TNT装药爆炸波在刚性平面上方传播反射的数值研究

为研究爆炸冲击波传播和平面反射现象,运用显式非线性动力有限元软件ANSYS/LS-DYNA对柱形TNT装药在刚性平面上方爆炸产生的冲击波的传播和反射进行了数值模拟,将数值计算结果与试验结果和公式计算值进行了对比,结果表明利用数值模拟能够较好地反映压力场分布情况及爆炸冲击波传播、正反射、正规斜反射到马赫反射的演变过程;研究了装药形状对反射平面测点超压的影响。     

水底对浅水中装药爆炸效果的影响

通过实验，对浅水中装药爆炸时水底作用的影响效果进行了研究，指出影响装药浅水中爆炸效果的因素主要有水底前驱波、水底马赫波、水底反射冲击波、水底反射和水底反射稀疏波，并对这些因素的主要作用进行了详尽的阐述。     

爆轰波碰撞聚能效应及其数值分析

为了掌握爆轰波碰撞时的爆压和能量汇聚的规律,对爆轰波各种碰撞的爆压变化进行研究。首先基于爆轰波碰撞理论分析.得出爆轰波在正碰撞、斜碰撞和马赫反射三种条件下的爆压变化,确定马赫反射发生的条件,然后绘制入射角、偏离角和反射角间的关系曲线。应用Ls-dyna数值软件对爆轰波碰撞产生马赫反射的过程进行模拟。对比模拟和理论计算结果得知.对于多方指数为2.4的铵油炸药,马赫反射发生在斜爆轰波入射角为46.4°时,此时马赫波后压强达到最大值13.2 GPa,并在马赫波后形成高压区域。     

爆轰波碰撞聚能效应及其数值分析

为了掌握爆轰波碰撞时的爆压和能量汇聚的规律,对爆轰波各种碰撞的爆压变化进行研究。首先基于爆轰波碰撞理论分析.得出爆轰波在正碰撞、斜碰撞和马赫反射三种条件下的爆压变化,确定马赫反射发生的条件,然后绘制入射角、偏离角和反射角间的关系曲线。应用Ls-dyna数值软件对爆轰波碰撞产生马赫反射的过程进行模拟。对比模拟和理论计算结果得知.对于多方指数为2.4的铵油炸药,马赫反射发生在斜爆轰波入射角为46.4°时,此时马赫波后压强达到最大值13.2 GPa,并在马赫波后形成高压区域。     

Boundaries of the ambiguity area upon reflection of compression shock waves

Oblique shock waves can be reflected from hard walls, the axis, or the plane of symmetry, as well as from other counterpropagating shock waves with the formation of regular and Mach shock wave configurations. The specific form of shock wave structures is determined by the parameters of the problem: Mach number and intensity of incident shock waves. On the plane of parameters, there exists an ambiguity area in which laws of conservation admit both the regular and Mach reflection of shock waves. The boundaries of this region have been determined.     

Formation of triple shock configurations with negative reflection angle in steady flows

Triple configurations of shock waves with negative reflection angles are considered. These configurations have been observed in quasi-steady cases of shock wave reflection from a planar wedge in real gases, while in steady cases three-shock configurations are only known to occur with positive reflection angles. Boundaries for the appearance of a three-shock configuration with a negative reflection angle in steady cases are analytically determined as dependent on the initial Mach number of the flow, angle of incidence, and adiabatic index. The formation of a three-shock configuration with a negative reflection angle in a steady flow must lead to a change in the character of the wave pattern, and under certain conditions it can lead to instability.     

The effect of the pattern of gas/surface interaction on the relation for Knudsen layer under conditions of strong subsonic condensation

The moments method is used within the model of diffuse reflection to investigate the effect of the temperature accommodation coefficient α_T on the flow behind the Knudsen layer under conditions of strong subsonic condensation. An explicit expression is obtained for dimensionless pressure as a function of temperature and Mach number M, as well as of the coefficients of evaporation, condensation, and temperature accommodation. It is demonstrated that the difference of α_T from unity may have a significant effect on the flow parameters and, in particular, on the value of Mach number that is the maximal value attainable under conditions of subsonic condensation. It is further demonstrated that this effect increases in the case of mirror reflection of molecules from the surface. The adiabatic exponent is investigated as well.     

Numerical investigation of the onset of instability of triple shock configurations in steady supersonic gas flows

Triple configurations of shock waves that arise in a steady supersonic flow of a real gas have been numerically simulated. Previously, we have theoretically predicted that a new triple shock configuration with a negative reflection angle can appear in a gas flow at large Mach numbers and small adiabatic indices. This configuration is now obtained for the first time in numerical experiments. It is shown that the formation of this triple shock configuration leads to instability of the entire flow pattern.     

工业炸药线型聚能切割器的研制

首先 ,简要介绍了对现有预裂爆破技术的类型及其特点 ;其次 ,根据马赫反射原理 ,阐述了用高爆速炸药起爆低爆速炸药可增强低爆速炸药的爆压 ;然后概述了以 2号岩石炸药为主装药的线型聚能切割器的设计参数及切割试验。试验结果表明 ,所研制的线型切割器虽然采用了低爆速的工业炸药作为主装药 ,但其切割能力却和高能炸药的切割效果相当 ,同时还降低了炸药成本 ,提高了安全性     

工业炸药线型聚能切割器的研制

首先 ,简要介绍了对现有预裂爆破技术的类型及其特点 ;其次 ,根据马赫反射原理 ,阐述了用高爆速炸药起爆低爆速炸药可增强低爆速炸药的爆压 ;然后概述了以 2号岩石炸药为主装药的线型聚能切割器的设计参数及切割试验。试验结果表明 ,所研制的线型切割器虽然采用了低爆速的工业炸药作为主装药 ,但其切割能力却和高能炸药的切割效果相当 ,同时还降低了炸药成本 ,提高了安全性     

浅水爆炸下高桩钢管柱表面作用荷载实验研究

通过不同炸药量、不同爆炸距离、不同起爆深度的水中爆炸模型实验,研究了浅水爆炸条件下高桩钢管柱表面压力特征和空间分布规律,分析了比例爆距对冲击波峰值及空间分布影响,给出了钢管柱表面冲击波反射系数、绕射系数和抗爆设计中实际作用冲击波的工程算法。研究结果表明:水中爆炸作用下,反射和绕射冲击波近似同时作用在钢管柱表面,峰值沿柱身高度方向非均匀分;冲击波受水面影响程度相对较小,二次气泡脉动受水面影响程度较大;反射和绕射冲击波峰值均随炸药量增加、作用距离减小而增加。比例爆距相同,反射冲击波峰值相同,但炸药量小、爆炸距离近的实验工况绕射冲击波峰值相对较小;钢管柱表面冲击波反射系数和绕射系数随比例爆距增加而减小。比例爆距≥1.71时,钢管柱实际作用冲击波峰值可近似按自由场冲击波峰值的1.37倍计算。     

Zur analytischen Behandlung von Machreflexionen beim Eintritt einer ebenen Strömung in einen Kanal

Summary Plane supersonic flow with Mach reflection is investigated. The Mach reflection is represented by the interaction of an oblique shock wave with another, nearly normal shock. The subsonic flow behind the reflection may then be determined with the aid of a pressure potential. Boundary conditions follow from the linearized shock equations. An integral equation of the Carleman type is obtained which can be solved in closed form. As an example the flow in the inlet section of a channel with parabolic walls is calculated.

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Zur analytischen Behandlung von Machreflexionen beim Eintritt einer ebenen Strömung in einen Kanal

Zusammenfassung Es wird das Verhalten einer ebenen Überschallströmung mit Machreflexion untersucht. Die Machreflexion wird durch das Auftreffen einer Stoßfront auf einen zweiten, nahezu senkrechten Stoß dargestellt. Die Unterschallströmung hinter der Reflexion läßt sich dann mit Hilfe eines Druckpotentials bestimmen. Die Randbedingungen folgen aus den linearisierten Stoßbeziehungen. Es ergibt sich eine Integralgleichung vom Carlemanschen Typ, für die sich eine Lösung in geschlossener Form angeben läßt. Als Beispiel wird die Einlaufströmung in einen Kanal mit parabelförmigen Wänden berechnet.

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Mit 14 Textabbildungen     

Finite element computation of unsteady viscous transonic flows past stationary airfoils

Results are presented for computations of unsteady viscous transonic flows past a stationary NACA0012 airfoil at various angles of attack. The Reynolds number, based on the chord-length of the airfoil, is 10,000 and the Mach number is 0.85. Stabilized finite-element formulations are employed to solve the compressible Navier-Stokes equations. The equation systems, resulting from the discretization, are solved iteratively by using the preconditioned GMRES technique. Time integration of the governing equations is carried out for large values of the non-dimensional time to understand the unsteady dynamics and long-term behavior of the flows. The results show interesting flow patterns and a complex interaction between the boundary/shear layers, shock/expansion waves and the lateral boundaries of the computational domain. For transonic flow past an airfoil at various angles of attack in a narrow channel/wind-tunnel one can observe solutions that are qualitatively different from each other. At low angles of attack an unsteady wake is observed. At moderate angles of attack the interaction between the shock system and the lateral walls becomes significant and the temporal activity in the wake decreases and eventually disappears. At high angles of attack a reflection shock is formed. Hysteresis is observed at an angle of attack 8^∘. For the flow in a domain with the lateral boundaries located far away, the unsteadiness in the flow increases with an increase in the angle of attack. Computations for a Mach 2, Re 106 flow past an airfoil at 10^∘ angle of attack compare well with numerical and experimental results from other researchers     

Mach number distribution over the axis of supersonic underexpanded jets

The limiting flow parameters are determined directly behind the central shock for Mach numbers M ? 1 in front of the shock. A formula for the Mach number distribution over the jet axis is derived.     

再谈茅山革命纪念碑军号声成因

江苏镇江苏南抗战胜利纪念碑有个奇特的声学现象:人们放鞭炮后传回来的声音不是鞭炮声,而是变成了嘹亮的军号声。对此现象进行了实地测量,现场录音,综合分析了军号声现象是在鞭炮爆炸冲击波的作用下,经碑前台阶的反射而产生的,台阶的步长决定了反射声的音调;台阶的组数决定了音节数;连接各组台阶中间的平台对应着音节间的间隔;如此形成由6个音符组成的军号声。文章对此作出比较详细的分析及解释。     

大尺寸反射镜高精度光学镜面Ni-P过渡层的制备方法

为了解决高精度光学系统中铝合金、铍反射镜易钝化、难加工的问题,采用自催化镍-磷合金作为过渡层后进行抛光的方法得到了高精度光学镜面．采用该方法所得到的镍-磷合金过渡层厚度为85gm,磷质量分数为11．88％,镀层显微硬度为730MPa镍-磷合金过渡层与反射镜结合牢固、耐蚀性较好,可通过±200℃热震试验及96h中性盐雾试验检测,适用于进行古典法抛光．经抛光后反射镜面形精度均方根值（RMS）为0．049λ（面形检测波长λ为0．6328μm）,表面疵病等级为Ⅳ级,能够满足光学系统的要求．     

The influence of a steel rear barrier on the detonation response of a steel covered explosive struck by a steel projectile

Experiments by Weickert showed that the critical impact velocity of a shaped charge jet, required to cause detonation of a steel/explosive/steel laminate, reduced when the explosive thickness reduced. This paper examines the cause of this change using hydrocode simulations with and without a temperature based burn model. The simulations show that the change in critical impact velocity is caused by the reflected shock from the rear plate exceeding the shock at the cover plate. At this point the site of the detonation moves from the cover plate to the rear plate. Further reduction in explosive thickness causes further reduction in critical impact velocity due to the reduced dissipation of the shock reaching the back plate. The change in critical velocity for hemispherical-nosed projectiles is predicted to be not as sharply defined as for flat-nosed projectiles. This is due to a later, third stage reflection from the bulge of the advancing cover plate.     

Modelling of the impact of air shock wave on obstacle covered by porous screen

The procedure based on the modified two-step Lax–Wendroff scheme has been suggested for calculation of one-dimensional non-stationary motion of porous media described by the mathematical two-velocity model with two stress tensors. Results of computer modeling of the processes of passing the boundary between gas and porous medium by air shock wave and the reflection from rigid wall covered by the porous layer are presented.This work is supported by INTAS (Project 2000–50) and Grant of the President of the Russian Federation for State Support of Leading Scientific Schools of the Russian Federation (N Sh–2059.2003.1).     

Outer shock structure of shock-waves propagating in partially ionized gases

Structure of a shock wave propagating through a partially ionized gas is divided into an inner heavy particle shock and two surrounding outer regions. The electron and heavy particle properties are calculated at the two edges of the inner shock and are found to vary, for a given free stream Mach number M₁, almost linearly with the degree of ionization. The Mach number that characterizes the inner shock decreases monotonically from M₁ as the degree of ionization increases and reaches a limiting value, for a given M₁, as the gas becomes fully ionized. The width of the outer regions is found to be of the order of length for electron heat conduction when this conduction is equal to the convected internal energy.     

负折射现象的研究进展

负折射现象是一种崭新的现象,是上个世纪60年代理论预言,直到一年前被实验证明微波照射在左手化媒质(LHM)上,折射方向不同于Snell定律所描述的.介绍了这种负折射现象研究的最新发展.着重于LHM的人工合成,理论解释以及负折射率的实验证明等几个方面,以便进一步开展这方面的工作.