M1近似应用于强爆炸火球辐射输运数值模拟

推导了P1近似、Minerbo近似和M1近似模型中Eddington因子和辐射输运方程的最大特征值随各向异性因子的变化关系。采用M1近似模型对1kt TNT当量的强爆炸火球的辐射输运过程进行了数值模拟,给出了火球阵面和冲击波阵面走时,并与已有计算结果进行了比较。结果表明:辐射扩张阶段M1近似下得到的辐射波波速快于P1近似下的计算结果,落后于Minerbo近似下的计算结果,而在冲击波扩张阶段三者计算结果又趋于一致。     

炸药水中爆炸的冲击波性能

采用PCB138压力传感器测量了TNT、RS211、HLZY-1和HLZY-3等几种炸药水中爆炸冲击波远场的压力时间历程,计算得到了这几种炸药水中爆炸冲击波性能参数及其相似常数。研究表明,含铝炸药水中爆炸冲击波远场的传播服从指数变化的相似律,其冲击波性能比标准炸药TNT优越。含铝炸药HLZY-1具有较好的水中爆炸冲击波性能。     

坑道内爆炸条件下温压炸药的爆炸特性及其影响因素

温压炸药在坑道内爆炸时会产生多种毁伤元,对坑道内人员和设备造成严重威胁。基于不同药量的温压炸药爆炸试验,对坑道内爆炸条件下温压炸药的爆炸特性开展了研究,分析了爆炸热效应演化特征、冲击波传播规律和氧浓度降低情况,讨论了坑道对铝粉后燃的约束作用规律以及形成高烈度后燃效应的药量条件。研究表明：温压炸药火球辐射亮度高于TNT,且其火球温度峰值超过TNT温度峰值的1.3倍。在火球演化过程中,火球在后燃阶段的温度峰值较火球形态刚稳定时提升超过10%。在冲击波传播规律方面,超压峰值与正压时间的TNT当量系数分别约为1.4与1.65。另外,铝粉后燃产生的压缩波对冲击波能够形成多种补充效果,陡峭升压的压缩波能够使冲击波峰值升高,持续时间长但升压速率慢的压缩波能够限制冲击波的衰减,延长整体正压作用时间。受坑道约束作用,温压炸药爆炸火球将与坑道壁面发生相互作用,进而提高铝粉的燃烧烈度。当温压炸药质量立方根与坑道直径的比值大于0.28 kg^1/3/m时,将产生高烈度后燃效应。     

固态燃料空气炸药空爆实验研究

通过四组无约束固态燃料空气炸药(FAE)装置与等质量的TNT在野外开放空间的一次起爆对比实验,测得了不同配方组份FAE装置在不同距离的爆炸超压分布,FAE装置峰值超压比相同距离的TNT高1.14~1.6倍;并运用空气冲击波峰值超压公式计算出了FAE的等效爆炸TNT当量随距离的变化关系,在爆炸场边缘区,FAE装置爆炸当量达到了3.88倍TNT当量;通过高速摄影的图片得到了爆炸产生火球的持续时间和最大作用范围,与等质量TNT爆炸火球相比,FAE的优势明显;运用粉尘爆炸下极限浓度估算了云雾爆轰区半径,并分析了测量到的固态FAE爆炸场的压力分布单调衰减的原因;建议在保持超压不变的情况下,把提高爆温作为提高FAE爆炸性能的主要途径。     

均匀大气中的强爆炸一维辐射流体力学数值解

利用实际空气的状态方程和辐射平均自由程,对均匀大气中能量为8.36×1013焦耳（相当于二万吨TNT的爆炸能量）的强爆炸进行了一维辐射流体力学的数值计算。获得了冲击波参数、火球参数及等温球参数。其冲击波阵面参数与流体力学结果基本一致,波后参量比流体力学结果有明显改进,所得到的火球及等温球参数与实测结果基本符合。     

液体推进剂爆炸理论与实验研究

建立了自燃液体火箭推进剂爆炸热辐射效应和冲击波特性理论模型，介绍了实验研究的方法，给出了Ｎ２Ｏ４／ＵＤＭＨ液体推进剂爆炸产生的火球直径、火球温度、火球辐射热流、爆炸冲击波超压值等参数计算与实验观测结果，结果表明计算结果与实验观测结果吻合。由Ｎ２Ｏ４／ＵＤＭＨ液体火箭推进剂爆炸产生的火球最大直径Ｄｍａｘ和火球持续时间ｔ０是推进剂总重量Ｗ０的函数，根据实验数据整理的函数关系式:利用该理论模型预测了大型Ｎ２Ｏ４／ＵＤＭＨ组元液体推进剂运载火箭发生爆炸事故产生的上述参数，以及热辐射和冲击波不发生破坏和危害的安全距离。该计算模型可为载人航天器逃逸系统及航天靶场设计提供理论数据。     

负压环境对乳化炸药爆炸温度场和有害效应的影响

为了探究负压条件下乳化炸药的爆轰反应机制，利用自制的可视化球形爆炸罐，通过高速摄像机、压力传感器和噪声仪分别记录乳化炸药的爆炸火焰传播过程、爆轰波压力和爆炸噪声，采用比色测温技术重构了爆炸火球的二维温度场，并深入研究了初始真空度对乳化炸药爆炸温度场、爆轰波特征参数以及爆炸噪声的影响。实验结果表明：随着初始真空度的提高，爆炸火球亮度更高，持续时间更长，形态更稳定；当真空度为0 k Pa时，火球在19.35μs时破裂，而当真空度为100 k Pa时，火球在58.05μs才开始破裂；低初始真空度对火球温度影响较小，而60 k Pa以上的初始真空度会显著提高乳化炸药的爆炸温度；冲击波峰值压力和比冲量均随着初始真空度的升高而降低，但初始真空度对冲击波正压作用时间变化的影响不明显。AUTODYN数值模拟结果表明，随着真空度的提高，冲击波峰值压力降低，冲击波速度逐渐降低至与爆轰产物的膨胀速度接近。此外，初始真空度的提高有利于降低爆炸噪声，与常压相比，当罐体内真空度为100 k Pa时，爆炸噪声的声压级降低了35.9 d B，降幅为29.8%。     

小当量水中爆炸气泡的脉动现象

为研究水中爆炸气泡的脉动现象,设计了用于小当量(10 g TNT)水中爆炸研究的爆炸水箱,在爆炸水箱装置中进行了多次0.125、1.000、3.370、8.000 g TNT当量的PETN球形炸药水中爆炸试验。采用高速摄影系统获得了气泡脉动图片;给出试验范围内气泡脉动过程中气泡直径、速度及加速度随时间变化的拟合曲线。对气泡脉动直径和周期数据进行了分析,这些数据基本符合爆炸相似律。     

水中爆炸近场测试技术研究

通过2发JH-9005炸药水中爆炸实验,探索利用高速相机测量水中爆炸近场冲击波的轨迹和冲击波在水域中的传播历程,得到分幅图像和扫描图像,并对图像进行数字化分析;利用Rankine-Hugoniot关系从冲击波的扫描轨迹求得冲击波阵面压力,并外推至冲击波的初始压力。用锰铜压力传感器测量了冲击波的初始压力并与光测结果对比,结果表明,两种测试方法取得的结果符合得很好。     

离心机水下爆炸缩比实验原理及数值研究

对离心机水下爆炸缩比实验方法进行探究,对离心机水下爆炸缩比实验的相似理论进行了推导,通过数值计算分析,探究了原模型、离心机缩比实验及常规缩比实验的冲击波载荷、气泡载荷以及气泡动力学行为。结果表明:常规缩比实验不能对气泡行为及垂直方向的近场载荷进行准确的预报,若要保证远场气泡脉冲峰值误差小于10%,则爆距需大于9.5倍气泡最大半径。而离心机缩比实验能够对原模型进行准确的预报,以小当量装药模拟大当量装药水下爆炸整个物理过程,且冲击波和气泡两个阶段完全相似。同时,水深也可以进行几何缩比,克服了常规缩比方法的缺陷。     

Radiation hydrodynamics of supernova shock breakouts

The first powerful burst of photon radiation in a supernova appears when the shock front is a few photon mean-free paths below the star photosphere. This is called “shock breakout” and it is the first observable event after the neutrino and gravitational wave bursts in core-collapsing supernovae. Any early information about collapse is vitally important for understanding the physics of explosion, constraining speed of neutrino propagation etc. Direct observations of shock breakouts have been carried out in a few supernovae. We discuss some puzzles related to those objects. Finally, we describe our current understanding of the most luminous (hyper-)supernovae. Their long living radiative shocks pause many interesting problems in numerical and laboratory astrophysics and may have important applications in cosmology.     

Long time evolution of collisionless shocks in laser produced counterstreaming plasmas

Long time evolution of collisionless shocks in laser-produced plasmas is discussed. By irradiating a double plane target a high Mach number collisionless shock has been observed in laser produced counterstreaming plasmas [Kuramitsu et al., Phys. Rev. Lett., 106, 175002 (2011)]. While in early time we observe the shock in front of one plane, which is irradiated with the laser, we observe another shock in front of the other plane in much later time than the first shock formation. These two shocks coexist and collide or merge with each other as time passes. This means that the upstream plasmas for the first and second shocks have to be provided from the second and first shock sides, respectively, i.e., both the first and second shock have to be collisionless. There are two major candidates to account for the long time evolution of the collisionless shocks. One is that the secondary plasmas at the planes can be continuously created by the plasmas from the other planes. Another is that the actual shock thickness is much thiner than the detection limit, as indicated by numerical simulations.     

Effects of Surface Tension on the Stability of Dynamical Liquid-Vapor Interfaces

The persistence of sharp and flat interfaces under multidimensional perturbations is investigated from a viewpoint analogous to Majdas treatment of classical shocks. The main novelty here is that jump conditions for the free interfaces take into account surface tension. This means that, unlike classical jump conditions, they are non-homogeneous, containing first-order and second-order differentials of the front. A normal modes analysis shows that neutral modes may propagate along the front. In the standard setting, this would imply a weak stability result, involving energy estimates with loss of derivatives. In our case the lack of homogeneity of the underlying boundary value problem implies that neutral modes can only be of large enough wave length. Suitable frequency cut-offs then yield energy estimates without loss of derivatives – for the constant-coefficients linearized problem, as in the case of uniformly stable classical shocks.     

Initiation of Combustion in a Supersonic Hydrogen-Air Mixture Flow by CO<Subscript>2</Subscript>-Laser Radiation

Features of the ignition kinetics of an H₂/air mixture in the supersonic flow behind an inclined shock front are analyzed when asymmetric vibrations of a small amount (<1%) of O₃ molecules specially introduced into the initial mixture are excited by 9.7 μm wavelength radiation. It is shown that this radiation leads to intensification of the chain reactions and makes it possible to organize combustion at small distances from the front (of the order of 1 m) of even relatively weak shocks at small values of the laser radiation energies absorbed by the gas. This method of initiating combustion in a supersonic flow is 10–100 times more efficient than the thermal method.__________Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, 2005, pp. 157–167.Original Russian Text Copyright © 2005 by Lukhovitskii, Starik, and Titova.     

点火位置对氢气-空气预混气体泄爆过程的影响

利用高速纹影和压力测试系统对不同点火位置及不同破膜压力条件下氢气-空气预混气的泄爆特性进行研究。研究结果表明:在所有情况下,中心点火时火焰传播速率和面积最大,产生了最大的内部压力峰值,尾端点火时火焰传播速率和面积次之,产生的内部压力峰值也次之;前端点火时火焰传播速率和面积均最小,产生了最小的内部压力峰值。前端点火时,容器内部压力出现了3个明显的压力峰值,中心和尾端点火时,只能观察到第1个和第3个压力峰值。并且,随着破膜压力的增加,中心和尾端点火时,火焰面积均增大,产生的内部压力峰值均增大。在前端点火的条件下出现了声学振荡的现象,对内部压力产生了显著的影响。     

Application of background oriented schlieren for quantitative measurements of shock waves from explosions

This paper describes application of a background oriented schlieren technique in order to obtain quantitative measurements of shock waves from explosions by processing high speed digital video recordings. The technique is illustrated by an analysis of two explosions, a high explosive test and a hydrogen gas explosion test. The visualization of the shock front is utilized to calculate the shock Mach number, leading to a predicted shock front pressure. For high explosives the method agreed quite well with a standard curve for side-on shock pressures. In the case of the gas explosion test we can also show that the shock front is non-spherical. It should be possible to develop this technique to investigate external blast waves and external explosions from vented gas explosions in more details. This paper is based on work that was presented at the 21th International Colloquium on the Dynamics of Explosions and Reactive Systems, Poitiers, France, July 23–27, 2007.     

Initial stage of the collision of blast waves

The collision of two blast waves is analyzed for the case of variable parameters of the gas behind the wave front and wave reflection at a plane, a cylindrical, and a spherical obstacle. The reflection of a blast wave from a nonmoving obstacle is investigated in detail. The problem of the collision of two shock waves with constant parameters behind the front is solved both in the symmetrical case (reflection from a nonmoving wall) and in the case of waves of different amplitudes by a system of algebraic relations for the compression shocks. The reflection of a strong point-source spherical shock wave from a wall has been treated in [1, 2]. The present article examines the initial stage of wave collision for an arbitrary distribution of the parameters behind the front.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 41–48, September–October, 1971.The authors are grateful to V. P. Korobeinikov for a discussion of the results and to V. P. Kolgan for furnishing the numerical solutions.     

聚心火焰与激波相互作用的数值研究

基于带化学反应的2维轴对称Euler方程,利用带有monotonized centered(MC)限制器的波传播算法,在两端敞开的圆桶中对惰性介质的聚心激波和氢气-空气混合物的聚心火焰与激波的相互作用进行了数值模拟。数值结果表明,在惰性介质中激波在轴心的每次汇聚均可成长为马赫干,马赫干的追赶使激波得到一定程度的增强,但整体还呈下降趋势。在氢气-空气混合物中,燃烧诱导的激波,由于与火焰的反复作用,使激波在轴心处产生马赫干的频率和强度皆高于惰性介质中的情形。同时,火焰在与激波的相互作用过程中发生失稳变形,使其形状呈扁平头部的蘑菇云。     

Blast waves in inhomogeneous atmospheres with counterpressure and heat transfer effects

The study on blast waves in cold exponential atmospheres by Bach, Kuhl, and Oppenheim is extended to provide a uniformly valid numerical solution of a point explosion problem in isothermal exponential atmospheres with finite temperature at the centre. This is achieved initially by solving the equations of motion with the help of a perturbation technique which takes into account thermal radiation and heat conduction. Whereas the extended perturbation solution for the strong shock regime (i.e. short times after initiation) serves as a starting solution for the numerical integration, the solution using the method of characteristics is valid for the whole flow field since counterpressure effects and energy losses at the front are not neglected.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Flow of a supersonic ideal gas over a planar cascade in the case of a subsonic normal component in regimes with attached shocks

The supersonic flow of an inviscid gas that does not conduct heat over a cascade of planar pointed profiles is considered in the case when the component of the velocity vector of the undisturbed flow normal to the cascade front is subsonic. The investigation is restricted to regimes without separation and shock waves attached to the leading edges of the profiles and fairly dense cascades, for which the characteristics or shock waves leaving the trailing edges do not enter the region in front of the cascade. In such cases, the conditions behind the cascade do not influence the flow in front of it. In this sense, the flow in the cascade, as in a Laval nozzle in the case of supercritical gradients is trapped, In the hodograph plane, trapped regimes of flow over the cascade correspond to velocity vectors of the undisturbed flow that lie on a certain line (see, for example, [1–3]), which is constructed in the process of solution of the problem. This property has been called the directing influence of the cascade on the oncoming flow. Regimes with detached shocks can also be trapped if the separation of the shocks is due to the profiles being blunt. A method is proposed that for regimes with attached shocks makes it possible to calculate the entire flow field, including the wave structure at large distances from the cascade front; some results obtained by the method are also given. The study of regimes with attached shocks, for which the analysis is simplest, is, first, of interest in its own right and, second, is a stage in the creation of methods of calculation and subsequent investigation of cascades with arbitrary regimes.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 108–113, July–August, 1979.We are grateful to M. Ya. Ivanov for assistance in updating the supersonic flow calculation program of [7], to G. Yu. Stepanov for helpful comments, and to E. V. Buganov and V. A. Vostretsov for assistance in preparing the paper.