高速液体受限射流扩展形态研究

采用一种火药燃烧驱动液体喷射的新装置及其测试系统，研究受限空间中高速惰性液体射流的扩展结构。观察了环境反压、液体粘性、喷嘴结构等参量对射流扩展形态的影响，分析了射流雾化机理。研究结果对改进燃烧室设计及控制燃烧稳定性有一定的指导意义。     

高速液体射流流动特性的实验测试方法

基于RLPG高压喷射环境建立了射流流动特性的实验测定系统和分析方法．利用这种方法测出高压下喷口的流量系数,得到射流头部贯穿速度及射流核形态．     

高速气流中横向液体射流雾化研究进展

在涡轮燃烧室和以液态碳氢燃料为工质的超燃冲压发动机中,高速气流中横向液体射流雾化是一个重要而复杂的过程.雾化过程进行的好坏直接关系到燃料的掺混和燃烧,进而影响发动机的性能. 针对高速气流中横向射流雾化的特点,对现阶段的实验和数值模拟研究进展进行了综述.实验方面结合国内外现状,阐明了一次、二次雾化的机理和雾化过程中的波现象,对穿透深度的确定方法及其影响因素进行了概括总结,分析了气液混合区的结构性质, 并列举和分析了常用的测量手段.数值模型研究介绍了现阶段的一次雾化和二次雾化常用的计算模型.最后提出了存在的问题和未来的研究方向.      

高速穿甲过程的热-结构耦合数值模拟

研究子弹侵彻炮弹药筒及发射药的高速穿甲问题及其热变化.利用有限元方法进行数值模拟,计算两种不同药筒情况下的结构及温度变化.观察整个穿甲侵彻过程,绘制应力、应力变化率、应变、应变率、温度等常规参数及可能引燃或引爆发射药的相应参数的变化云图及时间历程曲线,为发射药安全性分析和设计提供参考意见及一些有价值的数据.     

轴对称液体射流的Hamilton表述

证明带有自由面的轴对称液体圆射流和环状射流的控制方程在有势运动的情况下具有 Hamilton结构, 其Hamilton函数为射流的总能量, 并给出正则变量的表达式.     

等离子射流与渐扩边界中液体工质相互作用特性的模拟实验

为了探索整装式液体工质电热化学炮中药室边界形状对燃烧控制的影响,采用数字高速录像系统对等离子体射流在液体工质中的扩展过程进行了测试,研究了不同放电电压、不同喷嘴直径、不同渐扩边界结构下等离子射流与液体工质的相互作用特性.获得了等离子射流在液体工质中扩展形态的时间序列图,处理出不同工况下Taylor空腔扩展的轴向位移与时...     

水下欠膨胀高速气体射流的实验研究

采用实验途径研究了下水高速气体射流的动力学特性,研制了水下高速气体射流实验系统并发展了相应的测试手段。实验中,用插入式静压探针测量了射流轴线静压分布;用γ射线衰减法测量了径向空隙率分布,从而揭示了水下高速气体射流均压和掺混两个过程的基本规律。测量结果表明：水下高速气体射流在欠膨胀工况下运行时,近场将出现含有复杂波系结构的膨胀压缩区域,由于气水的掺混作用,水下欠膨胀气体射流均压化过程比空气中衰减得快。测量结果还表明,水下射流在近场区的混合层由气水两相占据,其流态从靠近气体侧的液滴流型过渡到靠近液体侧的气泡流型。     

高压燃气射流在整装液体中扩展过程的实验和数值模拟

为研究高压燃气射流在整装液体中的扩展规律,探索提高射流稳定性的控制方法,设计了4级渐扩型圆柱观察室.采用高速录像系统,观察了燃气射流在液体模拟工质中扩展与掺混的过程,获得了射流扩展形态的序列照片,测量了Taylor空腔的扩展速度,对比了观察室内壁形状对射流扩展过程的影响.建立了二维轴对称气液两相湍流模型,模拟射流扩展过...     

气液活塞式脉冲液体射流泵装置稳定性的理论研究

气液活赛式脉冲液体射流泵装置用于输送有毒、高温或放射性液体,装置在运行时,气液活塞筒内的气液交界面必须稳定在活塞筒内,形成稳定的脉冲运动,才能保证装置正常的稳定运行,本文在分析影响气液活塞式脉冲液体射流泵装置稳定性的主要因素基础上,运用流体力学的基本理论,导出了装置稳定性的基本方程组以及简化方程组,通过试验对上述理论进行了验证。     

含能气体射流与液体相互作用的实验研究

为了研究整装式液体发射药的燃烧稳定性的控制方法,设计了点火喷射模拟装置及4种多级渐扩型观察室,利用数字高速摄像系统,观察含能气体射流在液体模拟工质中的扩展过程,并对实验中出现的喷孔壅塞现象进行了分析. 结果表明: 射流在渐扩型结构中扩展稳定,喷射压力、喷孔直径和渐扩结构对射流扩展形态和气液掺混过程有显著影响,通过合理调整这些参数,可以实现对射流扩展过程的有效控制;喷孔壅塞时射流扩展形态非对称,影响气液掺混,不利于控制射流的稳定性.     

Homogenization of Stiff Plates and Two-Dimensional High-Viscosity Stokes Equations

The paper deals with the homogenization of stiff heterogeneous plates. Assuming that the coefficients are equi-bounded in L ¹, we prove that the limit of a sequence of plate equations remains a plate equation which involves a strongly local linear operator acting on the second gradients. This compactness result is based on a div-curl lemma for fourth-order equations. On the other hand, using an intermediate stream function we deduce from the plates case a similar result for high-viscosity Stokes equations in dimension two, so that the nature of the Stokes equation is preserved in the homogenization process. Finally, we show that the L ¹-boundedness assumption cannot be relaxed. Indeed, in the case of the Stokes equation the concentration of one very rigid strip on a line induces the appearance of second gradient terms in the limit problem, which violates the compactness result obtained under the L ¹-boundedness condition.     

Oblique Perforation of Thick Metallic Plates by Rigid Projectiles

Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.The English text was polished by Keren Wang     

在圆锥头弹体正冲击下薄壁金属圆板破裂模式的实验研究

报道了四种不同材料的薄金属圆板在不同锥头子弹正冲击下破裂的实验结果，实验中测量了薄金属圆板在不同锥头子弹正冲击下的临界破裂速度，确定了正冲击下圆板的破裂模式。     

Experimental Study on the Perforation Process of 5754-H111 and 6082-T6 Aluminium Plates Subjected to Normal Impact by Conical,Hemispherical and Blunt Projectiles

This paper presents an experimental investigation on the perforation behaviour of 5754-H111 and 6082-T6 aluminium alloys. The mechanical response of these materials has been characterized in compression with strain rates in the range of $10^{-3}~s^{-1} < \dot {\varepsilon } < 5 \cdot 10^{3}~s^{-1}$ . Moreover, penetration tests have been conducted on 5754-H111 and 6082-T6 plates of $4~mm$ thickness using conical, hemispherical and blunt projectiles. The perforation experiments covered impact velocities in the range of $50~m/s < V_{0} < 200~m/s$ . The initial and residual velocities of the projectile were measured and the ballistic limit velocity obtained for the two aluminium alloys for the different nose shapes. Failure mode and post-mortem deflection of the plates have been examined and the perforation mechanisms associated to each projectile/target configuration investigated. It has been shown that the energy absorption capacity of the impacted plates is the result of the collective role played by target material behaviour, projectile nose shape and impact velocity in the penetration mechanisms.     

AN EXPERIMENTAL INVESTIGATION ON THE IMPACT PERFORATION FAILURE OF WATER-FILLED-PRESSURIZED PIPELINES

Some experimental data recorded from impact tests on empty and water-filled pressurized mild steel pipes are presented. The pipes were supported as a three-span continuous beam and impacted laterally by a rigid indenter at the mid-span of middle span. Three kinds of indenter nose shapes were used: blunt-nose, hemisphere-nose and 90?conical-nose. The internal pressure ranged up to 20 MPa. The perforation failure modes and corresponding critical impact energies were obtained under different test conditions. The time-history curves of the internal pressure and impact force were given. The experiments show that the media filled in the tube greatly decreased the ballistic limit energy.     

Perforation of 7075-T651 Aluminum Armor Plates with 7.62 mm APM2 Bullets

We conducted an experimental and analytical study to better understand the mechanisms and dominant parameters for 7.62 mm APM2 bullets that perforate 7075-T651 aluminum armor plates. The 7.62-mm-diameter, 10.7 g, APM2 bullet consists of a brass jacket, lead filler, and a 5.25 g, ogive-nose, hard steel core. The brass and lead were stripped from the APM2 bullets by the targets, so we conducted ballistic experiments with both the APM2 bullets and only the hard steel cores. These projectiles were fired from a rifle to striking velocities between 600 and 1,100 m/s. Targets were 20 and 40-mm-thick, where the 40-mm-thick targets were made up of layered 20-mm-thick plates in contact with each other. The measured ballistic-limit velocities for the APM2 bullets were 1% and 8% smaller than that for the hard steel cores for the 20 and 40-mm-thick targets, respectively. Thus, the brass jacket and lead filler had a relatively small effect on the perforation process. Predictions from a cylindrical cavity-expansion model for the hard steel core projectiles are shown to be in good agreement with measured ballistic-limit and residual velocity data. The results of this study complement our previous paper with 5083-H116 aluminum target plates in that the ultimate tensile strength of 7075-T651 is about 1.8 times greater than that of 5083-H116. We also present a scaling law that shows a square root relationship between ballistic-limit velocity and plate thickness and material strength.     

自由梁中部在平头子弹横向正冲击下的穿透及变形

研究了均匀矩形截面自由梁中部在小尺寸、平头、刚性、圆柱形弹体正撞击下的变形及穿透过程。当子弹冲击速度接近或高于临界穿透速度时 ,在梁上与子弹接触区的周围会形成一个剪切冲塞 ,子弹通过冲塞作用在梁上的剪应力会引起梁的整体弯曲变形。通过动力分析 ,确定了子弹穿透梁的临界穿透速度。对子弹穿透梁的局部剪切过程和梁的各个变形阶段进行了数值计算 ,估算出局部剪切能、梁弯曲变形能、子弹及梁的残余动能在子弹初动能中所占的比例。     

Features of High-Viscosity Fluid Flow Through a Porous Medium Heated by Electromagnetic Radiation

Models describing the process of flow of a high- viscosity fluid through a porous medium heated by electromagnetic radiation are investigated analytically and numerically with allowance for the temperature dependence of the fluid viscosity and density. In addition to ordinary heating, the nonlinear electromagnetic heating regime associated with variation of the radiation absorption coefficient with temperature is considered.     

加筋板弹性大挠度的冲击响应分析

用半解析的方法分析了横向冲击载荷下加筋板的非线性瞬态响应。考虑膜力的存在 ,忽略筋截面上的剪切应力 ,引入板的应力函数 ,采用离散加筋板模型 ,运用能量原理建立加筋板的动响应控制方程。假设挠度为双级数形式 ,运用迦辽金法 ,将加筋板的动响应方程转化为一个多自由度的动力系统 ,采用数值方法来求解。最后给出了几个模型的计算结果。