强爆炸早期火球现象的一维数值研究

采用一维球对称辐射流体力学方程组,构建直接求解辐射输运方程的一种数值方法,得到强爆炸早期火球发展过程中火球阵面、弹壳冲击波的形成发展过程.计算结果与Brode结果进行对比,二者一致,证明数值方法的合理性.数值模拟爆炸源区不同当量、不同密度以及不同爆炸高度等条件下强爆炸早期火球发展过程中火球阵面、弹壳冲击波的形成发展过程,对计算结果进行比较分析.     

爆炸载荷下X70钢管道的局部破坏效应

对大直径X70钢油气管道在接触爆炸下的破坏效应进行了野外化爆实验,获得了不同装药量及不同壁厚条件下钢管道的接触爆炸破坏特征。实验结果表明:接触爆炸载荷作用下管壁迎爆面局部破坏明显,且呈花瓣形破口,同时产生具有较大质量和动能的爆炸破片,破片与对面管壁碰撞后形成凹坑,甚至发生贯穿现象。基于动力有限元程序LS-DYNA及Lagrangian-Eulerian耦合方法,对钢管在外接触爆炸载荷作用下的非线性动态响应过程进行三维数值模拟,得到管壁迎爆面的变形破坏及对面管壁在爆炸破片碰撞下的后效作用过程,计算结果与实验结果符合良好。研究结果为在役油气管道的抗爆能力分析及安全性评估提供了参考依据。     

模拟X射线作用于圆锥壳载荷的柔爆索加载技术

在软X射线辐照作用下，物体表层瞬时形成大量的能量沉积，使材料受照部分表层发生熔化、汽化，出现物质的反冲喷射现象，产生喷射冲量载荷，使结构发生动态弹塑性变形、动屈曲等，实验室模拟X射线作用下的结构响应是重要的研究方法。在文中小尺寸、圆柱壳柔爆索加载技术的基础上，研究解决了圆锥壳体的柔爆索加载三维载荷设计方法、模拟自由边界的柔爆索加载实施方法、爆炸粒子的有效防护方法、爆炸粒子线动量标定方法和大尺寸锥壳结构的加载等效性等关键技术，发展建立了模拟X射线作用载荷的柔爆索加载三维设计与实验方法。     

吸气式激光推进中激光能量沉积过程的数值模拟

 结合辐射输运方程,在流体力学方程组的能量方程中加入包括空气吸收的激光能量以及高温气体向周围辐射损失的能量源项,转化为辐射流体力学方程组,建立了用于模拟吸气式激光推进中能量沉积过程的物理力学模型和计算方法。该辐射流体力学计算程序可以很好地模拟激光能量沉积过程中空气对激光能量的吸收、等离子体对激光的屏蔽作用以及激光维持的爆轰波的传播规律,计算得到激光能量的沉积效率约为57%,激光维持的爆轰波的传播速度与同等条件下的理论和实验结果吻合得较好。     

Z-FFR聚变靶室物理状态分析与聚变X射线防护的初步设计

利用MULTI程序建立了大空间-时间尺度、Z-FFR聚变靶室气体氛围的辐射流体力学模型,研究了聚变X射线能量传输、气体氛围温度密度演化以及冲击波的形成和传播等物理过程,获得了第一壁表面辐射温度、冲击压力随时间的变化等重要参数。同时利用Geant4程序计算了静态X射线在第一壁耐烧蚀涂层中的能量沉积分布,研究了不同能量X射线在聚变靶室气氛中的衰减规律。综合动态和静态计算结果,完成了聚变X射线防护初步设计,确定第一壁入射X射线能量密度阈值约为0.2J/cm2,Ar气氛围压强为2000Pa。     

爆炸荷载下不同壁厚圆柱壳动力学行为的研究

对爆炸荷载下圆柱壳的动力学行为进行了实验研究及数值模拟。将外径均为100mm的3种壁厚的Q235钢质圆柱壳置于由TNT药柱产生的爆炸场中进行冲击实验,系统分析了在不同装药高度及壳壁厚度参数条件下圆柱壳的冲击变形模式,即迎爆面局部凹陷变形模式(ModeⅠ)、迎爆面局部凹陷与壳整体弯曲变形耦合模式(ModeⅡ)、整体变形失效模式(ModeⅢ)及局部穿透与整体变形失效耦合模式(ModeⅣ)。采用LS-DYNA有限元程序及Lagrangian-Eulerian流固耦合算法,对圆柱壳的非线性动力响应过程进行了数值模拟,分析了圆柱壳的变形历程及最终残余变形的情况,计算结果与实验现象吻合较好。研究结论可为圆柱壳结构爆炸破坏分级及抗爆技术设计提供科学依据。     

带载丝电爆炸提高沉积能量的研究

在丝电爆过程中,金属丝的沉积能量是决定爆炸效果的关键参数。在研发连续送丝电爆装置的基础上,提出带载丝电爆炸提高金属丝沉积能量的方法。根据金属丝在电爆过程中的相变理论及旁路并联电阻的非线性时变性,建立了金属丝负载的电阻-能量分段模型。使用带载丝和裸丝分别开展电爆炸实验,同步采集丝电爆过程中的放电波形并分析计算,探究带载丝电爆炸相关机理以及沉积能量的变化规律。结果表明,电爆炸前期,由于载丝带具有绝缘性,其旁路并联电阻大于裸丝,从而使得带载丝电阻大于裸丝;随着欧姆加热的进行,带载丝中液态金属沿轴向由两端向中间聚集,加快了电爆炸相变过程,等效电阻减小,延缓了沿面击穿过程,从而获得更多的能量。     

宇宙中最古老的爆炸

γ射线爆是一种发射强γ射线的激烈爆炸，可持续几毫秒到约一百秒的时间、继初始的爆炸后，会有波长较长的辐射的“余辉”，持续几周甚至几年、许多天文学家认为，当一个大质量的恒星在其“寿命”尽头经历超新星爆炸并崩塌成黑洞时发生γ射线爆。     

刚性柱附近浅水爆炸荷载特性研究

刚性柱附近浅水爆炸时冲击波传播、气泡射流受多种因素影响。考虑水面、水底、刚性柱与水下爆炸冲击波及气泡的耦合作用,基于LS-DYNA有限元软件,建立浅水爆炸全耦合模型,通过经验公式验证有限元模型的正确性。研究表明:采用炸药直径1/3～1/2中心渐变网格能够较好地保证数值模拟精度。在冲击波传播阶段,刚性柱迎爆区冲击波峰值上升并产生切断现象,冲击波下降段被"截断",而背爆区冲击波峰值衰减约50%,同时正压作用时间增加;在气泡脉动阶段,气泡在收缩阶段产生指向刚性柱的气泡射流,当刚性柱与炸药之间的距离约为一个气泡半径时,刚性柱附近的脉冲荷载增幅最大,脉冲荷载最大测点水深较爆心上移。     

金属氧化物半导体场效应管长期辐射效应的数值模拟

将粒子输运的蒙特卡罗方法与器件数值模拟的有限体积法相耦合来模拟典型金属氧化物半导体场效应管(MOSFET)的长期辐射效应。二氧化硅中的陷阱电荷及硅中的自由电子和空穴均使用漂移扩散模型来描述,入射粒子的能量沉积可作为源项耦合至漂移扩散模型方程,并根据有限体积法得到控制方程的离散格式,方程的数值解即为MOSFET的长期辐射响应结果。使用该方法模拟了MOSFET受射线粒子辐照后的阈值电压漂移与关态漏电流现象。结果表明,耦合方法适用于典型半导体器件长期辐射效应模拟,其阈值电压漂移及漏电流计算结果与文献符合较好。     

Specific features of the oxidation of hydrogen and methane near the third ignition limit in quartz and metal reactors

Heat release during the sublimit reaction, induction period, and explosion in stoichiometric hydrogen-oxygen and methane-oxygen mixtures near the third ignition limit is measured. It is shown that, for the hydrogen-oxygen reaction, the third limit pressure, sublimit reaction rate, and reaction rate during the induction period depend not only on the state and nature of the reactor wall surface, but also on the sequence of introduction of the reactants. It was found that heat released during the induction period is close to that released during the explosion. Changing the order of introduction of the explosive mixture components into the reactor leads to a drastic change in the dark reaction rate. It was found that the main reaction (90%) in detonating gas below the ignition limit and during the induction period occurs with the participation of the reactor wall surface. The main product of the heterogeneous reaction is hydrogen peroxide, which accumulates and, together with the initial mixture, creates conditions for ignition. An analysis of the results and literature data suggests that the ignition of detonating gas is a degenerate process (in N.N. Semenov’s terminology). For the methane-oxygen reaction, the third limit pressure, as well as the rates of the sublimit and induction-period reactions, depend on the state and nature of the reactor wall surface, while being independent of the order of introduction of the reactants.     

Numerical Study on the Whole Process of Fireball Evolution in Strong Explosion *

With the actual mean free path for radiation in air and a simplified nuclear device, a one-dimension simulation research on fireball phenomenon in a sea level atmosphere is carried out based on the multi-group radiation hydrodynamic codes (RDMG). It is shown that our theoretical calculations can describe the whole process of the fireball evolution for strong explosions from the early X-ray expansion stage to the shock wave propagation stage. The radius of the shock wave and the brightness of the fireball are in good agreement with the experimental results. The whole thermal radiation power curve of the fireball evolution for strong atmospheric explosion at sea level is plotted for the first time. The impact of radiation opacity of the nuclear device material on the early fireball phenomenon is also studied. It is found that trajectories of the radiation fronts and case shocks change with the opacity of equivalent device material. From our simulations, we find that only the early fireball depends on the details of the nuclear device, and after the formation of main shock, the evolution is determined by the properties of hot air for strong atmospheric explosion.     

Fully implicit 1D radiation hydrodynamics: Validation and verification

A fully implicit finite difference scheme has been developed to solve the hydrodynamic equations coupled with radiation transport. Solution of the time-dependent radiation transport equation is obtained using the discrete ordinates method and the energy flow into the Lagrangian meshes as a result of radiation interaction is fully accounted for. A tridiagonal matrix system is solved at each time step to determine the hydrodynamic variables implicitly. The results obtained from this fully implicit radiation hydrodynamics code in the planar geometry agrees well with the scaling law for radiation driven strong shock propagation in aluminium. For the point explosion problem the self similar solutions are compared with results for pure hydrodynamic case in spherical geometry. Results obtained when radiation interaction is also accounted agree with those of point explosion with heat conduction for lower input energies. Having, thus, benchmarked the code, self convergence of the method w.r.t. time step is studied in detail for both the planar and spherical problems. Spatial as well as temporal convergence rates are ?1 as expected from the difference forms of mass, momentum and energy conservation equations. This shows that the asymptotic convergence rate of the code is realized properly.     

Wave dynamics of electric explosion in solids

A mathematical model of an electric explosion is developed that consistently describes the expansion of the explosion channel with regard to the parameters of the discharge circuit of a high-voltage pulse generator, radiation, and propagation of stress waves in a solid. The dynamics of conversion of the stored energy to a wave and the formation of mechanical stresses due to electric explosion in a solid immersed in a liquid are considered. In the context of electro-discharge destruction of hard materials, the resulting stress field and the relationship between the discharge circuit parameters and characteristics of the wave are analyzed and the most efficient discharge modes are determined.     

强点火作用下C3HF7对甲烷-空气爆炸的抑制

为解决瓦斯输送过程中的爆炸安全问题,探索寻找绿色环保且阻火性能优越的新型抑爆剂,开展了当量比下甲烷-空气预混气体爆炸传播过程中的七氟丙烷抑爆效果研究。实验采用长径比L/D=108的水平管道爆炸特性测试系统,研究了在强点火作用下不同体积分数的七氟丙烷对9.5%甲烷-空气预混气体最大爆炸压力、最大压力上升速率和火焰传播速度的影响。实验结果显示:将2.5 m长的管段作为七氟丙烷抑爆区时,七氟丙烷阻断9.5%甲烷-空气预混气体爆炸火焰传播的最小体积分数为5%;当七氟丙烷的体积分数为1%~4%时,不仅无法阻断爆炸火焰的传播,而且与对照组相比,会使火焰传播速度加快;当七氟丙烷的体积分数为1%~6%时,爆炸源及管道末端处的爆炸压力峰值随着七氟丙烷体积分数的增加而逐渐减小;当七氟丙烷的体积分数为3%时,抑爆区处的爆炸压力峰值与对照组相比增幅为10.9%。     

The explosion of a spherical drop under the action of laser radiation

The existence of an explosive cycle is proposed for the action of laser radiation on a water droplet, when the droplet during the time of action of the pulse is converted to supercritical steam with unchanged density. A calculation is carried out of the gas-dynamic parameters of the expanding explosion products. An estimate is made of the change of optical attenuation cross section of the expanding steam.     

Maximal design basis accident of fusion neutron source DEMO-TIN

When analyzing the safety of nuclear (including fusion) facilities, the maximal design basis accident at which the largest release of activity is expected must certainly be considered. Such an accident is usually the failure of cooling systems of the most thermally stressed components of a reactor (for a fusion facility, it is the divertor or the first wall). The analysis of safety of the ITER reactor and fusion power facilities (including hybrid fission–fusion facilities) shows that the initial event of such a design basis accident is a large-scale break of a pipe in the cooling system of divertor or the first wall outside the vacuum vessel of the facility. The greatest concern is caused by the possibility of hydrogen formation and the inrush of air into the vacuum chamber (VC) with the formation of a detonating mixture and a subsequent detonation explosion. To prevent such an explosion, the emergency forced termination of the fusion reaction, the mounting of shutoff valves in the cooling systems of the divertor and the first wall or blanket for reducing to a minimum the amount of water and air rushing into the VC, the injection of nitrogen or inert gas into the VC for decreasing the hydrogen and oxygen concentration, and other measures are recommended. Owing to a continuous feed-out of the molten-salt fuel mixture from the DEMO-TIN blanket with the removal period of 10 days, the radioactivity release at the accident will mainly be determined by tritium (up to 360 PBq). The activity of fission products in the facility will be up to 50 PBq.     

强爆炸火球数值模拟中的算子分裂方法

采用算子分裂方法将辐射流体力学方程组分裂为对流项和刚性源项,设计一种高效求解刚性源项方程组的数值方法.数值实验表明:该方法对时间步长不敏感,计算精度能够满足工程计算要求.在不对方程组做任何近似的情况下,数值给出了较长时间内火球冲击波阵面压力峰值及阵面位置的变化,结果与实际强爆炸中的经验公式吻合较好.     

Scattering of optical radiation by fog water droplets

The behavior of local optical characteristics of an aerosol medium in the radiation field of a microsecond-pulse CO₂ laser is experimentally investigated. Using measurements of the scattering intensity of a sounding beam, the dynamics behind the formation of a propagation channel over the interaction time is studied for different energy densities, and the characteristic times over which the channel is clouding and clearing, the dimensions of the explosion products, and the degree of their evaporation are established. Scattering of radiation in the visual range by shock waves is observed that is caused by the gas-dynamic explosion of fog droplets.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 79–84, February, 1987.