of a blast wave. It has been previously established that the energy spectrum is an effective feature by which to characterize a blast wave. In fact, the higher the energy spectra in a frequency band of a blast wave, the greater the damage to a target in the same frequency band. However, most current research focuses on analyzing wave signals in the time domain or frequency domain rather than considering the energy spectrum. We propose here an improved HHT method combined with a wavelet packet to extract the energy spectrum feature of a blast wave. When applying the HHT, the signal is first roughly decomposed into a series of intrinsic mode functions (IMFs) by empirical mode decomposition. The wavelet packet method is then performed on each IMF to eliminate noise on the energy spectrum. Second, a coefficient is introduced to remove unrelated IMFs. The energy of each instantaneous frequency can be derived through the Hilbert transform. The energy spectrum can then be obtained by adding up all the components after the wavelet packet filters and screens them through a coefficient to obtain the effective IMFs. The effectiveness of the proposed method is demonstrated by 12 groups of experimental data, and an energy attenuation model is established based on the experimental data. The improved HHT is a precise method for blast wave signal analysis. For other shock wave signals from blasting experiments, an energy frequency time distribution and energy spectrum can also be obtained through this method, allowing for more practical applications.
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.
Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects.
Courtney, Amy C; Andrusiv, Lubov P; Courtney, Michael W
2012-04-01
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 pressures from 204 kPa to 1187 kPa (with 0.5-5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.
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...
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.
Synchrotron signature of a relativistic blast wave with decaying microturbulence
Lemoine, M
2012-01-01
Microphysics of weakly magnetized relativistic collisionless shock waves, corroborated by recent high performance numerical simulations, indicate the presence of a microturbulent layer of large magnetic field strength behind the shock front, which must decay beyond some hundreds of skin depths. The present paper discusses the dynamics of such microturbulence, borrowing from these same numerical simulations, and calculates the synchrotron signature of a powerlaw of shock accelerated particles. The decaying microturbulent layer is found to leave distinct signatures in the spectro-temporal evolution of the spectrum $F_\
Sharma, Anupam; Long, Lyle N.
2004-10-01
A particle approach using the Direct Simulation Monte Carlo (DSMC) method is used to solve the problem of blast impact with structures. A novel approach to model the solid boundary condition for particle methods is presented. The solver is validated against an analytical solution of the Riemann shocktube problem and against experiments on interaction of a planar shock with a square cavity. Blast impact simulations are performed for two model shapes, a box and an I-shaped beam, assuming that the solid body does not deform. The solver uses domain decomposition technique to run in parallel. The parallel performance of the solver on two Beowulf clusters is also presented.
Monte Carlo simulation as a tool to predict blasting fragmentation based on the Kuz Ram model
Morin, Mario A.; Ficarazzo, Francesco
2006-04-01
Rock fragmentation is considered the most important aspect of production blasting because of its direct effects on the costs of drilling and blasting and on the economics of the subsequent operations of loading, hauling and crushing. Over the past three decades, significant progress has been made in the development of new technologies for blasting applications. These technologies include increasingly sophisticated computer models for blast design and blast performance prediction. Rock fragmentation depends on many variables such as rock mass properties, site geology, in situ fracturing and blasting parameters and as such has no complete theoretical solution for its prediction. However, empirical models for the estimation of size distribution of rock fragments have been developed. In this study, a blast fragmentation Monte Carlo-based simulator, based on the Kuz-Ram fragmentation model, has been developed to predict the entire fragmentation size distribution, taking into account intact and joints rock properties, the type and properties of explosives and the drilling pattern. Results produced by this simulator were quite favorable when compared with real fragmentation data obtained from a blast quarry. It is anticipated that the use of Monte Carlo simulation will increase our understanding of the effects of rock mass and explosive properties on the rock fragmentation by blasting, as well as increase our confidence in these empirical models. This understanding will translate into improvements in blasting operations, its corresponding costs and the overall economics of open pit mines and rock quarries.
Numerical Simulation of 3-D Wave Crests
Institute of Scientific and Technical Information of China (English)
YU Dingyong; ZHANG Hanyuan
2003-01-01
A clear definition of 3-D wave crest and a description of the procedures to detect the boundary of wave crest are presented in the paper. By using random wave theory and directional wave spectrum, a MATLAB-platformed program is designed to simulate random wave crests for various directional spectral conditions in deep water. Statistics of wave crests with different directional spreading parameters and different directional functions are obtained and discussed.
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.
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.
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
Nonlinear propagation of high-frequency energy from blast waves as it pertains to bat hearing
Loubeau, Alexandra
Close exposure to blast noise from military weapons training can adversely affect the hearing of both humans and wildlife. One concern is the effect of high-frequency noise from Army weapons training on the hearing of endangered bats. Blast wave propagation measurements were conducted to investigate nonlinear effects on the development of blast waveforms as they propagate from the source. Measurements were made at ranges of 25, 50, and 100 m from the blast. Particular emphasis was placed on observation of rise time variation with distance. Resolving the fine shock structure of blast waves requires robust transducers with high-frequency capability beyond 100 kHz, hence the limitations of traditional microphones and the effect of microphone orientation were investigated. Measurements were made with a wide-bandwidth capacitor microphone for comparison with conventional 3.175-mm (⅛-in.) microphones with and without baffles. The 3.175-mm microphone oriented at 90° to the propagation direction did not have sufficient high-frequency response to capture the actual rise times at a range of 50 m. Microphone baffles eliminate diffraction artifacts on the rise portion of the measured waveform and therefore allow for a more accurate measurement of the blast rise time. The wide-band microphone has an extended high-frequency response and can resolve shorter rise times than conventional microphones. For a source of 0.57 kg (1.25 lb) of C-4 plastic explosive, it was observed that nonlinear effects steepened the waveform, thereby decreasing the shock rise time, from 25 to 50 m. At 100m, the rise times had increased slightly. For comparison to the measured blast waveforms, several models of nonlinear propagation are applied to the problem of finite-amplitude blast wave propagation. Shock front models, such as the Johnson and Hammerton model, and full-waveform marching algorithms, such as the Anderson model, are investigated and compared to experimental results. The models
Energy Technology Data Exchange (ETDEWEB)
Timofeev, E.V.; Saito, T.; Takayama, K. [Tohoku Univ., Inst. of Fluid Science, Shock Wave Research Center, Sendai (Japan)]. E-mail: timo@ceres.ifs.tohoku.ac.jp; Voinovich, P.A. [Russian Academy of Sciences, Supercomputer Center at the A.F. Ioffe Physico-Technical Inst., St. Petersburg (Russian Federation); Galyukov. A.O. [Soft-Impact Ltd., St. Petersburg (Russian Federation); Tahir, R.B.; Molder, S. [Ryerson Polytechnic Univ., Toronto, Ontario (Canada)
2002-07-01
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.
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.
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.
Booij, S.M.; Absil, L.H.J.; Bruinsma, A.J.A.; Braat, J.J.M.; Brug, H. van
1999-01-01
An optical study of blast wave propagation and interaction with multiple structures is presented, as well as a method for obtaining quantitative information on the pressure distribution from a number of phase-stepped images. The blast load distribution on buildings is studied by scaling down the bui
Physics of shock tube simulated IED blast for mTBI research
Mediavilla Varas, J.; Philippens, M.M.G.M.; Meijer, S.R.
2010-01-01
The objective of this research is to understand the blast propagation into the human skull and brain causing mTBI and use this knowledge for enabling design of effective protection measures against them. A shock tube including sensor system was optimized to simulate realistic IED blast profiles obta
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
Performance tests of a fast-acting valve for the driver tubes of a large blast/thermal simulator
Stacey, Marcela R.
1992-05-01
This document describes the testing of a fast-acting throat valve element designed by Eaton Consolidated Controls for use in driver tubes, (blast generators) of a Large Blast/Thermal Simulator (LB/TS). An LB/TS is used to simulate decaying blast waves such as are generated by nuclear explosions. The Eaton Throat Valve Element (ETVE) was tested at the Idaho National Engineering Laboratory (INEL) to evaluate its performance against the design criteria. The ETVE was mounted at the end of a driver tube and actuated 16 times at 6 different driver pressures ranging from 396 kPa to 12.4 MPa (57.5 psi to 1,800 psi). The valve seals survived successfully all 16 tests with the driver gas at room temperature and maintained an acceptable leak rate throughout the test program. The average valve lag time was determined to vary from 36 to 120 ms; however, the valve was found to chatter, going through several (up to 20) opening/closing cycles after actuation before settling in the open position. An increase in the pneumatic supply pressure driving the valve showed a minor decrease in the number of chattering cycles. When the valve was actuated with no pressure in the driver tube, no chattering was observed. At the conclusion of the test sequence, the valve seals were inspected and were in good condition. The shock waves appeared to agree with code predictions when the chattering effects were disregarded.
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.
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.
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.
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.
Impulsive dispersion of a granular layer by a weak blast wave
Rodriguez, V.; Saurel, R.; Jourdan, G.; Houas, L.
2017-03-01
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.
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.
Water Temperature and Concentration Measurements Within the Expanding Blast Wave of a High Explosive
2011-03-15
housing was made of 1018 steel , and the gauge roof was extended to shield the opto- mechanical components from the primary blast wave. The input fiber...regions of each image indicate the steel frame and support crossbars of the gauge. This set of images provides a sense of the speed with which the shock was...University Press) [3] Peuker J M, Lynch P, Krier H and Glumac N 2009 Optical depth measurements of fireballs from aluminized high explosives Opt
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.
Quick Estimates of Peak Overpressure from Two Simultaneous Blast Waves
1977-12-01
C. S. Knauth, Nuclear Blast Standard (1 kT), Air Force Weapons Laboratory, Krtland A-r Force Base, New Mexico , AFWL-TR-73-55, (Revised) 1975. 6 C. E...Needham, Private Communication, Air Force Weapons Laboratory, Kirtland Air Force Base, New Mexico , November 1977. 36i If 1I * I I| ~~’.0 DISTRIBUTION...for Ops. & Plans Defense Communications Agency ATTN: Dep. Dir. for Nuc. Chem. Matters ATTN: Code 930 ATTN: MOCA -ADL ATTN: CCTC/C672, F. Moore Deputy
Large eddy simulation of breaking waves
DEFF Research Database (Denmark)
Christensen, Erik Damgaard; Deigaard, Rolf
2001-01-01
is described by large eddy simulation where the larger turbulent features are simulated by solving the flow equations, and the small scale turbulence that is not resolved by the flow model is represented by a sub-grid model. A simple Smagorinsky sub-grid model has been used for the present simulations......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....... The 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...
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...
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.
Nemeth, A.A.; Hulscher, S.J.M.H.; Damme, van R.M.J.
2003-01-01
Sand waves form a prominent regular pattern in the offshore seabeds of sandy shallow seas. A two dimensional vertical (2DV) flow and morphological numerical model describing the behaviour of these sand waves has been developed. The model contains the 2DV shallow water equations, with a free water su
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
Velocities and Displacements of Shrapnel and a Shock Wave during Blast
Institute of Scientific and Technical Information of China (English)
ZHAO De-hui; TIAN Da-zhan; XU Jin-yu; ZHANG Hai-rong
2007-01-01
It is important to minimize the destruction of defense works when blasted. In our opinion,information in the available literature is very deficient. We now present our research results on better and simpler formulas for calculating the velocities and displacements of shrapnel and a shock wave;these formulas are indispensable for understanding the destruction of blast. Formulas now available in China are too complicated. In this paper, we derive Equation (13) as the formula for calculating the velocity of shrapnel and Equation (18) as that for calculating the velocity of a shock wave. We used the test data of Denver Research Institute, as reported in Reference 4, as numerical example and found that our Equations (13) and (18) give calculated results that agree well with their test data in two respects: (1) both test data and our calculations show that at first a shock wave is ahead of shrapnel,then their displacements are equal, and finally shrapnel is ahead of the shock wave; (2) when the displacements of shrapnel and shock wave are equal, the time is 0.34 s according to test data and 0.31 s according to our calculations.
Orlando, S; Miceli, M
2016-01-01
The symbiotic nova V745 Sco was observed in outburst on 2014 February 6. Its observations by the Chandra X-ray Observatory at days 16 and 17 have revealed a spectrum characterized by asymmetric and blue-shifted emission lines. Here we investigate the origin of these asymmetries through three-dimensional hydrodynamic simulations describing the outburst during the first 20 days of evolution. The model takes into account thermal conduction and radiative cooling and assumes a blast wave propagates through an equatorial density enhancement. From the simulations, we synthesize the X-ray emission and derive the spectra as they would be observed with Chandra. We find that both the blast wave and the ejecta distribution are efficiently collimated in polar directions due to the presence of the equatorial density enhancement. The majority of the X-ray emission originates from the interaction of the blast with the equatorial density enhancement and is concentrated on the equatorial plane as a ring-like structure. Our "be...
A Numerical Study on the Screening of Blast-Induced Waves for Reducing Ground Vibration
Park, Dohyun; Jeon, Byungkyu; Jeon, Seokwon
2009-06-01
Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock, but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact, and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration. The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration, namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes, distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method of blast-induced waves was considerably effective under certain design conditions. The design details for field application have also been proposed.
Simulation of blast action on civil structures using ANSYS Autodyn
Fedorova, N. N.; Valger, S. A.; Fedorov, A. V.
2016-10-01
The paper presents the results of 3D numerical simulations of shock wave spreading in cityscape area. ANSYS Autodyne software is used for the computations. Different test cases are investigated numerically. On the basis of the computations, the complex transient flowfield structure formed in the vicinity of prismatic bodies was obtained and analyzed. The simulation results have been compared to the experimental data. The ability of two numerical schemes is studied to correctly predict the pressure history in several gauges placed on walls of the obstacles.
Battery Lifetime Analysis and Simulation Tool (BLAST) Documentation
Energy Technology Data Exchange (ETDEWEB)
Neubauer, J. [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2014-12-01
The deployment and use of lithium-ion (Li-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 (SOC) 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 (NREL) has developed the Battery Lifetime Analysis and Simulation Tool (BLAST) suite. 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.
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.
Ocean Wave Simulation Based on Wind Field.
Li, Zhongyi; Wang, Hao
2016-01-01
Ocean wave simulation has a wide range of applications in movies, video games and training systems. Wind force is the main energy resource for generating ocean waves, which are the result of the interaction between wind and the ocean surface. While numerous methods to handle simulating oceans and other fluid phenomena have undergone rapid development during the past years in the field of computer graphic, few of them consider to construct ocean surface height field from the perspective of wind force driving ocean waves. We introduce wind force to the construction of the ocean surface height field through applying wind field data and wind-driven wave particles. Continual and realistic ocean waves result from the overlap of wind-driven wave particles, and a strategy was proposed to control these discrete wave particles and simulate an endless ocean surface. The results showed that the new method is capable of obtaining a realistic ocean scene under the influence of wind fields at real time rates.
Numerical Simulation of Shock（Blast）Wave Interaction with Bodies
Institute of Scientific and Technical Information of China (English)
JialingLE
1999-01-01
Some typical results of computation on the shock(blast)wave interaction (2-D and 3-D) with bodies and its experimental validation in shock tube are summarized,suggestions for improving the numerical method(Difference scheme and grid systems).developing 3-D optical quantitative visualization technology and further studying the unsteady turbulent flow are put forward.
Physics of IED blast shock tube simulations for mTBI research
Mediavilla Varas, J.; Philippens, M.M.G.M.; Meijer, S.R.; Berg, A.C. van den; Sibma, P.C.; Bree, J.L.M.J. van; Vries, D.V.W.M. de
2011-01-01
Shock tube 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. A shock tube including sensor system is optimized to simulate realistic impro-vised explosive device bla
Application of Wavelet Analysis in Signal De-noising of Blast Shock Wave Overpressure
Institute of Scientific and Technical Information of China (English)
Jian-wei JIANG; Yu-jun FANG; Li-zhen WAN; Jian-bing MEN
2010-01-01
It's a problem to be solved how to de-noise the signal of blast shock wave overpressure.In the conventional methods,the high frequency of the signal is cut directly by some mathematics algorithms,such as Fourier Transform,but some of the useful signal will be cut together.We adopt a new method for the signal de-noising of shock wave overpressure by wavelet analysis.There are four steps in this method.Firstly,the original signal is de-cpmposed.Then the time-frequency features of the signal and noise are analyzed.Thirdly,the noise is separated from the signal by only cutting its frequency while the useful signal frequency is reserved as much as possible.Lastly,the useful signal with least loss of information is recovered by reconstruction process.To verify this method,a blast shock wave signal is de-noised with FFT to make a comparison.The results show that the signal de-noised by wavelet analysis approximates the ideal signal well.
Blast Overpressure Studies with Animals and Man: Biological Response to Complex Blast Waves
1993-10-31
armored vehicle. 4. To investigate the relative importance of the quasi- static pressure rise component of complex waves in I producing trauma by...were to be protected were blocked with a selected I earplug. Each sheep received a preanesthetic intramuscular (IM) injection of atropine sulfate (0.44...ketamine hydrochloride (22 mg/kg), exsanguinated by severing the jugular veins and carotid I arteries, and necropsied. Each animal was assessed for
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.
Maximal exercise performance-impairing effects of simulated blast overpressure in sheep.
Januszkiewicz, A J; Mundie, T G; Dodd, K T
1997-07-25
Lung contusion has been identified as a primary blast injury. These experiments addressed a fundamental and overt endpoint of primary blast injury, incapacitation (performance decrement). Respiration, hemodynamics, and blood gases were measured in sheep undergoing incremental exercise challenge before and 1 h after simulated blast exposure of the thorax. Pathologic examination of lung tissue was performed after exposure and exercise testing. Blast overpressure was simulated in the laboratory using a compressed air-driven shock tube. Three levels of lung injury (Levels 1-3, 'Trivial', 'Slight', and 'Moderate' injury, respectively) were examined for effects on maximal oxygen consumption (VO[2max]), an index of cardiorespiratory fitness. Resting hemodynamics and blood gases were relatively normal an hour after exposure, immediately before exercise. However, Levels 1-3 lung injury were associated with average 4.8, 29.9 and 49.3% VO(2max). decreases, respectively. These performance decrements for Levels 2 and 3 were significantly different from respective controls (non-exposed). Exercise caused significant hemoconcentration in sheep under control conditions, before exposure (resting 9.5 +/- 0.9, end-exercise 11.8 +/- 0.9 g/100 ml). Blast exposure resulted in average decreases of 4.9 +/- 3.4, 12.8 +/- 4.0, and 12.6 +/- 3.3% in exercise-induced hemoconcentration for Levels 1-3 injury, respectively. Normal exercise-induced hemodynamic increases were also attenuated after exposure. Levels 2 and 3 injury resulted in average 22.6 +/- 2.9 and 18.5 +/- 11.2% stroke volume decreases, and also 22.3 +/- 8.4 and 29.0 +/- 14.2% cardiac output decreases, respectively, during exercise. While blast lung pathology and pulmonary function changes could account for post-blast performance decrements, these experiments suggest that in sheep, early after exposure, diminished hemoconcentration and cardiac disfunction may also contribute to decreased exercise performance.
Absorption Phenomena and a Probable Blast Wave in the 13 July 2004 Eruptive Event
Grechnev, V V; Slemzin, V A; Chertok, I M; Kuzmenko, I V; Shibasaki, K; 10.1007/s11207-008-9178-8
2008-01-01
We present a case study of the 13 July 2004 solar event, in which disturbances caused by eruption of a filament from an active region embraced a quarter of the visible solar surface. Remarkable are absorption phenomena observed in the SOHO/EIT 304 A channel; they were also visible in the EIT 195 A channel, in the H-alpha line, and even in total radio flux records. Coronal and Moreton waves were also observed. Multi-spectral data allowed reconstructing an overall picture of the event. An explosive filament eruption and related impulsive flare produced a CME and blast shock, both of which decelerated and propagated independently. Coronal and Moreton waves were kinematically close and both decelerated in accordance with an expected motion of the coronal blast shock. The CME did not resemble a classical three-component structure, probably, because some part of the ejected mass fell back onto the Sun. Quantitative evaluations from different observations provide close estimates of the falling mass, ~3 10^15 g, whic...
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...
VISAR Unfold Analysis of MagLIF Laser Blast Wave Experiments
Hess, Mark; Peterson, Kyle; Harvey-Thompson, Adam
2015-06-01
MagLIF (Magnetized Liner Inertial Fusion) is a fusion energy scheme, which utilizes a short laser pulse to preheat a fuel, and a magnetically driven cylindrical liner to compress the fuel to high energy density plasma conditions. Recently, a set of successful experiments have been performed to evaluate the effectiveness of our preheat process in MagLIF using the Z-Beamlet laser at Sandia. The fuel is preheated in the liner, with no compression from the Z-machine, and a VISAR diagnostic was fielded on the outer surface of the liner to measure velocity of the liner due to the pressure of the laser blast wave on the inner surface of the liner. In support of this program, we developed a fast unfold method of the VISAR data using semi-analytical techniques/numerical methods. The method incorporates appropriate boundary conditions at both edges of the VISAR foil, realistic EOS tables, and an additional pressure pulse time-delay feature for accurately unfolding the time-dependent pressure from the VISAR data. Our fully automated method can produce high-quality unfolds of the laser blast wave in under a minute. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE-AC04-94AL85000.
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...
Energy Technology Data Exchange (ETDEWEB)
Sakamoto, I. [Traffic Safety and Nuisance Research Inst., Tokyo (Japan); Higashino, F. [Tokyo Univ. of Agriculture and Technology, Tokyo (Japan). Faculty of Technology
1996-08-25
In order to simulate behavior of shock wave propagating in a square kinked duct, a numerical method based on the TVD scheme was developed. Both initial conditions and mesh sizes were tested to simulate the experimental results obtained from exploding wire experiments. Numerical density contours showed qualitatively good agreement with experimental results of schlieren photographs. Measured pressure ratios across the shock front also showed good agreement when they were compared quantitatively with computations along the upper edge, lower edge and center line of the duct. The present method using a narrow high pressure region in a duct as an initial condition was shown to be useful for predicting blast wave decay. 6 refs., 11 figs., 1 tab.
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.
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.
Terahertz/mm wave imaging simulation software
Fetterman, M. R.; Dougherty, J.; Kiser, W. L., Jr.
2006-10-01
We have developed a mm wave/terahertz imaging simulation package from COTS graphic software and custom MATLAB code. In this scheme, a commercial ray-tracing package was used to simulate the emission and reflections of radiation from scenes incorporating highly realistic imagery. Accurate material properties were assigned to objects in the scenes, with values obtained from the literature, and from our own terahertz spectroscopy measurements. The images were then post-processed with custom Matlab code to include the blur introduced by the imaging system and noise levels arising from system electronics and detector noise. The Matlab code was also used to simulate the effect of fog, an important aspect for mm wave imaging systems. Several types of image scenes were evaluated, including bar targets, contrast detail targets, a person in a portal screening situation, and a sailboat on the open ocean. The images produced by this simulation are currently being used as guidance for a 94 GHz passive mm wave imaging system, but have broad applicability for frequencies extending into the terahertz region.
Mathematical simulation of steep waves at a focus point
Institute of Scientific and Technical Information of China (English)
XU Li; ZHANG Min; WANG Yan-ying
2007-01-01
Mathematical models simulating steep waves at a focus point are presented in this paper. Simulations of extreme waves in a model basin were used to determine the loads on floating structures induced by the waves. Based on a new wave theory, numerical test results show that the simulation procedure is effective and the induced motion of water particles in the front of waves is an important factor influencing impact loads on floating bodies.
Institute of Scientific and Technical Information of China (English)
石秉良; 周孔亢; 张云; 祁涛
2016-01-01
In order to explore the response of vehicle cab bottom under the non-contact blast wave of improvised explosive device, mine, etc. smoothed particle hydrodynamics (SPH) algorithm is employed. The energy, stress contours and destruction form of a square plate restricted by four sides under blast wave with SPH algorithm are analyzed, and the results is highly comparable with empirical formula and the classical method arbitrary Lagrangian-Eulerian (ALE), the SPH algorithm is available for the transient dynamic response analysis of structure under blast wave. The SPH algorithm is employed to analyze the response of vehicle bottom under explosive blast wave, and the response of fuel tank, battery support, cabin floor and chassis, etc. are validated with physical test. A conclusion can be made that SPH needs simpler model and lower cost, and the result is more accurate. So SPH can be used to predict the vehicle cab bottom shell structure’s response under the blast wave, and provide a reference to the anti-explosion design of vehicle bottom structure.%针对地雷等简易爆炸装置在车辆驾驶室底部非接触爆炸问题，引入无网格光滑粒子流体动力学(Smoothed particle hydrodynamics, SPH)算法模拟爆炸冲击波作用下车辆底部结构的响应。以四边约束靶板为研究对象，分析靶板在爆炸冲击下的能量、应力变化和破坏形态，通过与传统的任意拉格朗日欧拉(Arbitrary Lagrangian-Eulerian, ALE)固流耦合分析法和经验公式计算结果对比，验证SPH算法应用于处理此类问题的可行性；利用SPH算法对爆炸冲击波作用下驾驶室底部结构进行数值仿真，分析车辆底部的油箱、电瓶支架、驾驶室地板、车架等关键结构的冲击响应，并与试验做出对比验证。仿真结果表明，基于 SPH 算法的爆炸仿真分析具有精度较高、建模简单、耗费计算资源少等优势，能够应用于爆炸冲击波作用下驾驶室底部板
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
Developing Serpent-Type Wave Generators to Create Solitary Wave Simulations with BEM
Institute of Scientific and Technical Information of China (English)
Wen-Kai WENG; Ruey-Syan SHIH; Chung-Ren CHOU
2013-01-01
Developing serpent-type wave generators to generate solitary waves in a 3D-basin was investigated in this study. Based on the Lagrangian description with time-marching procedures and finite differences of the time derivative, a 3D multiple directional wave basin with multidirectional piston wave generators was developed to simulate ocean waves by using BEM with quadrilateral elements, and to simulate wave-caused problems with fully nonlinear water surface conditions. The simulations of perpendicular solitary waves were conducted in the first instance to verify this scheme. Furthermore, the comparison of the waveform variations confirms that the estimation of 3D solitary waves is a feasible scheme.
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.
Orlando, Salvatore; Drake, Jeremy J.; Miceli, Marco
2017-02-01
The symbiotic nova V745 Sco was observed in outburst on 2014 February 6. Its observations by the Chandra X-ray Observatory at days 16 and 17 have revealed a spectrum characterized by asymmetric and blueshifted emission lines. Here we investigate the origin of these asymmetries through 3D hydrodynamic simulations describing the outburst during the first 20 d of evolution. The model takes into account thermal conduction and radiative cooling, and assumes that a blast wave propagates through an equatorial density enhancement (EDE). From these simulations, we synthesize the X-ray emission and derive the spectra as they would be observed with Chandra. We find that both the blast wave and the ejecta distribution are efficiently collimated in polar directions due to the presence of the EDE. The majority of the X-ray emission originates from the interaction of the blast with the EDE and is concentrated on the equatorial plane as a ring-like structure. Our `best-fitting' model requires a mass of ejecta in the outburst Mej ≈ 3 × 10-7 M⊙ and an explosion energy Eb ≈ 3 × 1043 erg, and reproduces the distribution of emission measure versus temperature and the evolution of shock velocity and temperature inferred from the observations. The model predicts asymmetric and blueshifted line profiles similar to those observed and explains their origin as due to substantial X-ray absorption of redshifted emission by ejecta material. The comparison of predicted and observed Ne and O spectral line ratios reveals no signs of strong Ne enhancement and suggests that the progenitor is a CO white dwarf.
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.
SUPERNOVAE AND THEIR EXPANDING BLAST WAVES DURING THE EARLY EVOLUTION OF GALACTIC GLOBULAR CLUSTERS
Energy Technology Data Exchange (ETDEWEB)
Tenorio-Tagle, Guillermo; Silich, Sergiy [Instituto Nacional de Astrofísica Óptica y Electrónica, AP 51, 72000 Puebla, México (Mexico); Muñoz-Tuñón, Casiana [Instituto de Astrofísica de Canarias (Spain); Cassisi, Santi, E-mail: gtt@inaoep.mx, E-mail: cmt@iac.es, E-mail: cassisi@oa-teramo.inaf.it [INAF—Astronomical Observatory of Collurania, via M. Maggini, I-64100 Teramo (Italy)
2015-11-20
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 ≥ 10{sup 6} M{sub ⊙}), 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.
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.
Blast wave mitigation by dry aqueous foam: numerical modelling and experimental investigation
Counilh, Denis; Ballanger, Felix; Rambert, Nicolas; Haas, Jean-Francois; Chinnayya, Aschwin; Lefrancois, Alexandre
2016-11-01
Dry aqueous foams (two-phase media with water liquid fraction lower than 5%) are known to mitigate blast wave effects induced by an explosion. The CEA has calibrated his numerical multiphase code MOUSSACA from shock tube and high-explosive experiments. The shock tube experiments have highlighted the foam fragmentation into droplets and the momentum transfer between the liquid and gas phases of the foam. More recently, experiments with hemispheric explosive charges from 3 g to 120 g have provided more findings about the pressure and impulse mitigation properties of foams. We have also taken into account the heat and mass transfer, as well as the droplets secondary breakup, characterized by the Weber number, ratio of inertia over surface tension. Good agreement is found between the calculation and the experiments. co-supervisor of the Felix Ballanger 's doctoral thesis.
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.
Institute of Scientific and Technical Information of China (English)
XU Guo-yuan; YAN Chang-bin
2006-01-01
Dynamic analysis steps and general flow of fast lagrangian analysis of continua in 3 dimensions (FLAC3D) were discussed. Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area was carried out with FLAC3D. The whole analytical process was divided into two steps, including the static analysis and the dynamic analysis which were used to simulate the influence of excavation process and blasting vibration respectively. The results show that the shape of right upper boundary is extremely irregular after excavation, and stress concentration occurs at many places and higher tensile stress appears. The maximum tensile stress is higher than the tensile strength of rock mass, and surrounding rock of right roof will be damaged with tension fracture. The maximum displacement of surrounding rock is 4.75 mm after excavation. However, the maximum displacement increases to 5.47 mm after the blasting dynamic load is applied. And the covering area of plastic zones expands obviously, especially at the foot of right upper slope. The analytical results are in basic accordance with the observed results on the whole. Damage and disturbance on surrounding rock to some degree are caused by excavation, while blasting dynamic load increases the possibility of occurrence of dynamic instability and destruction further. So the effective supporting and vibration reducing measures should be taken during mining.
How to test brain and brain simulant at ballistic and blast strain rates.
Zhang, Jiangyue; Song, Bo; Pintar, Frank A; Yoganandan, Narayan; Chen, Weinong; Gennarelli, Thomas A
2008-01-01
Mechanical properties of brain tissue and brain simulant at strain rate in the range of 1000 s-1 are essential for computational simulation of intracranial responses for ballistic and blast traumatic brain injury. Testing these ultra-soft materials at high strain rates is a challenge to most conventional material testing methods. The current study developed a modified split Hopkinson bar techniques using the combination of a few improvements to conventional split Hopkinson bar including: using low impedance aluminum bar, semiconductor strain gauge, pulse shaping technique and annular specimen. Feasibility tests were conducted using a brain stimulant, Sylgard 527. Stress-strain curves of the simulant were successfully obtained at strain rates of 2600 and 2700 s-1 for strain levels up to 60%. This confirmed the applicability of Hopkinson bar for mechanical properties testing of brain tissue in the ballistic and blast domain.
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.
Slamming Simulations in a Conditional Wave
DEFF Research Database (Denmark)
Seng, Sopheak; Jensen, Jørgen Juncher
2012-01-01
A study of slamming events in conditional waves is presented in this paper. The ship is sailing in head sea and the motion is solved for under the assumption of rigid body motion constrained to two degree-of-freedom i.e. heave and pitch. Based on a time domain non-linear strip theory most probable...... 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....
Numerical Simulation of Solitary Kinetic Alfven Waves
Institute of Scientific and Technical Information of China (English)
DING Jian; LI Yi; WANG Shui
2008-01-01
Using the two-fluid model in the case of α1 (α=β/2Q, β is the ratio of thermal pressure to magnetic pressure, and Q=m,e/m,I), we numerically investigate the interactions between two solitary kinetic Alfven waves (SKAWs) and between an SKAW and a density discontinuity. The results show that the two SKAWs would remain in their original shapes and propagate at their initiating speeds, which indicates that SKAWs behave just like standard solitons. The simulation also shows that SKAWs will reflect and refract when crossing a discontinuity and propagating into a higher density region. The transmission wave is an SKAW with increasing density, and the reverberation is a disturbance with lower amplitude.
Numerical Simulation of Energy Saving Potential in Dispersing Process of Blasted Smoke in Mines
Institute of Scientific and Technical Information of China (English)
Ge Zhang; Yingying Hong; Qinhai Yang; Hongguang Ji; Guilin Lv
2015-01-01
The dispersing process of the blasted smoke in underground mines by ventilation is very important for the safety of personnel, and its energy consumption is also worthy of concern. In this study, the impact of supply air flow rate on the decay process of harmful gases and fan energy, and the role of harmful gases buried by blasted pile in the smoke dispersing process is analyzed with three⁃dimensional numerical simulation. According to the results, air flow facilitates quick smoke dispersion and the gas emits from the blasted pile is only significant at the beginning of ventilation. It is thus recommended that large amount of air supply is taken to disperse the smoke quickly until the concentration of harmful gases reaches relevant standards, and reduce the amount of air in the remain time with frequency conversion technology to save energy. In the given study, 12 m/s air flow rate is taken for dispersing smoke and 3 m/s air flow rate is taken for the waiting time. The energy consumption for ventilation is reduced by about 50%. In addition, due to the gases in the blasted pile remains very high concentration after the dispersing process, it is recommended to keep suitable amount of ventilation in the consequent process.
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...
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.
Compression Waves and Phase Plots: Simulations
Orlikowski, Daniel
2011-01-01
Compression wave analysis started nearly 50 years ago with Fowles.[1] Coperthwaite and Williams [2] gave a method that helps identify simple and steady waves. We have been developing a method that gives describes the non-isentropic character of compression waves, in general.[3] One result of that work is a simple analysis tool. Our method helps clearly identify when a compression wave is a simple wave, a steady wave (shock), and when the compression wave is in transition. This affects the analysis of compression wave experiments and the resulting extraction of the high-pressure equation of state.
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.
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.
Sparrow, Victor Ward
1990-01-01
This study has concerned the propagation of finite amplitude, i.e. weakly non-linear, acoustical blast waves from explosions over hard and porous media models of outdoor ground surfaces. The nonlinear acoustic propagation effects require a numerical solution in the time domain. To model a porous ground surface, which in the frequency domain exhibits a finite impedance, the linear phenomenological porous model of Morse and Ingard was used. The phenomenological equations are solved in the time domain for coupling with the time domain propagation solution in the air. The numerical solution is found through the method of finite differences. The second-order in time and fourth -order in space MacCormack method was used in the air, and the second-order in time and space MacCormack method was used in the porous medium modeling the ground. Two kinds of numerical absorbing boundary conditions were developed for the air propagation equations to truncate the physical domain for solution on a computer. Radiation conditions first were used on those sides of the domain where there were outgoing waves. Characteristic boundary conditions secondly are employed near the acoustic source. The numerical model agreed well with the Pestorius algorithm for the propagation of electric spark pulses in the free field, and with a result of Pfriem for normal plane reflection off a hard surface. In addition, curves of pressure amplification versus incident angle for waves obliquely incident on the hard and porous surfaces were produced which are similar to those in the literature. The model predicted that near grazing finite amplitude acoustic blast waves decay with distance over hard surfaces as r to the power -1.2. This result is consistent with the work of Reed. For propagation over the porous ground surface, the model predicted that this surface decreased the decay rate with distance for the larger blasts compared to the rate expected in the linear acoustics limit.
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.
Institute of Scientific and Technical Information of China (English)
王珂; 尹群; 嵇春艳; 苏艳艳
2011-01-01
采用等效TNT方法计算了海洋平台复杂结构在油气爆炸冲击波作用下的动态响应,采用多欧拉一拉格朗日耦合方法对三种不同防爆墙结构进行数值模拟研究.模拟结果显示:在油气爆炸冲击波的作用下,平台舱室变形、失效后破裂,冲击波通过破口传入平台其它舱室；对海洋平台爆炸舱室的围壁采用原结构、梯形结构和半椭圆三种防爆墙结构进行数值对比研究,考虑防爆墙的能量吸收和甲板能量吸收这两个方面,半椭圆防爆墙结构具有更好的防爆效果.%In this paper the equivalent TNT method is used in computing the dynamical responses of offshore platform under explosion pressure of flammable gases and an explicit coupled multiple Euler-Largrange method in the commercial FEM codes MSC/Dytran are used to simulate the three different blast walls. The result shows that, by the impact of shock wave, the cabin of offshore platform deforms, fails and gas blast flow into the other cabins. The paper studies the original plate structure, the trapezoidal blast wall and the half elliptic blast wall. Based on the energy absorbing of the decks and blast walls, the half ellipsed blast wall has the most effective for anti-blast.
Computational simulation of wave propagation problems in infinite domains
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper deals with the computational simulation of both scalar wave and vector wave propagation problems in infinite domains. Due to its advantages in simulating complicated geometry and complex material properties, the finite element method is used to simulate the near field of a wave propagation problem involving an infinite domain. To avoid wave reflection and refraction at the common boundary between the near field and the far field of an infinite domain, we have to use some special treatments to this boundary. For a wave radiation problem, a wave absorbing boundary can be applied to the common boundary between the near field and the far field of an infinite domain, while for a wave scattering problem, the dynamic infinite element can be used to propagate the incident wave from the near field to the far field of the infinite domain. For the sake of illustrating how these two different approaches are used to simulate the effect of the far field, a mathematical expression for a wave absorbing boundary of high-order accuracy is derived from a two-dimensional scalar wave radiation problem in an infinite domain, while the detailed mathematical formulation of the dynamic infinite element is derived from a two-dimensional vector wave scattering problem in an infinite domain. Finally, the coupled method of finite elements and dynamic infinite elements is used to investigate the effects of topographical conditions on the free field motion along the surface of a canyon.
Research on fast rise time EMP radiating-wave simulator
Fan, Lisi; Liu, Haitao; Wang, Yun
2013-03-01
This paper presents an antenna of High altitude electromagnetic pulse (HEMP) radiating-wave simulator which expands the testing zone larger than the traditional transmission line simulator. The numerical results show that traverse electramagnetic (TEM) antenna can be used to radiate HEMP simulation radiating wave, but in low frequency band the emissive capability is poor. The experiment proves the numerical model is valid. The results of this paper show that TEM antenna can be used to HEMP radiating-wave simulator, and can prove the low frequency radiation capability through resistance loaded method.
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.
Numerical Simulation of a Negative Impulsive Wave
Institute of Scientific and Technical Information of China (English)
ToshiakiSETOGUCHI; ShenYU; 等
1996-01-01
A compression wave discharged from an open end of a tube causes positive impulsive noise,Active noise cancellation which is the cancelling of the noise by the addition of an inverse wave is a useful technique for reducing impulsive noise,The main objective of this study is to present the design for a negative impulsive wave generator utilizing unsteady mass influx.In this paper,in order to clarify the relationship between the unsteady mass influx and the negative impulsive wave,numerical and aeroacoustic analyses have been carried out using an unsteady expansion wave discharged from an open end of a shock tube.As a result,the effect of an unsteady expansion wave on a negative impulsive wave was charified.
Energy Technology Data Exchange (ETDEWEB)
Miles, Aaron R. [Univ. of Maryland, College Park, MD (United States)
2004-01-01
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
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
Simulation of Wave Overtopping of Maritime Structures in a Numerical Wave Flume
Directory of Open Access Journals (Sweden)
Tiago C. A. Oliveira
2012-01-01
Full Text Available A numerical wave flume based on the particle finite element method (PFEM is applied to simulate wave overtopping for impermeable maritime structures. An assessment of the performance and robustness of the numerical wave flume is carried out for two different cases comparing numerical results with experimental data. In the first case, a well-defined benchmark test of a simple low-crested structure overtopped by regular nonbreaking waves is presented, tested in the lab, and simulated in the numerical wave flume. In the second case, state-of-the-art physical experiments of a trapezoidal structure placed on a sloping beach overtopped by regular breaking waves are simulated in the numerical wave flume. For both cases, main overtopping events are well detected by the numerical wave flume. However, nonlinear processes controlling the tests proposed, such as nonlinear wave generation, energy losses along the wave propagation track, wave reflection, and overtopping events, are reproduced with more accuracy in the first case. Results indicate that a numerical wave flume based on the PFEM can be applied as an efficient tool to supplement physical models, semiempirical formulations, and other numerical techniques to deal with overtopping of maritime structures.
Hummel, David; Ivan, Lucian
2017-03-15
A "dirty bomb" is a type of radiological dispersal device (RDD) that has been the subject of significant safety and security concerns given the disruption that would result from a postulated terrorist attack. Assessing the risks of radioactive dose in a hypothetical scenario requires models that can accurately predict dispersion in a realistic environment. Modelling a RDD is complicated by the fact that the most important phenomena occur over vastly disparate spatial and temporal length scales. Particulate dispersion in the air is generally considered on scales of hundreds to thousands of meters, and over periods of minutes and hours. Dispersion models are extremely sensitive, however, to the particle size and source characterization, which are determined in distances measured in micrometers to meters, over milliseconds or less. This study examines the extent to which the explosive blast determines the transport of contaminant particles relative to the atmospheric wind over distances relevant to "near-field" dispersion problems (i.e., hundreds of meters), which are relevant to urban environments. Our results indicate that whether or not the effect of the blast should be included in a near-field dispersion model is largely dependent on the size of the contaminant particle. Relatively large particles (i.e., >40 μm in diameter), which are most likely to be produced by a RDD, penetrate the leading shock front, thereby avoiding the reverse blast wind. Consequently, they travel much farther than suspended aerosols (<10 μm) before approaching the ambient wind velocity. This suggests that, for these "near-field" dispersion problems in urban environments, the transport of contaminants from the blast wave may be integral to accurately predicting their dispersion.
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 of Typhoon-Driven Waves in the Yangtze Estuary with Multiple-Nested Wave Models
Institute of Scientific and Technical Information of China (English)
XU Fu-min; Will Perrie; ZHANG Jun-lun; SONG Zhi-yao; Bechara Toulany
2005-01-01
Typhoon-generated waves are simulated with two numerical wave models, the SWAN model for the coastal and Yangtze Estuary domain, nested within the WAVEWATCHIII (WW3) for the basin-scale East China Sea domain. Typhoon No. 8114 is chosen because it was very strong, and generated high waves in the Estuary. WW3 was implemented for the East China Sea coarse-resolution computational domain, to simulate the waves over a large spatial scale and provide boundary conditions for SWAN model simulations, implemented on a fine-resolution nested domain for the Yangtze Estuary area. The Takahashi wind model is applied to the simulation of the East China Sea scale (3-hourly) and Yangtze Estuary scale (1-hourly) winds. Simulations of significant wave heights in the East China Sea show that the highest waves are on the right side of the storm track, and maxima tend to occur at the eastern deep-water open boundary of the Yangtze Estuary. In the Yangtze Estuary, incoming swell is dominant over locally generated waves before the typhoon approaches the Estuary. As the typhoon approaches the Estuary, wind waves and swell coexist, and the wave direction is mainly influenced by the swell direction and the complex topography.
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.
Discrete element simulation of charging and mixed layer formation in the ironmaking blast furnace
Mitra, Tamoghna; Saxén, Henrik
2016-11-01
The burden distribution in the ironmaking blast furnace plays an important role for the operation as it affects the gas flow distribution, heat and mass transfer, and chemical reactions in the shaft. This work studies certain aspects of burden distribution by small-scale experiments and numerical simulation by the discrete element method (DEM). Particular attention is focused on the complex layer-formation process and the problems associated with estimating the burden layer distribution by burden profile measurements. The formation of mixed layers is studied, and a computational method for estimating the extent of the mixed layer, as well as its voidage, is proposed and applied on the results of the DEM simulations. In studying a charging program and its resulting burden distribution, the mixed layers of coke and pellets were found to show lower voidage than the individual burden layers. The dynamic evolution of the mixed layer during the charging process is also analyzed. The results of the study can be used to gain deeper insight into the complex charging process of the blast furnace, which is useful in the design of new charging programs and for mathematical models that do not consider the full behavior of the particles in the burden layers.
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.
Wave energy power take off system control and simulation
Energy Technology Data Exchange (ETDEWEB)
Zhoul, Z.; Holland, P.M.; Igic, P. [Swansea Univ., Swansea, Wales (United Kingdom). School of Engineering; Knapp, W. [Technische Univ. Muenchen, Munich (Germany); MacEnri, J. [ESB International, Dublin (Ireland); Srensen, H.Ch.; Friis-Madsen, E. [Wave Dragon APS and LTD, Copenhagen (Denmark)
2008-07-01
The generation of electric power from wave energy using an offshore wave energy take-off system has received global interest. Several different wave energy take off techniques have been suggested. Among these, the Wave Dragon is one of the most efficient wave energy conversion systems. This paper presented a wave energy power take off system control and simulation scheme. The characteristics of low pressure hydro turbine were described. A variable speed control scheme using IGBT alternating current/direct current converter for low-head hydro-turbine was described in order to achieve maximum efficiency. The electrical system configuration, operation and grid connection issues were presented. Last, in order to investigate the long electro-mechanical process, a simulation model was developed for simulating the generator-turbine starting-stop process. The simulated parameters included the effects of the water head on the torque, speed and output power. Simulation results were presented and discussed. It was concluded that the proposed model is suitable for investigating the overall performance of a wave energy power take off system. 12 refs., 14 figs.
Numerical simulation of sediment transport in coastal waves and wave-induced currents
Institute of Scientific and Technical Information of China (English)
TANG Jun; LYU Yigang; SHEN Yongming
2016-01-01
Prediction of coastal sediment transport is of particularly importance for analyzing coast erosion accurately and solving the corresponding coast protection engineering problems. The present study provided a numerical scheme for sediment transport in coastal waves and wave-induced currents. In the scheme, the sand transport model was implemented with wave refraction-diffraction model and near-shore current model. Coastal water wave was simulated by using the parabolic mild-slope equation in which wave refraction, diffraction and breaking effects are considered. Wave-induced current was simulated by using the nonlinear shallow water equations in which wave provides radiation stresses for driving current. Then, sediment transport in waves and wave-induced currents was simulated by using the two-dimensional suspended sediment transport equations for suspended sediment and the bed-load transport equation for bed load. The numerical scheme was validated by experiment results from the Large-scale Sediment Transport Facility at the US Army Corps of Engineer Research and Development Center in Vicksburg. The numerical results showed that the present scheme is an effective tool for modeling coastal sediment transport in waves and near-shore currents.
An animal-to-human scaling law for blast-induced traumatic brain injury risk assessment.
Jean, Aurélie; Nyein, Michelle K; Zheng, James Q; Moore, David F; Joannopoulos, John D; Radovitzky, Raúl
2014-10-28
Despite recent efforts to understand blast effects on the human brain, there are still no widely accepted injury criteria for humans. Recent animal studies have resulted in important advances in the understanding of brain injury due to intense dynamic loads. However, the applicability of animal brain injury results to humans remains uncertain. Here, we use advanced computational models to derive a scaling law relating blast wave intensity to the mechanical response of brain tissue across species. Detailed simulations of blast effects on the brain are conducted for different mammals using image-based biofidelic models. The intensity of the stress waves computed for different external blast conditions is compared across species. It is found that mass scaling, which successfully estimates blast tolerance of the thorax, fails to capture the brain mechanical response to blast across mammals. Instead, we show that an appropriate scaling variable must account for the mass of protective tissues relative to the brain, as well as their acoustic impedance. Peak stresses transmitted to the brain tissue by the blast are then shown to be a power function of the scaling parameter for a range of blast conditions relevant to TBI. In particular, it is found that human brain vulnerability to blast is higher than for any other mammalian species, which is in distinct contrast to previously proposed scaling laws based on body or brain mass. An application of the scaling law to recent experiments on rabbits furnishes the first physics-based injury estimate for blast-induced TBI in humans.
Continuity waves in fully resolved simulations of settling particles
Willen, Daniel; Sierakowski, Adam; Prosperetti, Andrea
2016-11-01
Fully resolved simulations of 500 to 2,000 particles settling in a fluid have been conducted with the Physalis method. A new approach to the reconstruction of pseudo-continuum fields is described and is used to examine the results with the purpose of identifying concentration waves. The velocity of concentration waves is successfully deduced from the simulations. A comparison of the results with continuity wave theory shows good agreement. Several new insights about the particle microstructure conditionally averaged on volume fraction and velocity are also described. This work is supported by NSF award CBET1335965.
A Model to Simulate Titanium Behavior in the Iron Blast Furnace Hearth
Guo, Bao-Yu; Zulli, Paul; Maldonado, Daniel; Yu, Ai-Bing
2010-08-01
The erosion of hearth refractory is a major limitation to the campaign life of a blast furnace. Titanium from titania addition in the burden or tuyere injection can react with carbon and nitrogen in molten pig iron to form titanium carbonitride, giving the so-called titanium-rich scaffold or buildup on the hearth surface, to protect the hearth from subsequent erosion. In the current article, a mathematical model based on computational fluid dynamics is proposed to simulate the behavior of solid particles in the liquid iron. The model considers the fluid/solid particle flow through a packed bed, conjugated heat transfer, species transport, and thermodynamic of key chemical reactions. A region of high solid concentration is predicted at the hearth bottom surface. Regions of solid formation and dissolution can be identified, which depend on the local temperature and chemical equilibrium. The sensitivity to the key model parameters for the solid phase is analyzed. The model provides an insight into the fundamental mechanism of solid particle formation, and it may form a basic model for subsequent development to study the formation of titanium scaffold in the blast furnace hearth.
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.
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.
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)
3D Ultrasonic Wave Simulations for Structural Health Monitoring
Campbell, Leckey Cara A/; Miler, Corey A.; Hinders, Mark K.
2011-01-01
Structural health monitoring (SHM) for the detection of damage in aerospace materials is an important area of research at NASA. Ultrasonic guided Lamb waves are a promising SHM damage detection technique since the waves can propagate long distances. For complicated flaw geometries experimental signals can be difficult to interpret. High performance computing can now handle full 3-dimensional (3D) simulations of elastic wave propagation in materials. We have developed and implemented parallel 3D elastodynamic finite integration technique (3D EFIT) code to investigate ultrasound scattering from flaws in materials. EFIT results have been compared to experimental data and the simulations provide unique insight into details of the wave behavior. This type of insight is useful for developing optimized experimental SHM techniques. 3D EFIT can also be expanded to model wave propagation and scattering in anisotropic composite materials.
Laboratory simulation of magnetospheric chorus wave generation
Van Compernolle, B.; An, X.; Bortnik, J.; Thorne, R. M.; Pribyl, P.; Gekelman, W.
2017-01-01
Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. A laboratory experiment (Van Compernolle et al 2015 Phys. Rev. Lett. 114 245002, An et al 2016 Geophys. Res. Lett.) in the large plasma device at UCLA was designed to closely mimic the scaled plasma parameters observed in the inner magnetosphere, and shed light on the excitation of discrete frequency whistler waves. It was observed that a rich variety of whistler wave emissions is excited by a gyrating electron beam. The properties of the whistler emissions depend strongly on plasma density, beam density and magnetic field profiles.
Roll waves numerical simulation in closed channels
2013-01-01
Resumo: Utilizando um método numérico especializado em problemas hiperbólicos chamado Riemann Solver, é feito um estudo para avaliar o processo de evolução de roll waves em canais fechados. Todo o estudo se baseia em fenômenos de propagação de ondas hiperbólicas do tipo ondas de gravidade. Foi utilizado um modelo unidimensional para representar a dinâmica das roll waves. Inicialmente foi feita uma análise das velocidades características envolvidas, a qual indicou, para o arranjo estratificado...
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
Simulation of the interaction of tsunami waves with underwater barriers
Boshenyatov, B. V.; Zhiltsov, K. N.
2016-10-01
This article examines the experimental and numerical simulation of the processes of distribution and interaction of tsunami-type gravitational waves with one barrier and a complex of two barriers. Experiments were conducted in a hydrodynamic channel using high-precision sensors for the measurement of the wave processes. Mathematical modelling was carried out using two-dimensional non-stationary Navier-Stokes equations for an incompressible fluid using the freely available software package OpenFOAM. It is shown that for small-amplitude waves, when their advance speed is described by the linear theory of shallow water, the interaction with the underwater barriers has important non-linear and viscous effects. Our results explain why a complex of two barriers spaced at a definite distance from each other has a significant impact on the power of the transmitted wave. The energy of the waves passing through the two barriers can be reduced to 35% of the incident wave.
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
For wave energy to become feasible it is a requirement that the efficiency and reliability of the power take-off (PTO) systems are significantly improved. The cost of installing and testing PTO-systems at sea are however very high, and the focus of the current paper is therefore on the design...... of a full scale wave simulator for testing PTO-systems for point absorbers. The main challenge is here to design a system, which mimics the behavior of a wave when interacting with a given PTO-system. The paper includes a description of the developed system, located at Aalborg University......, and the considerations behind the design. Based on the description a model of the system is presented, which, along with a description of the wave theory applied, makes the foundation for the control strategy. The objective of the control strategy is to emulate not only the wave behavior, but also the dynamic wave...
Efficient Simulation of Freak Waves in Random Oceanic Sea States
Institute of Scientific and Technical Information of China (English)
ZHANG Yun-qiu; HU Jin-peng; ZHANG Ning-chuan
2009-01-01
Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum.The evolution of initial random wave trains is numerically carried out within the framework of the modified fourorder nonlinear Schruedinger equation (mNLSE),and some involved influence factors are also discussed.Results show that if the sideband instability is satisfied,a random wave train may evolve into a freak wave train,and simultaneously the setting of the Phillips parameter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves.The way to increase the generation efficiency of freak waves thsough changing the involved parameters is also presented.
Variational approaches to water wave simulations
Gagarina, Elena Vitalyevna
2014-01-01
This thesis starts with the study the theoretical aspects of water wave modelling using a variational framework, which is directly associated with phase space and energy conservation laws. In particular, we focus on a new variational model based on the work of Cotter and Bokhove. The new model inclu
Wave overtopping simulator tests in Vietnam
Trung, L.H.; Van der Meer, J.M.; Schiereck, G.J.; Cat, V.M.; Van der Meer, G.
2010-01-01
Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm surg
Quantification of Aleatory Uncertainty in Blast Wave Problem%爆炸波问题中偶然不确定度的量化
Institute of Scientific and Technical Information of China (English)
梁霄; 王瑞利
2016-01-01
As uncertainty always exists in the modeling and simulation of complex engineering problems, the identification and analysis of its source and the quantification of its degrees play an important role in assessing the credibility of the modeling and simulation results.In this paper,the concept of uncertainty as well as uncertainty quantification process was presented in the modeling and simulation,with the blast wave problem used as a typical example to illustrate the detailed process for the quantification of the aleatory uncertainty.The expectations and variances of density,pressure,velocity and internal energy were calculated and,moreover,the probability density function of the shock wave position was obtained using the Monte-Carlo and the non-intrusive polynomial chaos (NIPC).The results were consistent with each other,which verified that the NIPC method is an efficient approach in the uncertainty quantification of a complex nonlinear system.%复杂工程建模与模拟中始终存在不确定度，分析与辨识不确定度的来源及量化不确定度对建模与模拟可信度评估具有重要意义。为此，给出了建模与模拟中误差与不确定度的概念以及不确定度量化的过程，并以爆炸波问题为例说明量化偶然不确定度的过程，得到了爆炸波问题的期望和标准差以及激波位置的概率密度函数，验证了非嵌入多项式混沌方法在复杂非线性系统不确定度量化中的有效性。
Numerical Simulation of Sediment Transport due to Plunging Breaking Waves
DEFF Research Database (Denmark)
Pedersen, Claus
A numerical model simulating the sediment transport due to plunging breaking waves has been developed. The model is two-dimensional, assuming conditions in the long-shore direction invariable. A plunging breaker is simulated by superimposing a non-breaking wave with a jet. Based on the description...... of the sediment transport rates, a simple model describing the morphological changes has been applied to simulate the evolution of a plunge point generated vorticity included, the bottom topography from the experiments by Dette & Uliczka was not in equilibrium according to the model....
Guerrero, A; Goñi, S
2002-01-01
The efficiency of a blast furnace slag cement (Spanish CEM III/B) for immobilizing simulated radioactive borate liquid waste [containing H3BO3, NaCl, Na2SO4 and Na(OH)] has been evaluated by means of a leaching attack in de-mineralized water at the temperature of 40 degrees C over 180 days. The leaching was carried out according to the ANSI/ANS-16.1-1986 test. Moreover, changes of the matrix microstructure were characterized through porosity and pore-size distribution analysis carried out by mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and thermal analysis (TG). The results were compared with those obtained from a calcium aluminate cement matrix, previously published.
Numerical simulation of landslide-generated impulse wave
Institute of Scientific and Technical Information of China (English)
赵兰浩; 毛佳; 刘晓青; 李同春
2014-01-01
A numerical model is proposed for the simulation of impulse waves generated by landslides. The fluid-like landslide is modeled as a generalized non-Newtonian visco-plastic fluid. The conservative level set method is extended to the n-phase flow and applied to capture the interfaces of air, water and landslide. Numerical results show an excellent performance of the current model to capture the whole process of the landslide and the impulse wave generation.
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.
Zuckerman, Amitai; Ram, Omri; Ifergane, Gal; Matar, Michael A; Sagi, Ram; Ostfeld, Ishay; Hoffman, Jay R; Kaplan, Zeev; Sadot, Oren; Cohen, Hagit
2017-01-01
The intense focus in the clinical literature on the mental and neurocognitive sequelae of explosive blast-wave exposure, especially when comorbid with post-traumatic stress-related disorders (PTSD) is justified, and warrants the design of translationally valid animal studies to provide valid complementary basic data. We employed a controlled experimental blast-wave paradigm in which unanesthetized animals were exposed to visual, auditory, olfactory, and tactile effects of an explosive blast-wave produced by exploding a thin copper wire. By combining cognitive-behavioral paradigms and ex vivo brain MRI to assess mild traumatic brain injury (mTBI) phenotype with a validated behavioral model for PTSD, complemented by morphological assessments, this study sought to examine our ability to evaluate the biobehavioral effects of low-intensity blast overpressure on rats, in a translationally valid manner. There were no significant differences between blast- and sham-exposed rats on motor coordination and strength, or sensory function. Whereas most male rats exposed to the blast-wave displayed normal behavioral and cognitive responses, 23.6% of the rats displayed a significant retardation of spatial learning acquisition, fulfilling criteria for mTBI-like responses. In addition, 5.4% of the blast-exposed animals displayed an extreme response in the behavioral tasks used to define PTSD-like criteria, whereas 10.9% of the rats developed both long-lasting and progressively worsening behavioral and cognitive "symptoms," suggesting comorbid PTSD-mTBI-like behavioral and cognitive response patterns. Neither group displayed changes on MRI. Exposure to experimental blast-wave elicited distinct behavioral and morphological responses modelling mTBI-like, PTSD-like, and comorbid mTBI-PTSD-like responses. This experimental animal model can be a useful tool for elucidating neurobiological mechanisms underlying the effects of blast-wave-induced mTBI and PTSD and comorbid mTBI-PTSD.
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.
Armaghani, Danial Jahed; Mahdiyar, Amir; Hasanipanah, Mahdi; Faradonbeh, Roohollah Shirani; Khandelwal, Manoj; Amnieh, Hassan Bakhshandeh
2016-09-01
Flyrock is considered as one of the main causes of human injury, fatalities, and structural damage among all undesirable environmental impacts of blasting. Therefore, it seems that the proper prediction/simulation of flyrock is essential, especially in order to determine blast safety area. If proper control measures are taken, then the flyrock distance can be controlled, and, in return, the risk of damage can be reduced or eliminated. The first objective of this study was to develop a predictive model for flyrock estimation based on multiple regression (MR) analyses, and after that, using the developed MR model, flyrock phenomenon was simulated by the Monte Carlo (MC) approach. In order to achieve objectives of this study, 62 blasting operations were investigated in Ulu Tiram quarry, Malaysia, and some controllable and uncontrollable factors were carefully recorded/calculated. The obtained results of MC modeling indicated that this approach is capable of simulating flyrock ranges with a good level of accuracy. The mean of simulated flyrock by MC was obtained as 236.3 m, while this value was achieved as 238.6 m for the measured one. Furthermore, a sensitivity analysis was also conducted to investigate the effects of model inputs on the output of the system. The analysis demonstrated that powder factor is the most influential parameter on fly rock among all model inputs. It is noticeable that the proposed MR and MC models should be utilized only in the studied area and the direct use of them in the other conditions is not recommended.
Simulation of Wave-Plus-Current Scour beneath Submarine Pipelines
DEFF Research Database (Denmark)
Eltard-Larsen, Bjarke; Fuhrman, David R.; Sumer, B. Mutlu
2016-01-01
A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier–Stokes equations, coupled with k-ω turbulence closure, with additional bed and suspen......A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier–Stokes equations, coupled with k-ω turbulence closure, with additional bed...
Multiscale Simulation of Breaking Wave Impacts
DEFF Research Database (Denmark)
Lindberg, Ole
-distance based adaptivity method and redistributed via a point position filtering method. The incompressible and inviscid ALE-WLS model is applied to the following standard validation test cases: deforming elliptical drop, small amplitude standing waves and the dam break problem. The deforming elliptical drop...... and mass conservation is satisfied through a pressure-corrector type calculation of the pressure. The weighted least squares method (WLS) is combined with approximate Riemann solvers to introduce numerical smoothing of the solution around steep gradients in the velocity and pressure fields. The Poisson...... equation is solved and the pressure boundary conditions are satisfied by a generalized finite pointset method (GFPM); This provides a geometrically flexible and stable solution for the fluid pressure. The numerical approximations of these equations are performed on unstructured point distributions...
Simulation of Random Waves and Associated Laminar Bottom Shear Stresses
Institute of Scientific and Technical Information of China (English)
Mao-Lin SHEN; Ching-Jer HUANG
2008-01-01
This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundary conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves are determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the numerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug's model (1995). The transfer function method is also employed to determine the maximum shear stress, and is proved accurate.
Wave climate of the Adriatic Sea: a future scenario simulation
Directory of Open Access Journals (Sweden)
A. Benetazzo
2012-06-01
Full Text Available We present a study on expected wind wave severity changes in the Adriatic Sea for the period 2070–2099 and their impact on extremes. To do so, the phase-averaged spectral wave model SWAN is forced using wind fields computed by the high-resolution regional climate model COSMO-CLM, the climate version of the COSMO meteorological model downscaled from a global climate model running under the IPCC-A1B emission scenario. Namely, the adopted wind fields are given with a horizontal resolution of 14 km and 40 vertical levels, and they are prepared by the Italian Aerospace Research Centre (CIRA. Firstly, in order to infer the wave model accuracy in predicting seasonal variability and extreme events, SWAN results are validated against a control simulation, which covers the period 1965–1994. In particular, numerical predictions of the significant wave height H_{s} are compared against available in-situ data. Further, a statistical analysis is carried out to estimate changes on wave storms and extremes during the simulated periods (control and future scenario simulations. In particular, the generalized Pareto distribution is used to predict changes of storm peak H_{s} for frequent and rare storms in the Adriatic Sea. Finally, Borgman's theory is applied to estimate the spatial pattern of the expected maximum wave height H_{max} during a storm, both for the present climate and that of the future scenario. Results show a future wave climate in the Adriatic Sea milder than the present climate, even though increases of wave severity can occur locally.
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...
Design of full scale wave simulator for testing Power Take Off systems for wave energy converters
DEFF Research Database (Denmark)
Pedersen, H. C.; Hansen, R. H.; Hansen, Anders Hedegaard
2016-01-01
For wave energy to become a major future contributor of renewable energy it is a requirement that the efficiency and reliability of the Power Take-Off (PTO) systems is significantly improved. However, the cost of installing and testing PTO-systems at sea is very high. The focus of the current paper...... is therefore on the design and commissioning of a full scale wave simulator for testing PTO-systems for point absorbers. The challenge is to be able to design a system, which mimics the behavior of a wave when interacting with a given PTO-system – especially when considering discrete type PTO......-systems. The paper presents the designed system, including the major design considerations. A model of the complete system is presented and controllers for the system are developed. These enable the system to emulate the wave behavior and the wave–float interaction. Finally both simulation and experimental results...
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
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.
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...... Research and Forecasting (WRF) Model with the thirdgeneration ocean wave modelSWAN. This study investigates mainly two issues: spatial resolution and the wind-wave interface parameter roughness length(z0). To study the impact of resolution, the nesting function for both WRF and SWAN is used, with spatial...... resolution ranging from 25km to 2km. Meanwhile, the atmospheric forcing data of dierent spatial resolution, with one about 100km (FNL) and the other about 38km (CFSR) are both used. In addition, bathymatry data of diferent resolutions (1arc-minute and 30arc-seconds) are used. We used three approaches...
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.
Simulation of guided wave propagation near numerical Brillouin zones
Kijanka, Piotr; Staszewski, Wieslaw J.; Packo, Pawel
2016-04-01
Attractive properties of guided waves provides very unique potential for characterization of incipient damage, particularly in plate-like structures. Among other properties, guided waves can propagate over long distances and can be used to monitor hidden structural features and components. On the other hand, guided propagation brings substantial challenges for data analysis. Signal processing techniques are frequently supported by numerical simulations in order to facilitate problem solution. When employing numerical models additional sources of errors are introduced. These can play significant role for design and development of a wave-based monitoring strategy. Hence, the paper presents an investigation of numerical models for guided waves generation, propagation and sensing. Numerical dispersion analysis, for guided waves in plates, based on the LISA approach is presented and discussed in the paper. Both dispersion and modal amplitudes characteristics are analysed. It is shown that wave propagation in a numerical model resembles propagation in a periodic medium. Consequently, Lamb wave propagation close to numerical Brillouin zone is investigated and characterized.
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
Simulating and understanding sand wave variation: A case study of the Golden Gate sand waves
Sterlini, F.; Hulscher, S.J.M.H.; Hanes, D.M.
2009-01-01
In this paper we present a detailed comparison between measured features of the Golden Gate sand wave field and the results of a nonlinear sand wave model. Because the Golden Gate sand waves exhibit large variation in their characteristics and in their environmental physics, this area gives us the opportunity to study sand wave variation between locations, within one well-measured, large area. The nonlinear model used in this paper is presently the only tool that provides information on the nonlinear evolution of large-amplitude sand waves. The model is used to increase our understanding of the coupling between the variability in environmental conditions and the sand wave characteristics. Results show that the model is able to describe the variation in the Golden Gate sand waves well when both the local oscillating tidal current and the residual current are taken into account. Current and water depth seem to be the most important factors influencing sand wave characteristics. The simulation results give further confidence in the underlying model hypothesis and assumptions. Copyright 2009 by the American Geophysical Union.
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 mass ...
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.
Simulation of Surface Wave with Large Eddy Simulation in σ-Coordinate System
Institute of Scientific and Technical Information of China (English)
王玲玲
2004-01-01
A three-dimensional numerical model in the σ-coordinate system is developed to study the problem of waves. Turbulence effects are modeled by a subgrid-scale (SGS) model with the concept of large eddy simulation (LES). The σ-coordinate transformation is introduced to map the irregular physical domain of the wavy free surface and uneven bottom onto the regular computational domain of the shape of rectangular prism. The operator splitting method, which splits the solution procedure into the advection, diffusion, and propagation steps, is used to solve the modified Navier-Stokes Equation.The model is used to simulate the propagation of solitary wave and wave passing over a submerged breakwater. Numerical results are compared with available analytical solutions and experimental data in terms of velocity profiles, free surface displacement, and energy conservation. Good agreement is obtained. The method is proved to be of high accuracy and efficiency in simulating surface wave propagation and wave-structure interaction. It is suitable for the large and irregular physical domain, and requiring the non-uniform grid system. The present work provides a foundation for further studies of random waves, wave-structure interaction, wave-discharge interaction,etc.
Simulated Obstructive Sleep Apnea Increases P-Wave Duration and P-Wave Dispersion
Wons, Annette M.; Rossi, Valentina; Bratton, Daniel J.; Schlatzer, Christian; Schwarz, Esther I.; Camen, Giovanni; Kohler, Malcolm
2016-01-01
Background A high P-wave duration and dispersion (Pd) have been reported to be a prognostic factor for the occurrence of paroxysmal atrial fibrillation (PAF), a condition linked to obstructive sleep apnea (OSA). We tested the hypothesis of whether a short-term increase of P-wave duration and Pd can be induced by respiratory manoeuvres simulating OSA in healthy subjects and in patients with PAF. Methods 12-lead-electrocardiography (ECG) was recorded continuously in 24 healthy subjects and 33 patients with PAF, while simulating obstructive apnea (Mueller manoeuvre, MM), obstructive hypopnea (inspiration through a threshold load, ITH), central apnea (AP), and during normal breathing (BL) in randomized order. The P-wave duration and Pd was calculated by using dedicated software for ECG-analysis. Results P-wave duration and Pd significantly increased during MM and ITH compared to BL in all subjects (+13.1ms and +13.8ms during MM; +11.7ms and +12.9ms during ITH; p<0.001 for all comparisons). In MM, the increase was larger in healthy subjects when compared to patients with PAF (p<0.05). Conclusion Intrathoracic pressure swings through simulated obstructive sleep apnea increase P-wave duration and Pd in healthy subjects and in patients with PAF. Our findings imply that intrathoracic pressure swings prolong the intra-atrial and inter-atrial conduction time and therefore may represent an independent trigger factor for the development for PAF. PMID:27071039
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...
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
FEM Simulations of Leaky Lamb Wave in Ultrasonic Waveguide Sensor
Energy Technology Data Exchange (ETDEWEB)
Bae, Jin Ho; Joo, Young Sang; Kim, Jong Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2011-05-15
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 A{sub 0}-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
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.
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 ...
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
Large Eddy Simulation of the ventilated wave boundary layer
DEFF Research Database (Denmark)
Lohmann, Iris P.; Fredsøe, Jørgen; Sumer, B. Mutlu
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...... 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...... significantly. Ventilation therefore results in a net current, even in symmetric waves....
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...... with moving net structures....
Simulations of shock wave propagation in heterogeneous solids
Hertzsch, Jan-Martin; Ivanov, Boris A.; Kenkmann, Thomas
2002-11-01
Studies of shock wave propagation in heterogeneous materials are important for the interpretation of impact deformation and impact metamorphism of natural rocks. Reflection, refraction, and interference of shock waves caused by inhomogeneities lead to localised concentrations of pressure, temperature, and deformation rate, and in some cases to phase transitions. We have simulated numerically the shock compression of complex media in selected geometries with the aim of modelling shock recovery experiments and have observed reversible phase transitions in the target, shock heating alone may not be sufficient for the formation of impact melt, but localised shear at material boundaries results in considerable temperature increase which makes partial melting possible.
Ducrozet, Guillaume; BONNEFOY, Félicien; Ferrant, Pierre
2016-01-01
International audience; This paper deals with the reproduction of unidirectional extreme events in a numerical wave basin. From a rogue wave measurement at a given location , experiments or numerical simulations are conducted with the same wave profiles using reproduction procedures. Although it is recognized that many different physical mechanisms may be at play in freak wave formation, reproduction procedures generally use frequency focusing to generate these high waves. This paper intends ...
Effects Of Primary Blast Overpressure On Retina And Optic Tract In Rats
Directory of Open Access Journals (Sweden)
James eDemar
2016-04-01
Full Text Available 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 post-optic 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 < 0.0001. Exposure of one eye to a blast wave, comparable to that causing human injury, produced injury to the retina as determined by ERG and histopathology, and to both post-chiasmatic 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.
Rossby Wave Instability of Thin Accretion Disks - III. Nonlinear Simulations
Li, H; Wendroff, B; Liska, R
2000-01-01
(abridged) We study the nonlinear evolution of the Rossby wave instability in thin disks using global 2D hydrodynamic simulations. The key questions we are addressing in this paper are: (1) What happens when the instability becomes nonlinear? Specifically, does it lead to vortex formation? (2) What is the detailed behavior of a vortex? (3) Can the instability sustain itself and can the vortex last a long time? Among various initial equilibria that we have examined, we generally find that there are three stages of the disk evolution: (1) The exponential growth of the initial small amplitude perturbations. This is in excellent agreement with the linear theory; (2) The production of large scale vortices and their interactions with the background flow, including shocks. Significant accretion is observed due to these vortices. (3) The coupling of Rossby waves/vortices with global spiral waves, which facilitates further accretion throughout the whole disk. Even after more than 20 revolutions at the radius of vortic...
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(perpendi......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......)] to gain new understanding into the nature of FWMC in tokamaks. The massively-parallel-processor version of TORIC is also now capable of running with sufficient resolution to model planned lower hybrid range of frequencies experiments in the Alcator C-Mod. (C) 2004 American Institute of Physics....
Xiao, Jianyuan; 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 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 cur...
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_\
Simulations of nonlinear continuous wave pressure fields in FOCUS
Zhao, Xiaofeng; Hamilton, Mark F.; McGough, Robert J.
2017-03-01
The Khokhlov - Zabolotskaya - Kuznetsov (KZK) equation is a parabolic approximation to the Westervelt equation that models the effects of diffraction, attenuation, and nonlinearity. Although the KZK equation is only valid in the far field of the paraxial region for mildly focused or unfocused transducers, the KZK equation is widely applied in medical ultrasound simulations. For a continuous wave input, the KZK equation is effectively modeled by the Bergen Code [J. Berntsen, Numerical Calculations of Finite Amplitude Sound Beams, in M. F. Hamilton and D. T. Blackstock, editors, Frontiers of Nonlinear Acoustics: Proceedings of 12th ISNA, Elsevier, 1990], which is a finite difference model that utilizes operator splitting. Similar C++ routines have been developed for FOCUS, the `Fast Object-Oriented C++ Ultrasound Simulator' (http://www.egr.msu.edu/˜fultras-web) to calculate nonlinear pressure fields generated by axisymmetric flat circular and spherically focused ultrasound transducers. This new routine complements an existing FOCUS program that models nonlinear ultrasound propagation with the angular spectrum approach [P. T. Christopher and K. J. Parker, J. Acoust. Soc. Am. 90, 488-499 (1991)]. Results obtained from these two nonlinear ultrasound simulation approaches are evaluated and compared for continuous wave linear simulations. The simulation results match closely in the farfield of the paraxial region, but the results differ in the nearfield. The nonlinear pressure field generated by a spherically focused transducer with a peak surface pressure of 0.2MPa radiating in a lossy medium with β = 3.5 is simulated, and the computation times are also evaluated. The nonlinear simulation results demonstrate acceptable agreement in the focal zone. These two related nonlinear simulation approaches are now included with FOCUS to enable convenient simulations of nonlinear pressure fields on desktop and laptop computers.
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.
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.
The dynamics and excitation of torsional waves in geodynamo simulations
Teed, Robert J; Tobias, Steven M
2013-01-01
The predominant force balance in rapidly rotating planetary cores is between Coriolis, pressure, buoyancy and Lorentz forces. This magnetostrophic balance leads to a Taylor state where the spatially averaged azimuthal Lorentz force is compelled to vanish on cylinders aligned with the rotation axis. Any deviation from this state leads to a torsional oscillation, signatures of which have been observed in the Earth's secular variation and are thought to influence length of day variations via angular momentum conservation. In order to investigate the dynamics of torsional oscillations, we perform several three-dimensional dynamo simulations in a spherical shell. We find torsional oscillations, identified by their propagation at the correct Alfv\\'{e}n speed, in many of our simulations. We find that the frequency, location and direction of propagation of the waves are influenced by the choice of parameters. Torsional waves are observed within the tangent cylinder and also have the ability to pass through it. Severa...
Global 3D MHD Simulations of Waves in Accretion Discs
Directory of Open Access Journals (Sweden)
Romanova M.M.
2013-04-01
Full Text Available We discuss results of the first global 3D MHD simulations of warp and density waves in accretion disks excited by a rotating star with a misaligned dipole magnetic field. A wide range of cases are considered. We find for example that if the star’s magnetosphere corotates approximately with the inner disk, then a strong one-arm bending wave or warp forms. The warp corotates with the star and has a maximum amplitude (|zw|/r ~ 0.3 between the corotation radius and the radius of the vertical resonance. If the magnetosphere rotates more slowly than the inner disk, then a bending wave is excited at the disk-magnetosphere boundary, but it does not form a large-scale warp. In this case the angular rotation of the disk [Ω(r] has a maximum as a function of r so that there is an inner region where dΩ/dr > 0. In this region we observe radially trapped density waves in approximate agreement with the theoretical prediction of a Rossby wave instability in this region.
Electromagnetic Wave Scattering on Nonspherical Particles Basic Methodology and Simulations
Rother, Tom
2009-01-01
This book gives a detailed overview of the theory of electromagnetic wave scattering on single, homogeneous, but nonspherical particles. A related Green’s function formalism is systematically developed which provides a powerful mathematical basis not only for the development of numerical approaches but also to discuss those general aspects like symmetry, unitarity, and the validity of Rayleigh’s hypothesis. Example simulations are performed in order to demonstrate the usefulness of the developed formalism as well as to introduce the simulation software which is provided on a CD-ROM with the book.
Wave optics approach for incoherent imaging simulation through distributed turbulence
Underwood, Thomas A.; Voelz, David G.
2013-09-01
An approach is presented for numerically simulating incoherent imaging using coherent wave optics propagation methods. The approach employs averaging of irradiance from uncorrelated coherent waves to produce incoherent results. Novel aspects of the method include 1) the exploitation of a spatial windowing feature in the wave optics numerical propagator to limit the angular spread of the light and 2) a simple propagation scaling concept to avoid aliased field components after the focusing element. Classical linear systems theory is commonly used to simulate incoherent imaging when it is possible to incorporate aberrations and/or propagation medium characteristics into an optical transfer function (OTF). However, the technique presented here is useful for investigating situations such as "instantaneous" short-exposure imaging through distributed turbulence and phenomena like anisoplanatism that are not easily modeled with the typical linear systems theory. The relationships between simulation variables such as spatial sampling, source and aperture support, and intermediate focal plane are discussed and the requirement or benefits of choosing these in certain ways are demonstrated.
Rayleigh wave inversion using heat-bath simulated annealing algorithm
Lu, Yongxu; Peng, Suping; Du, Wenfeng; Zhang, Xiaoyang; Ma, Zhenyuan; Lin, Peng
2016-11-01
The dispersion of Rayleigh waves can be used to obtain near-surface shear (S)-wave velocity profiles. This is performed mainly by inversion of the phase velocity dispersion curves, which has been proven to be a highly nonlinear and multimodal problem, and it is unsuitable to use local search methods (LSMs) as the inversion algorithm. In this study, a new strategy is proposed based on a variant of simulated annealing (SA) algorithm. SA, which simulates the annealing procedure of crystalline solids in nature, is one of the global search methods (GSMs). There are many variants of SA, most of which contain two steps: the perturbation of model and the Metropolis-criterion-based acceptance of the new model. In this paper we propose a one-step SA variant known as heat-bath SA. To test the performance of the heat-bath SA, two models are created. Both noise-free and noisy synthetic data are generated. Levenberg-Marquardt (LM) algorithm and a variant of SA, known as the fast simulated annealing (FSA) algorithm, are also adopted for comparison. The inverted results of the synthetic data show that the heat-bath SA algorithm is a reasonable choice for Rayleigh wave dispersion curve inversion. Finally, a real-world inversion example from a coal mine in northwestern China is shown, which proves that the scheme we propose is applicable.
CFD simulation of a 300 Hz thermoacoustic standing wave engine
Yu, Guoyao; Dai, W.; Luo, Ercang
2010-09-01
High frequency operation of standing wave thermoacoustic heat engines is attractive for space applications due to compact size and high reliability. To expedite practical use, further improvement and optimization should be based on deep understanding and quantitative analysis. This article focuses on using computational fluid dynamics (CFD) to investigate nonlinear phenomena and processes of a 300 Hz standing wave thermoacoustic engine (SWTE). The calculated model was tested in detail, which indicated that the co-axially stacked tube model was suitable for the simulation of SWTEs. Two methods of imposing temperature gradient across the stack were studied, and the processes of mean pressure increasing, pressure wave amplification and saturation were obtained under the thermal boundary condition of applying heating power. The acoustic fields were given, and the flow vortices and their evolution in both ends of the stack and resonator were observed. Moreover, a comparison between the simulation and experiments was made, which demonstrated the validity and power of the CFD simulation for characterizing complicated nonlinear phenomenon involved in the self-excited SWTEs.
Blasting Vibration Generated by Breaking-Blasting Large Barriers with EBBLB
Wang Zhen-xiong; Gu Wen-bin; Liang Ting; Liu Jian-qing; Xu Jing-lin; Liu Xin
2016-01-01
Equipment for breaking and blasting large barriers (EBBLB) is new break-blast equipment, which inevitably induces ground vibration and may cause substantial damage to rock mass and nearby structures as well as human beings. The ground vibration induced by break-blast is one of the inevitable outcomes. By monitoring vibration at measuring points at different distances from blasting center, time history curve of vibrating velocity can be obtained; it can be drawn that blasting seismic waves are...
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.
Institute of Scientific and Technical Information of China (English)
LEI Wei-dong; TENG Jun; HEFNY A; ZHAO Jian; GUAN Jiong
2006-01-01
In the process of 2-D compressional wave propagation in a rock mass with multiple parallel joints along the radian direction normal to the joints, the maximum possible wave amplitude corresponding to the points between the two adjacent joints in the joint set is controlled by superposition of the multiple transmitted and the reflected waves, measured by the maximum rebound ratio. Parametric studies on the maximum rebound ratio along the radian direction normal to the joints were performed in universal distinct element code. The results show that the maximum rebound ratio is influenced by three factors, i.e., the normalized normal stiffness of joints, the ratio of joint spacing to wavelength and the joint from which the wave rebounds. The relationship between the maximum rebound ratio and the influence factors is generalized into five charts. Those charts can be used as the prediction model for estimating the maximum rebound ratio.
Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A
Dwek, E; Bouchet, P; Burrows, D N; Challis, P; Danziger, I J; De Buizer, J M; Gehrz, R D; Kirshner, R P; McCray, R; Park, S; Polomski, E F; Woodward, C E
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 ~ 1.1E-6 Msun of silicate grains radiating at a temperature of ~180+20-15 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 Large Magellanic Cloud dust abundances. IRX has decreased by a factor of ~ 2 between days 6190 and 7137, providing...
Cassam-Chenai, Gamil; Reynoso, Estela M; Badenes, Carles; Moffett, David
2008-01-01
Using radio, X-ray and optical observations, we present evidence for morphological changes due to efficient cosmic ray ion acceleration in the structure of the southeastern region of the supernova remnant SN 1006. SN 1006 has an apparent bipolar morphology in both the radio and high-energy X-ray synchrotron emission. In the optical, the shock front is clearly traced by a filament of Balmer emission in the southeast. This optical emission enables us to trace the location of the blast wave (BW) even in places where the synchrotron emission from relativistic electrons is either absent or too weak to detect. The contact discontinuity (CD) is traced using images in the low-energy X-rays (oxygen band) which we argue reveals the distribution of shocked ejecta. We interpret the azimuthal variations of the ratio of radii between the BW and CD plus the X-ray and radio synchrotron emission at the BW using CR-modified hydrodynamic models. We assumed different azimuthal profiles for the injection rate of particles into th...
Numerical simulations of shoaling internal solitary waves of elevation
Xu, Chengzhu; Subich, Christopher; Stastna, Marek
2016-07-01
We present high-resolution, two- and three-dimensional direct numerical simulations of large amplitude internal solitary waves of elevation on the laboratory scale, shoaling onto and over a small-amplitude shelf. The three-dimensional, mapped coordinate, spectral collocation method used for the simulations allows for accurate modelling of both the shoaling waves and the bottom boundary layer. The shoaling of the waves is characterized by the formation of a quasi-trapped core which undergoes a spatially growing stratified shear instability at its edge and a lobe-cleft instability in its nose. Both of these instabilities develop and three-dimensionalize concurrently, leading to strong bottom shear stress. We explore significant regions of Schmidt and Reynolds number space and demonstrate that the formation of shear instabilities during shoaling is robust and should be readily observable in a number of standard laboratory setups. In the experiments with a corrugated bottom boundary, boundary layer separation is found inside each of the corrugations during shoaling. This more complex boundary layer phenomenology precludes the formation of the lobe-cleft instability almost completely and hence provides a different mechanism for fluid and material exchange across the bottom boundary layer. Our analyses suggest that all of these wave-induced instabilities can lead to enhanced turbulence in the water column and increased shear stress on the bottom boundary. Through the generation and evolution of these instabilities, the shoaling of internal solitary waves of elevation is likely to provide systematic mechanisms for material mixing, cross-boundary layer transport, and sediment resuspension.
Directory of Open Access Journals (Sweden)
Ashok K Shetty
2014-08-01
Full Text Available 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 from exposure to BSWs appears to be the dysfunction or disruption of the blood-brain barrier (BBB. Studies in animal models suggest that exposure to relatively milder BSWs (123 kPa initially induces free radical generating enzymes in and around brain capillaries, which enhances oxidative stress resulting in loss of tight junction proteins, edema formation, and leakiness of BBB with disruption or loss of its components pericytes and astrocyte end-feet. On the other hand, exposure to more intense BSWs (145-323 kPa causes acute disruption of the BBB with vascular lesions in the brain. Both of these scenarios lead to apoptosis of endothelial and neural cells and neuroinflammation in and around capillaries, which may progress into chronic traumatic encephalopathy and/or a variety of neurological impairments, depending on brain regions that are afflicted with such lesions. This review discusses studies that examined alterations in the brain milieu causing dysfunction or disruption of the BBB and neuroinflammation following exposure to different intensities of BSWs. Furthermore, potential of early intervention strategies capable of easing oxidative stress, repairing the BBB or blocking inflammation for minimizing delayed neurological deficits resulting from exposure to BSWs is conferred.
Numerical Simulation of Long-period Surface Wave in Sediments
Li, Yiqiong; Yu, Yanxiang
2016-04-01
Studies have shown that the western Taiwan coastal plain is influenced by long-period ground motion from the 1999 Chi-Chi, Taiwan, earthquake, and engineering structures with natural vibration long-period are damaged by strong surface wave in the western coastal plain. The thick sediments in the western coastal plain are the main cause of the propagation of strong long-period ground motion. The thick sediments similar to in the western coastal plain also exist in northern China. It is necessary to research the effects of thick sediments to long-period ground motion in northern China. The numerical simulation of ground motion based on theoretical seismology is one of important means to study the ground motion. We will carry out the numerical simulation of long-period ground motion in northern China by using the existing tomographic imaging results of northern China to build underground medium model, and adopting finite fault source model for wave input. In the process of simulation, our previous developed structure-preserving algorithm, symplectic discrete singular convolution differentiator (SDSCD), is used to deal with seismic wave field propagation. Our purpose is to reveal the formation and propagation of long-period surface wave in thick sediments and grasp the amplification effect of long-period ground motion due to the thick sediments. It will lay the foundation on providing the reference for the value of the long-period spectrum during determining the ground motion parameters in seismic design. This work has been supported by the National Natural Science Foundation of China (Grant No.41204046, 42574051).
Numerical Simulation of Wave Propagation and Phase Transition of Tin under Shock-Wave Loading
Institute of Scientific and Technical Information of China (English)
SONG Hai-Feng; LIU Hai-Feng; ZHANG Guang-Cai; ZHAO Yan-Song
2009-01-01
We undertake a numerical simulation of shock experiments on tin reported in the literature,by using a multiphase equation of state (MEOS) and a multiphase Steinberg Guinan (MSG) constitutive model for tin in the β,γ and liquid phases.In the MSG model,the Bauschinger effect is considered to better describe the unloading behavior.The phase diagram and Hugoniot of tin are calculated by MEOS,and they agree well with the experimental data.Combined with the MEOS and MSG models,hydrodynamic computer simulations are successful in reproducing the measured velocity profile of the shock wave experiment.Moreover,by analyzing the mass fraction contour as well as stress and temperature profiles of each phase for tin,we further discuss the complex behavior of tin under shock-wave loading.
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.
Yang, Si-Tong; Wei, Jiu-Chuan; Cheng, Jiu-Long; Shi, Long-Qing; Wen, Zhi-Jie
2016-12-01
Currently, numerical simulations of seismic channel waves for the advance detection of geological structures in coal mine roadways focus mainly on modeling twodimensional wave fields and therefore cannot accurately simulate three-dimensional (3-D) full-wave fields or seismic records in a full-space observation system. In this study, we use the first-order velocity-stress staggered-grid finite difference algorithm to simulate 3-D full-wave fields with P-wave sources in front of coal mine roadways. We determine the three components of velocity V x, V y, and V z for the same node in 3-D staggered-grid finite difference models by calculating the average value of V y, and V z of the nodes around the same node. We ascertain the wave patterns and their propagation characteristics in both symmetrical and asymmetric coal mine roadway models. Our simulation results indicate that the Rayleigh channel wave is stronger than the Love channel wave in front of the roadway face. The reflected Rayleigh waves from the roadway face are concentrated in the coal seam, release less energy to the roof and floor, and propagate for a longer distance. There are surface waves and refraction head waves around the roadway. In the seismic records, the Rayleigh wave energy is stronger than that of the Love channel wave along coal walls of the roadway, and the interference of the head waves and surface waves with the Rayleigh channel wave is weaker than with the Love channel wave. It is thus difficult to identify the Love channel wave in the seismic records. Increasing the depth of the receivers in the coal walls can effectively weaken the interference of surface waves with the Rayleigh channel wave, but cannot weaken the interference of surface waves with the Love channel wave. Our research results also suggest that the Love channel wave, which is often used to detect geological structures in coal mine stopes, is not suitable for detecting geological structures in front of coal mine roadways
Self-destructing Spiral Waves: Global Simulations of a Spiral-wave Instability in Accretion Disks
Bae, Jaehan; Nelson, Richard P.; Hartmann, Lee; Richard, Samuel
2016-09-01
We present results from a suite of three-dimensional global hydrodynamic simulations that shows 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 α ˜ 5 × 10-4 in our reference model). The instability is found to operate in a wide range of disk models, including those with isothermal or adiabatic equations of state, and in viscous disks where the dimensionless kinematic viscosity ν ≤ 10-5. This robustness suggests that the instability will have applications to a broad range of astrophysical disk-related phenomena, including those in close binary systems, planets embedded in protoplanetary disks (including Jupiter in our own solar system) and FU Orionis outburst models. Further work is required to determine the nature of the instability and to evaluate its observational consequences in physically more complete disk models than we have considered in this paper.
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...... through a refractivity field which has been calculated with the use of numerical weather prediction models. The numerical weather prediction model used in this paper is a model from the European Centre for Medium-Range Weather Forecasts (ECMWF). The wave propagator has been used to simulate a number...... radio occultations can be simulated when the simulations are based on wave propagation and refractivity field inputs from a numerical weather prediction model....
Large eddy simulation of vertical turbulent jets under JONSWAP waves
Institute of Scientific and Technical Information of China (English)
Jun Lu; Ling-Ling Wang; Hong-Wu Tang; Hui-Chao Dai
2011-01-01
The effect of random waves on vertical plane turbulent jets is studied numerically and the mechanism behind the interaction of the jet and waves is analyzed. The large eddy simulation method is used and the σ-coordinate system is adopted. Turbulence is modeled by a dynamic coherent eddy model. The σ-coordinate transformation is introduced to map the irregular physical domain with a wavy free surface and an uneven bottom onto a regular computational domain. The fractional step method is used to solve the filtered Navier-Stokes equations. Results presented include the distribution of velocity, the decay law of the mean velocity along the jet axis, self-similar characteristics and volume flux per unit width. In particular, the role of coherent structures on the momentum transfer along the jet centerline and the jet instantaneous characteristics in JONSWAP waves are a special focus of this research. The numerical results obtained are of great theoretical importance in understanding the behavior of turbulent jets in random wave environments.
RF Wave Simulation Using the MFEM Open Source FEM Package
Stillerman, J.; Shiraiwa, S.; Bonoli, P. T.; Wright, J. C.; Green, D. L.; Kolev, T.
2016-10-01
A new plasma wave simulation environment based on the finite element method is presented. MFEM, a scalable open-source FEM library, is used as the basis for this capability. MFEM allows for assembling an FEM matrix of arbitrarily high order in a parallel computing environment. A 3D frequency domain RF physics layer was implemented using a python wrapper for MFEM and a cold collisional plasma model was ported. This physics layer allows for defining the plasma RF wave simulation model without user knowledge of the FEM weak-form formulation. A graphical user interface is built on πScope, a python-based scientific workbench, such that a user can build a model definition file interactively. Benchmark cases have been ported to this new environment, with results being consistent with those obtained using COMSOL multiphysics, GENRAY, and TORIC/TORLH spectral solvers. This work is a first step in bringing to bear the sophisticated computational tool suite that MFEM provides (e.g., adaptive mesh refinement, solver suite, element types) to the linear plasma-wave interaction problem, and within more complicated integrated workflows, such as coupling with core spectral solver, or incorporating additional physics such as an RF sheath potential model or kinetic effects. USDoE Awards DE-FC02-99ER54512, DE-FC02-01ER54648.
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
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。%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.
Shock tubes and blast injury modeling
Institute of Scientific and Technical Information of China (English)
Ya-Lei Ning; Yuan-Guo Zhou
2015-01-01
Explosive blast injury has become the most prevalent injury in recent military conflicts and terrorist attacks.The magnitude of this kind of polytrauma is complex due to the basic physics of blast and the surrounding environments.Therefore,development of stable,reproducible and controllable animal model using an ideal blast simulation device is the key of blast injury research.The present review addresses the modeling of blast injury and applications of shock tubes.
Directory of Open Access Journals (Sweden)
Zhao-xi XU
2016-06-01
Full Text Available Mild traumatic brain injury (mTBI caused by blast shock waves (BSWs is one of the most common injuries among soldiers in the war. Such mTBI can also happen in civilians if exposed to shock waves of accidental explosion disasters, bomb attacks by terrorists and so on. This injury often results in cognitive problems, memory dysfunction and emotional disorder, and these neurological deficits are closely related to the dysfunction or disruption of the blood-brain barrier (BBB. The present paper discusses mainly the relationship between dysfunction or disruption of BBB and inflammatory reaction in mild brain injury associated with explosive shock wave and effects of early intervention of oxidative stress injury, repairing the BBB and blocking inflammation on relieving delayed neurological deficits. DOI: 10.11855/j.issn.0577-7402.2016.05.15
Aerodynamic Simulation of the MARINTEK Braceless Semisubmersible Wave Tank Tests
Stewart, Gordon; Muskulus, Michael
2016-09-01
Model scale experiments of floating offshore wind turbines are important for both platform design for the industry as well as numerical model validation for the research community. An important consideration in the wave tank testing of offshore wind turbines are scaling effects, especially the tension between accurate scaling of both hydrodynamic and aerodynamic forces. The recent MARINTEK braceless semisubmersible wave tank experiment utilizes a novel aerodynamic force actuator to decouple the scaling of the aerodynamic forces. This actuator consists of an array of motors that pull on cables to provide aerodynamic forces that are calculated by a blade-element momentum code in real time as the experiment is conducted. This type of system has the advantage of supplying realistically scaled aerodynamic forces that include dynamic forces from platform motion, but does not provide the insights into the accuracy of the aerodynamic models that an actual model-scale rotor could provide. The modeling of this system presents an interesting challenge, as there are two ways to simulate the aerodynamics; either by using the turbulent wind fields as inputs to the aerodynamic model of the design code, or by surpassing the aerodynamic model and using the forces applied to the experimental turbine as direct inputs to the simulation. This paper investigates the best practices of modeling this type of novel aerodynamic actuator using a modified wind turbine simulation tool, and demonstrates that bypassing the dynamic aerodynamics solver of design codes can lead to erroneous results.
Simulations of Shock Wave Interaction with a Particle Cloud
Koneru, Rahul; Rollin, Bertrand; Ouellet, Frederick; Annamalai, Subramanian; Balachandar, S.'Bala'
2016-11-01
Simulations of a shock wave interacting with a cloud of particles are performed in an attempt to understand similar phenomena observed in dispersal of solid particles under such extreme environment as an explosion. We conduct numerical experiments in which a particle curtain fills only 87% of the shock tube from bottom to top. As such, the particle curtain upon interaction with the shock wave is expected to experience Kelvin-Helmholtz (KH) and Richtmyer-Meshkov (RM) instabilities. In this study, the initial volume fraction profile matches with that of Sandia Multiphase Shock Tube experiments, and the shock Mach number is limited to M =1.66. In these simulations we use a Eulerian-Lagrangian approach along with state-of-the-art point-particle force and heat transfer models. Measurements of particle dispersion are made at different initial volume fractions of the particle cloud. A detailed analysis of the evolution of the particle curtain with respect to the initial conditions is presented. This work was supported by the U.S. Department of Energy, National Nuclear Security Administration, Advanced Simulation and Computing Program, as a Cooperative Agreement under the Predictive Science Academic Alliance Program, Contract No. DE-NA0002378.
Numerical Homogenization of Jointed Rock Masses Using Wave Propagation Simulation
Gasmi, Hatem; Hamdi, Essaïeb; Bouden Romdhane, Nejla
2014-07-01
Homogenization in fractured rock analyses is essentially based on the calculation of equivalent elastic parameters. In this paper, a new numerical homogenization method that was programmed by means of a MATLAB code, called HLA-Dissim, is presented. The developed approach simulates a discontinuity network of real rock masses based on the International Society of Rock Mechanics (ISRM) scanline field mapping methodology. Then, it evaluates a series of classic joint parameters to characterize density (RQD, specific length of discontinuities). A pulse wave, characterized by its amplitude, central frequency, and duration, is propagated from a source point to a receiver point of the simulated jointed rock mass using a complex recursive method for evaluating the transmission and reflection coefficient for each simulated discontinuity. The seismic parameters, such as delay, velocity, and attenuation, are then calculated. Finally, the equivalent medium model parameters of the rock mass are computed numerically while taking into account the natural discontinuity distribution. This methodology was applied to 17 bench fronts from six aggregate quarries located in Tunisia, Spain, Austria, and Sweden. It allowed characterizing the rock mass discontinuity network, the resulting seismic performance, and the equivalent medium stiffness. The relationship between the equivalent Young's modulus and rock discontinuity parameters was also analyzed. For these different bench fronts, the proposed numerical approach was also compared to several empirical formulas, based on RQD and fracture density values, published in previous research studies, showing its usefulness and efficiency in estimating rapidly the Young's modulus of equivalent medium for wave propagation analysis.
Thermal nuclear blast simulation at the National Solar Thermal Test Facility
Energy Technology Data Exchange (ETDEWEB)
Cameron, C.P.; Ghanbari, C.M.
1989-01-01
The National Solar Thermal Test Facility is operated by Sandia National Laboratories and located on Kirtland Air Force Base in Albuquerque, New Mexico. The facility includes a heliostat field and associated receiver tower, two solar furnaces, and two point-focus parabolic concentrators. All can be used for simulating the thermal portion of nuclear pulses. The heliostat field contains 222 computer-controlled mirrors, which reflect concentrated solar energy to test stations on a 61-m tower. The field produces a peak flux density of 250 W/cm/sup 2/ over a 15-cm diameter with a total beam power of over 5 MW/sub t/. Thermal nuclear blasts have been simulated using a high-speed shutter (opening and closing time of 0.15 sec over a 1-m wide aperture) in combination with heliostat control to produce square or shaped pulses. The shutter can accommodate samples up to 1 /times/ 1 m and it has been used by several US and Canadian agencies. A glass-windowed wind tunnel located behind the shutter can accommodate samples up to 48 /times/ 76 cm with simultaneous exposure to the thermal flux and air flow at velocities up to 120 m/s. Each solar furnace at the facility includes a heliostat, a non-tracking parabolic concentrator, and an attenuator. One solar furnace produces flux levels of 270 W/cm/sup 2/ over a 6-mm diameter and total power of 16 kW/sub t/. A second furnace, currently under construction, will produce flux levels up to 1000 W/cm/sup 2/ over a 4-cm diameter and total power of 65 kW/sub t/. Both furnaces include shutters and attenuators that can provide square or shaped pulses. The two 11-m diameter tracking parabolic point-focusing concentrators at the facility can each produce peak flux levels of 1500 W/cm/sup 2/ over a 2.5-cm diameter and total power of 75 kW/sub t/. High-speed shutters have been used to produce square pulses. 5 figs.
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.
Simulation and Experimental Validation of Hypersonic Shock Wave Interaction
Directory of Open Access Journals (Sweden)
Li Jing
2013-12-01
Full Text Available The present paper examines the relevance of grid and simulation accuracy of hypersonic CFD in terms of hypersonic sharp double-cone flow. The flow grid and normal grid each adopted 250×100, 500×100, 1000×100, 500×200, 1000×200, 1000×400 and so on grids. When the normal grid was 100, the wall pressure and heat flux distribution obtained from flow grid 500 and 1000 were consistent, indicating that the solution of flow grid convergence was obtained. However, some difference was observed when the separation zone was compared with the experimental data. In increasing the normal grid number and adopting grid 500×200, the position of the separation point, wall pressure and heat flux peak was shown to be consistent with the experiment. When the grid was further encrypted, the calculation using grid 1000×200 and 1000×400 was equal to that using grid 500×200. The simulation of hypersonic sharp double-cone flow also showed that when the separation zone of the simulation was less than the experimental measurement, the wall pressure and heat flux peak moved forward. This is because the backwardness of the intersection of the separation shock and the first shock resulted in the forwardness of the intersection of the first shock and the second shock after interference, making the work region of the induction shock and boundary layer move forward. The key challenge in achieving the correct simulation of the hypersonic sharp double-cone flow is explained as follows: the algorithm can not only capture shock wave strength correctly and give the adverse pressure gradient formed by the interfering shock wave near the wall accurately. It can also prevent the numerical dissipation of the algorithm from affecting the simulation accuracy of the viscous boundary layer to ensure the correct prediction of the size of the separation zone.
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.
Numerical Simulation of Hydrodynamic Behaviors of Gravity Cage in Waves
Institute of Scientific and Technical Information of China (English)
ZHAO Yun-peng; LI Yu-cheng; DONG Guo-hai; GUI Fu-kun
2007-01-01
This paper aims at investigation of the dynamic properties of gravity cage exposed to waves by use of a numerical model. The numerical model is developed, based on lumped mass method to set up the equations of motion of the whole cage; meanwhile the solutions of equations are solved by the Runge-Kutta-Verner fifth-order and sixth-order method. Physical model tests have been carried out to examine the validity of the numerical model. The results by the numerical simulation agree well with the experimental data.
NUMERICAL SIMULATION OF SHOCK WAVE REFRACTION ON INCLINED CONTACT DISCONTINUITY
Directory of Open Access Journals (Sweden)
P. V. Bulat
2016-05-01
Full Text Available We consider numerical simulation of shock wave refraction on plane contact discontinuity, separating two gases with different density. Discretization of Euler equations is based on finite volume method and WENO finite difference schemes, implemented on unstructured meshes. Integration over time is performed with the use of the third-order Runge–Kutta stepping procedure. The procedure of identification and classification of gas dynamic discontinuities based on conditions of dynamic consistency and image processing methods is applied to visualize and interpret the results of numerical calculations. The flow structure and its quantitative characteristics are defined. The results of numerical and experimental visualization (shadowgraphs, schlieren images, and interferograms are compared.
Simulation of surface acoustic wave motor with spherical slider.
Morita, T; Kurosawa, M K; Higuchi, T
1999-01-01
The operation of a surface acoustic wave (SAW) motor using spherical-shaped sliders was demonstrated by Kurosawa et al. (1994). It was necessary to modify the previous simulation models for usual ultrasonic motors because of this slider shape and the high frequency vibration. A conventional ultrasonic motor has a flat contact surface slider and a hundredth driving frequency; so, the tangential motion caused by the elasticity of the slider and stator with regard to the spherical slider of the SAW motor requires further investigation. In this paper, a dynamic simulation model for the SAW motor is proposed. From the simulation result, the mechanism of the SAW motor was clarified (i.e., levitation and contact conditions were repeated during the operation). The transient response of the motor speed was simulated. The relationships between frictional factor and time constant and vibration velocity of the stator and the slider speed were understood. The detailed research regarding the elastic deformation caused by preload would be helpful to construct an exact simulation model for the next work.
Simulations of short-crested harbour waves with variational Boussinesq modelling
Adytia, Didit
2014-01-01
Waves propagating from the deep ocean to the coast show large changes in wave height, wave length and direction. The challenge to simulate the essential wave characteristics is in particular to model the speed and nonlinear interaction correctly. All these physical phenomena are present, but hidden,
Molecular dynamics simulations of microscopic structure of ultra strong shock waves in dense helium
Liu, Hao; Kang, Wei; Zhang, Qi; Zhang, Yin; Duan, Huilin; He, X. T.
2016-12-01
Hydrodynamic properties and structure of strong shock waves in classical dense helium are simulated using non-equilibrium molecular dynamics methods. The shock speed in the simulation reaches 100 km/s and the Mach number is over 250, which are close to the parameters of shock waves in the implosion process of inertial confinement fusion. The simulations show that the high-Mach-number shock waves in dense media have notable differences from weak shock waves or those in dilute gases. These results will provide useful information on the implosion process, especially the structure of strong shock wave front, which remains an open question in hydrodynamic simulations.
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 ...
Numerical simulation of supersquare patterns in Faraday waves
Kahouadji, L.; Périnet, N.; Tuckerman, L. S.; Shin, S.; Chergui, J.; Juric, D.
2015-06-01
We report the first simulations of the Faraday instability using the full three-dimensional Navier-Stokes equations in domains much larger than the characteristic wavelength of the pattern. We use a massively parallel code based on a hybrid Front-Tracking/Level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. Simulations performed in rectangular and cylindrical domains yield complex patterns. In particular, a superlattice-like pattern similar to those of [Douady & Fauve, Europhys. Lett. 6, 221-226 (1988); Douady, J. Fluid Mech. 221, 383-409 (1990)] is observed. The pattern consists of the superposition of two square superlattices. We conjecture that such patterns are widespread if the square container is large compared to the critical wavelength. In the cylinder, pentagonal cells near the outer wall allow a square-wave pattern to be accommodated in the center.
Detecting shock waves in cosmological smoothed particle hydrodynamics simulations
Pfrommer, C; Ensslin, T A; Jubelgas, M; Pfrommer, Christoph; Springel, Volker; Ensslin, Torsten A.; Jubelgas, Martin
2006-01-01
We develop a formalism for the identification and accurate estimation of the strength of structure formation shocks during cosmological smoothed particle hydrodynamics simulations. Shocks not only play a decisive role for the thermalization of gas in virialising structures but also for the acceleration of relativistic cosmic rays (CRs) through diffusive shock acceleration. Our formalism is applicable both to ordinary non-relativistic thermal gas, and to plasmas composed of CRs and thermal gas. To this end, we derive an analytical solution to the one-dimensional Riemann shock tube problem for a composite plasma of CRs and thermal gas. We apply our methods to study the properties of structure formation shocks in high-resolution hydrodynamic simulations of the LCDM model. We find that most of the energy is dissipated in weak internal shocks with Mach numbers M~2 which are predominantly central flow shocks or merger shock waves traversing halo centres. Collapsed cosmological structures are surrounded by external ...
Wave packet molecular dynamics simulations of warm dense hydrogen
Knaup, M; Toepffer, C; Zwicknagel, G
2003-01-01
Recent shock-wave experiments with deuterium in a regime where a plasma phase-transition has been predicted and their theoretical interpretation are the matter of a controversial discussion. In this paper, we apply 'wave packet molecular dynamics' (WPMD) simulations to investigate warm dense hydrogen. The WPMD method was originally used by Heller for a description of the scattering of composite particles such as simple atoms and molecules; later it was applied to Coulomb systems by Klakow et al. In the present version of our model the protons are treated as classical point-particles, whereas the electrons are represented by a completely anti-symmetrized Slater sum of periodic Gaussian wave packets. We present recent results for the equation of state of hydrogen at constant temperature T = 300 K and of deuterium at constant Hugoniot E - E sub 0 + 1/2(1/n - 1/n sub 0)(p + p sub 0) = 0, and compare them with the experiments and several theoretical approaches.
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.
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.
Wave Energy Converter Annual Energy Production Uncertainty Using Simulations
Directory of Open Access Journals (Sweden)
Clayton E. Hiles
2016-09-01
Full Text Available Critical to evaluating the economic viability of a wave energy project is: (1 a robust estimate of the electricity production throughout the project lifetime and (2 an understanding of the uncertainty associated with said estimate. Standardization efforts have established mean annual energy production (MAEP as the metric for quantification of wave energy converter (WEC electricity production and the performance matrix approach as the appropriate method for calculation. General acceptance of a method for calculating the MAEP uncertainty has not yet been achieved. Several authors have proposed methods based on the standard engineering approach to error propagation, however, a lack of available WEC deployment data has restricted testing of these methods. In this work the magnitude and sensitivity of MAEP uncertainty is investigated. The analysis is driven by data from simulated deployments of 2 WECs of different operating principle at 4 different locations. A Monte Carlo simulation approach is proposed for calculating the variability of MAEP estimates and is used to explore the sensitivity of the calculation. The uncertainty of MAEP ranged from 2%–20% of the mean value. Of the contributing uncertainties studied, the variability in the wave climate was found responsible for most of the uncertainty in MAEP. Uncertainty in MAEP differs considerably between WEC types and between deployment locations and is sensitive to the length of the input data-sets. This implies that if a certain maximum level of uncertainty in MAEP is targeted, the minimum required lengths of the input data-sets will be different for every WEC-location combination.
High-low-blasting technology and its application in methane dynamic disaster prevention
Institute of Scientific and Technical Information of China (English)
LI Xian-zhong; LIN Bai-quan; YANG Wei; NI Guan-hua; LI Quan-gui
2011-01-01
The gas cooperative control model combined local pressure-relief with regional pressure-relief was established,based on the theory of multi-parameters cooperative.For the status of high gas contents,high in-situ stress and low-permeability of Ji-15 seam of No.12 coal mine in Pingmei Group.The law of detonation wave propagation and ground-stress change distribution were simulated by means of the finite element analysis software.The technology of high-low-blasting,composed of high blasting(deep crossing hole controlled hydraulic blasting) and low blasting (special roadway deep hole controlled blasting) were developed.The research shows that around control hole produce maximum tension fracture failure,and result in directional and controlled blasting,when the distance between control hole and blasting hole is 1.2 m.The theory makes blasting force and hydraulic force advantage superimpose,which raises the effect of pressure relief and permeability enhancements compared with general blasting.High blasting influence radius and low blasting influence radius superimposed with each other,that prevents methane dynamic disaster.The result of type approval test shows that the technology can increase gas permeability as high as 22.7～36.2 ratio,decrease gas pressure from 2.85 MPa to 0.30 MPa,increase drilling influence radius to about 9 m.The technology realizes regional overall permeability improvement,that provides a new technical measure for methane dynamic disaster prevention.
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.
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.
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
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.
Rock blasting and explosives engineering
Energy Technology Data Exchange (ETDEWEB)
Persson, P.-A.; Holmberg, R.; Lee, J. (New Mexico Institute of Mining and Technology, Socorro, NM (United States). Research Center for Energetic Materials)
1994-01-01
The book covers the practical engineering aspects of different kinds of rock blasting. It includes a thorough analysis of the cost of the entire process of tunneling by drilling and blasting compared with full-face boring. It covers the economics of the entire rock blasting operation and its dependence on the size of excavation. The book highlights the fundamentals of rock mechanics, shock waves and detonation, initiation and mechanics of rock motion. It describes the engineering design principles and computational techniques for many separate mining methods and rock blasting operations. 274 refs.
Low Model Analysis and Synchronous Simulation of the Wave Mechanics
Directory of Open Access Journals (Sweden)
Wenyuan Duan
2016-01-01
Full Text Available The dynamic behavior of a chaotic system in the internal wave dynamics and the problem of the tracing and synchronization are investigated, and the numerical simulation is carried out in this paper. The globally exponentially attractive set and positive invariant set of the chaotic system are studied via constructing the positive definite and radial unbounded Lyapunov function. There are no equilibrium positions, periodic solutions, quasi-period motions, wandering recovering motions, and other chaotic attractors of the system out of the globally exponentially attractive set. Strange attractors can only locate in the globally exponentially attractive set. A feedback controller is designed for the chaotic system to realize the control of the unstable point. The second method of Lyapunov is used to discuss theoretically the rationality of the design of the controller. The driving-response synchronization method is used to realize the globally exponential synchronization. The numerical simulation is carried out by MATLAB software, and the simulation results show that the method is effective.
2015-09-30
1 A multiscale nested modeling framework to simulate the interaction of surface gravity waves with nonlinear internal gravity waves...Minnesota LONG-TERM GOALS Our long-term goal is to develop a multiscale nested modeling framework that simulates, with the finest resolution...frameworks such as the proposed HYCOM-LZSNFS-SUNTANS-LES nested model are crucial for understanding multiscale processes that are unresolved, and hence
Elastomeric Polymer-by-Design for Blast-Induced Shock-Wave Management
2015-06-01
continuum scale ), is reported. At the nanoscale, molecular dynamics (MD) simulations have been performed with the accurate COMPASS potential for...dependent dynamic scaling function calibrated to match the self -diffusion of the atomistic and coarse-grained models. Master curves computed from the...characteristics at moleeular/nano-, micro-, meso- and macro- scales . An integrated approach was used to address the fabrication, modeling, and characterization
2015-08-06
US Army TARDEC Mr. Dave Gunter, Acting Associate Director, Analytics, US Army TARDEC Dr. Dave Horner, Director, DoD HPC Mod Program Mr...specific contact or rigid wall. The switching behavior can be tailored with additional timing controls on the card as required. The blast energy causes...or service by trade name, trademark, manufacturer , or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or
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.
Design and simulation of a standing wave oscillator based PLL
Institute of Scientific and Technical Information of China (English)
Wei ZHANG; You-de HU; Li-rong ZHENG
2016-01-01
A standing wave oscillator (SWO) is a perfect clock source which can be used to produce a high frequency clock signal with a low skew and high reliability. However, it is difficult to tune the SWO in a wide range of frequencies. We introduce a frequency tunable SWO which uses an inversion mode metal-oxide-semiconductor (IMOS) field-effect transistor as a varactor, and give the simulation results of the frequency tuning range and power dissipation. Based on the frequency tunable SWO, a new phase locked loop (PLL) architecture is presented. This PLL can be used not only as a clock source, but also as a clock distribution network to provide high quality clock signals. The PLL achieves an approximately 50% frequency tuning range when designed in Global Foundry 65 nm 1P9M complementary metal-oxide-semiconductor (CMOS) technology, and can be used directly in a high performance multi-core microprocessor.
Full Wave Simulation of Integrated Circuits Using Hybrid Numerical Methods
Tan, Jilin
Transmission lines play an important role in digital electronics, and in microwave and millimeter-wave circuits. Analysis, modeling, and design of transmission lines are critical to the development of the circuitry in the chip, subsystem, and system levels. In the past several decays, at the EM modeling level, the quasi-static approximation has been widely used due to its great simplicity. As the clock rates increase, the inter-connect effects such as signal delay, distortion, dispersion, reflection, and crosstalk, limit the performance of microwave systems. Meanwhile, the quasi-static approach loses its validity for some complex system structures. Since the successful system design of the PCB, MCM, and the chip packaging, rely very much on the computer aided EM level modeling and simulation, many new methods have been developed, such as the full wave approach, to guarantee the successful design. Many difficulties exist in the rigorous EM level analysis. Some of these include the difficulties in describing the behavior of the conductors with finite thickness and finite conductivity, the field singularity, and the arbitrary multilayered multi-transmission lines structures. This dissertation concentrates on the full wave study of the multi-conductor transmission lines with finite conductivity and finite thickness buried in an arbitrary lossy multilayered environment. Two general approaches have been developed. The first one is the integral equation method in which the dyadic Green's function for arbitrary layered media has been correctly formulated and has been tested both analytically and numerically. By applying this method, the double layered high dielectric permitivitty problem and the heavy dielectrical lossy problem in multilayered media in the CMOS circuit design have been solved. The second approach is the edge element method. In this study, the correct functional for the two dimensional propagation problem has been successfully constructed in a rigorous way
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.
Modelling Blast Effects on a Reinforced Concrete Bridge
Directory of Open Access Journals (Sweden)
Markellos Andreou
2016-01-01
Full Text Available The detailed investigation of blast phenomena and their catastrophic effects on existing structures are the main objectives of the present paper. It is well known that blast phenomena may be characterized by significant complexity, often involving complicated wave propagation effects as well as distinguishable material behaviors. Considering the above and in an attempt to provide a simplified modelling approach for the simulation of blast effects, a novel procedure is presented herein based on well-established methodologies and common engineering practices. In the above framework, firstly, the “predominant” deformation shape of the structure is estimated based on elastic finite element simulations under blast loads and then the structural response of the system is evaluated as a result of common computational beam-element tools such as displacement-based pushover analysis. The proposed methodology provides an immediate first estimation of the structural behavior under blast loads, based on familiar engineering procedures. A two-span reinforced concrete bridge was thoroughly investigated and the results provide insightful information regarding the damage patterns and localization.
Parametric decay of a parallel propagating monochromatic whistler wave: Particle-in-cell simulations
Ke, Yangguang; Gao, Xinliang; Lu, Quanming; Wang, Shui
2017-01-01
In this paper, by using one-dimensional (1-D) particle-in-cell simulations, we investigate the parametric decay of a parallel propagating monochromatic whistler wave with various wave frequencies and amplitudes. The pump whistler wave can decay into a backscattered daughter whistler wave and an ion acoustic wave, and the decay instability grows more rapidly with the increase of the frequency or amplitude. When the frequency or amplitude is sufficiently large, a multiple decay process may occur, where the daughter whistler wave undergoes a secondary decay into an ion acoustic wave and a forward propagating whistler wave. We also find that during the parametric decay a considerable part of protons can be accelerated along the background magnetic field by the enhanced ion acoustic wave through the Landau resonance. The implication of the parametric decay to the evolution of whistler waves in Earth's magnetosphere is also discussed in the paper.
Comparison between wave generation methods for numerical simulation of bimodal seas
Directory of Open Access Journals (Sweden)
Daniel A. Thompson
2016-01-01
Full Text Available This paper describes an investigation of the generation of desired sea states in a numerical wave model. Bimodal sea states containing energetic swell components can be coastal hazards along coastlines exposed to large oceanic fetches. Investigating the effects of long-period bimodal seas requires large computational domains and increased running time to ensure the development of the desired sea state. Long computational runs can cause mass stability issues due to the Stokes drift and wave reflection, which in turn affect results through the variation of the water level. A numerical wave flume, NEWRANS, was used to investigate two wave generation methods: the wave paddle method, allowing for a smaller domain; and the internal mass source function method, providing an open boundary allowing reflected waves to leave the domain. The two wave generation methods were validated against experimental data by comparing the wave generation accuracy and the variance of mass in the model during simulations. Results show that the wave paddle method not only accurately generates the desired sea state but also provides a more stable simulation, in which mass fluctuation has less of an effect on the water depth during the long-duration simulations. As a result, it is suggested that the wave paddle method with active wave absorption is preferable to the internal wave maker option when investigating intermediate-depth long-period bimodal seas for long-duration simulations.
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...
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...
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.
SAR IMAGING SIMULATION OF HORIZONTAL FULLY TWO-DIMENSIONAL INTERNAL WAVES
Institute of Scientific and Technical Information of China (English)
SHEN Hui; HE Yi-Jun
2006-01-01
Based on the research of Lynett and Liu, a new horizontal fully two-dimensional internal wave propagation model with rotation effect was deduced, which can be used to simulate the characteristics of internal waves in a horizontal fully two-dimensional plane. By combining the imaging mechanism of Synthetic Aperture Radar(SAR), a simulation procedure was fatherly acquired, which can simulate the propagation characteristics of oceanic internal waves into SAR images. In order to evaluate the validity of the proposed simulation procedure, case studies are performed in South China Sea and results from simulation procedure are analyzed in detail. A very good consistency was found between the simulation results and satellite images. The proposed simulation procedure will be a possible foundation for the quantitative interpretation of internal waves from fully two-dimensional satellite images.
Bond, Charlotte; Freise, Andreas
2013-01-01
A comparison of analytic calculations and FINESSE simulations of interferometer responses to gravitational wave strain. The response to a gravitational wave is gradually built up from the effect of modulating a space by a gravitational wave to Sagnac and Michelson interferometers with and without arm cavities. This document details the steps necessary to perform such simulations in FINESSE and explicitly derives the interferometer response equations.
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.
Wave-Tide-Surge Coupled Simulation for Typhoon Maemi
Institute of Scientific and Technical Information of China (English)
Byung Ho Choi; Byung Il Min; Kyeong Ok Kim; Jin Hee Yuk
2013-01-01
The main task of this study focuses on studying the effect of wave-current interaction on currents,storm surge and wind wave as well as effects of current induced wave refraction and current on waves by using numerical models which consider the bottom boundary layer and sea surface roughness parameter for shallow and smooth bed area around Korean Peninsula.The coupled system (unstructured-mesh SWAN wave and ADCIRC) run on the same unstructured mesh.This identical and homogeneous mesh allows the physics of wave-circulation interactions to be correctly resolved in both models.The unstructured mesh can be applied to a large domain allowing all energy from deep to shallow waters to be seamlessly followed.There is no nesting or overlapping of structured wave meshes,and no interpolation is required.In response to typhoon Maemi (2003),all model components were validated independently,and shown to provide a faithful representation of the system's response to this storm.The waves and storm surge were allowed to develop on the continental shelf and interact with the complex nearshore environment.The resulting modeling system can be used extensively for prediction of the typhoon surge.The result show that it is important to incorporate the wave-current interaction effect into coastal area in the wave-tide-surge coupled model.At the same time,it should consider effects of depth-induced wave breaking,wind field,currents and sea surface elevation in prediction of waves.Specially,we found that:(1) wave radiation stress enhanced the current and surge elevation otherwise wave enhanced nonlinear bottom boundary layer decreased that,(2) wind wave was significantly controlled by sea surface roughness thus we cautiously took the experimental expression.The resulting modeling system can be used for hindcasting (prediction) the wave-tide-surge coupled environments at complex coastline,shallow water and fine sediment area like areas around Korean Peninsula.
框-筒结构建筑物的折叠爆破拆除%Numerical simulations on fold blasting demolition of frame-tube structures
Institute of Scientific and Technical Information of China (English)
杨国梁; 杨军; 姜琳琳
2009-01-01
采用共节点分离式钢筋混凝土模型,对框-简结构折叠倒塌进行了三维数值模拟,包括底部起爆和顶部起爆2种方式,并且在底部起爆方式中,采用了不同切口高度和延迟时间.对结构的倒塌过程、支撵立柱的破坏过程进行了比较分析.结果表明:采用底部起爆时,结构下部压碎程度较采用顶部起爆严重;同为底部起爆.延迟时间0.25 s的结构破碎比0.5 s严重;底层立柱采用不同的切口高度和延迟时间,结构的倒塌方向发生了改变,结构略向南倾倒;支撑柱的破坏过程不同,对结构的后坐距离产生影响,采用底部起爆时,结构的后坐距离小于顶部起爆.通过对混凝土和钢筋单元受力过程进行的分析,共节点分离式模型能够反映钢筋和混凝土2种材料的力学性能差异.%The common node separate reinforced concrete model was adopted to numerically simulate the fold blasting collapse processes of frame-tube structures. The two blasting methods used in the three-dimensional simulations included the bottom blasting and the top blasting. In the bottom blasting methods, different cut height and delay time were considered. The collapse processes of the frame-tube structures and the failure processes of the sustaining pillars were discussed. The bottom of the structure was crushed more seriously by using the bottom blasting method than that by using the top blasting method. For the bottom blasting method, more fragmentation appeared in the structure with the 0. 25 s delay time than that with 0. 5 s. The structure collapsed southward appreciably with the different cut heights and delay times. The failure processes of the sustaining pillars were different according to the different blasting methods, which influenced the backlash distance of the structure. The backlash distance of the structure under the bottom blasting was smaller than that under the top blasting. Stress analysis of the concrete and reinforcement
Test particle simulation study of whistler wave packets observed near Comet Giacobini-Zinner
Kaya, N.; Matsumoto, H.; Tsurutani, B. T.
1989-01-01
Nonlinear interactions of water group ions with large-amplitude whistler wave packets detected at the leading edge of steepened magnetosonic waves observed near Comet Giacobini-Zinner (GZ) are studied using test particle simulations of water-ion interactions with a model wave based on GZ data. Some of the water ions are found to be decelerated in the steepened portion of the magnetosonic wave to the resonance velocity with the whistler wave packets. Through resonance and related nonlinear interaction with the large-amplitude whistler waves, the water ions become trapped by the packet. An energy balance calculation demonstrates that the trapped ions lose their kinetic energy during the trapped motion in the packet. Thus, the nonlinear trapping motion in the wave structure leads to effective energy transfer from the water group ions to the whistler wave packets in the leading edge of the steepened MHD waves.
Institute of Scientific and Technical Information of China (English)
渐令; 张建松; 宋允全; 赵敏
2012-01-01
The existing finite element method and boundary element method simulating the blast furnace hearth erosion involve constructing mesh by hand, and the computation is complex when dealing with free surface. By solving the Possion differential equations, the body-fitted coordinates is introduced to transform the hearth irregular border into calculative plane. According to condition of the thermal electric couples in hearth of No.7 blast furnace at Handan Iron & Steel Co. Ltd, the numerical simulation of blast furnace hearth is given through solving the heat conduction equations in calculative plane. The model has been used in No.7 blast furnace at Handan Iron & Steel Co. Ltd and it can track the erosion state of blast furnace hearth dynamically.%现有有限元、边界元方法模拟高炉炉缸侵蚀状况需要对炉缸进行网格划分的前处理,对于自由变动边界问题,这类模型计算十分复杂.应用基于适体坐标的有限差分方法模拟高炉炉缸侵蚀状况:通过求解Possion微分方程建立适体坐标系,将炉缸的不规则边界变换到规则的计算平面上,利用有限差分方法在计算平面上离散并数值求解热传导方程,给出高炉炉缸等温线的数值模拟.该方法计算简单,运行时间短,适合在线实时监测,邯钢7号高炉在线运行表明模型可以动态地跟踪炉缸侵蚀状况.
Institute of Scientific and Technical Information of China (English)
WANG Zhong; LU Xiao-ping
2011-01-01
Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt's work、 the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory,using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems,with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear (Dawson) methods. Moreover,sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.
Effects of Simulated Heat Waves on Cardiovascular Functions in Senile Mice
Directory of Open Access Journals (Sweden)
Xiakun Zhang
2014-08-01
Full Text Available The mechanism of the effects of simulated heat waves on cardiovascular disease in senile mice was investigated. Heat waves were simulated in a TEM1880 meteorological environment simulation chamber, according to a heat wave that occurred in July 2001 in Nanjing, China. Eighteen senile mice were divided into control, heat wave, and heat wave BH4 groups, respectively. Mice in the heat wave and heat wave BH4 groups were exposed to simulated heat waves in the simulation chamber. The levels of ET-1, NO, HSP60, SOD, TNF, sICAM-1, and HIF-1α in each group of mice were measured after heat wave simulation. Results show that heat waves decreased SOD activity in the myocardial tissue of senile mice, increased NO, HSP60, TNF, sICAM-1, and HIF-1α levels, and slightly decreased ET-1 levels, BH4 can relieve the effects of heat waves on various biological indicators. After a comprehensive analysis of the experiments above, we draw the followings conclusions regarding the influence of heat waves on senile mice: excess HSP60 activated immune cells, and induced endothelial cells and macrophages to secrete large amounts of ICAM-1, TNF-α, and other inflammatory cytokines, it also activated the inflammation response in the body and damaged the coronary endothelial cell structure, which increased the permeability of blood vessel intima and decreased SOD activity in cardiac tissues. The oxidation of lipoproteins in the blood increased, and large amounts of cholesterol were generated. Cholesterol penetrated the intima and deposited on the blood vessel wall, forming atherosclerosis and leading to the occurrence of cardiovascular disease in senile mice. These results maybe are useful for studying the effects of heat waves on elderly humans, which we discussed in the discussion chapter.
Global Ray Tracing Simulations of the SABER Gravity Wave Climatology
2009-01-01
amplitudes, vertical wave- D08126 PREUSSE ET AL.: GRAVITY WAVES BY SATELLITE AND RAYTRACER 2 of 25 D08126 lengths and phases of the two strongest wave...with the wind ‘‘drift’’ large D08126 PREUSSE ET AL.: GRAVITY WAVES BY SATELLITE AND RAYTRACER 3 of 25 D08126 distances downstream in taking much...factor (IMF) attributed to the single SCEs in generating the composite. D08126 PREUSSE ET AL.: GRAVITY WAVES BY SATELLITE AND RAYTRACER 4 of 25 D08126
Inner Magnetosphere Simulations: Exploring Magnetosonic Wave Generation Conditions
Zaharia, S. G.; Jordanova, V. K.; MacDonald, E.; Thomsen, M. F.
2012-12-01
We investigate the conditions for magnetosonic wave generation in the near-Earth magnetosphere by performing numerical simulations with our newly improved self-consistent model, RAM-SCB. The magnetosonic (ion Bernstein) instability, a potential electron acceleration mechanism in the outer radiation belt, is driven by a positive slope in the ion distribution function perpendicular to the magnetic field, a so-called "velocity ring" distribution at energies above 1 keV. The formation of such distributions is dependent on the interplay of magnetic and electric drifts, as well as ring current losses, and therefore its study requires a realistic treatment of both plasma and field dynamics. The RAM-SCB model represents a 2-way coupling of the kinetic ring current-atmosphere interactions model (RAM) with a 3D plasma equilibrium code. In RAM-SCB the magnetic field is computed in force balance with the RAM anisotropic pressures and then returned to RAM to guide the particle dynamics. RAM-SCB thus properly treats both the kinetic drift physics crucial in the inner magnetosphere and the self-consistent interaction between plasma and magnetic field (required due to the strong field depressions during storms, depressions that strongly affect particle drifts). In order to provide output at geosynchronous locations, recently the RAM-SCB boundary has been expanded to 9 RE from Earth, with plasma pressure and magnetic field boundary conditions prescribed there from empirical models. This presentation will analyze, using event simulations with the improved model and comparisons with LANL MPA geosynchronous observations, the occurrence and location of magnetosonic unstable regions in the inner magnetosphere and their dependence on the following factors: 1). geomagnetic activity level (including quiet time, storm main phase and recovery); 2). magnetic field self-consistency (stretched vs. dipole fields). We will also discuss the physical mechanism for the occurrence of the velocity
Numerical Simulated Study on the Separation of Oblique Incident and Reflected Waves
Institute of Scientific and Technical Information of China (English)
邵利民; 俞聿修
2001-01-01
The Goda's method of separating the frequency spectrum of the unidirectional incident and reflected waves is improved. The proposed method can be applied to the separation of oblique incident and reflected waves and the two wave gauges can be arranged in an arbitrary angle in front of a structure. When the projected distance of the two probes on the incident wave direction is the multiple ofthe half length of the incident waves, the singular problem will emerge by using the method. It is advised that when the projected distance of the two measured points on the incident wave direction is 0.05～0.45 times the wave length of peak frequency wave, good results can be obtained. The simulated resultant waves are separated by the method of numerical simulation and the separated wave spectra are basically corresponding to the target spectra input. The wave trains calculated by the separated incident and reflected wave frequency spectrum are approximated to the input wave trains and the reflected coefficient can be derived correctly. Therefore, the method proposed in this paper is reliable.
Development and characterization of an open-ended shock tube for the study of blast mtbi.
Shah Ms, Alok S; Stemper Phd, Brian D; Pintar Phd, Frank A
2012-01-01
Shock tubes can be used to study traumatic brain injuries due to blast waves in a laboratory setting without the use of explosives. A literature review shows that several shock tubes used in these type of studies are large in size and have a high cost of conducting tests and maintaining the device. The purpose of this study was to design and characterize small shock tubes to simulate open field blast waves, which can be used in a laboratory with limited space and has low cost of operation. In addition, the shock tube can be used to induce localized blast in a small region to study the injury mechanisms in the desired region. Furthermore, the animal is placed outside of the shock tube, which provides the ability to expose the animal to a pure primary blast wave. A helium-driven shock tube with driven length of 3.04 m and driver length of 0.30 m was used in the present study. Transducers were placed at multiple locations and distances to characterize the blast wave outside the shock tube. The versatile design of the shock tube can generate a wide range of peak overpressure, rise times and durations. The shock tube was able to generate peak overpressure ranging from 25 kPa to 508 kPa and positive durations ranging from 97 µs to 797 µs. The literature review also showed several studies where the data were collected and analyzed improperly. The under-sampling or improper filtering can significantly affect the data. Additionally, the orientation of the transducer with respect to the shock wave can also affect the recorded peak overpressure. This paper reports various peak overpressures, durations and rise-times that can be developed with a small open-ended shock tube and the methodology to properly collect and analyze blast wave data generated by the shock tube.
Bingham, Jill; Hinders, Mark
2009-07-01
The development of automatic guided wave interpretation for detecting corrosion in aluminum aircraft structural stringers is described. The dynamic wavelet fingerprint technique (DWFT) is used to render the guided wave mode information in two-dimensional binary images. Automatic algorithms then extract DWFT features that correspond to the distorted arrival times of the guided wave modes of interest, which give insight into changes of the structure in the propagation path. To better understand how the guided wave modes propagate through real structures, parallel-processing elastic wave simulations using the finite integration technique (EFIT) has been performed. Three-dimensional (3D) simulations are used to examine models too complex for analytical solutions. They produce informative visualizations of the guided wave modes in the structures and mimic the output from sensors placed in the simulation space. Using the previously developed mode extraction algorithms, the 3D EFIT results are compared directly to their experimental counterparts.
Simulation of laser-driven plasma beat-wave propagation in collisional weakly relativistic plasmas
Kaur, Maninder; Nandan Gupta, Devki
2016-11-01
The process of interaction of lasers beating in a plasma has been explored by virtue of particle-in-cell (PIC) simulations in the presence of electron-ion collisions. A plasma beat wave is resonantly excited by ponderomotive force by two relatively long laser pulses of different frequencies. The amplitude of the plasma wave become maximum, when the difference in the frequencies is equal to the plasma frequency. We propose to demonstrate the energy transfer between the laser beat wave and the plasma wave in the presence of electron-ion collision in nearly relativistic regime with 2D-PIC simulations. The relativistic effect and electron-ion collision both affect the energy transfer between the interacting waves. The finding of simulation results shows that there is a considerable decay in the plasma wave and the field energy over time in the presence of electron-ion collisions.
Direct numerical simulations of an inertial wave attractor in linear and nonlinear regimes
Jouve, Laurène
2014-01-01
In a uniformly rotating fluid, inertial waves propagate along rays that are inclined to the rotation axis by an angle that depends on the wave frequency. In closed domains, multiple reflections from the boundaries may cause inertial waves to focus on to particular structures known as wave attractors. Such structures have previously been studied from a theoretical point of view, in laboratory experiments, in linear numerical calculations and in some recent numerical simulations. In the present paper, two-dimensional direct numerical simulations of an inertial wave attractor are presented. In the linear regime, we first recover the results of the linear calculations and asymptotic theory of Ogilvie (2005) who considered a prototypical problem involving the focusing of linear internal waves into a narrow beam centred on a wave attractor in a steady state. The velocity profile of the beam and its scalings with the Ekman number, as well as the asymptotic value of the dissipation rate, are found to be in agreement ...
Parametric instabilities of large-amplitude parallel propagating Alfven waves: 2-D PIC simulation
Nariyuki, Yasuhiro; Hada, Tohru
2008-01-01
We discuss the parametric instabilities of large-amplitude parallel propagating Alfven waves using the 2-D PIC simulation code. First, we confirmed the results in the past study [Sakai et al, 2005] that the electrons are heated due to the modified two stream instability and that the ions are heated by the parallel propagating ion acoustic waves. However, although the past study argued that such parallel propagating longitudinal waves are excited by transverse modulation of parent Alfven wave, we consider these waves are more likely to be generated by the usual, parallel decay instability. Further, we performed other simulation runs with different polarization of the parent Alfven waves or the different ion thermal velocity. Numerical results suggest that the electron heating by the modified two stream instability due to the large amplitude Alfven waves is unimportant with most parameter sets.
Digital core based transmitted ultrasonic wave simulation and velocity accuracy analysis
Zhu, Wei; Shan, Rui
2016-06-01
Transmitted ultrasonic wave simulation (TUWS) in a digital core is one of the important elements of digital rock physics and is used to study wave propagation in porous cores and calculate equivalent velocity. When simulating wave propagates in a 3D digital core, two additional layers are attached to its two surfaces vertical to the wave-direction and one planar wave source and two receiver-arrays are properly installed. After source excitation, the two receivers then record incident and transmitted waves of the digital rock. Wave propagating velocity, which is the velocity of the digital core, is computed by the picked peak-time difference between the two recorded waves. To evaluate the accuracy of TUWS, a digital core is fully saturated with gas, oil, and water to calculate the corresponding velocities. The velocities increase with decreasing wave frequencies in the simulation frequency band, and this is considered to be the result of scattering. When the pore fluids are varied from gas to oil and finally to water, the velocity-variation characteristics between the different frequencies are similar, thereby approximately following the variation law of velocities obtained from linear elastic statics simulation (LESS), although their absolute values are different. However, LESS has been widely used. The results of this paper show that the transmission ultrasonic simulation has high relative precision.
Simulation of breaking gravity waves during the south foehn of 7 - 13 January 1996
Energy Technology Data Exchange (ETDEWEB)
Schmid, H.; Doernbrack, A.
1998-07-01
A high-resolution mesoscale model with horizontal mesh size of 6 km is applied to simulate upper-level wave breaking above the Alps during a south foehn event in January 1996. The model reproduces the key synoptic and mesoscale features of cross-alpine airflow during foehn. High-resolution radiosonde ascents at Munich and Innsbruck are used to evaluate the quality of the model simulations. The simulations predict breaking gravity waves above the jet stream in a layer between 10 and 15 km altitude where the shear is maximum. In part of the foehn period a critical level is present at about 200 hPa that results in wave steepening below and no wave activity aloft. Regions where aircraft report clear-air turbulence encounters agree reasonably with the simulated locations of gravity wave breaking. (orig.)
Simulation and Optimization of Surface Acoustic Wave Devises
DEFF Research Database (Denmark)
Dühring, Maria Bayard
2007-01-01
In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model of a piezoele......In this paper a method to model the interaction of the mechanical field from a surface acoustic wave and the optical field in the waveguides of a Mach-Zehnder interferometer is presented. The surface acoustic waves are generated by interdigital transducers using a plane strain model...
Dynamic simulation of hydrodynamic model of drum level wave action and sloshing
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In order to build the model of the drum level wave action and sloshing, based on the method of modularization modeling,the hydrodynamic model of drum level wave action and sloshing was developed, and dynamic simulation researches were carried out based on the model. The results indicate that both drum level and drum length have functional relations with period of drum level wave action and sloshing. When the drum level decreases or drum length increases, the period of drum level wave action and sloshing increases, density of liquid and number of sub-module division have little influence on the period of drum level wave action and sloshing. The model was validated by the analytical solution theory of liquid's wave action and sloshing in cuboid container, and the 3D graphics of drum level wave action and sloshing was also obtained. The model can dynamically reflect the rules of wave action and sloshing of water in the container exactly.
THREE-DIMENSIONAL NUMERICAL SIMULATION OF WAVE SLAMMING ON AN OPEN STRUCTURE
Institute of Scientific and Technical Information of China (English)
DING Zhao-qiang; WANG Guo-yu; REN Bing
2012-01-01
The three-dimensional numerical simulation of wave slamming on an open structure in the splash zone is carried out based upon the Volume Of Fluid (VOF) method.A wave basin is established by solving the continuity equation and the Navier-Stoke equations.The linear wave-maker is placed on the left side of the basin,and the numerical sponge layer and the SRC are placed on the right side of the basin to damp the incident waves.The three-dimensional wave slamming boundary condition is adopted to model waves in contact with and separated from the underside of the structure.The numerical results of wave slamming on a foursquare structure for various parametric cases are verified by the experimental results.Meanwhile,the characteristics of the wave impact forces on the undersides of the rectangular structures with various length-breadth ratios are discussed.
Simulation of Storm Surge and Wave Due to Typhoon Isewan (5915)
Institute of Scientific and Technical Information of China (English)
Jin-Hee YUK; Kyeong Ok KIM; Han Soo LEE; Byung Ho CHOI
2015-01-01
An integrally coupled wave-tide-surge model was developed and then applied to the simulation of the wave-typhoon surge for the typhoon Isewan (typhoon Vera (5915)), which is the strongest typhoon that has struck Japan and caused incalculable damage. An integrally coupled tide-surge-wave model using identical and homogeneous meshes in an unstructured grid system was used to correctly resolve the physics of wave-circulation interaction in both models. All model components were validated independently. The storm surge and wave properties such as the surge height, the significant wave height, wave period and direction were reproduced reasonably under the meteorological forcing, which was reprocessed to be close to the observations. The resulting modeling system can be used extensively for the prediction of the storm surge and waves and the usual barotropic forecast.
Numerical Simulation of Wave Field near Submerged Bars by PLIC-VOF Model
Institute of Scientific and Technical Information of China (English)
LIU Cheng; LIU Xiao-qing; JIANG Chang-bo
2005-01-01
Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over submerged bars, using PLIC-VOF (Piecewise Linear Interface Construction) to trace the free surface of wave and finite difference method to solve vertical 2D Navier-Stokes (N-S) equations. A comparison of the numerical results for two kinds of submerged bars with the experimental ones shows that the PLIC-VOF model used in this study is effective and can compute the wave field precisely.
废塑料入炉喷吹的数值模拟研究%Numerical simulation of waste plastic injection in blast furnace
Institute of Scientific and Technical Information of China (English)
董树; 史岩彬; 耿啸
2016-01-01
基于高炉喷吹混合燃料的方法，探究废塑料作为燃料在高炉内的作用。以某2536 m3高炉为研究对象，将喷入的煤粉及塑料作为粉相，分析混合燃料的水分、灰分、挥发分和固定碳等化学指标，采用高炉高温区热平衡分析法，计算高炉单一喷吹和混合喷吹条件下的焦比，对高炉内喷吹过程进行模拟研究。计算机模拟结果表明，将煤粉与废塑料混合喷吹降低了高炉焦比，提高了煤的利用率。%Based on the method of blast furnace injection the mixing fuel , the effect of waste plastics as fuel in blast furnace injection was explored .The 2536 m3 blast furnace as an example , considering the pulverized coals and plastics as powder phase , moisture, ash, volatile and fixed carbon etc .The high temperature zone of blast furnace heat balance analysis method was used to calculate the coke ratio of single injection and mixing injection , and the process of blast furnace injection was studied .Com-puter simulation results show that the mixture injection of pulverized coal and waste plastic reduce coke ratio and improve the utilization rate of coal .
Numerical simulation of floating bodies in extreme free surface waves
Directory of Open Access Journals (Sweden)
Z. Z. Hu
2011-02-01
Full Text Available In this paper, we use the in-house Computational Fluid Dynamics (CFD flow code AMAZON-SC as a numerical wave tank (NWT to study wave loading on a wave energy converter (WEC device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water. The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Numerical simulation of floating bodies in extreme free surface waves
Hu, Z. Z.; Causon, D. M.; Mingham, C. G.; Qian, L.
2011-02-01
In this paper, we use the in-house Computational Fluid Dynamics (CFD) flow code AMAZON-SC as a numerical wave tank (NWT) to study wave loading on a wave energy converter (WEC) device in heave motion. This is a surface-capturing method for two fluid flows that treats the free surface as contact surface in the density field that is captured automatically without special provision. A time-accurate artificial compressibility method and high resolution Godunov-type scheme are employed in both fluid regions (air/water). The Cartesian cut cell method can provide a boundary-fitted mesh for a complex geometry with no requirement to re-mesh globally or even locally for moving geometry, requiring only changes to cut cell data at the body contour. Extreme wave boundary conditions are prescribed in an empty NWT and compared with physical experiments prior to calculations of extreme waves acting on a floating Bobber-type device. The validation work also includes the wave force on a fixed cylinder compared with theoretical and experimental data under regular waves. Results include free surface elevations, vertical displacement of the float, induced vertical velocity and heave force for a typical Bobber geometry with a hemispherical base under extreme wave conditions.
Integrated design and simulation for millimeter-wave antenna systems
Cwik, T.; Katz, D. S.; Villegas, F. J.
2000-01-01
In this paper the development and application of MODTool (Millimeter-wave Optics Design), a design tool that efficiently integrates existing millimeter-wave optics design software with a solid body modeler and thermal/structural analysis packages, will be discussed.
Wave Simulation in Truncated Domains for Offshore Applications
Wellens, P.R.
2012-01-01
URANS simulations of ship motion responses in long-crest irregular waves
Institute of Scientific and Technical Information of China (English)
沈志荣; 叶海轩; 万德成
2014-01-01
In this paper, numerical prediction of ship motion responses in long-crest irregular waves by the URANS-VOF method is presented. A white noise spectrum is applied to generate the incoming waves to evaluate the motion responses. The procedure can replace a decade of simulations in regular wave with one single run to obtain a complete curve of linear motion response, conside-rably reducing computation time. A correction procedure is employed to adjust the wave generation signal based on the wave spe-ctrum and achieves fairly better results in the wave tank. Three ship models with five wave conditions are introduced to validate the method. The computations in this paper are completed by using the solver naoe-FOAM-SJTU, a solver developed for ship and ocean engineering based on the open source code OpenFOAM. The computational motion responses by the irregular wave procedure are compared with the results by regular wave, experiments and strip theory. Transfer functions by irregular wave closely agree with the data obtained in the regular waves, showing negligible difference. The comparison between computational results and experiments also show good agreements. The results better predicted by CFD method than strip theories indicate that this method can compensate for the inaccuracy of the strip theories. The results confirm that the irregular wave procedure is a promising method for the accurate prediction of motion responses with less accuracy loss and higher efficiency compared with the regular wave procedure.
Institute of Scientific and Technical Information of China (English)
璩世杰; 尚峰华; 李宝辉; 王友成
2001-01-01
结合实例介绍了一种用于露天矿台阶垂直中深孔爆破设计并对爆破破碎效果和爆堆形状分别进行预测和模拟的软件系统——Blast-Code模型。该模型主要由采场地质地形数据库、爆破设计与模拟两大部分构成，前者可以准确和方便快捷地反映采场的地形条件、矿岩物理力学性质及地质构造等信息；后者则依据对爆区地形(包括台阶自由面条件 ) 、爆区内矿岩的物理力学性质与地质构造特征、炸药爆炸性能三类对爆破效果具有直接影响的关键因素的综合定量分析，由计算机自动进行完整的爆破设计，并可对矿岩的破碎效果和爆堆形状进行定量的模拟和预测。Blast-Code模型具有爆破参数选取的人工干预和钻孔爆破成本计算功能，可对多个设计方案进行技术经济对比分析，利于实现优化爆破。%This paper introduces a computer program, the Blast-Code, fo r design and simulation of open-pit blasting operations. In the Blast-Code, a geology and topogr aphy database is developed and used to provide the data on geological conditions , physical pro perties of rocks, topography environment within and nearby the blast. The dat a and the recognized explosive characteristics can be automatically analyzed and a complete design can be carried out with the model. Blast simulation includes prediction of resultant fragmentation in terms of looseness degree, fragment siz e average as well as the 3-D profile and any cross-sectional profile of a muck pile. The Blast-Code model permits interactive parameter selection and calcula ti on of drilling and blasting cost, so that result of different runs of blast desi gn can be compared in terms of the predicted outcome and cost and then an optimu m design can be selected.
Simulation Analysis of Wave Effect on Exceeding Water Gesture and Load of Submarine Launched Missile
Directory of Open Access Journals (Sweden)
Ke Zhao
2014-02-01
Full Text Available In this study, we have a research on wave action on the submarine launched missile water trajectory and gesture angles during the process between launch and exit from water. Infinite water depth plane wave was used as the wave model, mathematics models of missile exceeding water under different wave conditions were established based on ideal potential flow theory. The flow field velocity potential was obtained by solving the Laplace equation, thus can obtain missile surface pressure. Considering free surface effects, simple Green’s function was introduced to solve boundary value problems. Three-dimensional Fortran program and finite software ABAQUS were combined to complete the fluid-structure interaction simulation. The rules that wave level and phases effects on submarine-launched missile were finally obtained, which shows wave affect cannot be neglected. Simulation methods and results of this study have a certain reference value for the submarine-launched missile launching.
Finite-Difference Simulation of Elastic Wave with Separation in Pure P- and S-Modes
Directory of Open Access Journals (Sweden)
Ke-Yang Chen
2014-01-01
Full Text Available Elastic wave equation simulation offers a way to study the wave propagation when creating seismic data. We implement an equivalent dual elastic wave separation equation to simulate the velocity, pressure, divergence, and curl fields in pure P- and S-modes, and apply it in full elastic wave numerical simulation. We give the complete derivations of explicit high-order staggered-grid finite-difference operators, stability condition, dispersion relation, and perfectly matched layer (PML absorbing boundary condition, and present the resulting discretized formulas for the proposed elastic wave equation. The final numerical results of pure P- and S-modes are completely separated. Storage and computing time requirements are strongly reduced compared to the previous works. Numerical testing is used further to demonstrate the performance of the presented method.
Spreading of sediment due to underwater blasting and dredging
DEFF Research Database (Denmark)
Nielsen, Morten Holtegaard; Bach, Lis; Bollwerk, Sandra
2015-01-01
impacts of suspended sediment from underwater blasting, which could include coverage of the benthos or increased turbidity, can be managed by timing the blast favourably relative to currents, waves and stratification. It is argued that the environmental impact of blasting can be minimized by decreasing...
Numerical simulation of hydrodynamic wave loading by a compressible two-phase flow method
Wemmenhove, Rik; Luppes, Roelf; Veldman, Arthur; Bunnik, Tim
2015-01-01
Hydrodynamic wave loading on and in offshore structures is studied by carrying out numerical simulations. Particular attention is paid to complex hydrodynamic phenomena such as wave breaking and air entrapment. The applied CFD method, ComFLOW, solves the Navier–Stokes equations with an improved Volu
Lattice Boltzmann simulation for the spiral waves in the excitable medium
Institute of Scientific and Technical Information of China (English)
GuangwuYAN; LiYUAN
2000-01-01
We propose lattice Boltzmann method for the spiral waves. Using Chapman-Enskog expansion and multiscales technique, we obtain equilibrium distribution functions of the model. As an example, we simulate the Selkov reactions with scratching mark, i. e. using a scratching mark pacemaker, obtained one classical spiral waves.
Institute of Scientific and Technical Information of China (English)
Zhou Aitao; Wang Kai; Wang Li; Du Feng; Li Zhilei
2015-01-01
In order to analyze the propagation characteristics of shock wave and gas flow induced by outburst inten-sity, the governing equations of shock wave and gas flow propagation were put forward, and the numer-ical simulation boundary condition was obtained based on outburst characteristics. The propagation characteristics of shock wave and gas flow were simulated by Fluent software, and the simulation results were verified by experiments. The results show that air shock wave is formed due to air medium com-pressed by the transient high pressure gas which rapidly expands in the roadway;the shock wave and gas flow with high velocity are formed behind the shock wave front, which significantly decays due to limiting effect of the roadway wall. The attenuation degree is greater in the early stage than that in the late stage, and the velocity of gas convection transport is lower than the speed of the shock wave. The greater the outburst intensity is, the greater the pressure of the shock wave front is, and the higher the speed of the shock wave and gas flow is.
Statistical analysis of nonlinear wave interactions in simulated Langmuir turbulence data
Directory of Open Access Journals (Sweden)
J. Soucek
Full Text Available We present a statistical analysis of strong turbulence of Langmuir and ion-sound waves resulting from beam-plasma interaction. The analysis is carried out on data sets produced by a numerical simulation of one-dimensional Zakharov’s equations. The nonlinear wave interactions are studied using two different approaches: high-order spectra and Volterra models. These methods were applied to identify two and three wave processes in the data, and the Volterra model was furthermore employed to evaluate the direction and magnitude of energy transfer between the wave modes in the case of Langmuir wave decay. We demonstrate that these methods allow one to determine the relative importance of strongly and weakly turbulent processes. The statistical validity of the results was thoroughly tested using surrogated data set analysis.
Key words. Space plasma physics (wave-wave interactions; experimental and mathematical techniques; nonlinear phenomena
Lattice Boltzmann simulation of transverse wave travelling in Maxwell viscoelastic fluid
Institute of Scientific and Technical Information of China (English)
Li Hua-Bing; Fang Hai-Ping
2004-01-01
A nine-velocity lattice Boltzmann method for Maxwell viscoelastic fluid is proposed. Travelling of transverse wave in Maxwell viscoelastic fluid is simulated. The instantaneous oscillating velocity, transverse shear speed and decay rate agree with theoretical results very well.
Directory of Open Access Journals (Sweden)
Deng Shuaiqi
2013-05-01
Full Text Available The high-order staggering grid Finite-Difference (FD scheme based on first-order velocity-stress elastic wave equation has been deduced. The calculation method of PML boundary condition and stability condition established in this study can be used for numerical simulation of advanced detection of elastic wave in roadway, with the obtaining of high-precision seismogram. Then we systematically analyze the polarity of vector wave field in post-source observation system. The results indicate that the relationship between the vector wave field and the polarity of direct wave is related to reflection coefficient on the interface, while the polarity relationship between horizontal and vertical components of vector wave field is related to vertical position of the interface. During data processing for advanced detection of elastic waves, the sign of the reflection coefficient on the interface ahead can be determined based on the polarity relationship between reflected wave and direct wave from the seismograms; the soft and hard rock and other geological information on both sides of the interface is thus be determined. In addition, the direction of source wave depends on polarity relationship between horizontal and vertical components of reflected wave and is used to achieve the separation of up going and down going waves.
Tropical Waves and the Quasi-Biennial Oscillation in a 7-km Global Climate Simulation
Holt, Laura A.; Alexander, M. Joan; Coy, Lawrence; Molod, Andrea; Putman, William; Pawson, Steven
2016-01-01
This study investigates tropical waves and their role in driving a quasi-biennial oscillation (QBO)-like signal in stratospheric winds in a global 7-km-horizontal-resolution atmospheric general circulation model. The Nature Run (NR) is a 2-year global mesoscale simulation of the Goddard Earth Observing System Model, version 5 (GEOS-5). In the tropics, there is evidence that the NR supports a broad range of convectively generated waves. The NR precipitation spectrum resembles the observed spectrum in many aspects, including the preference for westward-propagating waves. However, even with very high horizontal resolution and a healthy population of resolved waves, the zonal force provided by the resolved waves is still too low in the QBO region and parameterized gravity wave drag is the main driver of the NR QBO-like oscillation (NRQBO). The authors suggest that causes include coarse vertical resolution and excessive dissipation. Nevertheless, the very-high-resolution NR provides an opportunity to analyze the resolved wave forcing of the NR-QBO. In agreement with previous studies, large-scale Kelvin and small-scale waves contribute to the NRQBO driving in eastward shear zones and small-scale waves dominate the NR-QBO driving in westward shear zones. Waves with zonal wavelength,1000 km account for up to half of the small-scale (,3300 km) resolved wave forcing in eastward shear zones and up to 70% of the small-scale resolved wave forcing in westward shear zones of the NR-QBO.
Simulating an ocean wave power plant with Homer
Directory of Open Access Journals (Sweden)
Jones S. Silva, Alexandre Beluco, Luiz Emílio B. de Almeida
2014-01-01
Full Text Available In recent years, renewable resources have become an important alternative to increase the capacity of power generation. Among the resources available, the energy in the oceans have attracted more interest and experiencing a period of strong development. Wave energy is the one that is currently closest to reach a stage of technical and economic maturity. In this process, computational tools to facilitate evaluation of the feasibility of power systems including ocean wave power plants are critical. This paper presents the use of software Homer, version Legacy, for evaluation of technical and economic feasibility of hybrid energy systems including contribution of wave energy. Homer is a software designed for the optimization of micro power systems that has a very broad spectrum of applications. A case study in southern Brazil is presented, studying the inclusion of an ocean wave power plant in a wind biodiesel hybrid system and showing the functionality of Homer for this purpose.
Numerical Simulation of Monitoring Corrosion in Reinforced Concrete Based on Ultrasonic Guided Waves
Zheng, Zhupeng; Lei, Ying; Xue, Xin
2014-01-01
Numerical simulation based on finite element method is conducted to predict the location of pitting corrosion in reinforced concrete. Simulation results show that it is feasible to predict corrosion monitoring based on ultrasonic guided wave in reinforced concrete, and wavelet analysis can be used for the extremely weak signal of guided waves due to energy leaking into concrete. The characteristic of time-frequency localization of wavelet transform is adopted in the corrosion monitoring of re...
Blast Valve Design and Related Studies : A Review
Directory of Open Access Journals (Sweden)
P. K. Sharma
2016-04-01
Full Text Available 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 of the critical components of blast valve have been discussed. The merits and demerits of sensing mechanisms viz. remote and direct sensing are discussed. The leakage of blast pressure during finite closing period of the valve (one of the critical problems and the shock tube as a major experimental facility for testing of blast valves are briefly discussed.
Simulation of the interaction between Alfven waves and fast particles
Energy Technology Data Exchange (ETDEWEB)
Feher, Tamas Bela
2014-02-18
There is a wide variety of Alfven waves in tokamak and stellarator plasmas. While most of them are damped, some of the global eigenmodes can be driven unstable when they interact with energetic particles. By coupling the MHD code CKA with the gyrokinetic code EUTERPE, a hybrid kinetic-MHD model is created to describe this wave-particle interaction in stellarator geometry. In this thesis, the CKA-EUTERPE code package is presented. This numerical tool can be used for linear perturbative stability analysis of Alfven waves in the presence of energetic particles. The equations for the hybrid model are based on the gyrokinetic equations. The fast particles are described with linearized gyrokinetic equations. The reduced MHD equations are derived by taking velocity moments of the gyrokinetic equations. An equation for describing the Alfven waves is derived by combining the reduced MHD equations. The Alfven wave equation can retain kinetic corrections. Considering the energy transfer between the particles and the waves, the stability of the waves can be calculated. Numerically, the Alfven waves are calculated using the CKA code. The equations are solved as an eigenvalue problem to determine the frequency spectrum and the mode structure of the waves. The results of the MHD model are in good agreement with other sophisticated MHD codes. CKA results are shown for a JET and a W7-AS example. The linear version of the EUTERPE code is used to study the motion of energetic particles in the wavefield with fixed spatial structure, and harmonic oscillations in time. In EUTERPE, the gyrokinetic equations are discretized with a PIC scheme using the delta-f method, and both full orbit width and finite Larmor radius effects are included. The code is modified to be able to use the wavefield calculated externally by CKA. Different slowing-down distribution functions are also implemented. The work done by the electric field on the particles is measured to calculate the energy transfer
Lotekar, Ajay; Kakad, Amar; Kakad, Bharati
2016-10-01
One-dimensional fluid simulation is performed for the unmagnetized plasma consisting of cold fluid ions and superthermal electrons. Such a plasma system supports the generation of ion acoustic (IA) waves. A standard Gaussian type perturbation is used in both electron and ion equilibrium densities to excite the IA waves. The evolutionary profiles of the IA waves are obtained by varying the superthermal index and the amplitude of the initial perturbation. This simulation demonstrates that the amplitude of the initial perturbation and the superthermal index play an important role in determining the time evolution and the characteristics of the generated IA waves. The initial density perturbation in the system creates charge separation that drives the finite electrostatic potential in the system. This electrostatic potential later evolves into the dispersive and nondispersive IA waves in the simulation system. The density perturbation with the amplitude smaller than 10% of the equilibrium plasma density evolves into the dispersive IA waves, whereas larger density perturbations evolve into both dispersive and nondispersive IA waves for lower and higher superthermal index. The dispersive IA waves are the IA oscillations that propagate with constant ion plasma frequency, whereas the nondispersive IA waves are the IA solitary pulses (termed as IA solitons in the stability region) that propagate with the constant wave speed. The characteristics of the stable nondispersive IA solitons are found to be consistent with the nonlinear fluid theory. To the best of our knowledge, this is the first fluid simulation study that has considered the superthermal distributions for the plasma species to model the electrostatic solitary waves.
Simulations and measurements on muzzle blast mitigation with sound absorbing barriers
Eerden, F.J.M. van der; Berg, F.H.A. van den
2012-01-01
Environmental research is ongoing to predict and to mitigate the noise impact of heavy weapons or explosives. In the densely populated area of the Netherlands this is of particular interest for the Ministry of Defence as the shock waves can propagate over large distances. In this research program th
Simulation of the surface wind field and wind waves over the Oman Sea
Hamzeloo, Sima; Hadi Moeini, Mohammad; Jandaghi Alaee, Majid
2016-04-01
Surface wind field is one of the most important factors in the generation of the marine hydrodynamic phenomena such as wind waves that highly affected by the surface winds. Therefore, accessibility to the correct wind field is of great importance for accurate prediction and simulation of the hydrodynamic variables. Nowadays numerical mesoscale weather prediction models are widely applied as powerful tools to simulate wind and other atmospheric variables with predefined temporal and spatial resolution in desired areas. Despite appropriate results of the numerical models in many regions, there are still some complications in the simulation of the surface wind field in areas with complex orography since the surface wind field is highly affected by the local topography, land-sea discontinuity, temperature gradient etc. Nowadays, with the development of high-speed processors the third generation spectral models are generally used for simulation of wind waves. Wind data are the main input parameters of the numerical spectral wave model. Therefore, the quality of the input wind data can be assessed by comparison of the wave model outputs with measured values. The main goal of the current study is to simulate surface wind field over the Oman Sea using WRF modeling system. To verify the model results, the simulated wind speeds were compared with synoptic and buoy measurements and satellite observations. Wind-wave parameters simulated by the spectral model were also compared with wave measurements to verify simulated surface wind field as the input of the wave model. The Comparison simulated wind speed and directions in coastal synoptic stations and QuikSCAT satellite shows sufficient results for both offshore and coastal areas.
2-D Composite Model for Numerical Simulations of Nonlinear Waves
Institute of Scientific and Technical Information of China (English)
2000-01-01
－ A composite model, which is the combination of Boussinesq equations and Volume of Fluid (VOF) method, has been developed for 2-D time-domain computations of nonlinear waves in a large region. The whole computational region Ω is divided into two subregions. In the near-field around a structure, Ω2, the flow is governed by 2-D Reynolds Averaged Navier-Stokes equations with a turbulence closure model of k-ε equations and numerically solved by the improved VOF method; whereas in the subregion Ω1 (Ω1 = Ω - Ω2) the flow is governed by one-D Boussinesq equations and numerically solved with the predictor-corrector algorithm. The velocity and the wave surface elevation are matched on the common boundary of the two subregions. Numerical tests have been conducted for the case of wave propagation and interaction with a wave barrier. It is shown that the composite model can help perform efficient computation of nonlinear waves in a large region with the complicated flow fields near structures taken into account.
Numerical simulation of lowest-order short-crested wave instabilities
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.; Bingham, Harry
2006-01-01
A numerical study of doubly periodic deep-water short-crested wave instabilities, arising from various quartet resonant interactions, is conducted using a high-order Boussinesq-type model. The model is first verified through a series of simulations involving classical class I plane wave...... demonstrates a reasonably similar evolution. These simulations consider the simplest physical situations involving three-dimensional instabilities of genuinely three-dimensional progressive waves, revealing qualitative differences from classical two-dimensional descriptions. This study is therefore...
Energy Technology Data Exchange (ETDEWEB)
Hou, Wei; Qu, Zhi-ming; Pian, Long-jiang [University of Science and Technology Beijing, Beijing (China). School of Civil Engineering and Environment
2009-04-15
On the basis of a hypothesis, a physical and mathematical model of the propagation of shock waves in turn roadway was set up. The results of numerical simulation show that the pressure, velocity and temperature of shock wave will be attenuated during propagation. At the beginning of gas explosion, the quantity of parameters of shock wave front is increased gradually because of methane reaction. However, the pressure, velocity and temperature will be attenuated to a small extent after the chemical reaction. By comparison of the experiment, simulation and practice, the highly identical data shows that the numerical model is practicable. 9 refs., 7 figs.
Simulation of Asymmetric Lamb Waves for Sensing and Actuation in Plates
Directory of Open Access Journals (Sweden)
A. Ghoshal
2005-01-01
Full Text Available Two approaches used for monitoring the health of thin aerospace structures are active interrogation and passive monitoring. The active interrogation approach generates and receives diagnostic Lamb waves to detect damage, while the passive monitoring technique listens for acoustic waves caused by damage growth. For the application of both methods, it is necessary to understand how Lamb waves propagate through a structure. In this paper, a Physics-Based Model (PBM using classical plate theory is developed to provide a basic understanding of the actual physical process of asymmetric Lamb mode wave generation and propagation in a plate. The closed-form model uses modal superposition to simulate waves generated by piezoceramic patches and by simulated acoustic emissions. The generation, propagation, reflection, interference, and the sensing of the waves are represented in the model, but damage is not explicitly modeled. The developed model is expected to be a useful tool for the Structural Health Monitoring (SHM community, particularly for studying high frequency acoustic wave generation and propagation in lieu of Finite Element models and other numerical models that require significant computational resources. The PBM is capable of simulating many possible scenarios including a variety of test cases, whereas experimental measurements of all of the cases can be costly and time consuming. The model also incorporates the sensor measurement effect, which is an important aspect in damage detection. Continuous and array sensors are modeled, which are efficient for measuring waves because of their distributed nature.
Global particle in cell simulation of radio frequency waves in tokamak ∖fs20
Kuley, Animesh; Lin, Z.; Bao, J.; Lau, C.; Sun, G. Y.
2016-10-01
We are looking into a new nonlinear kinetic simulation model to study the radio frequency heating and current drive of fusion plasmas using toroidal code GTC. In this model ions are considered as fully kinetic (FK) particles using Vlasov equation and the electrons are treated as drift kinetic (DK) particles using drift kinetic equation. We have benchmarked this numerical model to verify the linear physics of normal modes, conversion of slow and fast waves and its propagation in the core region of the tokamak using the Boozer coordinates. In the nonlinear simulation of ion Bernstein wave (IBW) in a tokamak, parametric decay instability (PDI) is observed where a large amplitude pump wave decays into an IBW sideband and an ion cyclotron quasi-mode (ICQM). The ICQM induces an ion perpendicular heating, with a heating rate proportional to the pump wave intensity. Finally, in the electromagnetic LH simulation, nonlinear wave trapping of electrons is verified and plasma current is nonlinearly driven. Presently we are working on the development of new PIC simulation model using cylindrical coordinates to address the RF wave propagation from the edge of the tokamak to the core region and the parametric instabilities associated with this RF waves. We have verified the cyclotron integrator using Boris push method.
Well-posedness and generalized plane waves simulations of a 2D mode conversion model
Imbert-Gérard, Lise-Marie
2015-01-01
Certain types of electro-magnetic waves propagating in a plasma can undergo a mode conversion process. In magnetic confinement fusion, this phenomenon is very useful to heat the plasma, since it permits to transfer the heat at or near the plasma center. This work focuses on a mathematical model of wave propagation around the mode conversion region, from both theoretical and numerical points of view. It aims at developing, for a well-posed equation, specific basis functions to study a wave mode conversion process. These basis functions, called generalized plane waves, are intrinsically based on variable coefficients. As such, they are particularly adapted to the mode conversion problem. The design of generalized plane waves for the proposed model is described in detail. Their implementation within a discontinuous Galerkin method then provides numerical simulations of the process. These first 2D simulations for this model agree with qualitative aspects studied in previous works.
Lieu, Binh K; Jovanović, Mihailo R
2010-01-01
This work builds on and confirms the theoretical findings of Part 1 of this paper, Moarref & Jovanovi\\'c (2010). We use direct numerical simulations of the Navier-Stokes equations to assess the efficacy of blowing and suction in the form of streamwise traveling waves for controlling the onset of turbulence in a channel flow. We highlight the effects of the modified base flow on the dynamics of velocity fluctuations and net power balance. Our simulations verify the theoretical predictions of Part 1 that the upstream traveling waves promote turbulence even when the uncontrolled flow stays laminar. On the other hand, the downstream traveling waves with parameters selected in Part 1 are capable of reducing the fluctuations' kinetic energy, thereby maintaining the laminar flow. In flows driven by a fixed pressure gradient, a positive net efficiency as large as 25 % relative to the uncontrolled turbulent flow can be achieved with downstream waves. Furthermore, we show that these waves can also relaminarize full...
Numerical simulation of scattering wave imaging in a goaf
Institute of Scientific and Technical Information of China (English)
Li Juanjuan; Pan Dongming; Liao Taiping; Hu Mingshun; Wang Linlin
2011-01-01
Goafs are threats to safe mining. Their imaging effects or those of other complex geological bodies are often poor in conventional reflected wave images. Hence, accurate detection of goals has become an important problem, to be solved with a sense of urgency. Based on scattering theory, we used an equivalent offset method to extract Common Scattering Point gathers, in order to analyze different scattering wave characteristics between Common Scattering Point and Common Mid Point gathers and to compare stack and migration imaging effects. Our research results show that the scattering wave imaging method is more efficient than the conventional imaging method and is therefore a more effective imaging method for detecting goats and other complex geological bodies. It has important implications for safe mining procedures and infrastructures.
Zhou, Yong; Ni, Sidao; Chu, Risheng; Yao, Huajian
2016-08-01
Numerical solvers of wave equations have been widely used to simulate global seismic waves including PP waves for modelling 410/660 km discontinuity and Rayleigh waves for imaging crustal structure. In order to avoid extra computation cost due to ocean water effects, these numerical solvers usually adopt water column approximation, whose accuracy depends on frequency and needs to be investigated quantitatively. In this paper, we describe a unified representation of accurate and approximate forms of the equivalent water column boundary condition as well as the free boundary condition. Then we derive an analytical form of the PP-wave reflection coefficient with the unified boundary condition, and quantify the effects of water column approximation on amplitude and phase shift of the PP waves. We also study the effects of water column approximation on phase velocity dispersion of the fundamental mode Rayleigh wave with a propagation matrix method. We find that with the water column approximation: (1) The error of PP amplitude and phase shift is less than 5 per cent and 9° at periods greater than 25 s for most oceanic regions. But at periods of 15 s or less, PP is inaccurate up to 10 per cent in amplitude and a few seconds in time shift for deep oceans. (2) The error in Rayleigh wave phase velocity is less than 1 per cent at periods greater than 30 s in most oceanic regions, but the error is up to 2 per cent for deep oceans at periods of 20 s or less. This study confirms that the water column approximation is only accurate at long periods and it needs to be improved at shorter periods.
Nonlinear evolution of parallel propagating Alfven waves: Vlasov - MHD simulation
Nariyuki, Y; Kumashiro, T; Hada, T
2009-01-01
Nonlinear evolution of circularly polarized Alfv\\'en waves are discussed by using the recently developed Vlasov-MHD code, which is a generalized Landau-fluid model. The numerical results indicate that as far as the nonlinearity in the system is not so large, the Vlasov-MHD model can validly solve time evolution of the Alfv\\'enic turbulence both in the linear and nonlinear stages. The present Vlasov-MHD model is proper to discuss the solar coronal heating and solar wind acceleration by Alfve\\'n waves propagating from the photosphere.
Yasuda, Shugo
2015-01-01
A Monte Carlo simulation for the chemotactic bacteria is developed on the basis of the kinetic modeling, i.e., the Boltzmann transport equation, and applied to the one-dimensional traveling population wave in a micro channel.In this method, the Monte Carlo method, which calculates the run-and-tumble motions of bacteria, is coupled with a finite volume method to solve the macroscopic transport of the chemical cues in the field. The simulation method can successfully reproduce the traveling population wave of bacteria which was observed experimentally. The microscopic dynamics of bacteria, e.g., the velocity autocorrelation function and velocity distribution function of bacteria, are also investigated. It is found that the bacteria which form the traveling population wave create quasi-periodic motions as well as a migratory movement along with the traveling population wave. Simulations are also performed with changing the sensitivity and modulation parameters in the response function of bacteria. It is found th...
Consolidating guided wave simulations and experimental data: a dictionary learning approach
Alguri, K. Supreet; Harley, Joel B.
2016-04-01
Modeling and simulating guided wave propagation in complex, geometric structures is a topic of significant interest in structural health monitoring. These models have the potential to benefit damage detection, localization, and characterization in structures where traditional algorithms fail. Numerical modelling (for example, using finite element or semi-analytical finite element methods) is a popular approach for simulating complex wave behavior. Yet, using these models to improve experimental data analysis remains difficult. Numerical simulations and experimental data rarely match due to uncertainty in the properties of the structures and the guided waves traveling within them. As a result, there is a significant need to reduce this uncertainty by incorporating experimental data into the models. In this paper, we present a dictionary learning framework to address this challenge. Specifically, use dictionary learning to combine numerical wavefield simulations with 24 simulated guided wave measurements with different frequency-dependent velocity characteristics (emulating an experimental system) to make accurate, global predictions about experimental wave behavior. From just 24 measurements, we show that we can predict and extrapolate guided wave behavior with accuracies greater than 92%.
Simulation of Blast Loading on an Ultrastructurally-based Computational Model of the Ocular Lens
2015-10-01
public release; distribution unlimited The views, opinions and/or findings contained in this report are those of the author(s) and should not be...cells) is stressed by the passing shock wave. Traumatic cataract can result in a partially or fully clouded lens, complete dislo- cation of the lens...CSLM), and type IV collagen ultrastructure in lens capsule using cyro- electron tomography: 6b - On as-received porcine lens capsules, image type IV
Institute of Scientific and Technical Information of China (English)
刘帆; 杜红棉; 范锦彪; 赖富文; 焦耀晗; 苗松珍; 岳掌宽; 闫鹏飞
2014-01-01
为了评估炮口冲击波对相关操作人员及设备造成的损伤和破坏程度，将存储测试技术应用到炮口冲击波测试中，并结合无线传输技术，使得测试主控制台可以在一定距离外进行有效监控。通过对测试系统进行的激波管动态校准，符合国军标对炮口冲击波超压测试的基本要求。测试装置在无线触发状态和多次重触发状态进行了测试试验，均成功获取到炮口冲击波超压曲线。试验结果表明所设计的炮口冲击波无线存储测试系统能有效工作，同时具有操作简单等优点，具有良好的应用前景。%In order to evaluate the damage of relevant operators and equipments caused by muzzle blast wave,The muzzle blast wave test system applied Storage testing technology combined with Wireless transmission technology,to make the main test console monitoring effectively in a certain distance. The results of dynamic calibration based on shock tube showed the test system meets the basic requirements of military specifications on the muzzle blast wave overpressure test. The test devices in both wireless trigger state and multiple re-trigger state obtained the curves of the muzzle blast wave overpressure successfully. The results show that the designed muzzle blast wave wireless storage test system can work effectively,has the advantage of easy operation and has a good application prospect.
Institute of Scientific and Technical Information of China (English)
WU; Shaoping(吴少平); YI; Fan(易帆)
2002-01-01
By using FICE scheme, a numerical simulation of nonlinear propagation of gravity wave packet in three-dimension compressible atmosphere is presented. The whole nonlinear propagation process of the gravity wave packet is shown; the basic characteristics of nonlinear propagation and the influence of the ambient winds on the propagation are analyzed. The results show that FICE scheme can be extended in three-dimension by which the calculation is steady and kept for a long time; the increase of wave amplitude is faster than the exponential increase according to the linear gravity theory; nonlinear propagation makes the horizontal perturbation velocity increase greatly which can lead to enhancement of the local ambient winds; the propagation path and the propagation velocity of energy are different from the results expected by the linear gravity waves theory, the nonlinearity causes the change in propagation characteristics of gravity wave; the ambient winds alter the propagation path and group velocity of gravity wave.
A study on dynamic response of slopes under wave action using simulation tests
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
After the erection of the Three Gorges Dam, the water level of Yangtze River will reach 175 m, and the average wave crest will be up to 1 m. Therefore the wave action cannot be neglected for the slope stability. Through simulation tests, the waveinduced dynamic response of the slope is analyzed. The soil body is taken as linear elastic body when it has a small deformation under the small wave action. Based on tests, the excess pore pressure and slope displacement under the loading in different wave period are analyzed. The ratio of dynamic strength and static strength to the breaking process of the slope is discussed. It is demonstrated that smaller wave period gives rise to a larger strain of the slope under the same stress. At different depth of water, different weakness effect on the stability of the soil slope is observed and the slope has an adaptability to the wave action to some extent.
Variational Boussinesq model for simulations of coastal waves and tsunamis
Adytia, Didit; Groesen, van E.; Tan, Soon Keat; Huang, Zhenhua
2009-01-01
In this paper we describe the basic ideas of a so-called Variational Boussinesq Model which is based on the Hamiltonian structure of gravity surface waves. By using a rather simple approach to prescribe the profile of vertical fluid potential in the expression for the kinetic energy, we obtain a set
Aiding Design of Wave Energy Converters via Computational Simulations
Jebeli Aqdam, Hejar; Ahmadi, Babak; Raessi, Mehdi; Tootkaboni, Mazdak
2015-11-01
With the increasing interest in renewable energy sources, wave energy converters will continue to gain attention as a viable alternative to current electricity production methods. It is therefore crucial to develop computational tools for the design and analysis of wave energy converters. A successful design requires balance between the design performance and cost. Here an analytical solution is used for the approximate analysis of interactions between a flap-type wave energy converter (WEC) and waves. The method is verified using other flow solvers and experimental test cases. Then the model is used in conjunction with a powerful heuristic optimization engine, Charged System Search (CSS) to explore the WEC design space. CSS is inspired by charged particles behavior. It searches the design space by considering candidate answers as charged particles and moving them based on the Coulomb's laws of electrostatics and Newton's laws of motion to find the global optimum. Finally the impacts of changes in different design parameters on the power takeout of the superior WEC designs are investigated. National Science Foundation, CBET-1236462.
Impact of simulated heat waves on soybean physiology and yield
With increases in mean global temperatures and associated climate change, extreme temperature events are predicted to increase in both intensity and frequency. Despite the clearly documented negative public health impacts of heat waves, the impact on physiology and yields of key agricultural species...
Simulation study of acoustic wave propagation in ocean
Digital Repository Service at National Institute of Oceanography (India)
Mohite-Patil, T.B; Saran, A.K; Sawant, S.R.; Chile, R.H; Mohite-Patil, T.T.
Many reports are available on the sound attenuation and speed in the deep ocean, as a function of different ingredients of sea. The absorption and speed of sound waves are related to the change in sound speed, depth, salinity, temperature, PH...
Using AORSA to simulate helicon waves in DIII-D
Energy Technology Data Exchange (ETDEWEB)
Lau, C., E-mail: lauch@ornl.gov; Blazevski, D.; Green, D. L.; Murakami, M.; Park, J. M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN (United States); Jaeger, E. F.; Berry, L. A. [XCEL Engineering, Inc., 1066 Commerce Park Dr., Oak Ridge, TN (United States); Bertelli, N. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Pinsker, R. I.; Prater, R. [General Atomics, San Diego, CA (United States)
2015-12-10
Recent efforts have shown that helicon waves (fast waves at > 20ω{sub ci}) may be an attractive option for driving efficient off-axis current drive during non-inductive tokamak operation for DIII-D, ITER and DEMO. For DIII-D scenarios, the ray tracing code, GENRAY, has been extensively used to study helicon current drive efficiency and location as a function of many plasma parameters. The full wave code, AORSA, which is applicable to arbitrary Larmor radius and can resolve arbitrary ion cyclotron harmonic order, has been recently used to validate the ray tracing technique at these high cyclotron harmonics. If the SOL is ignored, it will be shown that the GENRAY and AORSA calculated current drive profiles are comparable for the envisioned high beta advanced scenarios for DIII-D, where there is high single pass absorption due to electron Landau damping and minimal ion damping. AORSA is also been used to estimate possible SOL effects on helicon current drive coupling and SOL absorption due to collisional and slow wave effects.
Nonlinear mhd simulations of wave dissipation in flux tubes
Poedts, S.; Toth, G.; Belien, A. J. C.; Goedbloed, J. P.
1997-01-01
The phase mixing and resonant dissipation of Alfven waves is studied in both the 'closed' magnetic loops and the 'open' coronal holes observed in the hot solar corona. The resulting energy transfer from large to small length scales contributes to the heating of these magnetic str
Numerical simulations of impulsively generated Alfvén waves in solar magnetic arcades
Energy Technology Data Exchange (ETDEWEB)
Chmielewski, P.; Murawski, K. [Group of Astrophysics, UMCS, ul. Radziszewskiego 10, 20-031 Lublin (Poland); Musielak, Z. E. [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States); Srivastava, A. K. [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)
2014-09-20
We perform numerical simulations of impulsively generated Alfvén waves in an isolated solar arcade, which is gravitationally stratified and magnetically confined. We study numerically the propagation of Alfvén waves along the magnetic structure that extends from the lower chromosphere, where the waves are generated, to the solar corona, and analyze the influence of the arcade size and the width of the initial pulses on the wave propagation and reflection. Our model of the solar atmosphere is constructed by adopting the temperature distribution based on the semi-empirical VAL-C model and specifying the curved magnetic field lines that constitute the asymmetric magnetic arcade. The propagation and reflection of Alfvén waves in this arcade is described by 2.5-dimensional magnetohydrodynamic equations that are numerically solved by the FLASH code. Our numerical simulations reveal that the Alfvén wave amplitude decreases as a result of a partial reflection of Alfvén waves in the solar transition region, and that the waves that are not reflected leak through the transition region and reach the solar corona. We also find the decrement of the attenuation time of Alfvén waves for wider initial pulses. Moreover, our results show that the propagation of Alfvén waves in the arcade is affected by the spatial dependence of the Alfvén speed, which leads to phase mixing that is stronger for more curved and larger magnetic arcades. We discuss the processes that affect the Alfvén wave propagation in an asymmetric solar arcade and conclude that besides phase mixing in the magnetic field configuration, the plasma properties of the arcade, the size of the initial pulse, and the structure of the solar transition region all play a vital role in the Alfvén wave propagation.
Numerical Simulation of Solitary Wave Induced Flow Motion around a Permeable Submerged Breakwater
Directory of Open Access Journals (Sweden)
Jisheng Zhang
2012-01-01
Full Text Available This paper presents a numerical model for the simulation of solitary wave transformation around a permeable submerged breakwater. The wave-structure interaction is obtained by solving the Volume-Averaged Reynolds-Averaged Navier-Stokes governing equations (VARANS and volume of fluid (VOF theory. This model is applied to understand the effects of porosity, equivalent mean diameter of porous media, structure height, and structure width on the propagation of a solitary wave in the vicinity of a permeable submerged structure. The results show that solitary wave propagation around a permeable breakwater is essentially different from that around impermeable one. It is also found that the structure porosity has more impact than equivalent mean diameter on the wave transformation and flow structure. After interacting with the higher structure, the wave has smaller wave height behind the structure with a lower travelling speed. When the wave propagates over the breakwater with longer width, the wave travelling speed is obviously reduced with more wave energy dissipated inside porous structure.
Simulation of the RF Coupler for TRIUMF ISAC-II Superconducting Quarter Wave Resonators
Zvyagintsev, V
2004-01-01
The inductive RF coupler for the TRIUMF ISAC-II 106 MHz superconducting accelerating quarter wave resonators was used as a basis for the simulation model of stationary transmission processes of RF power and thermal fluxes. Electromagnetic simulation of the coupler was done with ANSOFT HFSS code. Transmission line theory was used for electromagnetic wave calculations along the drive line to the Coupler. An analogy between electric and thermal processes allows the thermal calculations to be expressed in terms of electrical circuits. The data obtained from the simulation are compared to measured values on the RF coupler.
Simulation of Lamb wave reflections at plate edges using the semi-analytical finite element method.
Ahmad, Z A B; Gabbert, U
2012-09-01
In typical Lamb wave simulation practices, effects of plate edge reflections are often not considered in order to simplify the wave signal interpretations. Methods that are based on infinite plates such as the semi-analytical finite element method is effective in simulating Lamb waves as it excludes the effect of plate edges. However, the inclusion of plate edges in a finite plate could render this method inapplicable, especially for transient response simulations. Here, by applying the ratio of Lamb mode reflections at plate edges, and representing the reflection at plate edges using infinite plate solutions, the semi-analytical finite element method can be applied for transient response simulation, even when the plate is no longer infinite.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN (Simulating Waves Nearshore) model. The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecapping dissipation, respectively. Besides the above-mentioned source terms, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulation errors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differences in significant wave height (SWH) have a good correlation with the differences in dissipation energy caused by whitecapping. This indicates that the whitecapping dissipation source term plays an important role in the resultant differences of the simulated SWH between the two experiments.
Chen, Zaigao; Wang, Jianguo; Wang, Yue; Qiao, Hailiang; Zhang, Dianhui; Guo, Weijie
2013-11-01
Optimal design method of high-power microwave source using particle simulation and parallel genetic algorithms is presented in this paper. The output power, simulated by the fully electromagnetic particle simulation code UNIPIC, of the high-power microwave device is given as the fitness function, and the float-encoding genetic algorithms are used to optimize the high-power microwave devices. Using this method, we encode the heights of non-uniform slow wave structure in the relativistic backward wave oscillators (RBWO), and optimize the parameters on massively parallel processors. Simulation results demonstrate that we can obtain the optimal parameters of non-uniform slow wave structure in the RBWO, and the output microwave power enhances 52.6% after the device is optimized.
Hindmarsh, Mark; Huber, Stephan J.; Rummukainen, Kari; Weir, David J.
2015-12-01
We present details of numerical simulations of the gravitational radiation produced by a first order thermal phase transition in the early Universe. We confirm that the dominant source of gravitational waves is sound waves generated by the expanding bubbles of the low-temperature phase. We demonstrate that the sound waves have a power spectrum with a power-law form between the scales set by the average bubble separation (which sets the length scale of the fluid flow Lf) and the bubble wall width. The sound waves generate gravitational waves whose power spectrum also has a power-law form, at a rate proportional to Lf and the square of the fluid kinetic energy density. We identify a dimensionless parameter Ω˜GW characterizing the efficiency of this "acoustic" gravitational wave production whose value is 8 π Ω˜GW≃0.8 ±0.1 across all our simulations. We compare the acoustic gravitational waves with the standard prediction from the envelope approximation. Not only is the power spectrum steeper (apart from an initial transient) but the gravitational wave energy density is generically larger by the ratio of the Hubble time to the phase transition duration, which can be 2 orders of magnitude or more in a typical first order electroweak phase transition.
Numerical simulations of impulsively generated Alfv\\'en waves in solar magnetic arcades
Chmielewski, P; Musielak, Z E; Srivastava, A K
2014-01-01
We perform numerical simulations of impulsively generated Alfv\\'en waves in an isolated solar arcade, which is gravitationally stratified and magnetically confined. We study numerically the propagation of Alfv\\'en waves along such magnetic structure that extends from the lower chromosphere, where the waves are generated, to the solar corona, and analyze influence of the arcade size and width of the initial pulses on the wave propagation and reflection. Our model of the solar atmosphere is constructed by adopting the temperature distribution based on the semi-empirical VAL-C model and specifying the curved magnetic field lines that constitute the asymmetric magnetic arcade. The propagation and reflection of Alfv\\'en waves in this arcade is described by 2.5D magnetohydrodynamic equations that are numerically solved by the FLASH code. Our numerical simulations reveal that the Alfv\\'en wave amplitude decreases as a result of a partial reflection of Alfv\\'en waves in the solar transition region, and that the waves...
Pathak, Ashish; Raessi, Mehdi
2016-11-01
Using an in-house computational framework, we have studied the interaction of water waves with pitching flap-type ocean wave energy converters (WECs). The computational framework solves the full 3D Navier-Stokes equations and captures important effects, including the fluid-solid interaction, the nonlinear and viscous effects. The results of the computational tool, is first compared against the experimental data on the response of a flap-type WEC in a wave tank, and excellent agreement is demonstrated. Further simulations at the model and prototype scales are presented to assess the validity of the Froude scaling. The simulations are used to address some important questions, such as the validity range of common WEC modeling approaches that rely heavily on the Froude scaling and the inviscid potential flow theory. Additionally, the simulations examine the role of the Keulegan-Carpenter (KC) number, which is often used as a measure of relative importance of viscous drag on bodies exposed to oscillating flows. The performance of the flap-type WECs is investigated at various KC numbers to establish the relationship between the viscous drag and KC number for such geometry. That is of significant importance because such relationship only exists for simple geometries, e.g., a cylinder. Support from the National Science Foundation is gratefully acknowledged.
Dobie, Gordon; Spencer, Andrew; Burnham, Kenneth; Pierce, S Gareth; Worden, Keith; Galbraith, Walter; Hayward, Gordon
2011-04-01
A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The ability to reconfigure the scanner adaptively requires an understanding of the ultrasonic wave generation, its propagation and interaction with potential defects and boundaries. Transducer behaviour has been simulated using a linear systems approximation, with wave propagation in the structure modelled using the local interaction simulation approach (LISA). Integration of the linear systems and LISA approaches are validated for use in Lamb wave scanning by comparison with both analytic techniques and more computationally intensive commercial finite element/difference codes. Starting with fundamental dispersion data, the paper goes on to describe the simulation of wave propagation and the subsequent interaction with artificial defects and plate boundaries, before presenting a theoretical image obtained from a team of sensing agents based on the current generation of sensors and instrumentation.
RANSE Simulation of High-speed Planning Craft in Regular Waves
Institute of Scientific and Technical Information of China (English)
Shuo Wang; Yumin Su; Xi Zhang; Jinglei Yang
2012-01-01
This paper presents a study on the numerical simulation of planing crafts sailing in regular waves.This allows an accurate estimate of the seas keeping performance of the high speed craft.The simulation set in six-degree of freedom motions is based on the Reynolds averaged Navier Stokes equations volume of fluid (RANSE VOF) solver.The trimming mesh technique and integral dynamic mesh method are used to guarantee the good accuracy of the hydrodynamic force and high efficiency of the numerical simulation.Incident head waves,oblique waves and beam waves are generated in the simulation with three different velocities (Fn =1.0,1.5,2.0).The motions and sea keeping performance of the planing craft with waves coming from different directions are indicated in the flow solver.The ship designer placed an emphasis on the effects of waves on sailing amplitude and pressure distribution of planing craft in the configuration of building high speed crafts.
Numerical simulation of tsunami-scale wave boundary layers
DEFF Research Database (Denmark)
Williams, Isaac A.; Fuhrman, David R.
2016-01-01
, is newly extended to incorporate a transitional variant of the standard two-equation k–ω turbulence closure. The developed numerical model is successfully validated against recent experimental measurements involving transient solitary wave boundary layers as well as for oscillatory flows, collectively......This paper presents a numerical study of the boundary layer flow and properties induced by tsunami-scalewaves. For this purpose, an existing one-dimensional vertical (1DV) boundary layer model, based on the horizontal component of the incompressible Reynolds-averaged Navier–Stokes (RANS) equations...... demonstrating the ability to reproduce accurate velocity profiles, turbulence, and bed shear stresses on both smooth and rough beds.The validated model is then employed for the study of transient wave boundary layers at full tsunami scales,covering a wide and realistic geophysical range in terms of the flow...
Design Optimization and Simulation of Wave Propagation in Metamaterials
2014-09-24
simple-cubic lattices. wave propagation, metamaterials, periodic media, band - gap optimization, semidefinite programming, photonic crystal design...Robust topology optimization of three-dimensional photonic -crystal band - gap structures,” with H. Men, K. Y. K. Lee, J. Peraire, and S. G...crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and
FDTD Simulation on Terahertz Waves Propagation Through a Dusty Plasma
Wang, Maoyan; Zhang, Meng; Li, Guiping; Jiang, Baojun; Zhang, Xiaochuan; Xu, Jun
2016-08-01
The frequency dependent permittivity for dusty plasmas is provided by introducing the charging response factor and charge relaxation rate of airborne particles. The field equations that describe the characteristics of Terahertz (THz) waves propagation in a dusty plasma sheath are derived and discretized on the basis of the auxiliary differential equation (ADE) in the finite difference time domain (FDTD) method. Compared with numerical solutions in reference, the accuracy for the ADE FDTD method is validated. The reflection property of the metal Aluminum interlayer of the sheath at THz frequencies is discussed. The effects of the thickness, effective collision frequency, airborne particle density, and charge relaxation rate of airborne particles on the electromagnetic properties of Terahertz waves through a dusty plasma slab are investigated. Finally, some potential applications for Terahertz waves in information and communication are analyzed. supported by National Natural Science Foundation of China (Nos. 41104097, 11504252, 61201007, 41304119), the Fundamental Research Funds for the Central Universities (Nos. ZYGX2015J039, ZYGX2015J041), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120185120012)
Experimental animal models for studies on the mechanisms of blast induced neurotrauma
Directory of Open Access Journals (Sweden)
Mårten eRisling
2012-04-01
Full Text Available A blast injury is a complex type of physical trauma resulting from the detonation of explosive compounds and has become an important issue due to the use of improvised explosive devices (IED in current military conflicts. Blast induced neurotrauma (BINT is a major concern in contemporary military medicine and includes a variety of injuries that range from mild to lethal. BINT is characterized by extreme forces and their complex propagation. Modern body protection and the development of armored military vehicles can be assumed to have changed the outcome of BINT. Primary blast injuries are caused by overpressure waves whereas secondary, tertiary and quaternary blast injuries can have more varied origins such as the impact of fragments, abnormal movements or heat. The characteristics of the blast wave can be assumed to be significantly different in open field detonations compared to explosions in a confined space, such an armored vehicle. Important parameters include peak pressure, duration and shape of the pulse. Reflections from walls and armor can make the prediction of effects in individual cases very complex. Epidemiological data do not contain information of the relative importance of the different blast mechanisms. It is therefore important to generate data in carefully designed animal models. Such models can be selective reproductions of a primary blast, penetrating injuries from fragments, acceleration movements or combinations of such mechanisms. It is of crucial importance that the physical parameters of the employed models are well characterized so that the experiments can be reproduced in different laboratory settings. Ideally, pressure recordings should be calibrated by using the same equipment in several laboratories. With carefully designed models and thoroughly evaluated animal data it should be possible to achieve a translation of data between animal and clinical data. Imaging and computer simulation represent a possible link
Koenders, C.; Perschke, C.; Goetz, C.; Richter, I.; Motschmann, U.; Glassmeier, K. H.
2016-10-01
Context. A new type of low-frequency wave was detected by the magnetometer of the Rosetta Plasma Consortium at the comet during the initial months after the arrival of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. This large-amplitude, nearly continuous wave activity is observed in the frequency range from 30 mHz to 80 mHz where 40 mHz to 50 mHz is the dominant frequency. This type of low frequency is not closely related to the gyrofrequency of newborn cometary ions, which differs from previous wave activity observed in the interaction region of comets with the solar wind. Aims: This work aims to reveal a global view on the wave activity region using simulations of the comet-solar wind interaction region. Parameters, such as wavelength, propagation direction, and propagation patterns, are within the focus of this study. While the Rosetta observations only provide local information, numerical simulations provide further information on the global wave properties. Methods: Standard hybrid simulations were applied to the comet-solar wind interaction scenario. In the model, the ions were described as particles, which allows us to describe kinetic processes of the ions. The electrons were described as a fluid. Results: The simulations exhibit a threefold wave structure of the interaction region. A Mach cone and a Whistler wing are observed downstream of the comet. The third kind of wave activity found are low-frequency waves at 97 mHz, which corresponds to the waves observed by Richter et al. (2015, Ann. Geophys., 33, 1031). These waves are caused by the initial pick-up of the cometary ions that are perpendicular to the solar wind flow and in the interplanetary magnetic field direction. The associated electric current becomes unstable. The simulations show that wave activity is only detectable in the + E hemisphere and that the Mach cone and whistler wings need to be distinguished from the newly found instability driven wave activity. The movie associated to
Recovering the damping rates of cyclotron damped plasma waves from simulation data
Schreiner, Cedric; Spanier, Felix
2016-01-01
Plasma waves with frequencies close to the particular gyrofrequencies of the charged particles in the plasma lose energy due to cyclotron damping. We briefly discuss the gyro-resonance of low frequency plasma waves and ions particularly with regard to particle-in-cell (PiC) simulations. A setup is outlined which uses artificially excited waves in the damped regime of the wave mode's dispersion relation to track the damping of the wave's electromagnetic fields. Extracting the damping rate directly from the field data in real or Fourier space is an intricate and non-trivial task. We therefore present a simple method of obtaining the damping rate {\\Gamma} from the simulation data. This method is described in detail, focusing on a step-by-step explanation of the course of actions. In a first application to a test simulation we find that the damping rates obtained from this simulation generally are in good agreement with theoretical predictions. We then compare the results of one-, two- and three-dimensional simul...
Comparison of Hydrocode Simulations with Measured Shock Wave Velocities
Energy Technology Data Exchange (ETDEWEB)
Hixson, R. S. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States); Veeser, L. R. [National Security Technologies, LLC. (NSTec), Mercury, NV (United States)
2014-11-30
We have conducted detailed 1- and 2-dimensional hydrodynamics calculations to assess the quality of simulations commonly made to understand various shock processes in a sample and to design shock experiments. We began with relatively simple shock experiments, where we examined the effects of the equation of state and the viscoplastic strength models. Eventually we included spallation in copper and iron and a solid-solid phase transformation in iron to assess the quality of the damage and phase transformation simulations.
Tubman, Norm; Hammes-Schiffer, Sharon; Ceperley, David
2016-01-01
Simulating nonadiabatic effects with many-body wave function approaches is an open field with many challenges. Recent interest has been driven by new algorithmic developments and improved theoretical understanding of properties unique to electron-ion wave functions. Fixed-node diffusion Monte Caro is one technique that has shown promising results for simulating electron-ion systems. In particular, we focus on the CH molecule for which previous results suggested a relatively significant contribution to the energy from nonadiabatic effects. We propose a new wave function ansatz for diatomic systems which involves interpolating the determinant coefficients calculated from configuration interaction methods. We find this to be an improvement beyond previous wave function forms that have been considered. The calculated nonadiabatic contribution to the energy in the CH molecule is reduced compared to our previous results, but still remains the largest among the molecules under consideration.
Extreme Value Predictions using Monte Carlo Simulations with Artificially Increased Wave Height
DEFF Research Database (Denmark)
Jensen, Jørgen Juncher
2010-01-01
accurate. In the present paper the generality of this relation is investigated, considering the probability that the design wave-induced hogging bending moment in a container ship is exceeded, accounting for both non-linear wave load effects (bow flare slamming) and hull flexibility (whipping vibrations)....... accurate result can be obtained by Monte Carlo simulations, but the necessary length of the time domain simulations for very low out-crossing rates might be prohibitively long. The present paper investigates whether the FORM property regarding the dependency of the reliability index on the significant wave...... to the actual significant wave height using this property. Previous results have been presented by Tonguc and Söding (1986), albeit in a more empirical way, and by Jensen (2010), where, considering the overturning of a jack-up rig, a slightly more general relation of the type ß=a(r)+b(r)/Hs was found to be very...
NUMERICAL SIMULATION OF TRAVELING WAVE CONVECTION IN A WEAKLY NONLINEAR REGIME
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper presents a simulational result on a blinking traveling wave (BTW) state in binary fluid convection in a rectangular cell. The numerical simulations were made using the two-dimensional perturbation equations of full hydrodynamic equations. We found for the first time that the BTW or sloshing traveling wave state is a type of modulated traveling wave (MTW) generated by the motion of a source defect which originates from the reflection effect at the end walls and depends on the reduced Rayleigh number r. Comparison with the localized traveling wave (LTW) shows that the BTW is convective patterns on a weakly nonlinear branch with a small amplitude and the LTW is those on a full nonlinear branch whth a large amplitude. They have different dynamical behaviour. A discontinuous jump from the BTW branch to the stable LTW branch takes place as the oscillatory period lengthens and the amplitude grows above the upper critical value of the BTW.
Institute of Scientific and Technical Information of China (English)
XIAO Fu-Liang; HE Zhao-Guo; ZHANG Sai; SU Zhen-Peng; CHEN Liang-Xu
2011-01-01
Temporal evolution of outer radiation belt electron dynamics resulting from superluminous L-O mode waves is simulated at L＝6.5. Diffusion rates are evaluated and then used as inputs to solve a 2D momentum-pitch-angle diffusion equation, particularly with and without cross diffusion terms. Simulated results demonstrate that phase space density(PSD) of energetic electrons due to L-O mode waves can enhance significantly within 24 h, covering a broader pitch-angle range in the absence of cross terms than that in the presence of cross terms. PSD evolution is also determined by the peak wave frequency, particularly at high kinetic energies. This result indicates that superluminous waves can be a potential candidate responsible for outer radiation belt electron dynamics.
A HIGHER-ORDER NON-HYDROSTATIC MODEL FOR SIMULATING WAVE PROPAGATION OVER IRREGULAR BOTTOMS
Institute of Scientific and Technical Information of China (English)
AI Cong-fang; XING Yah; JIN Sheng
2011-01-01
A higher-order non-hydrostatic model is developed to simulate the wave propagation over irregular bottoms based on a vertical boundary-fitted coordinate system.In the model,an explicit projection method is adopted to solve the unsteady Euler equations.Advection terms are integrated explicitly with the MacCormack's scheme,with a second-order accuracy in both space and time.Two classical examples of surface wave propagation are used to demonstrate the capability of the model.It is found that the model with only two vertical layers could accurately simulate the motion of waves,including wave shoaling,nonlinearity,dispersion,refraction,and diffraction phenomena.
Numerical Simulation of Freak Waves Based on the Four-Order Nonlinear Schr(o)dinger Equation
Institute of Scientific and Technical Information of China (English)
ZHANG Yun-qiu; ZHANG Ning-chuan; PEI Yu-guo
2007-01-01
A numerical wave model based on the modified four-order nonlinear Schrodinger (NLS) equation in deep water is developed to simulate freak waves. A standard split-step, pseudo-spectral method is used to solve NLS equation. The validation of the model is firstly verified, and then the simulation of freak waves is performed by changing sideband conditions. Results show that freak waves entirely consistent with the definition in the evolution of wave trains are obtained. The possible occurrence mechanism of freak waves is discussed and the relevant characteristics are also analyzed.
Institute of Scientific and Technical Information of China (English)
文潮; 王占江; 李运良; 门朝举; 陈立强
2012-01-01
由于裂隙或者沟槽对炸药爆炸引起的震动具有良好的隔震作用,所以用现场试验的方法对比研究了用导爆索爆炸形成减震沟槽和人工开挖沟槽的减震效果.用3发50 g TNT当量、lm埋深的爆炸实验,研究了爆破成形和人工开挖预制的两种沟槽的隔震效果.实验结果表明,在爆破成形沟槽的两边存在一定宽度的裂隙区.两种沟槽均有效地降低了爆破震动的幅度并改变了地震波的频谱,而爆破成形沟槽的减震效果优于人工开挖的.离减震沟槽越近,隔震效果越明显.减震沟槽对中远区地震波低频部分隔震效果明显.%Cap or slot has an important effect on reduction of blasting vibration. The effect of vibration isolation and damping of gap or slot, which formed by detonation of the blasting fuse and excavation through manual work, is studied in this paper. In order to investigate the action of gap or slot, three underground explosion experiments were carried out an the north side of gap or slot, whose equivalent is 50g TNT and embedded depth is 1 m. The Pre-split crack zone exists in both sides of gap or slot formed by detonation of the blasting fuse. The experimental results show that the effects of gap or slot on reduction of blasting vibration are distinct and the explosion earthquake wave frequency spectrum characteristics are changed. The effect of gap or slot formed by detonation of the blasting fuse is superior to that of men-made gap or slot. The closer to gap or slot excavation face, the better the effect on reduction of blasting vibration is; The effects on vibration reduction are distinct to low frequency seismic wave at far distance from the gap or slot excavation face.
2015-08-01
southern boundary around 36 deg N latitude. The maxi - mum Hmo estimate locations are based (as is the wind speed) on an abso- lute value. If there are...validation events.) After remaining a weak tropical cyclone for several days, Gloria intensified into a hurricane on 22 September 1985. Gloria...significantly impacting the maxi - mum wave height solution for a preliminary Sandy simulation (the abso- lute difference in maximum wave height within
Simulation of Wave-Plus-Current Induced Scour Beneath Submarine Pipelines
DEFF Research Database (Denmark)
Eltard-Larsen, Bjarke; Fuhrman, David R.; Sumer, B. Mutlu
Scour beneath submarine pipelines has been the subject of much past research see eg. Sumer and Fredsøe (2002).To date most research, both numerical and experimental, has focused on scour induced by either pure waves or currents, while comparatively few studies have involved combined wave-plus-cur......Scour beneath submarine pipelines has been the subject of much past research see eg. Sumer and Fredsøe (2002).To date most research, both numerical and experimental, has focused on scour induced by either pure waves or currents, while comparatively few studies have involved combined wave......-plus-current environments. The present study, which is published in Larsen et al. (2016) focuses on the numerical simulation of wave-plus-current induced scour beneath submarine pipelines, based on a model solving Reynolds-averaged Navier-Stokes (RANS) equations, fully coupled with turbulence closure, bed and suspended...
Ruban, V P
2015-01-01
The nonlinear dynamics of an obliquely oriented wave packet at sea surface is studied both analytically and numerically for various initial parameters of the packet, in connection with the problem of oceanic rogue waves. In the framework of Gaussian variational ansatz applied to the corresponding (1+2D) hyperbolic nonlinear Schr\\"odinger equation, a simplified Lagrangian system of differential equations is derived, which determines the evolution of coefficients of the real and imaginary quadratic forms appearing in the Gaussian. This model provides a semi-quantitative description for the process of nonlinear spatio-temporal focusing, which is one of the most probable mechanisms of rogue wave formation in random wave fields. The system is integrated in quadratures, which fact allows us to understand qualitative differences between the linear and nonlinear regimes of the focusing of wave packet. Comparison of the Gaussian model predictions with results of direct numerical simulation of fully nonlinear long-cres...
Electromagnetic wave scattering on nonspherical particles basic methodology and simulations
Rother, Tom
2014-01-01
This book gives a detailed overview of the theory of electromagnetic wave scattering on single, homogeneous, but nonspherical particles. Beside the systematically developed Green’s function formalism of the first edition this second and enlarged edition contains additional material regarding group theoretical considerations for nonspherical particles with boundary symmetries, an iterative T-matrix scheme for approximate solutions, and two additional but basic applications. Moreover, to demonstrate the advantages of the group theoretical approach and the iterative solution technique, the restriction to axisymmetric scatterers of the first edition was abandoned.
Long Wave Infrared Detection of Chemical Weapons Simulants
Energy Technology Data Exchange (ETDEWEB)
Phillips, Mark C.; Taubman, Matthew S.; Scott, David C.; Myers, Tanya L.; Munley, John T.; Cannon, Bret D.
2007-04-27
The purpose of Task 3.b under PL02-OP211I-PD07 (CBW simulant detection) was to demonstrate the applicability of the sensor work developed under this project for chemical and biological weapons detection. To this end, the specific goal was to demonstrate the feasibility of detection of chemical agents via that of simulants (Freons) with similar spectroscopic features. This has been achieved using Freon-125 as a simulant, a tunable external cavity quantum cascade laser (ECQCL), and a Herriott cell-based sensor developed at Pacific Northwest National Laboratory (PNNL) specifically for this task. The experimentally obtained spectrum of this simulant matches that found in the Northwest Infrared (NWIR) spectral library extremely well, demonstrating the ability of this technique to detect the exact shape of this feature, which in turn indicates the ability to recognize the simulant even in the presence of significant interference. It has also been demonstrated that the detected features of a typical interferent, namely water, are so different in shape and width to the simulant, that they are easily recognized and separated from such a measurement. Judging from the signal-to-noise ratio (SNR) of the experimental data obtained, the noise equivalent absorption sensitivity is estimated to be 0.5 x 10-7 to 1 x 10-6 cm-1. For the particular feature of the simulant examined in this work, this corresponds to a relative concentration of 50 to 25 parts-per-billion by volume (ppbv). The corresponding relative concentrations of other chemical targets would differ depending on the particular transition strengths, and would thus have to be scaled accordingly.
Energy Technology Data Exchange (ETDEWEB)
Choi, Myunghee [Retired; Chan, Vincent S. [General Atomics
2014-02-28
This final report describes the work performed under U.S. Department of Energy Cooperative Agreement DE-FC02-08ER54954 for the period April 1, 2011 through March 31, 2013. The goal of this project was to perform iterated finite-orbit Monte Carlo simulations with full-wall fields for modeling tokamak ICRF wave heating experiments. In year 1, the finite-orbit Monte-Carlo code ORBIT-RF and its iteration algorithms with the full-wave code AORSA were improved to enable systematical study of the factors responsible for the discrepancy in the simulated and the measured fast-ion FIDA signals in the DIII-D and NSTX ICRF fast-wave (FW) experiments. In year 2, ORBIT-RF was coupled to the TORIC full-wave code for a comparative study of ORBIT-RF/TORIC and ORBIT-RF/AORSA results in FW experiments.
Brito, T.; Hudson, M. K.; Kress, B.; Paral, J.; Halford, A.; Millan, R.; Usanova, M.
2015-05-01
Balloon-borne instruments detecting radiation belt precipitation frequently observe oscillations in the millihertz frequency range. Balloons measuring electron precipitation near the poles in the 100 keV to 2.5 MeV energy range, including the MAXIS, MINIS, and most recently the Balloon Array for Relativistic Radiation belt Electron Losses balloon experiments, have observed this modulation at ULF wave frequencies. Although ULF waves in the magnetosphere are seldom directly linked to increases in electron precipitation since their oscillation periods are much larger than the gyroperiod and the bounce period of radiation belt electrons, test particle simulations show that this interaction is possible. Three-dimensional simulations of radiation belt electrons were performed to investigate the effect of ULF waves on precipitation. The simulations track the behavior of energetic electrons near the loss cone, using guiding center techniques, coupled with an MHD simulation of the magnetosphere, using the Lyon-Fedder-Mobarry code, during a coronal mass ejection (CME)-shock event on 17 March 2013. Results indicate that ULF modulation of precipitation occurs even without the presence of electromagnetic ion cyclotron waves, which are not resolved in the MHD simulation. The arrival of a strong CME-shock, such as the one simulated, disrupts the electric and magnetic fields in the magnetosphere and causes significant changes in both components of momentum, pitch angle, and L shell of radiation belt electrons, which may cause them to precipitate into the loss cone.
Internal wave generation by convection in water. Part 2. Numerical simulations
Lecoanet, Daniel; Burns, Keaton J; Vasil, Geoffrey M; Brown, Benjamin P; Quataert, Eliot; Oishi, Jeffrey S
2014-01-01
Water's density maximum at 4C makes it well suited to study internal gravity wave excitation by convection: an increasing temperature profile is unstable to convection below 4C, but stably stratified above 4C. We present numerical simulations of water near its density maximum in a two dimensional tank, similar to the experiment described in a companion paper (Le Bars et al. 2015). The simulations agree very well with the experiments, despite differences in lateral boundary conditions in the two systems. 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. In order to isolate the physical mechanism exciting internal waves, we use the novel spectral code Dedalus to run several simulations of the 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 th...
Velo: Riding the Knowledge Management Wave for Simulation and Modeling
Energy Technology Data Exchange (ETDEWEB)
Gorton, Ian; Sivaramakrishnan, Chandrika; Black, Gary D.; White, Signe K.; Purohit, Sumit; Madison, Michael C.; Schuchardt, Karen L.
2011-05-28
Modern scientific enterprises are inherently knowledge-intensive. In general, scientific studies in domains such as geosciences, climate, and biology require the acquisition and manipulation of large amounts of experimental and field data in order to create inputs for large-scale computational simulations. The results of these simulations must then be analyzed, leading to refinements of inputs and models and further simulations. Further, these results must be managed and archived to provide justifications for publications and regulatory decisions that are based on these models. In this paper we describe our Velo framework that is designed as a reusable, domain independent knowledge management infrastructure for modeling and simulation. Velo leverages, integrates, and extends open source collaborative and content management technologies to create a scalable and flexible core platform that can be tailored to specific scientific domains. In this paper we describe the architecture of Velo for managing and associating the various types of data that are used and created in modeling and simulation projects, as well as the framework for integrating domain-specific tools. To demonstrate a realization of Velo, we describe the Geologic Sequestration Software Suite (GS3) that has been developed to support geologic sequestration modeling. This provides a concrete example of the inherent extensibility and utility of our approach.
Simulation of the ocean surface mixed layer under the wave breaking
Institute of Scientific and Technical Information of China (English)
SUN Qun; SONG Jinbao; GUAN Changlong
2005-01-01
A one-dimensional mixed-layer model, including a Mellor-Yamada level 2.5 turbulence closure scheme, was implemented to investigate the dynamical and thermal structures of the ocean surface mixed layer in the northern South China Sea. The turbulent kinetic energy released through wave breaking was incorporated into the model as a source of energy at the ocean surface, and the influence of the breaking waves on the mixed layer was studied. The numerical simulations show that the simulated SST is overestimated in summer without the breaking waves. However, the cooler SST is simulated when the effect of the breaking waves is considered, the corresponding discrepancy with the observed data decreases up to 20% and the MLD calculated averagely deepens 3.8 m. Owing to the wave-enhanced turbulence mixing in the summertime, the stratification at the bottom of the mixed layer was modified and the temperature gradient spread throughout the whole thermocline compared with the concentrated distribution without wave breaking.
Combined analytical FEM approach for efficient simulation of Lamb wave damage detection.
Shen, Yanfeng; Giurgiutiu, Victor
2016-07-01
Lamb waves have been widely explored as a promising inspection tool for non-destructive evaluation (NDE) and structural health monitoring (SHM). This article presents a combined analytical finite element model (FEM) approach (CAFA) for the accurate, efficient, and versatile simulation of 2-D Lamb wave propagation and interaction with damage. CAFA used a global analytical solution to model wave generation, propagation, scattering, mode conversion, and detection, while the wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local FEM with non-reflective boundaries (NRB). The analytical procedure was coded using MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The methodology of obtaining WDICs from local FEM was presented. Case studies were carried out for Lamb wave propagation in a pristine plate and a damaged plate. CAFA predictions compared well with full scale multi-physics FEM simulations and experiments with scanning laser Doppler vibrometry (SLDV), while achieving remarkable performance in computational efficiency and computer resource saving compared with conventional FEM.
Directory of Open Access Journals (Sweden)
Z. Hashemiyan
2016-01-01
Full Text Available Properties of soft biological tissues are increasingly used in medical diagnosis to detect various abnormalities, for example, in liver fibrosis or breast tumors. It is well known that mechanical stiffness of human organs can be obtained from organ responses to shear stress waves through Magnetic Resonance Elastography. The Local Interaction Simulation Approach is proposed for effective modelling of shear wave propagation in soft tissues. The results are validated using experimental data from Magnetic Resonance Elastography. These results show the potential of the method for shear wave propagation modelling in soft tissues. The major advantage of the proposed approach is a significant reduction of computational effort.
Biktasheva, I V; Dierckx, H; Biktashev, V N
2015-02-13
A scroll wave in a very thin layer of excitable medium is similar to a spiral wave, but its behavior is affected by the layer geometry. We identify the effect of sharp variations of the layer thickness, which is separate from filament tension and curvature-induced drifts described earlier. We outline a two-step asymptotic theory describing this effect, including asymptotics in the layer thickness and calculation of the drift of so-perturbed spiral waves using response functions. As specific examples, we consider drift of scrolls along thickness steps, ridges, ditches, and disk-shaped thickness variations. Asymptotic predictions agree with numerical simulations.
Lemarchand, A.; Nowakowski, B.; Dumazer, G.; Antoine, C.
2011-01-01
We perform microscopic simulations using the direct simulation Monte Carlo approach to an exothermic chemical wave front of Fisher-Kolmogorov, Petrovsky, Piskunov-type in a one-dimensional gaseous medium. The results confirm the existence of a transition from a weak detonation or deflagration to a Chapman-Jouguet detonation wave, that we already investigated at the macroscopic scale [G. Dumazer et al., Phys. Rev. E 78, 016309 (2008)]. In the domain of weak detonation or deflagration, the discrepancy between the propagation speeds deduced from the simulations and the macroscopic balance equations of hydrodynamics is explained by two microscopic effects, the discretization of the variables, known as cutoff effect, and the departure from local equilibrium. Remarkably, the propagation speed of a Chapman-Jouguet detonation wave is not sensitive to these perturbations of microscopic origin.
Three-Dimensional Numerical Simulation of Surface-Wave Plasma Source
Institute of Scientific and Technical Information of China (English)
LAN Chaohui; CHEN Zhaoquan; LIU Minghai; JIANG Zhonghe; HU Xiwei
2009-01-01
A three-dimensional model of a surface-wave plasma(SWP)source is built numerically using the finite-difference time-domain(FDTD)method to investigate the structure of the surface wave propagation along the plasma-dielectric interface and the distributions of electromagnetic fields in the whole system.A good-performance excitation source technique for the waveguide which is pivotal to the simulation is presented.The technique can avoid the dc distortions of magnetic fields caused by the forcing electric wall.An example of simulation is given to confirm the existence of the surface waves.The simulation also shows that the code developed is a useful tool in the computer-aided design of the antenna of the SWP source.
Rudd, Kevin E; Leonard, Kevin R; Bingham, Jill P; Hinders, Mark K
2007-03-01
Although many technologies exist for inspecting piping systems, they are most successful on straight pipes and are often unable to accommodate the added complexities of pipe elbows, bends, twists, and branches, particularly if the region of interest is inaccessible. This paper presents a numerical technique based on the elastodynamic finite integration technique for simulating guided elastic wave propagation in piping systems. Comparisons show agreement between experimental and simulated data, and guided wave interaction with flaws, focusing, and propagation in pipe bends are presented. These examples demonstrate the ability of the simulation method to be used to study elastic wave propagation in piping systems which include three-dimensional pipe bends, and suggest its potential as a design tool for designing pipe inspection hardware and ultrasonic signal processing algorithms.
RANS Simulation of the Heave Response of a Two-Body Floating Point Wave Absorber: Preprint
Energy Technology Data Exchange (ETDEWEB)
Yu, Y.; Li, Y.
2011-03-01
A preliminary study on a two-body floating wave absorbers is presented in this paper. A Reynolds-Averaged Navier-Stokes computational method is applied for analyzing the hydrodynamic heave response of the absorber in operational wave conditions. The two-body floating wave absorber contains a float section and a submerged reaction section. For validation purposes, our model is first assumed to be locked. The two sections are forced to move together with each other. The locked single body model is used in a heave decay test, where the RANS result is validated with the experimental measurement. For the two-body floating point absorber simulation, the two sections are connected through a mass-spring-damper system, which is applied to simulate the power take-off mechanism under design wave conditions. Overall, the details of the flow around the absorber and its nonlinear interaction with waves are investigated, and the power absorption efficiency of the two-body floating wave absorber in waves with a constant value spring-damper system is examined.
Institute of Scientific and Technical Information of China (English)
ZHAO Tong-bin; LI Jian-gong; XIAO Ya-xun; CHENG Guo-qiang
2007-01-01
The energy caused by the dynamic impact in mining engineering forth release and spread by the way of seismic waves, monitoring is an effective way for forecasting mine dynamical disasters, such as rockburst and coal and gas outburst. Three-dimensional dynamic model was built to simulate the propagating progress of seismic waves in the elastoplastic tunnel rock and analyzed the propagating law of perturbation acceleration around tunnel, based on the finite element dynamic analysis software ANSYS/LS-DYNA.The simulation results indicate that: (1) The propagation attenuation of seismic wave is a negative index relationship; (2) The acceleration amplitude of seismic wave decays rapidly in near-field and decays slowly in far-field; (3) When the perturbation is generated in the dead ahead of tunnel, the acceleration of seismic wave become smaller and smaller away from the roadway-rib;(4) The elastic and plastic stress state of tunnel rock is also an important factor for propagation process of wave, the energy of seismic wave is mainly consumed for geometric spreading and plastic deformation in propagation in the elastoplastic medium model.
Hindmarsh, Mark; Rummukainen, Kari; Weir, David J
2015-01-01
We present details of numerical simulations of the gravitational radiation produced by a first order {thermal} phase transition in the early universe. We confirm that the dominant source of gravitational waves is sound waves generated by the expanding bubbles of the low-temperature phase. We demonstrate that the sound waves have a power spectrum with power-law form between the scales set by the average bubble separation (which sets the length scale of the fluid flow $L_\\text{f}$) and the bubble wall width. The sound waves generate gravitational waves whose power spectrum also has a power-law form, at a rate proportional to $L_\\text{f}$ and the square of the fluid kinetic energy density. We identify a dimensionless parameter $\\tilde\\Omega_\\text{GW}$ characterising the efficiency of this "acoustic" gravitational wave production whose value is $8\\pi\\tilde\\Omega_\\text{GW} \\simeq 0.8 \\pm 0.1$ across all our simulations. We compare the acoustic gravitational waves with the standard prediction from the envelope appr...
Blanco, Joaquín. E.; Nolan, David S.; Tulich, Stefan N.
2016-10-01
Convectively coupled Kelvin waves (CCKWs) represent a significant contribution to the total variability of the Intertropical Convergence Zone (ITCZ). This study analyzes the structure and propagation of CCKWs simulated by the Weather Research and Forecasting (WRF) model using two types of idealized domains. These are the "aquachannel," a flat rectangle on a beta plane with zonally periodic boundary conditions and length equal to the Earth's circumference at the equator, and the "aquapatch," a square domain with zonal extent equal to one third of the aquachannel's length. A series of simulations are performed, including a doubly nested aquapatch, in which convection is solved explicitly along the equator. The model intercomparison is carried out throughout the use of several techniques such as power spectra, filtering, wave tracking, and compositing, and it is extended to some simulations from the Aquaplanet Experiment (APE). Results show that despite the equatorial superrotation bias produced by the WRF simulations, the CCKWs simulated with this model propagate with similar phase speeds (relative to the low-level mean flow) as the corresponding waves from the APE simulations. Horizontal and vertical structures of the CCKWs simulated with aquachannels are also in overall good agreement with those from aquaplanet simulations and observations, although there is a distortion of the zonal extent of anomalies when the shorter aquapatch is used.
Numerical simulation of super-square patterns in Faraday waves
Kahouadji, L; Tuckerman, L S; Shin, S; Chergui, J; Juric, D
2015-01-01
We report the first simulations of the Faraday instability using the full three-dimensional Navier-Stokes equations in domains much larger than the characteristic wavelength of the pattern. We use a massively parallel code based on a hybrid Front-Tracking/Level-set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces. Simulations performed in rectangular and cylindrical domains yield complex patterns. In particular, a superlattice-like pattern similar to those of [Douady & Fauve, Europhys. Lett. 6, 221-226 (1988); Douady, J. Fluid Mech. 221, 383-409 (1990)] is observed. The pattern consists of the superposition of two square superlattices.
Energy Technology Data Exchange (ETDEWEB)
Takiya, Toshio; Terada, Yukihiro; Komura, Akio [Hitachi Zosen Corp., Osaka (Japan); Higashino, Fumio; Miyajima, Shinichi; Ando, Masami
1997-05-01
A simulation for shock wave propagation in a vacuum tube has been conducted from the viewpoint of protection from vacuum accidents in beamlines of a synchrotron radiation facility. Inserted devices in beamlines such as absorbers, slits, masks and beryllium windows were replaced with orifices installed in a shock tube as a simulation model. One-dimensional Euler`s equations with friction terms were used for estimating the effects on shock wave decay as well as the effects of friction along a tube on shock attenuation. The results indicated that the entrance diameter of the shock tube was an important parameter for determining the strength of shock waves generated by the expansion of gases at the tube entrance and that the friction effects were too large to delay the arrival time of shock waves at the end of a long tube. Moreover, shock wave propagation in a long beamline model based on the MR beamline in the National Laboratory for High Energy Physics was simulated for designing adequate protection from vacuum accidents. The present simulation provides necessary information for the design of a protection system for vacuum accidents in other facilities. (author)
An Improved Coupling of Numerical and Physical Models for Simulating Wave Propagation
DEFF Research Database (Denmark)
Yang, Zhiwen; Liu, Shu-xue; Li, Jin-xuan
2014-01-01
An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model (FEM) based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used fo...... that the proposed numerical scheme and transfer function modulation method are efficient for the data transfer from the numerical model to the physical model up to a deterministic level.......An improved coupling of numerical and physical models for simulating 2D wave propagation is developed in this paper. In the proposed model, an unstructured finite element model (FEM) based Boussinesq equations is applied for the numerical wave simulation, and a 2D piston-type wavemaker is used...... for the physical wave generation. An innovative scheme combining fourth-order Lagrange interpolation and Runge-Kutta scheme is described for solving the coupling equation. A Transfer function modulation method is presented to minimize the errors induced from the hydrodynamic invalidity of the coupling model and...
Institute of Scientific and Technical Information of China (English)
YU Shi-jian; Cheng Jiu-long; LIU Jia-qi
2007-01-01
This paper took the abnormal geological objects with high or low resistivity in the coal face as the background to establish the physical model. 2D forward numerical simulation for electromagnetic wave equation was implemented by the finite-difference scheme. According to the simulative results, the attenuation-absorption coefficient were calculated respectively based on field intensity and frequency shift parameter. Research result indicates, when coal-bed contains high electric resistivity geological abnormal object or low electric resistivity geological abnormal object, absorption attenuation function researched by frequency shift parameter of electromagnetic wave signal is more sensitive than by electromagnetic field intensity parameter.
Mesh Size and Damped Edge Effects in Micromagnetic Spin Wave Simulation
Venkat, G; Fangohr, H; Prabhakar, A
2014-01-01
We have studied the dependence of spin wave dispersion on the characteristics of the mesh used in a finite element micromagnetic simulation. It is shown that the dispersion curve has a cut off at a frequency which is analytically predictable. The frequency depends on the average mesh length used for the simulation. Based on this, a recipe to effectively obtain the dispersion relation has been suggested. In a separate study, spin wave reflections are absorbed by introducing highly damped edges in the device. However, an abrupt change in the damping parameter causes reflections. We compare damping profiles and identify an exponential damping profile as causing significantly less reflections.
Analog quantum simulation of gravitational waves in a Bose-Einstein condensate
Energy Technology Data Exchange (ETDEWEB)
Bravo, Tupac; Sabin, Carlos; Fuentes, Ivette [University of Nottingham, School of Mathematical Sciences, Nottingham (United Kingdom)
2015-01-04
We show how to vary the physical properties of a Bose-Einstein condensate (BEC) in order to mimic an effective gravitational-wave spacetime. In particular, we focus in the simulation of the recently discovered creation of particles by a real spacetime distortion in box-type traps. We show that, by modulating the speed of sound in the BEC, the phonons experience the effects of a simulated spacetime ripple with experimentally amenable parameters. These results will inform the experimental programme of gravitational wave astronomy with cold atoms. (orig.)
Investigation on the Use of a Multiphase Eulerian CFD solver to simulate breaking waves
DEFF Research Database (Denmark)
Tomaselli, Pietro D.; Christensen, Erik Damgaard
2015-01-01
for mass and momentum transfer among phases, was satisfactorily tested against an experimental bubble column flow. The model was then used to simulate the propagation of a laboratory solitary breaking wave. The motion of the free surface was successfully reproduced up to the breaking point. Further......The main challenge in CFD multiphase simulations of breaking waves is the wide range of interfacial length scales occurring in the flow: from the free surface measurable in meters down to the entrapped air bubbles with size of a fraction of a millimeter. This paper presents a preliminary...
DEFF Research Database (Denmark)
Beels, Charlotte; Troch, Peter; Visch, Kenneth De;
2010-01-01
in a time-dependent mild-slope equation model by using numerical sponge layers. In this paper the developed WEC implementation is applied to a single Wave Dragon WEC and multiple Wave Dragon WECs. The Wave Dragon WEC is a floating offshore converter of the overtopping type. Two wave reflectors focus...... and reservoir) are simulated as porous structures, exhibiting the same reflection, respectively absorption characteristics as obtained for the prototype Wave Dragon WEC. The wake effects behind a single Wave Dragon WEC are studied in detail for uni- and multidirectional waves. The shadow zone indicating...... the wake effect is decreasing with increasing directional spreading. The wake in the lee of a farm of five Wave Dragon WECs, installed in a staggered grid (3 WECs in the first row and 2 WECs in the second row), is calculated for three in-between distances of respectively D, 2D and 3D, with D the distance...
Ongaro, T. E.; Clarke, A.; Neri, A.; Voight, B.; Widiwijayanti, C.
2005-12-01
For the first time the dynamics of directed blasts from explosive lava-dome decompression have been investigated by means of transient, multiphase flow simulations in 2D and 3D. Multiphase flow models developed for the analysis of pyroclastic dispersal from explosive eruptions have been so far limited to 2D axisymmetric or Cartesian formulations which cannot properly account for important 3D features of the volcanic system such as complex morphology and fluid turbulence. Here we use a new parallel multiphase flow code, named PDAC (Pyroclastic Dispersal Analysis Code) (Esposti Ongaro et al., 2005), able to simulate the transient and 3D thermofluid-dynamics of pyroclastic dispersal produced by collapsing columns and volcanic blasts. The code solves the equations of the multiparticle flow model of Neri et al. (2003) on 3D domains extending up to several kilometres in 3D and includes a new description of the boundary conditions over topography which is automatically acquired from a DEM. The initial conditions are represented by a compact volume of gas and pyroclasts, with clasts of different sizes and densities, at high temperature and pressure. Different dome porosities and pressurization models were tested in 2D to assess the sensitivity of the results to the distribution of initial gas pressure, and to the total mass and energy stored in the dome, prior to 3D modeling. The simulations have used topographies appropriate for the 1997 Boxing Day directed blast on Montserrat, which eradicated the village of St. Patricks. Some simulations tested the runout of pyroclastic density currents over the ocean surface, corresponding to observations of over-water surges to several km distances at both locations. The PDAC code was used to perform 3D simulations of the explosive event on the actual volcano topography. The results highlight the strong topographic control on the propagation of the dense pyroclastic flows, the triggering of thermal instabilities, and the elutriation
Simulation on the electronic wave packet cyclotron motion in a Weyl semimetal slab.
Yao, Haibo; Zhu, Mingfeng; Jiang, Liwei; Zheng, Yisong
2017-04-20
We perform a numerical simulation on the time evolution of an electronic wave packet in a Weyl semimetal (WSM) slab driven by a magnetic field. We find that the evolution trajectory of the wave packet depends sensitively on its initial spin state. Only with initial spin state identical to that of the Fermi arc state at the surface it localized, does the wave packet evolution demonstrate the characteristic cyclotron orbit of WSM previously predicted from a semiclassical viewpoint. By analyzing the eigen-expansion of the electronic wave packet, we find the chiral Landau levels (LLs) of the WSM slab, as ingredients of the wave packet, to be responsible for establishing the characteristic WSM cyclotron orbit. In contrast, the nonchiral LLs contribute irregular oscillations to the wave packet evolution, going against the formation of a well-defined cyclotron orbit. In addition, the tilted magnetic field does not affect the motion of the electronic wave packet along the Fermi arcs in the momentum space. It does, however, alter the evolution trajectory of the electronic wave packet in real space and spin space. Finally, the energy disalignment of the Weyl nodes results in a 3D cyclotron orbit in real space.
A Computer Simulation Study of Anatomy Induced Drift of Spiral Waves in the Human Atrium
Directory of Open Access Journals (Sweden)
Sanjay R. Kharche
2015-01-01
Full Text Available The interaction of spiral waves of excitation with atrial anatomy remains unclear. This simulation study isolates the role of atrial anatomical structures on spiral wave spontaneous drift in the human atrium. We implemented realistic and idealised 3D human atria models to investigate the functional impact of anatomical structures on the long-term (∼40 s behaviour of spiral waves. The drift of a spiral wave was quantified by tracing its tip trajectory, which was correlated to atrial anatomical features. The interaction of spiral waves with the following idealised geometries was investigated: (a a wedge-like structure with a continuously varying atrial wall thickness; (b a ridge-like structure with a sudden change in atrial wall thickness; (c multiple bridge-like structures consisting of a bridge connected to the atrial wall. Spiral waves drifted from thicker to thinner regions and along ridge-like structures. Breakthrough patterns caused by pectinate muscles (PM bridges were also observed, albeit infrequently. Apparent anchoring close to PM-atrial wall junctions was observed. These observations were similar in both the realistic and the idealised models. We conclude that spatially altering atrial wall thickness is a significant cause of drift of spiral waves. PM bridges cause breakthrough patterns and induce transient anchoring of spiral waves.
Directory of Open Access Journals (Sweden)
Li Ma
2016-01-01
Full Text Available The impact energy produced by blast casting is able to break and cast rocks, yet the strong vibration effects caused at the same time would threaten the safety of mines. Based on the theory of Janbu’s Limit Equilibrium Method (LEM, pseudo-static method has been incorporated to analyze the influence of dynamic loads of blasting on slope stability. The horizontal loads produced by blast vibrations cause an increase in sliding forces, and this leads to a lower slope stability coefficient. When the tensile stresses of the two adjacent blast holes are greater than the tensile strength of rock mass, the radical oriented cracks are formed, which is the precondition for the formation of presplit face. Thus, the formula for calculating the blast hole spacing of presplit blasting can be obtained. Based on the analysis of the principles of vibration tester and vibration pick-up in detecting blast vibrations, a detection scheme of blast vibration is worked out by taking the blast area with precrack rear and non-precrack side of the detection object. The detection and research results of blast vibration show that presplit blasting can reduce the attenuation coefficient of stress wave by half, and the vibration absorption ratio could reach 50.2%; the impact of dynamic loads on the end-wall slope stability coefficient is 1.98%, which proves that presplit blasting plays an important role in shock absorption of blast casting.
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere.
Claudepierre, S G; Toffoletto, F R; Wiltberger, M
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Global MHD modeling of resonant ULF waves: Simulations with and without a plasmasphere
Claudepierre, S. G.; Toffoletto, F. R.; Wiltberger, M.
2016-01-01
We investigate the plasmaspheric influence on the resonant mode coupling of magnetospheric ultralow frequency (ULF) waves using the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model. We present results from two different versions of the model, both driven by the same solar wind conditions: one version that contains a plasmasphere (the LFM coupled to the Rice Convection Model, where the Gallagher plasmasphere model is also included) and another that does not (the stand-alone LFM). We find that the inclusion of a cold, dense plasmasphere has a significant impact on the nature of the simulated ULF waves. For example, the inclusion of a plasmasphere leads to a deeper (more earthward) penetration of the compressional (azimuthal) electric field fluctuations, due to a shift in the location of the wave turning points. Consequently, the locations where the compressional electric field oscillations resonantly couple their energy into local toroidal mode field line resonances also shift earthward. We also find, in both simulations, that higher-frequency compressional (azimuthal) electric field oscillations penetrate deeper than lower frequency oscillations. In addition, the compressional wave mode structure in the simulations is consistent with a radial standing wave oscillation pattern, characteristic of a resonant waveguide. The incorporation of a plasmasphere into the LFM global MHD model represents an advance in the state of the art in regard to ULF wave modeling with such simulations. We offer a brief discussion of the implications for radiation belt modeling techniques that use the electric and magnetic field outputs from global MHD simulations to drive particle dynamics.
Determining Heat Waves from Observations and COSMO-CLM Simulations in Istanbul
Yuruk, Cemre; Unal, Yurdanur; Irem Bilgen, Simge; Topcu, Sema; Mentes, Sibel
2016-04-01
Climate change has crucial effects on cities and especially for informal settlements, urban poor and other vulnerable groups by influencing human health, assets and livelihoods. These impacts directly result from the variations in temperature and precipitation, and emergence of heat waves, droughts, floods and fires (IPCC, 2014). Summertime episodes with extremely high air temperatures which last for several days or longer are addressed to as heat waves and affect the weather and climate in the globe. The aim of this study is to analyze the occurrence of heat waves in terms of quantity, duration and frequency and also to evaluate the accuracy of the COSMO-CLM (CCLM) model coupled with MPI-ESM-LR in reproducing the characteristics of heat waves in Istanbul. The summer maximum temperatures of six Turkish State Meteorological Service (TSMS) stations are selected between 1960 and 2013 to estimate the characteristics of heat waves in Istanbul. We define the heat wave if the maximum temperatures exceed a threshold value for at least three consecutive days. The threshold value is determined as 30.5 °C from the 90th percentile of all six station's observations. Then it is used in the detection of the hot days, heat waves and their durations. The results show that not only the number of heat waves but also duration of heat waves increase towards the end of the study period. Especially, a significant increase in heat wave events is evident after 1990s. An example of this situation is observed in a Kilyos station located northern part of the city. Kilyos experiences only one heat wave in the beginning of 1970s whereas the number of heat waves increases in years and reaches to the maximum value of 5 in 2000. Furthermore, Kartal as an urban area in the Asian side of the city, exhibits highest heat wave duration with 18 consecutive days in 1998. In addition to station data analyses, the local climate of Istanbul and its vicinity is simulated by CCLM model with approximately 3
The Vajont disaster: a 3D numerical simulation for the slide and the waves
Rubino, Angelo; Androsov, Alexey; Vacondio, Renato; Zanchettin, Davide; Voltzinger, Naum
2016-04-01
A very high resolution O(5 m), 3D hydrostatic nonlinear numerical model was used to simulate the dynamics of both the slide and the surface waves produced during the Vajont disaster (north Italy, 1963), one of the major landslide-induced tsunamis ever documented. Different simulated wave phenomena like, e.g., maximum run-up on the opposite shore, maximum height, and water velocity were analyzed and compared with data available in literature, including the results of a fully 3D simulation obtained with a Smoothed Particle Hydrodynamic code. The difference between measured and simulated after-slide bathymetries was calculated and used in an attempt to quantify the relative magnitude and extension of rigid and fluid motion components during the event.
Software Radio Implementation of RF Short-Wave Wideband Channel Simulator
Institute of Scientific and Technical Information of China (English)
DINGYahui; GANLiangcai; XIELing
2005-01-01
A novel radio frequency short-wave wideband channel simulator which can be used to evaluate wideband SW communication system performance over shortwave channel with time-variant and dispersive property, is proposed in this paper. The channel simulator consists of RF transmitting, receiving module and baseband digital signal processing module. In particular, a wideband channel model is introduced into this project that can exhibit various short-wave characteristic such as delay spread, Doppler shift, Doppler spread and all kinds of noise and interference. At the same time, this paper makes a great improvement on SW wideband channel model proposed in Ref.[2] and utilizes some idea of software radio to design the channel simulator's RF part. Therefore, the channel simulator described in the paper can be applicable to not only theoretical research, but also practical application.
Numerical simulation of ultrasonic wave transmission experiments in rocks of shale gas reservoirs
Chen, Qiao; Yao, Guanghua; Zhu, Honglin; Tan, Yanhu; Xu, Fenglin
2017-01-01
Shale gas reservoirs have risen in importance in China's new power source exploration and development program. The investigation of the propagation of ultrasonic waves in shale forms the basis for the full waveform application of acoustic logging data to the exploration of shale gas. Using acoustic wave theory, initial conditions, vibration source conditions, and stability conditions are developed in combination with experimental background of ultrasonic wave transmission. With improved boundary conditions, we performed numerical simulations of the ultrasound transmission experiments in shale using the high-order staggered-grid finite difference method (second-order in the time domain and fourth-order in the space domain). With programs developed within MatLab, the results obtained from numerical simulations agree well with experimental results based on physical models. In addition, using snapshots of the wave field that give a microscopic perspective, the propagation laws for ultrasonic waves can be analyzed. Using this method, human error is avoided, transmission experiments costs can be reduced and efficiency improved. This method extends the scope of experimental investigations regarding the transmission of ultrasonic waves in a shale gas reservoir with increasing stratification, and thus has great theoretical value and practical significance.
Numerical simulation of ultrasonic wave transmission experiments in rocks of shale gas reservoirs
Directory of Open Access Journals (Sweden)
Qiao Chen
2017-01-01
Full Text Available Shale gas reservoirs have risen in importance in China’s new power source exploration and development program. The investigation of the propagation of ultrasonic waves in shale forms the basis for the full waveform application of acoustic logging data to the exploration of shale gas. Using acoustic wave theory, initial conditions, vibration source conditions, and stability conditions are developed in combination with experimental background of ultrasonic wave transmission. With improved boundary conditions, we performed numerical simulations of the ultrasound transmission experiments in shale using the high-order staggered-grid finite difference method (second-order in the time domain and fourth-order in the space domain. With programs developed within MatLab, the results obtained from numerical simulations agree well with experimental results based on physical models. In addition, using snapshots of the wave field that give a microscopic perspective, the propagation laws for ultrasonic waves can be analyzed. Using this method, human error is avoided, transmission experiments costs can be reduced and efficiency improved. This method extends the scope of experimental investigations regarding the transmission of ultrasonic waves in a shale gas reservoir with increasing stratification, and thus has great theoretical value and practical significance.
Simulation of systems for shock wave/compression waves damping in technological plants
Sumskoi, S. I.; Sverchkov, A. M.; Lisanov, M. V.; Egorov, A. F.
2016-09-01
At work of pipeline systems, flow velocity decrease can take place in the pipeline as a result of the pumps stop, the valves shutdown. As a result, compression waves appear in the pipeline systems. These waves can propagate in the pipeline system, leading to its destruction. This phenomenon is called water hammer (water hammer flow). The most dangerous situations occur when the flow is stopped quickly. Such urgent flow cutoff often takes place in an emergency situation when liquid hydrocarbons are being loaded into sea tankers. To prevent environment pollution it is necessary to stop the hydrocarbon loading urgently. The flow in this case is cut off within few seconds. To prevent an increase in pressure in a pipeline system during water hammer flow, special protective systems (pressure relief systems) are installed. The approaches to systems of protection against water hammer (pressure relief systems) modeling are described in this paper. A model of certain pressure relief system is considered. It is shown that in case of an increase in the intensity of hydrocarbons loading at a sea tanker, presence of the pressure relief system allows to organize safe mode of loading.
Vlasov Simulations of Electron-Ion Collision Effects on Damping of Electron Plasma Waves
Banks, J W; Berger, R L; Tran, T M
2016-01-01
Collisional effects can play an essential role in the dynamics of plasma waves by setting a minimum damping rate and by interfering with wave-particle resonances. Kinetic simulations of the effects of electron-ion pitch angle scattering on Electron Plasma Waves (EPWs) are presented here. In particular, the effects of such collisions on the frequency and damping of small-amplitude EPWs for a range of collision rates and wave phase velocities are computed and compared with theory. Both the Vlasov simulations and linear kinetic theory find the direct contribution of electron-ion collisions to wave damping is about a factor of two smaller than is obtained from linearized fluid theory. To our knowledge, this simple result has not been published before. Simulations have been carried out using a grid-based (Vlasov) approach, based on a high-order conservative finite difference method for discretizing the Fokker-Planck equation describing the evolution of the electron distribution function. Details of the implementat...
Simulation of Ab Initio Molecular Dynamics of Shock Wave on Copper
Institute of Scientific and Technical Information of China (English)
张林; 蔡灵仓; 向士凯; 经福谦; 陈栋泉
2003-01-01
The relation between particle velocity Up, up to 4 km/s, and shock wave velocity Us in copper has been simulated with ab initio molecular dynamics. The simulated relationship without considering the correction of zero-point and finite temperature effects is Us = 4.23 + 1.53Up. After considering the correction the relation becomes Us = 4.08 + 1.53Up, which is consistent with the experimental result.
Numerical simulation of seismic wave propagation in complex media by convolutional differentiator
Institute of Scientific and Technical Information of China (English)
LI Xin-fu; LI Xiao-fan
2008-01-01
We apply the forward modeling algorithm constituted by the convolutional Forsyte polynomial differentiator pro- posed by former worker to seismic wave simulation of complex heterogeneous media and compare the efficiency and accuracy between this method and other seismic simulation methods such as finite difference and pseudospec- tral method. Numerical experiments demonstrate that the algorithm constituted by convolutional Forsyte polyno- mial differentiator has high efficiency and accuracy and needs less computational resources, so it is a numerical modeling method with much potential.
Wave optics simulation of diode pumped alkali laser (DPAL)
Endo, Masamori; Nagaoka, Ryuji; Nagaoka, Hiroki; Nagai, Toru; Wani, Fumio
2016-03-01
A numerical simulation code for a diode pumped alkali laser (DPAL) was developed. The code employs the Fresnel- Kirchhoff diffraction integral for both laser mode and pump light propagations. A three-dimensional rate equation set was developed to determine the local gain. The spectral divergence of the pump beam was represented by a series of monochromatic beams with different wavelengths. The calculated results showed an excellent agreements with relevant experimental results. It was found that the main channel of the pump power drain is the spontaneous emission from the upper level of the lasing transition.
Huang, Y.; Weisberg, R.H.; Zheng, L.; Zijlema, M.
2013-01-01
The effects of wind input parameterizations on wave estimations under hurricane conditions are examined using the unstructured grid, third-generation wave model, Simulating WAves Nearshore (SWAN). Experiments using Hurricane Ike wind forcing, which impacted the Gulf of Mexico in 2008, illustrate tha
Simulation of response of sodium layer to the propagation of gravity wave
Institute of Scientific and Technical Information of China (English)
XU Jiyao
2004-01-01
A time-dependent two-dimensional photochemical-dynamical coupling gravity wave model of sodium layer is developed, which combines the sodium photochemical theory, a time-dependent two-dimensional atmospheric photochemical model, a two-dimensional gravity wave model, and the International Reference Ionosphere model (IRI-95)with the diabatic process induced by photochemical reactions and the transport of chemical species by gravity waves included. The pseudospectral method is used in the horizontal direction, the finite difference approximations are used in vertical direction z and time t. And FICE method is used to solve the model. The simulation results indicate that intense perturbations of the sodium layer can be induced by the propagation of gravity waves. The results are consistent with the observations.
Numerical simulation of four-wave mixing efficiency and its induced relative intensity noise
Institute of Scientific and Technical Information of China (English)
Chen Wei; Meng Zhou; Zhou Hui-Juan; Luo Hong
2012-01-01
Four-wave mixing,as well as its induced intensity noise,is harmful to wavelength division multiplexing systems.The efficiency and the relative intensity noise of four-wave mixing are numerically simulated for the two-wave and the three-wave fiber transmissions.It is found that the efficiency decreases with the increase of both the frequency spacing and the fiber length,which can be explained using the quasi-phase-matching condition.Furthermore,the relative intensity noise decreases with the increase of frequency spacing,while it increases with the increase of fiber length,which is due to the considerable power loss of the pump light.This investigation presents a good reference for the practical application of wavelength division multiplexing systems.
Simulation of Organized Convection and Tropical-wave Coupling in a YOTC MJO
Moncrieff, M. W.; Liu, C.
2015-12-01
Organized precipitating convection coupled to various tropical waves was impressively complex in the eastern Indian Ocean in the April 2009 MJO, one of the six MJOs that occurred during the YOTC virtual global field campaign (May 2008-April 2010). Organized convection in the form of a westward-propagating synoptic-scale supercluster and a family of eastward-propagating mesoscale squall lines formed west of Sumatra. The supercluster was strongly coupled to a westward inertio-gravity wave. All these features are embedded in an equatorial Rossby wave, and the MJO overall. The 1.3 km inner-grid of the WRF model, nested in a 4 km-grid outer-grid spanning the Indian Ocean and the western Maritime Continent region, successfully simulated the timing, location, propagation, and life-cycle of this multiscale convection-wave interaction as verified by TRMM measurements.
Numerical simulation of nonlinear long waves interacting with arrays of emergent cylinders
Zainali, Amir; Weiss, Robert; Irish, Jennifer L; Yang, Yongqian
2016-01-01
We presented numerical simulation of long waves, interacting with arrays of emergent cylinders inside regularly spaced patches, representing discontinues patchy coastal vegetation. We employed the fully nonlinear and weakly dispersive Serre-Green-Naghdi equations (SGN) until the breaking process starts, while we changed the governing equations to nonlinear shallow water equations (NSW) at the vicinity of the breaking-wave peak and during the runup stage. We modeled the cylinders as physical boundaries rather than approximating them as macro-roughness friction. We showed that the cylinders provide protection for the areas behind them. However they might also cause amplification in local water depth in those areas. The presented results are extensively validated against the existing numerical and experimental data. Our results demonstrate the capability and reliability of our model in simulating wave interaction with emergent cylinders.
Numerical Simulations of Magnetoacoustic-Gravity Waves in the Solar Atmosphere
Murawski, K; McLaughlin, J A; Oliver, R
2012-01-01
We investigate the excitation of magnetoacoustic-gravity waves generated from localized pulses in the gas pressure as well as in vertical component of velocity. These pulses are initially launched at the top of the solar photosphere that is permeated by a weak magnetic field. We investigate three different configurations of the background magnetic field lines: horizontal, vertical and oblique to the gravitational force. We numerically model magnetoacoustic-gravity waves by implementing a realistic (VAL-C) model of solar temperature. We solve two-dimensional ideal magnetohydrodynamic equations numerically with the use of the FLASH code to simulate the dynamics of the lower solar atmosphere. The initial pulses result in shocks at higher altitudes. Our numerical simulations reveal that a small-amplitude initial pulse can produce magnetoacoustic-gravity waves, which are later reflected from the transition region due to the large temperature gradient. The atmospheric cavities in the lower solar atmosphere are foun...
A combined ADER-DG and PML approach for simulating wave propagation in unbounded domains
Amler, Thomas
2012-09-19
In this work, we present a numerical approach for simulating wave propagation in unbounded domains which combines discontinuous Galerkin methods with arbitrary high order time integration (ADER-DG) and a stabilized modification of perfectly matched layers (PML). Here, the ADER-DG method is applied to Bérenger’s formulation of PML. The instabilities caused by the original PML formulation are treated by a fractional step method that allows to monitor whether waves are damped in PML region. In grid cells where waves are amplified by the PML, the contribution of damping terms is neglected and auxiliary variables are reset. Results of 2D simulations in acoustic media with constant and discontinuous material parameters are presented to illustrate the performance of the method.
Institute of Scientific and Technical Information of China (English)
吴开腾; 宁建国
2003-01-01
A numerical method is presented that simulates 3D explosive field problems. A code MMIC3D using this method can be used to simulate the propagation and reflected effects of all kinds of rigid boundaries to shock waves produced by an explosive source. These numerical results indicate that the code MMIC3D has the ability in computing cases such as 3D shock waves produced by air explosion, vortex region of the shock wave, the Mach wave, and reflected waves behind rigid boundaries.
Directory of Open Access Journals (Sweden)
Wang Jiang
2014-03-01
Full Text Available When partial discharge occurs in Gas Insulated Switchgear (GIS with insulation defects, Ultrahigh-Frequency (UHF electromagnetic wave up to several MHz and GHz will be exited and propagate inside GIS cavity. This study, based on the propagation theory of electromagnetic waves in coaxial waveguide, performs simulation analysis of the relationship between PD pulse form and the exited UHF electromagnetic wave using Finite-Deferential Time-Domain (FDTD algorithm. First, we study the relationship of partial discharge magnitude and electric field strength of electromagnetic wave. It is found that the changes of partial discharge magnitude have little effect on electric field strength of electromagnetic wave at certain variation rate of PD pulse current. Next, we examine the relationship of variation rate of PD pulse current to electric field strength of electromagnetic wave. It is pointed out that, at a certain partial discharge magnitude, the two are approximately linearly related. Finally, we study the impact of variation rate of PD pulse current on higher mode components. Variation coefficient is used to analyze the proportion of higher mode components in electromagnetic wave. The proportion of higher mode components increases with increasing variation rate of PD pulse current.
NUMERICAL SIMULATION OF SOLITARY WAVE RUN-UP AND OVERTOPPING USING BOUSSINESQ-TYPE MODEL
Institute of Scientific and Technical Information of China (English)
TSUNG Wen-Shuo; HSIAO Shih-Chun; LIN Ting-Chieh
2012-01-01
In this article,the use of a high-order Boussinesq-type model and sets of laboratory experiments in a large scale flume of breaking solitary waves climbing up slopes with two inclinations are presented to study the shoreline behavior of breaking and non-breaking solitary waves on plane slopes.The scale effect on run-up height is briefly discussed.The model simulation capability is well validated against the available laboratory data and present experiments.Then,serial numerical tests are conducted to study the shoreline motion correlated with the effects of beach slope and wave nonlinearity for breaking and non-breaking waves.The empirical formula proposed by Hsiao et al.for predicting the maximum run-up height of a breaking solitary wave on plane slopes with a wide range of slope inclinations is confirmed to be cautious.Furthermore,solitary waves impacting and overtopping an impermeable sloping seawall at various water depths are investigated.Laboratory data of run-up height,shoreline motion,free surface elevation and overtopping discharge are presented.Comparisons of run-up,run-down,shoreline trajectory and wave overtopping discharge are made.A fairly good agreement is seen between numerical results and experimental data.It elucidates that the present depth-integrated model can be used as an efficient tool for predicting a wide spectrum of coastal problems.
Multiple-mode Lamb wave scattering simulations using 3D elastodynamic finite integration technique.
Leckey, Cara A C; Rogge, Matthew D; Miller, Corey A; Hinders, Mark K
2012-02-01
We have implemented three-dimensional (3D) elastodynamic finite integration technique (EFIT) simulations to model Lamb wave scattering for two flaw-types in an aircraft-grade aluminum plate, a rounded rectangle flat-bottom hole and a disbond of the same shape. The plate thickness and flaws explored in this work include frequency-thickness regions where several Lamb wave modes exist and sometimes overlap in phase and/or group velocity. For the case of the flat-bottom hole the depth was incrementally increased to explore progressive changes in multiple-mode Lamb wave scattering due to the damage. The flat-bottom hole simulation results have been compared to experimental data and are shown to provide key insight for this well-defined experimental case by explaining unexpected results in experimental waveforms. For the rounded rectangle disbond flaw, which would be difficult to implement experimentally, we found that Lamb wave behavior differed significantly from the flat-bottom hole flaw. Most of the literature in this field is restricted to low frequency-thickness regions due to difficulties in interpreting data when multiple modes exist. We found that benchmarked 3D EFIT simulations can yield an understanding of scattering behavior for these higher frequency-thickness regions and in cases that would be difficult to set up experimentally. Additionally, our results show that 2D simulations would not have been sufficient for modeling the complicated scattering that occurred.
Numerical simulation of wave-induced scour and backfilling processes beneath submarine pipelines
DEFF Research Database (Denmark)
Fuhrman, David R.; Baykal, Cüneyt; Sumer, B. Mutlu
2014-01-01
A fully-coupled hydrodynamic/morphodynamic numerical model is presented and utilized for the simulation of wave-induced scour and backfilling processes beneath submarine pipelines. The model is based on solutions to Reynolds-averaged Navier–Stokes equations, coupled with k−ω turbulence closure...
Numerical simulation of terrain-induced vortex/wave shedding at the Hong Kong International Airport
Energy Technology Data Exchange (ETDEWEB)
Li, Lei; Zhang, Li-Jie; Mao, Hui [Shenzhen National Climate Observatory, Meteorological Bureau of Shenzhen Municipality (China); Chan, P.W. [Hong Kong Observatory (China)
2013-10-15
The present study aims at simulating the shedding of vortex/wave from a mountain nearby the Hong Kong International Airport using a computational fluid dynamics model by employing high resolution terrain data without smoothing. The successful simulation of this shedding would have an important application in the short-term forecasting of the chance of occurrence of terrain-induced windshear at an operating airport. Two typical cases of vortex/wave shedding are considered, namely, in neutral atmosphere associated with the passage of a typhoon, and in stably stratified atmosphere in spring-time easterly flow with continental origin. The model is found to successfully capture the salient features of the shedding. The simulated radial velocity fields of weather radar/LIDAR compare well with actual observations. In particular, the creation and the propagation of the vortex/wave through shedding from a mountain nearby the airport are captured well in the model simulation. The shedding periods are also reproduced. From the limited number of cases studied in this paper, it appears that the model has the capability of forecasting the occurrence of vortex/wave shedding by coupling with a mesoscale meteorological model. (orig.)
Numerical simulation of terrain-induced vortex/wave shedding at the Hong Kong International Airport
Directory of Open Access Journals (Sweden)
Li Lei
2013-07-01
Full Text Available The present study aims at simulating the shedding of vortex/wave from a mountain nearby the Hong Kong International Airport using a computational fluid dynamics model by employing high resolution terrain data without smoothing. The successful simulation of this shedding would have an important application in the short-term forecasting of the chance of occurrence of terrain-induced windshear at an operating airport. Two typical cases of vortex/wave shedding are considered, namely, in neutral atmosphere associated with the passage of a typhoon, and in stably stratified atmosphere in spring-time easterly flow with continental origin. The model is found to successfully capture the salient features of the shedding. The simulated radial velocity fields of weather radar/LIDAR compare well with actual observations. In particular, the creation and the propagation of the vortex/wave through shedding from a mountain nearby the airport are captured well in the model simulation. The shedding periods are also reproduced. From the limited number of cases studied in this paper, it appears that the model has the capability of forecasting the occurrence of vortex/wave shedding by coupling with a mesoscale meteorological model.
Nagatani, Yoshiki; Imaizumi, Hirotaka; Fukuda, Takashi; Matsukawa, Mami; Watanabe, Yoshiaki; Otani, Takahiko
2006-09-01
In cancellous bone, longitudinal waves often separate into fast and slow waves depending on the alignment of bone trabeculae. This interesting phenomenon becomes an effective tool for the diagnosis of osteoporosis because wave propagation behavior depends on the bone structure. We have, therefore, simulated wave propagation in such a complex medium by the finite-difference time-domain (FDTD) method, using a three-dimensional X-ray computer tomography (CT) model of an actual cancellous bone. In this simulation, experimentally observed acoustic constants of the cortical bone were adopted. As a result, the generation of fast and slow waves was confirmed. The speed of fast waves and the amplitude of slow waves showed good correlations with the bone volume fraction. The simulated results were also compared with the experimental results obtained from the identical cancellous bone.
Sayago, Isabel; Matatagui, Daniel; Fernández, María Jesús; Fontecha, José Luis; Jurewicz, Izabela; Garriga, Rosa; Muñoz, Edgar
2016-02-01
A Love-wave device with graphene oxide (GO) as sensitive layer has been developed for the detection of chemical warfare agent (CWA) simulants. Sensitive films were fabricated by airbrushing GO dispersions onto Love-wave devices. The resulting Love-wave sensors detected very low CWA simulant concentrations in synthetic air at room temperature (as low as 0.2 ppm for dimethyl-methylphosphonate, DMMP, a simulant of sarin nerve gas, and 0.75 ppm for dipropylene glycol monomethyl ether, DPGME, a simulant of nitrogen mustard). High responses to DMMP and DPGME were obtained with sensitivities of 3087 and 760 Hz/ppm respectively. Very low limit of detection (LOD) values (9 and 40 ppb for DMMP and DPGME, respectively) were calculated from the achieved experimental data. The sensor exhibited outstanding sensitivity, good linearity and repeatability to all simulants tested. The detection mechanism is here explained in terms of hydrogen bonding formation between the tested CWA simulants and GO.
Institute of Scientific and Technical Information of China (English)
GEBBEKEN Norbert
2006-01-01
The identification of the critical infrastructure has shown that the build civil engineering infrastructure is almost involved everywhere,even with the IT-infrastructure.Therefore,the passive safety of structures is demanded.Security associations have analysed that most assaults came along with explosion and impact scenarios,which amount in 80% of assaults.Consequently,these are the extraordinary loads the structures have to be planned and designed for.To carry out such an engineering job,the engineer has to be educated in multiple disciplines as physics,material science,continuum mechanics,numerical mechanics,testing,structural engineering and related specific fields as wave propagation etc.In this paper we will concentrate on the subjects of numerical simulation and testing.
Energy Technology Data Exchange (ETDEWEB)
Tsujii, N., E-mail: tsujii@k.u-tokyo.ac.jp [The University of Tokyo, Kashiwa (Japan); Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts (United States); Jaeger, E. F. [XCEL Engineering, Oak Ridge, Tennessee (United States); Green, D. L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States); Harvey, R. W. [CompX, Del Mar, California (United States)
2015-12-10
Waves in the ion cyclotron range of frequencies (ICRF) are one of the major tools to heat fusion plasmas. Full-wave simulations are essential to predict the wave propagation and absorption quantitatively, and it is important that these codes be validated against actual experimental measurements. In this work, the absolute intensity of the ICRF waves previously measured with a phase contrast imaging diagnostic was recalibrated and compared once more with full-wave predictions. In the earlier work, significant discrepancies were found between the measured and the simulated mode converted wave intensity [N. Tsujii et al., Phys. Plasmas 19, 082508]. With the new calibration of the detector array, the measured mode converted wave intensity is now in much better agreement with the full-wave predictions. The agreement is especially good for comparisons performed close to the antenna.
Investigation of cavitation as a possible damage mechanism in blast-induced traumatic brain injury.
Goeller, Jacques; Wardlaw, Andrew; Treichler, Derrick; O'Bruba, Joseph; Weiss, Greg
2012-07-01
Cavitation was investigated as a possible damage mechanism for war-related traumatic brain injury (TBI) due to an improvised explosive device (IED) blast. When a frontal blast wave encounters the head, a shock wave is transmitted through the skull, cerebrospinal fluid (CSF), and tissue, causing negative pressure at the contrecoup that may result in cavitation. Numerical simulations and shock tube experiments were conducted to determine the possibility of cranial cavitation from realistic IED non-impact blast loading. Simplified surrogate models of the head consisted of a transparent polycarbonate ellipsoid. The first series of tests in the 18-inch-diameter shock tube were conducted on an ellipsoid filled with degassed water to simulate CSF and tissue. In the second series, Sylgard gel, surrounded by a layer of degassed water, was used to represent the tissue and CSF, respectively. Simulated blast overpressure in the shock tube tests ranged from a nominal 10-25 pounds per square inch gauge (psig; 69-170 kPa). Pressure in the simulated CSF was determined by Kulite thin line pressure sensors at the coup, center, and contrecoup positions. Using video taken at 10,000 frames/sec, we verified the presence of cavitation bubbles at the contrecoup in both ellipsoid models. In all tests, cavitation at the contrecoup was observed to coincide temporally with periods of negative pressure. Collapse of the cavitation bubbles caused by the surrounding pressure and elastic rebound of the skull resulted in significant pressure spikes in the simulated CSF. Numerical simulations using the DYSMAS hydrocode to predict onset of cavitation and pressure spikes during cavity collapse were in good agreement with the tests. The numerical simulations and experiments indicate that skull deformation is a significant factor causing cavitation. These results suggest that cavitation may be a damage mechanism contributing to TBI that requires future study.
Camporeale, Enrico; Zimbardo, G.
2015-01-01
We present a self-consistent Particle-in-Cell simulation of the resonant interactions between anisotropic energetic electrons and a population of whistler waves, with parameters relevant to the Earths radiation belt. By tracking PIC particles, and comparing with test-particle simulations we emphasize the importance of including nonlinear effects and time evolution in the modeling of wave-particle interactions, which are excluded in the resonant limit of quasi- linear theory routinely used in ...
Energy Technology Data Exchange (ETDEWEB)
Beels, Charlotte; Troch, Peter; De Visch, Kenneth; De Backer, Griet [Ghent University, Department of Civil Engineering, Technologiepark 904, B-9052 Zwijnaarde (Belgium); Kofoed, Jens Peter [Aalborg University, Department of Civil Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg (Denmark)
2010-08-15
Time-dependent mild-slope equations have been extensively used to compute wave transformations near coastal and offshore structures for more than 20 years. Recently the wave absorption characteristics of a Wave Energy Converter (abbreviated as WEC) of the overtopping type have been implemented in a time-dependent mild-slope equation model by using numerical sponge layers. In this paper the developed WEC implementation is applied to a single Wave Dragon WEC and multiple Wave Dragon WECs. The Wave Dragon WEC is a floating offshore converter of the overtopping type. Two wave reflectors focus the incident wave power towards a ramp. The focussed waves run up the ramp and overtop in a water reservoir above mean sea level. The obtained potential energy is converted into electricity when the stored water drains back to the sea through hydro turbines. The wave reflectors and the main body (ramp and reservoir) are simulated as porous structures, exhibiting the same reflection, respectively absorption characteristics as obtained for the prototype Wave Dragon WEC. The wake effects behind a single Wave Dragon WEC are studied in detail for uni- and multidirectional waves. The shadow zone indicating the wake effect is decreasing with increasing directional spreading. The wake in the lee of a farm of five Wave Dragon WECs, installed in a staggered grid (3 WECs in the first row and 2 WECs in the second row), is calculated for three in-between distances of respectively D, 2D and 3D, with D the distance between the tips of the wave reflectors of a single WEC. As a result, a farm of five Wave Dragon WECs installed in a staggered grid with an in-between distance of 2D is preferred, when taking cost and spatial considerations into account. (author)
Note: A table-top blast driven shock tube.
Courtney, Michael W; Courtney, Amy C
2010-12-01
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 design is simple: it is an explosive driven shock tube employing a rifle primer that explodes when impacted by the firing pin. The firearm barrel acts as the shock tube, and the shock wave emerges from the muzzle. The small size of this shock tube can facilitate localized application of a blast wave to a subject, tissue, or material under test.
A Table-top Blast Driven Shock Tube
Courtney, Michael; 10.1063/1.3518970
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 design is simple: it is an explosive driven shock tube employing a rifle primer which explodes when impacted by the firing pin. The firearm barrel acts as the shock tube, and the shock wave emerges from the muzzle. The small size of this shock tube can facilitate localized application of a blast wave to a subject, tissue, or material under test.
Source model for blasting vibration
Institute of Scientific and Technical Information of China (English)
DING; Hua(丁桦); ZHENG; Zhemin(郑哲敏)
2002-01-01
By analyzing and comparing the experimental data, the point source moment theory and the cavity theory, it is concluded that the vibrating signals away from the blasting explosive come mainly from the natural vibrations of the geological structures near the broken blasting area. The source impulses are not spread mainly by the inelastic properties (such as through media damping, as believed to be the case by many researchers) of the medium in the propagation pass, but by this structure. Then an equivalent source model for the blasting vibrations of a fragmenting blasting is proposed, which shows the important role of the impulse of the source's time function under certain conditions. For the purpose of numerical simulation, the model is realized in FEM, The finite element results are in good agreement with the experimental data.
Alari, Victor; Staneva, Joanna; Breivik, Øyvind; Bidlot, Jean-Raymond; Mogensen, Kristian; Janssen, Peter
2016-08-01
Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling's. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.
Energy Technology Data Exchange (ETDEWEB)
Brunner, S. [Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne, Lausanne, (Switzerland); Berger, R. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Cohen, B. I. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hausammann, L. [Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Ecole Polytechnique Fédérale de Lausanne, Lausanne, (Switzerland); Valeo, E. J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
2014-10-01
Kinetic Vlasov simulations of one-dimensional finite amplitude Electron Plasma Waves are performed in a multi-wavelength long system. A systematic study of the most unstable linear sideband mode, in particular its growth rate γ and quasi- wavenumber δk, is carried out by scanning the amplitude and wavenumber of the initial wave. Simulation results are successfully compared against numerical and analytical solutions to the reduced model by Kruer et al. [Phys. Rev. Lett. 23, 838 (1969)] for the Trapped Particle Instability (TPI). A model recently suggested by Dodin et al. [Phys. Rev. Lett. 110, 215006 (2013)], which in addition to the TPI accounts for the so-called Negative Mass Instability because of a more detailed representation of the trapped particle dynamics, is also studied and compared with simulations.
2016-06-12
liquid surface tension (Gamma), Capvol and Angles are associated with capillary forces. The parameters that define the behavior of wet material can be...effect of liquid surface tension , liquid bridge volume were analyzed. Effect of friction, and damping UNCLASSIFIED: Distribution Statement A...Occupant Injury during Under- Body Blast Events,” SAE Int. J. Trans. Safety 2(2), 2014, doi:10.4271/2014-01-0752, DTIC Report # ADA 599846. 11. Kulkarni
Aero-hydro-elastic simulation platform for wave energy systems and floating wind turbines
Energy Technology Data Exchange (ETDEWEB)
Kallesoee, B.S.
2011-01-15
This report present results from the PSO project 2008-1-10092 entitled Aero-Hydro-Elastic Simulation Platform for Wave Energy Systems and floating Wind Turbines that deals with measurements, modelling and simulations of the world's first combined wave and wind energy platform. The floating energy conversion platform, Poseidon, is owned and operated by Floating Power Plant A/S. The platform has been operating for two test periods; one period where it was operating as a wave energy conversion platform only and one period where the three turbines was mounted and the platform operated as a combined wind and wave energy platform. The PSO project has equipped the platform with comprehensive measurements equipment for measuring platform motion, wave and wind conditions and turbine loads. Data from the first test period has been used for determine if the turbine could be mounted on the platform. Preliminary analysis of data from the second test period indicates that the platform is suitable as wind turbine foundation and that the turbines reduce the platform motion. (Author)
Study on 3D simulation of wave fields in acoustic reflection image logging
Institute of Scientific and Technical Information of China (English)
2008-01-01
The borehole acoustic reflection imaging logging is a newly developed acoustic logging method that has attracted many interests. These converted and reflected waves for imaging are usually mixed up with borehole guided waves and therefore difficult to be clearly identified. To improve the downhole tool design and develop more sophisticate data processing and interpretation algorithms,studies on precisely numerical modeling of the wave fields in the acoustic reflection imaging logging are neces-sary and critical. This paper developed a parallelized scheme of 3D finite difference (3DFD) with non-uniform staggered grid and PML absorbing boundary to simulate the acoustic wave fields in isotropic and anisotropic formations. Applications of this scheme to the typical cases of isotropic and anisot-ropic formations and comparison with the results from published analytical solutions have demon-strated the validation and efficiency of the scheme. Higher accuracy and lower computation cost (3.5 times faster than the conventional schemes) have been achieved with this scheme for modeling such a complex wave fields of 60 dB dynamic range with higher frequency (10 kHz). This simulating program provides a quantitative analytical means for studying acoustic reflection imaging tool and development of the data processing and interpretation methods.
A CIP-Based Numerical Simulation of Free Surface Flow Related to Freak Waves
Institute of Scientific and Technical Information of China (English)
赵西增
2013-01-01
An enhanced numerical model for simulating two-dimensional incompressible viscous flow with distorted free surface is reported. The numerical simulation is carried out through the CIP (Constrained Interpolation Profile)-based method, which is described in the paper. A more accurate interface capturing scheme, the VOF/WLIC scheme (VOF:Volume-of-Fluid;WLIC:weighed line interface calculation), is adopted as the interface capturing method. To assess the developed algorithm and its versatility, a selection of test problems are examined, i.e. the square wave propagation, the Zalesak’s rigid body rotation, dam breaking problem with and without obstacles, wave sloshing in an excited wave tank and interaction between extreme waves and a floating body. Excellent agreements are obtained when numerical results are compared with available analytical, experimental, and other numerical results. These examples demonstrate that the use of the VOF/WLIC scheme in the free surface capturing makes better results and also the proposed CIP-based model is capable of predicting the freak wave-related phenomena.
Winjum, B. J.; Banks, J. W.; Berger, R. L.; Cohen, B. I.; Chapman, T.; Hittinger, J. A. F.; Rozmus, W.; Strozzi, D. J.; Brunner, S.
2012-10-01
We present results on the kinetic filamentation of finite-width nonlinear electron plasma waves (EPW). Using 2D simulations with the PIC code BEPS, we excite a traveling EPW with a Gaussian transverse profile and a wavenumber k0λDe= 1/3. The transverse wavenumber spectrum broadens during transverse EPW localization for small width (but sufficiently large amplitude) waves, while the spectrum narrows to a dominant k as the initial EPW width increases to the plane-wave limit. For large EPW widths, filaments can grow and destroy the wave coherence before transverse localization destroys the wave; the filaments in turn evolve individually as self-focusing EPWs. Additionally, a transverse electric field develops that affects trapped electrons, and a beam-like distribution of untrapped electrons develops between filaments and on the sides of a localizing EPW. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the Laboratory Research and Development Program at LLNL under project tracking code 12-ERD-061. Supported also under Grants DE-FG52-09NA29552 and NSF-Phy-0904039. Simulations were performed on UCLA's Hoffman2 and NERSC's Hopper.
Numerical simulation of wave propagation and snow failure from explosive loading
Sidler, Rolf; Dual, Jürg; Schweizer, Jürg
2016-01-01
Avalanche control by explosion is a widely applied method to minimize the avalanche risk to infrastructure in snow-covered mountain areas. However, the mechanisms involved leading from an explosion to the release of an avalanche are not well understood. Here we test the hypothesis that weak layers fail due to the stress caused by propagating acoustic waves. The underlying mechanism is that the stress induced by the acoustic waves exceeds the strength of the snow layers. We compare field measurements to a numerical simulation of acoustic wave propagation in a porous material. The simulation consists of an acoustic domain for the air above the snowpack and a poroelastic domain for the dry snowpack. The two domains are connected by a wave field decomposition and open pore boundary conditions. Empirical relations are used to derive a porous model of the snowpack from density profiles of the field experiment. Biot's equations are solved in the poroelastic domain to obtain simulated accelerations in the snowpack an...
The impact of atmospheric data assimilation on wave simulations in the Red Sea
Langodan, Sabique
2016-03-11
Although wind and wave modeling is rather successful in the open ocean, modeling enclosed seas, particularly seas with small basins and complex orography, presents challenges. Here, we use data assimilation to improve wind and wave simulations in the Red Sea. We generated two sets of wind fields using a nested, high-resolution Weather Research and Forecasting model implemented with (VARFC) and without (CTL) assimilation of observations. Available conventional and satellite data were assimilated using the consecutive integration method with daily initializations over one year (2009). By evaluating the two wind products against in-situ data from synoptic stations, buoys, scatterometers, and altimeters, we found that seasonal patterns of wind and wave variability were well reproduced in both experiments. Statistical scores for simulated winds computed against QuikSCAT, buoy, and synoptic station observations suggest that data assimilation decreases the root-mean-square error to values between 1 and 2 m s-1 and reduces the scatter index by 30% compared to the CTL. Sensitivity clearly increased around mountain gaps, where the channeling effect is better described by VARFC winds. The impact of data assimilation is more pronounced in wave simulations, particularly during extreme winds and in the presence of mountain jets. © 2016 Elsevier Ltd. All rights reserved.
On theory and simulation of heaving-buoy wave-energy converters with control
Energy Technology Data Exchange (ETDEWEB)
Eidsmoen, H.
1995-12-01
Heaving-buoy wave-energy converters with control were studied. The buoy is small compared to the wavelength. The resonance bandwidth is then narrow and the energy conversion in irregular waves can be significantly increased if the oscillatory motion of the device can be actively controlled, and the power output from the converter will vary less with time than the wave power transport. A system of two concentric cylinders of the same radius, oscillating in heave only, is analysed in the frequency-domain. The mathematical model can be used to study a tight-moored buoy, as well as a buoy reacting against a submerged body. The knowledge of the frequency-domain hydrodynamic parameters is used to develop frequency-domain and time-domain mathematical models of heaving-buoy wave energy converters. The main emphasis is on using control to maximize the energy production and to protect the machinery of the wave-energy converter in very large waves. Three different methods are used to study control. (1) In the frequency-domain explicit analytical expressions for the optimum oscillation are found, assuming a continuous sinusoidal control force, and from these expressions the optimum time-domain oscillation can be determined. (2) The second method uses optimal control theory, using a control variable as the instrument for the optimisation. Unlike the first method, this method can include non-linearities. But this method gives numerical time series for the state variables and the control variable rather than analytical expressions for the optimum oscillation. (3) The third method is time-domain simulation. Non-linear forces are included, but the method only gives the response of the system to a given incident wave. How the different methods can be used to develop real-time control is discussed. Simulations are performed for a tight-moored heaving-buoy converter with a high-pressure hydraulic system for energy production and motion control. 147 refs., 38 figs., 22 tabs.
Institute of Scientific and Technical Information of China (English)
REN Lin; MAO Zhihua; HUANG Haiqing; GONG Fang
2010-01-01
Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence. Both them have their own advantages and limitations. Scientists hope that SAR and satellite-based RAR can complement each other for the research on wave properties in the future. For this study, the authors aim to simulate the satellite-based RAR system to validate performance for measuring the directional wave spectrum. The principal measurements are introduced and the simulation methods based on the one developed by Hauser are adopted and slightly modified. To enhance the authenticity of input spectrum and the wave spectrum measuring consistency for SAR and satellite-based RAR, the wave height spectrum inversed from Envisat ASAR data by cross spectrum technology is used as the input spectrum of the simulation system. In the process of simulation, the sea surface, backscattering signal, modulation spectrum and the estimated wave height spectrum are simulated in each look direction. Directional wave spectrum are measured based on the simulated observations from 0° to 360~. From the estimated wave spectrum, it has an 180° ambiguity like SAR, but it has no special high wave number cut off in all the direction. Finally, the estimated spectrum is compared with the input one in terms of the dominant wave wavelength, direction and SWH and the results are promising. The simulation shows that satellite-based RAR should be capable of measuring the directional wave properties. Moreover, it indicates satellite-based RAR basically can measure waves that SAR can measure.
Characterizing the propagation of gravity waves in 3D nonlinear simulations of solar-like stars
Alvan, L; Brun, A S; Mathis, S; Garcia, R A
2015-01-01
The revolution of helio- and asteroseismology provides access to the detailed properties of stellar interiors by studying the star's oscillation modes. Among them, gravity (g) modes are formed by constructive interferences between progressive internal gravity waves (IGWs), propagating in stellar radiative zones. Our new 3D nonlinear simulations of the interior of a solar-like star allows us to study the excitation, propagation, and dissipation of these waves. The aim of this article is to clarify our understanding of the behavior of IGWs in a 3D radiative zone and to provide a clear overview of their properties. We use a method of frequency filtering that reveals the path of {individual} gravity waves of different frequencies in the radiative zone. We are able to identify the region of propagation of different waves in 2D and 3D, to compare them to the linear raytracing theory and to distinguish between propagative and standing waves (g modes). We also show that the energy carried by waves is distributed in d...
Dagrau, Franck; Rénier, Mathieu; Marchiano, Régis; Coulouvrat, François
2011-07-01
Numerical simulation of nonlinear acoustics and shock waves in a weakly heterogeneous and lossless medium is considered. The wave equation is formulated so as to separate homogeneous diffraction, heterogeneous effects, and nonlinearities. A numerical method called heterogeneous one-way approximation for resolution of diffraction (HOWARD) is developed, that solves the homogeneous part of the equation in the spectral domain (both in time and space) through a one-way approximation neglecting backscattering. A second-order parabolic approximation is performed but only on the small, heterogeneous part. So the resulting equation is more precise than the usual standard or wide-angle parabolic approximation. It has the same dispersion equation as the exact wave equation for all forward propagating waves, including evanescent waves. Finally, nonlinear terms are treated through an analytical, shock-fitting method. Several validation tests are performed through comparisons with analytical solutions in the linear case and outputs of the standard or wide-angle parabolic approximation in the nonlinear case. Numerical convergence tests and physical analysis are finally performed in the fully heterogeneous and nonlinear case of shock wave focusing through an acoustical lens.
Energy Technology Data Exchange (ETDEWEB)
Ruban, V. P., E-mail: ruban@itp.ac.ru [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation)
2015-05-15
The nonlinear dynamics of an obliquely oriented wave packet on a sea surface is analyzed analytically and numerically for various initial parameters of the packet in relation to the problem of the so-called rogue waves. Within the Gaussian variational ansatz applied to the corresponding (1+2)-dimensional hyperbolic nonlinear Schrödinger equation (NLSE), a simplified Lagrangian system of differential equations is derived that describes the evolution of the coefficients of the real and imaginary quadratic forms appearing in the Gaussian. This model provides a semi-quantitative description of the process of nonlinear spatiotemporal focusing, which is one of the most probable mechanisms of rogue wave formation in random wave fields. The system of equations is integrated in quadratures, which allows one to better understand the qualitative differences between linear and nonlinear focusing regimes of a wave packet. Predictions of the Gaussian model are compared with the results of direct numerical simulation of fully nonlinear long-crested waves.
Direct Simulations of Wind-Driven Breaking Ocean Waves with Data Assimilation
Dommermuth, Douglas G; Tran, Vu H; Valenciano, Miguel A
2014-01-01
A formulation is developed to assimilate ocean-wave data into the Numerical Flow Analysis (NFA) code. NFA is a Cartesian-based implicit Large-Eddy Simulation (LES) code with Volume of Fluid (VOF) interface capturing. The sequential assimilation of data into NFA permits detailed analysis of ocean-wave physics with higher bandwidths than is possible using either other formulations, such as High-Order Spectral (HOS) methods, or field measurements. A framework is provided for assimilating the wavy and vortical portions of the flow. Nudging is used to assimilate wave data at low wavenumbers, and the wave data at high wavenumbers form naturally through nonlinear interactions, wave breaking, and wind forcing. Similarly, the vertical profiles of the mean vortical flow in the wind and the wind drift are nudged, and the turbulent fluctuations are allowed to form naturally. As a demonstration, the results of a HOS of a JONSWAP wave spectrum are assimilated to study short-crested seas in equilibrium with the wind. Log pr...
Parchevsky, K; Khomenko, E; Olshevsky, V; Collados, M
2010-01-01
We present comparison of numerical simulations of propagation of MHD waves,excited by subphotospheric perturbations, in two different ("deep" and "shallow") magnetostatic models of the sunspots. The "deep" sunspot model distorts both the shape of the wavefront and its amplitude stronger than the "shallow" model. For both sunspot models, the surface gravity waves (f-mode) are affected by the sunspots stronger than the acoustic p-modes. The wave amplitude inside the sunspot depends on the photospheric strength of the magnetic field and the distance of the source from the sunspot axis. For the source located at 9 Mm from the center of the sunspot, the wave amplitude increases when the wavefront passes through the central part of the sunspot. For the source distance of 12 Mm, the wave amplitude inside the sunspot is always smaller than outside. For the same source distance from the sunspot center but for the models with different strength of the magnetic field, the wave amplitude inside the sunspot increases with...
Magneto-acoustic waves in sunspots from observations and numerical simulations
Felipe, T; Collados, M; Beck, C
2010-01-01
We study the propagation of waves from the photosphere to the chromosphere of sunspots. From time series of cospatial Ca II H (including its line blends) intensity spectra and polarimetric spectra of Si I 1082.7 nm and He I 1083.0 nm we retrieve the line-of-sight velocity at several heights. The analysis of the phase difference and amplification spectra shows standing waves for frequencies below 4 mHz and propagating waves for higher frequencies, and allows us to infer the temperature and height where the lines are formed. Using these observational data, we have constructed a model of sunspot, and we have introduced the velocity measured with the photospheric Si I 1082.7 nm line as a driver. The numerically propagated wave pattern fits reasonably well with the observed using the lines formed at higher layers, and the simulations reproduce many of the observed features. The observed waves are slow MHD waves propagating longitudinally along field lines.
Energy Technology Data Exchange (ETDEWEB)
Moll, J; Schulte, R T; Fritzen, C-P [Institute of Mechanics and Control Engineering - Mechatronics, University of Siegen (Germany); Rezk-Salama, C [Mediadesign University of Applied Science Duesseldorf (Germany); Klinkert, T; Kolb, A, E-mail: moll@imr.mb.uni-siegen.de [Computer Graphics and Multimedia Systems, University of Siegen (Germany)
2011-07-19
Structural health monitoring systems allow a continuous surveillance of the structural integrity of operational systems. As a result, it is possible to reduce time and costs for maintenance without decreasing the level of safety. In this paper, an integrated simulation and visualization environment is presented that enables a detailed study of Lamb wave propagation in isotropic and anisotropic materials. Thus, valuable information about the nature of Lamb wave propagation and its interaction with structural defects become available. The well-known spectral finite element method is implemented to enable a time-efficient calculation of the wave propagation problem. The results are displayed in an interactive visualization framework accounting for the human perception that is much more sensitive to motion than to changes in color. In addition, measurements have been conducted experimentally to record the full out-of-plane wave-field using a Laser-Doppler vibrometry setup. An aluminum structure with two synthetic cuts has been investigated, where the elongated defects have a different orientation with respect to the piezoelectric actuator. The resulting wave-field is also displayed interactively showing that the scattered wave-field at the defect is highly directional.
Kinetic Simulation of Slow Magnetosonic Waves and Quasi-periodic Upflows in the Solar Corona
Ruan, Wenzhi; Zhang, Lei; Vocks, Christian; Marsch, Eckart; Tu, Chuanyi; Peter, Hardi; Wang, Linghua
2016-01-01
Quasi-periodic disturbances of emission-line parameters are frequently observed in the corona. These disturbances propagate upward along the magnetic field with speeds $\\sim100~\\rm{km~s}^{-1}$. This phenomenon has been interpreted as evidence of the propagation of slow magnetosonic waves or argued to be signature of the intermittent outflows superposed on the background plasmas. Here we aim to present a new "wave + flow" model to interpret these observations. In our scenario, the oscillatory motion is a slow mode wave, and the flow is associated with a beam created by the wave-particle interaction owing to Landau resonance. With the help of a Vlasov model, we simulate the propagation of the slow mode wave and the generation of the beam flow. We find that weak periodic beam flows can be generated owing to Landau resonance in the solar corona, and the phase with strongest blueward asymmetry is ahead of that with strongest blueshift by about 1/4 period. We also find that the slow wave damps to the level of 1/e a...
Validation of input-noise model for simulations of supercontinuum generation and rogue waves
DEFF Research Database (Denmark)
Frosz, Michael Henoch
2010-01-01
A new model of pump noise in supercontinuum and rogue wave generation is presented. Simulations are compared with experiments and show that the new model provides significantly better agreement than the currently ubiquitously used one-photon-per-mode model. The new model also allows for a study...... of the influence of the pump spectral line width on the spectral broadening mechanisms. Specifically, it is found that for four-wave mixing (FWM) a narrow spectral line width ( 0.1 nm) initially leads to a build-up of FWM from quantum noise, whereas a broad spectral line width ( 1 nm) initially leads to a gradual...
Three dimensional full-wave nonlinear acoustic simulations: Applications to ultrasound imaging
Energy Technology Data Exchange (ETDEWEB)
Pinton, Gianmarco [Joint Department of Biomedical Engineering, University of North Carolina - North Carolina State University, 348 Taylor Hall, Chapel Hill, NC 27599, USA gfp@unc.edu (United States)
2015-10-28
Characterization of acoustic waves that propagate nonlinearly in an inhomogeneous medium has significant applications to diagnostic and therapeutic ultrasound. The generation of an ultrasound image of human tissue is based on the complex physics of acoustic wave propagation: diffraction, reflection, scattering, frequency dependent attenuation, and nonlinearity. The nonlinearity of wave propagation is used to the advantage of diagnostic scanners that use the harmonic components of the ultrasonic signal to improve the resolution and penetration of clinical scanners. One approach to simulating ultrasound images is to make approximations that can reduce the physics to systems that have a low computational cost. Here a maximalist approach is taken and the full three dimensional wave physics is simulated with finite differences. This paper demonstrates how finite difference simulations for the nonlinear acoustic wave equation can be used to generate physically realistic two and three dimensional ultrasound images anywhere in the body. A specific intercostal liver imaging scenario for two cases: with the ribs in place, and with the ribs removed. This configuration provides an imaging scenario that cannot be performed in vivo but that can test the influence of the ribs on image quality. Several imaging properties are studied, in particular the beamplots, the spatial coherence at the transducer surface, the distributed phase aberration, and the lesion detectability for imaging at the fundamental and harmonic frequencies. The results indicate, counterintuitively, that at the fundamental frequency the beamplot improves due to the apodization effect of the ribs but at the same time there is more degradation from reverberation clutter. At the harmonic frequency there is significantly less improvement in the beamplot and also significantly less degradation from reverberation. It is shown that even though simulating the full propagation physics is computationally challenging it
Laboratory investigation and direct numerical simulation of wind effect on steep surface waves
Troitskaya, Yuliya; Sergeev, Daniil; Druzhinin, Oleg; Ermakova, Olga
2015-04-01
particles 20 μm in diameter were injected into the airflow. The images of the illuminated particles were photographed with a digital CCD video camera at a rate of 1000 frames per second. For the each given parameters of wind and waves, a statistical ensemble of 30 movies with duration from 200 to 600 ms was obtained. Individual flow realizations manifested the typical features of flow separation, while the average vector velocity fields obtained by the phase averaging of the individual vector fields were smooth and slightly asymmetrical, with the minimum of the horizontal velocity near the water surface shifted to the leeward side of the wave profile, but do not demonstrate the features of flow separation. The wave-induced pressure perturbations, averaged over the turbulent fluctuations, were retrieved from the measured velocity fields, using the Reynolds equations. It ensures sufficient accuracy for study of the dependence of the wave increment on the wave amplitude. The dependences of the wave growth rate on the wave steepness are weakly decreasing, serving as indirect proof of the non-separated character of flow over waves. Also direct numerical simulation of the airflow over finite amplitude periodic surface wave was performed. In the experiments the primitive 3-dimensional fluid mechanics equations were solved in the airflow over curved water boundary for the following parameters: the Reynolds number Re=15000, the wave steepness ka=0-0.2, the parameter c/u*=0-10 (where u* is the friction velocity and c is the wave celerity). Similar to the physical experiment the instant realizations of the velocity field demonstrate flow separation at the crests of the waves, but the ensemble averaged velocity fields had typical structures similar to those excising in shear flows near critical levels, where the phase velocity of the disturbance coincides with the flow velocity. The wind growth rate determined by the ensemble averaged wave-induced pressure component in phase of the
Experimental study of blast mitigating devices based on combined construction
Takayama, K.; Silnikov, M. V.; Chernyshov, M. V.
2016-09-01
A robust blast inhibiting bin is the most often used device for damage blast effects suppression. In particular, a top open cylindrical bin significantly reduces a fragmentation effect resulted from a detonation of an explosive device placed inside the bin. However, reduction of blast wave overpressure and impulse by such cylindrical bins is not sufficient [1]. A reasonable alternative to endless increase of height and thickness of robust blast inhibiting bins is a development of destructible inhibitors having no solid elements in their structure and, therefore, excluding secondary fragmentation. So, the family of "Fountain" inhibitors [2,3] localizes and suppresses damaging blast effects due to multiphase working system. The present study is analyzing data obtained in testing of prototypes of new combined inhibitors. Their structure combines robust elements (bottoms, side surfaces) with elements responsible for blast loads reduction due to multi-phase working system (top and low transverse embeddings) and fairings impeding wave propagation in undesirable directions.
Babincová, M.; Babincová, N.; Durdík, S.; Bergemann, C.; Sourivong, P.
2016-06-01
A new method is developed for efficient delivery of short interference RNA into cells using combination of magnetophoresis for pre-concentration of siRNA-magnetic nanoparticle complex on the surface of cells with subsequent nanosecond laser pulse generating stress waves in transfection chamber, which is able to permeabilize cell membrane for the facilitated delivery of siRNA into the cell interior. As has been shown using siRNA inducing cell apoptosis, combination of these two physical factors increased the efficiency of three different human carcinoma cells transfection to 93%, 89%, and 84%, for HeLa (cervical carcinoma), MCF-7 (breast carcinoma), and UCI-107 (ovarian carcinoma) cells, respectively. This new physical method of siRNA delivery may have therefore far reaching applications in biotechnology and functional genomics.
Energy Technology Data Exchange (ETDEWEB)
Russell, C. T. [University of California, Los Angeles, CA 90095-1567 (United States); Mewaldt, R. A.; Cohen, C. M. S.; Leske, R. A. [California Institute of Technology, Pasadena, CA 91125 (United States); Luhmann, J. G. [University of California, Berkeley, CA 94720 (United States); Mason, G. M. [Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723 (United States); Von Rosenvinge, T. T. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gomez-Herrero, R. [University of Alcala, E-28871 Alcala de Henares (Spain); Klassen, A. [Kiel University, D-24118 Kiel (Germany); Galvin, A. B.; Simunac, K. D. C., E-mail: ctrussell@igpp.ucla.edu [University of New Hampshire, Durham, NH 03824 (United States)
2013-06-10
The giant, superfast, interplanetary coronal mass ejection, detected by STEREO A on 2012 July 23, well away from Earth, appears to have reached 1 AU with an unusual set of leading bow waves resembling in some ways a subsonic interaction, possibly due to the high pressures present in the very energetic particles produced in this event. Eventually, a front of record high-speed flow reached STEREO. The unusual behavior of this event is illustrated using the magnetic field, plasma, and energetic ion observations obtained by STEREO. Had the Earth been at the location of STEREO, the large southward-oriented magnetic field component in the event, combined with its high speed, would have produced a record storm.
Time-domain simulation for water wave radiation by floating structures (Part A)
Institute of Scientific and Technical Information of China (English)
XU Gang; DUAN Wen-yang
2008-01-01
Direct time-domain simulation of floating structures has advantages: it can calculate wave pressure fields and forces directly;and it is useful for coupled analysis of floating structures with a mooring system. A time-domain boundary integral equation method is presented to simulate three-dimensional water wave radiation problems. A stable form of the integration free-surface boundary condition (IFBC) is used to update velocity potentials on the free surface. A multi-transmitting formula (MTF) method with an artificial speed is introduced to the artificial radiation boundary (ARB). The method was applied to simulate a semi-spherical liquefied natural gas (LNG) carrier and a semi-submersible undergoing specified harmonic motion. Numerical parameters such as the form of the ARB,and the time and space discretization related to this method are discussed. It was found that a good agreement can be obtained when artificial speed is between 0.6 and 1.6 times the phase velocity of water waves in the MTF method. A simulation can be done for a long period of time by this method without problems of instability,and the method is also accurate and computationally efficient.
Sachdev, PL
2004-01-01
Understanding the causes and effects of explosions is important to experts in a broad range of disciplines, including the military, industrial and environmental research, aeronautic engineering, and applied mathematics. Offering an introductory review of historic research, Shock Waves and Explosions brings analytic and computational methods to a wide audience in a clear and thorough way. Beginning with an overview of the research on combustion and gas dynamics in the 1970s and 1980s, the author brings you up to date by covering modeling techniques and asymptotic and perturbative methods and ending with a chapter on computational methods.Most of the book deals with the mathematical analysis of explosions, but computational results are also included wherever they are available. Historical perspectives are provided on the advent of nonlinear science, as well as on the mathematical study of the blast wave phenomenon, both when visualized as a point explosion and when simulated as the expansion of a high-pressure ...
Experimental animal models for studies on the mechanisms of blast-induced neurotrauma.
Risling, Mårten; Davidsson, Johan
2012-01-01
A blast injury is a complex type of physical trauma resulting from the detonation of explosive compounds and has become an important issue due to the use of improvised explosive devices (IED) in current military conflicts. Blast-induced neurotrauma (BINT) is a major concern in contemporary military medicine and includes a variety of injuries that range from mild to lethal. Extreme forces and their complex propagation characterize BINT. Modern body protection and the development of armored military vehicles can be assumed to have changed the outcome of BINT. Primary blast injuries are caused by overpressure waves whereas secondary, tertiary, and quaternary blast injuries can have more varied origins such as the impact of fragments, abnormal movements, or heat. The characteristics of the blast wave can be assumed to be significantly different in open field detonations compared to explosions in a confined space, such an armored vehicle. Important parameters include peak pressure, duration, and shape of the pulse. Reflections from walls and armor can make the prediction of effects in individual cases very complex. Epidemiological data do not contain information of the comparative importance of the different blast mechanisms. It is therefore important to generate data in carefully designed animal models. Such models can be selective reproductions of a primary blast, penetrating injuries from fragments, acceleration movements, or combinations of such mechanisms. It is of crucial importance that the physical parameters of the employed models are well characterized so that the experiments can be reproduced in different laboratory settings. Ideally, pressure recordings should be calibrated by using the same equipment in several laboratories. With carefully designed models and thoroughly evaluated animal data it should be possible to achieve a translation of data between animal and clinical data. Imaging and computer simulation represent a possible link between experiments
PIC simulation of compressive and rarefactive dust ion-acoustic solitary waves
Li, Zhong-Zheng; Zhang, Heng; Hong, Xue-Ren; Gao, Dong-Ning; Zhang, Jie; Duan, Wen-Shan; Yang, Lei
2016-08-01
The nonlinear propagations of dust ion-acoustic solitary waves in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated by the particle-in-cell method. By comparing the simulation results with those obtained from the traditional reductive perturbation method, it is observed that the rarefactive KdV solitons propagate stably at a low amplitude, and when the amplitude is increased, the prime wave form evolves and then gradually breaks into several small amplitude solitary waves near the tail of soliton structure. The compressive KdV solitons propagate unstably and oscillation arises near the tail of soliton structure. The finite amplitude rarefactive and compressive Gardner solitons seem to propagate stably.
3-D NUMERICAL SIMULATION OF CONVOY-GENERATED WAVES IN A RESTRICTED WATERWAY
Institute of Scientific and Technical Information of China (English)
JI Sheng Cheng; OUAHSINE Abdellatif; SMAOUI Hassan; SERGENT Philippe
2012-01-01
We consider waves generated by the passing of convoys in a restricted waterway.The magnitude of these waves depends mainly on the geometrical and kinematical parameters of the convoy,such as the speed and the hull geometry.The objective of this study is to predict the relationship between these geometrical and kinematical parameters and the amplitude of ship-generated waves as well as the water plane drawdown.Numerical simulations are conducted by solving the 3-D Navier-Stokes equations along with the standard k-ε model for turbulent processes.The results are compared first with the empirical model and second with experimental measurements performed by the French company Compagnie National du Rh(o)ne (CNR).
Discrete Element Simulation of Elastoplastic Shock Wave Propagation in Spherical Particles
Directory of Open Access Journals (Sweden)
M. Shoaib
2011-01-01
Full Text Available Elastoplastic shock wave propagation in a one-dimensional assembly of spherical metal particles is presented by extending well-established quasistatic compaction models. The compaction process is modeled by a discrete element method while using elastic and plastic loading, elastic unloading, and adhesion at contacts with typical dynamic loading parameters. Of particular interest is to study the development of the elastoplastic shock wave, its propagation, and reflection during entire loading process. Simulation results yield information on contact behavior, velocity, and deformation of particles during dynamic loading. Effects of shock wave propagation on loading parameters are also discussed. The elastoplastic shock propagation in granular material has many practical applications including the high-velocity compaction of particulate material.
A Spectral Multiscale Method for Wave Propagation Analysis: Atomistic-Continuum Coupled Simulation
Patra, Amit K; Ganguli, Ranjan
2014-01-01
In this paper, we present a new multiscale method which is capable of coupling atomistic and continuum domains for high frequency wave propagation analysis. The problem of non-physical wave reflection, which occurs due to the change in system description across the interface between two scales, can be satisfactorily overcome by the proposed method. We propose an efficient spectral domain decomposition of the total fine scale displacement along with a potent macroscale equation in the Laplace domain to eliminate the spurious interfacial reflection. We use Laplace transform based spectral finite element method to model the macroscale, which provides the optimum approximations for required dynamic responses of the outer atoms of the simulated microscale region very accurately. This new method shows excellent agreement between the proposed multiscale model and the full molecular dynamics (MD) results. Numerical experiments of wave propagation in a 1D harmonic lattice, a 1D lattice with Lennard-Jones potential, a ...
Vlasov Simulations of Ladder Climbing and Autoresonant Acceleration of Langmuir Waves
Hara, Kentaro; Barth, Ido; Kaminski, Erez; Dodin, Ilya; Fisch, Nathaniel
2016-10-01
The energy of plasma waves can be moved up and down the spectrum using chirped modulations of plasma parameters, which can be driven by external fields. Depending on the discreteness of the wave spectrum, this phenomenon is called ladder climbing (LC) or autroresonant acceleration (AR) of plasmons, and was first proposed by Barth et al. based on a linear fluid model. Here, we report a demonstration of LC/AR from first principles using fully nonlinear Vlasov simulations of collisionless bounded plasma. We show that, in agreement to the basic theory, plasmons survive substantial transformations of the spectrum and are destroyed only when their wave numbers become large enough to trigger Landau damping. The work was supported by the NNSA SSAA Program through DOE Research Grant No. DE-NA0002948 and the DTRA Grant No. HDTRA1-11-1-0037.
An infrared achromatic quarter-wave plate designed based on simulated annealing algorithm
Pang, Yajun; Zhang, Yinxin; Huang, Zhanhua; Yang, Huaidong
2017-03-01
Quarter-wave plates are primarily used to change the polarization state of light. Their retardation usually varies depending on the wavelength of the incident light. In this paper, the design and characteristics of an achromatic quarter-wave plate, which is formed by a cascaded system of birefringent plates, are studied. For the analysis of the combination, we use Jones matrix method to derivate the general expressions of the equivalent retardation and the equivalent azimuth. The infrared achromatic quarter-wave plate is designed based on the simulated annealing (SA) algorithm. The maximum retardation variation and the maximum azimuth variation of this achromatic waveplate are only about 1.8 ° and 0.5 ° , respectively, over the entire wavelength range of 1250-1650 nm. This waveplate can change the linear polarized light into circular polarized light with a less than 3.2% degree of linear polarization (DOLP) over that wide wavelength range.
Internal wave attractors examined using laboratory experiments and 3D numerical simulations
Brouzet, Christophe; Scolan, H; Ermanyuk, E V; Dauxois, Thierry
2016-01-01
In the present paper, we combine numerical and experimental approaches to study the dynamics of stable and unstable internal wave attractors. The problem is considered in a classic trapezoidal setup filled with a uniformly stratified fluid. Energy is injected into the system at global scale by the small-amplitude motion of a vertical wall. Wave motion in the test tank is measured with the help of conventional synthetic schlieren and PIV techniques. The numerical setup closely reproduces the experimental one in terms of geometry and the operational range of the Reynolds and Schmidt numbers. The spectral element method is used as a numerical tool to simulate the nonlinear dynamics of a viscous salt-stratified fluid. We show that the results of three-dimensional calculations are in excellent qualitative and quantitative agreement with the experimental data, including the spatial and temporal parameters of the secondary waves produced by triadic resonance instability. Further, we explore experimentally and numeri...
Kobayashi, Manabu; Takemura, Shunsuke; Yoshimoto, Kazuo
2015-09-01
Frequency and distance changes in the apparent P-wave radiation pattern (0.75-12 Hz) are investigated using velocity seismograms of shallow strike-slip earthquakes occurring in Chugoku region, southwestern Japan. Data from a dense seismic monitoring network revealed that the four-lobe apparent P-wave radiation pattern was gradually distorted with increasing frequency and propagation distance. Observed features suggest that seismic wave scattering due to small-scale velocity heterogeneity in the crust may be a major cause of this distortion. The effects of seismic wave scattering on apparent P-wave radiation pattern were investigated via 3-D finite difference simulation of seismic wave propagation. Our simulations demonstrated that the scattering of seismic waves modified the apparent P-wave radiation pattern from the original four-lobe shape, and that the small-scale velocity heterogeneity, characterized by the von Kármán-type power spectral density function with correlation distance of 1 km, root-mean-square value of 0.03 and decay rate parameter of 0.5, might be adequate for modelling crustal heterogeneity in the target region. It was also found that the scattering attenuation of P wave expected from this heterogeneity is significantly smaller than the apparent P-wave attenuation and S-wave scattering attenuation reported by Multiple Lapse Time Window Analysis of previous studies in Japan. These results might imply that scattering attenuation is not the dominant mechanism of P-wave attenuation in the crust of Chugoku region.
Camporeale, E.; Zimbardo, G.
2014-01-01
We present self-consistent Particle-in-Cell simulations of the resonant interactions between anisotropic energetic electrons and a population of whistler waves, with parameters relevant to the Earth's radiation belt. By tracking PIC particles, and comparing with test-particles simulations we emphasi
Camporeale, E.; Zimbardo, G.
2015-01-01
We present self-consistent Particle-in-Cell simulations of the resonant interactions between anisotropic energetic electrons and a population of whistler waves, with parameters relevant to the Earth's radiation belt. By tracking PIC particles, and comparing with test-particles simulations we emphasi
Ring-plane traveling-wave tube slow-wave circuit design simulations at V-Band frequencies
Kory, Carol L.; Wilson, Jeffrey D.
1995-01-01
The V-Band frequency range of 59-64 GHz is a region of the millimeter-wave spectrum that has been designated for intersatellite communications. As a first effort to develop a high-efficiency V-band TWT, variations on a ring-plane slow-wave circuit were computationally investigated to develop an alternative to the more conventional ferruled coupled-cavity circuit. The ring-plane circuit was chosen because of its high interaction impedance, large beam aperture, and excellent thermal dissipation properties. Despite the high-power capabilities of the ring-plane TWT, disadvantages of low bandwidth and high voltage requirements have until now prevented its acceptance outside the laboratory. In this paper, we use the three-dimensional electromagnetic simulation code MAFIA to investigate methods of increasing the bandwidth and lowering the operating voltage. Dispersion, impedance, and attenuation calculations for various geometric variations and loading distributions were performed. Based on the results of the variations, a circuit termed the finned-ladder TWT slowwave circuit was designed and is compared here to the scaled ring-plane prototype and the conventional ferruled coupled-cavity TWT circuit over the V-band frequency range.
Institute of Scientific and Technical Information of China (English)
张洪生; 洪广文; 丁平兴; 曹振轶
2001-01-01
In this paper, the characteristics of different forms of mild slope equations for non-linear wave are analyzed, and new non-linear theoretic models for wave propagation are presented, with non-linear terms added to the mild slope equations for non-stationary linear waves and dissipative effects considered. Numerical simulation models are developed of non-linear wave propagation for waters of mildly varying topography with complicated boundary, and the effects are studied of different non-linear corrections on calculation results of extended mild slope equations. Systematical numerical simulation tests show that the present models can effectively reflect non-linear effects.
Simulating Negative Pickup Ions and Ion Cyclotron Wave Generation at Europa (Invited)
Desai, R. T.; Cowee, M.; Gary, S. P.; Wei, H.; Coates, A. J.; Kataria, D. O.; Fu, X.
2015-12-01
The mass loading of space environments through the ionisation of planetary atmospheres is a fundamental process governing the plasma interactions and long term evolution of celestial bodies across the solar system. Regions containing significant pickup ion populations have been observed to exhibit a rich variety of electromagnetic plasma wave phenomena, the characteristics and properties of which can be used to infer the ion species present, their spatial and temporal distributions, and the global ionisation rates of the neutral material. In this study we present hybrid (kinetic ion, massless fluid electron) simulations of ion pickup and Ion Cyclotron (IC) waves observed in the Jovian magnetosphere and draw comparisons to sub-alfvénic pickup observed by Cassini in the Saturnian system, and also to supra-alfvénic pickup at planetary bodies immersed directly in the solar wind. At Jupiter, Europa has been identified as the secondary mass loader in the magnetosphere, orbiting within a neutral gas torus at ~9.38 Rj. Near Europa, Galileo magnetometer observations displayed bursty IC wave characteristics at the gyrofrequency of a number of species including SO2, K, Cl, O2, and Na, suggesting a complex mass loading environment. A particular deduction from the dataset was the presence of both positively and negatively charged pickup ions, inferred from the left and right hand polarisations of the transverse waves. Using hybrid simulations for both positively and negatively charged Cl pickup ions we are able to self-consistently reproduce the growth of both right and left hand near-circularly polarised waves in agreement with linear theory and, using the observed wave amplitudes, estimate Cl pickup ion densities at Europa.
Che, Cheng-Xuan; Wang, Xiu-Ming; Lin, Wei-Jun
2010-06-01
Based on strong and weak forms of elastic wave equations, a Chebyshev spectral element method (SEM) using the Galerkin variational principle is developed by discretizing the wave equation in the spatial and time domains and introducing the preconditioned conjugate gradient (PCG)-element by element (EBE) method in the spatial domain and the staggered predictor/corrector method in the time domain. The accuracy of our proposed method is verified by comparing it with a finite-difference method (FDM) for a homogeneous solid medium and a double layered solid medium with an inclined interface. The modeling results using the two methods are in good agreement with each other. Meanwhile, to show the algorithm capability, the suggested method is used to simulate the wave propagation in a layered medium with a topographic traction free surface. By introducing the EBE algorithm with an optimized tensor product technique, the proposed SEM is especially suitable for numerical simulation of wave propagations in complex models with irregularly free surfaces at a fast convergence rate, while keeping the advantage of the finite element method.