非对称通气空泡多相流场特性研究

通气空泡的非对称介质分布将影响其水动力特性,继而影响空泡稳定控制,目前对其流动特性的认识较为局限.为揭示非对称通气空泡的流动机理,基于循环水洞实验及数值仿真开展了多相流场特性研究.结果 表明:非对称流动导致空泡形成非对称沾湿区,依据流动介质的不同,非对称沾湿区可分为透明气相区、水气混合区及沾湿区.水气混合边界由底端母线...     

一种定征层状平面结构界面粘接强度的兰姆波方法

置于层状平面结构表面的斜劈超声换能器被用于激发和接收多模兰姆波。文章首先分析了采用多模兰姆波的幅频特性定征界面粘接强度的可行性。基于Ritec-SNAP 超声测量系统,建立了采用兰姆波方法定征层状结构界面粘接强度的实验系统。对于给定的层状平面结构,将粘接层的固化过程用于模拟粘接层界面强度的变化过程。对于不同的粘接层固化时间,实验测得的多模兰姆波幅频曲线明显不同。借助于声——超声技术中的应力波因子,给出了兰姆波应力波因子的定义。实验结果显示,兰姆波应力波因子与间接表示界面粘接强度的固化时间之间存在确定的单调对应关系,表明将多模兰姆波的应力波因子用于定征层状平面结构的界面粘接强度是可行的。     

双源连续波对引信的辐照效应研究

为研究复杂电磁环境对某引信的影响,从双源连续波入手,运用双源连续波对工作状态某引信辐照的实验方法进行实验.实验结果表明,在以引信工作频率为中心的150MHz频率范围内对加电引信进行双源连续波辐照实验可使引信发火,辐照结束后引信工作正常,实验的重复性较好.两连续波频率间隔不同,可使引信发火的场强组合数值大小不相同,实验中当两连续波远离引信工作频率且频差10MHz以上时,发火场强组合近似呈线性.最后对双源连续波对引信的辐照效应机理作了分析,两连续波频率间隔不同,引信发火机理不同.     

轴向应力波作用下的圆柱壳弹塑性后屈曲

为揭示柱壳屈曲变形的发展机理及屈曲波与弹塑性应力波耦合传播间的关系,运用非线性显示动力学有限元分析方法对承受轴向高速冲击载荷作用下柱壳的弹塑性后屈曲过程进行了研究。分析结果表明:对于柱壳在轴向高速冲击下的弹塑性轴对称动力屈曲,主要屈曲变形发生在柱壳的两端,屈曲变形的产生及发展与应力波在壳中的传播过程密切相关;塑性应力波在整个屈曲过程中起了绝对支配的作用;屈曲波的产生及发展,都与塑性波的传播及反射有关;弹性应力波由于在整个屈曲过程中持续的时间极短,处于次要的地位。     

传热对水边界层流动的影响

本文评述了壁面传热对水边界层流体流动及其阻力的影响,同时分析了加热减阻的应用及其影响因素。传热不仅对层流流动、层流向湍流的转捩以及湍流流动有明显的影响,而且对流动分离以及由分离引起的空化也有显著影响。以热脉冲加热的主动式加热方式既可用来产生和消除边界层的T-S波,也能用来控制边界层的分离。因此,热控制技术可望在控制边界层转捩和分离,减小流动阻力等方面得到应用。     

轴对称物体空泡流动的数值计算

基于势流理论和边界元方法,对水下运动的回转体的空泡流进行了数值模拟.将半经验空泡封闭模型由平面流动推广至轴对称流动.对头部为圆锥的圆柱体空泡流动进行了数值计算.分析了空化数、半锥角、空泡长度间的关系.计算与实验结果符合较好.     

Chain damage effects of multi-spaced plates by reactive jet impact

Chain damage is a new phenomenon that occurs when a reactive jet impacts and penetrates multi-spaced plates.The reactive jet produces mechanical perforations on the spaced plates by its kinetic energy(KE),and then results in unusual chain rupturing effects and excessive structural damage on the spaced plates by its deflagration reaction.In the present study,the chain damage behavior is initially demonstrated by experiments.The reactive liners,composed of 26 wt％Al and 74 wt％PTFE,are fabricated through a pressing and sintering process.Three reactive liner thicknesses of 0.08 CD,0.10 CD and 0.12 CD(charge diameter)are chosen to carry out the chain damage experiments.The results show a chain rupturing phenomenon caused by reactive jet.The constant reaction delay time and the different penetration velocities of reactive jets from liners with different thicknesses result in the variation of the deflagration position,which consequently determines the number of ruptured plates behind the armor.Then,the finite-element code AUTODYN-3D has been used to simulate the kinetic energy only-induced rupturing effects on plates,based on the mechanism of behind armor debris(BAD).The significant discrepancies between simulations and experiments indicate that one enhanced damage mechanism,the behind armor blast(BAB),has acted on the ruptured plates.Finally,a theoretical model is used to consider the BAB-induced enhancement,and the analysis shows that the rupturing area on aluminum plates depends strongly upon the KE only-induced pre-perforations,the mass of reactive materials,and the thickness of plates.     

动态旋流器湍流流场的模拟研究

采用雷诺应力模型对动态旋流器湍流流场进行模拟.模拟结果与文献实验数据基本吻合,证明该模型的正确性.其中,轴向和切向速度的模拟结果和实际结果非常接近;径向速度的模拟将有助于旋流器结构及性能的分析.所建立的模型和所使用的计算方法为深入探讨动态水力旋流器的流场特性、分离机理及结构优化设计提供了一条有效的途径.     

Experimental study on the cavity evolution and liquid spurt of hydrodynamic ram

In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than 996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are 15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.     

Experimental research on the instability propagation characteristics of liquid kerosene rotating detonation wave

In order to study the instability propagation characteristics of the liquid kerosene rotating detonation wave (RDW), a series of experimental tests were carried out on the rotating detonation combustor (RDC) with air-heater. The fuel and oxidizer are room-temperature liquid kerosene and preheated oxygen-enriched air, respectively. The experimental tests keep the equivalence ratio of 0.81 and the oxygen mass fraction of 35% unchanged, and the total mass flow rate is maintained at about 1000 g/s, changing the total temperature of the oxygen-enriched air from 620 K to 860 K. Three different types of instability were observed in the experiments: temporal and spatial instability, mode transition and re-initiation. The interaction between RDW and supply plenum may be the main reason for the fluctuations of detonation wave velocity and pressure peaks with time. Moreover, the inconsistent mixing of fuel and oxidizer at different circumferential positions is related to RDW oscillate spatially. The phenomenon of single-double-single wave transition is analyzed. During the transition, the initial RDW weakens until disappears, and the compression wave strengthens until it becomes a new RDW and propagates steadily. The increased deflagration between the detonation products and the fresh gas layer caused by excessively high temperature is one of the reasons for the RDC quenching and re-initiation.     

Mitigation of the blast load effects on a building structure using newly composite structural configurations

In this study, a nonlinear three-dimensional hydrocode numerical simulation was carried out using AUTODYN-3D to investigate the effect of blasting of a high explosive material (TNT) against several configurations of the composite structure. Several numerical models were carried out to study the effect of varying the thickness of the walls and the effect of adding an air layer or aluminum foam layer inside two layers of concrete in mitigating the effect of blast waves on the structure walls. The results showed that increasing the thickness of walls has a good effect on mitigating the effect of blast waves. When a layer of air was added, the effect of blast waves was exaggerated, while when a layer of aluminum foam was added the blast wave effects were mitigated with a reasonable percentage.     

两道同侧扫掠激波作用下形成的三维平板边界层

为探索一种减弱扫掠激波/边界层干扰强度的侧压方式,采用数值计算方法研究两道同侧扫掠激波作用下形成的三维平板边界层。对三维边界层的流动机理进行研究,并与相同气流偏转角的一道扫掠激波作用下形成的三维边界层进行定量比较。研究表明,存在两道同侧扫掠激波时,第一道扫掠激波使侧壁附近边界层变薄,进而使第二道扫掠激波与再附形成的边界层的相互作用减弱,从而总的效果是两道扫掠激波与边界层的相互作用强度比一道扫掠激波的弱;两道扫掠激波的气流总偏转角与一道扫掠激波的相同,相交后汇聚成的激波强度与一道扫掠激波的基本相同,之前被两道扫掠激波"扫"起来的边界层在汇聚激波作用下还呈现锥形流动,分离线和来流的夹角也与一道扫掠激波的基本相同。     

冲床连杆瓦隔振有限元分析及降噪实验研究

在冲床连杆瓦背部设置弹性元件,可以显著地降低作用于床身的动载荷,阻止振动向床身传递.为了解隔振对床身动态特性的影响,预测其隔振效果,现运用有限元方法,利用SAP91软件对隔振前后的床身一隔振器系统的模态及动力响应进行分析比较,并对阻尼处理后的连杆瓦减振降噪效果进行了实验研究.     

轴向冲击载荷下圆柱壳的塑性动力屈曲

对于轴向冲击载荷下圆柱壳的轴对称塑性动力屈曲问题,将临界应力和屈曲惯性项指数参数作为双特征参数求解.由相邻平衡准则导出失稳控制方程、边界条件和波阵面上的连续条件.由失稳瞬间的能量转换和守恒准则,导出波阵面上的一个屈曲变形约束方程.由此得出定量求解2个特征参数和动力屈曲模态的完备定解条件.关于屈曲应力和屈曲波数的理论计算结果与已有实验吻合良好.     

(修，2撤3)关键几何参数对超声速膨胀器流场和性能影响的数值研究

为了揭示关键几何参数对超声速膨胀器流动特性影响的规律,对3种隔板安装角和5种出进口面积比超声速膨胀器设计工况下的流场进行了数值研究。结果表明：随隔板安装角增加,斜激波向出口迁移,斜激波强度略有降低,超声速膨胀器膨胀比减小,效率提高;随出进口面积比增加,流道内高速区显著扩大并逐渐靠近压力面,斜激波增强,出口流动损失增加,超声速膨胀器膨胀比增大,效率降低。为获得综合性能较优超声速膨胀器结构,需在较小出进口面积比和较大隔板安装角之间做折衷选择。     

考虑入口和出口容积效应的涡轮动力学模型

建立了考虑涡轮入口和出口容积效应的涡轮动力学模型 ,利用该模型计算了燃气涡轮气瓶启动的动态响应过程 ,分析了影响涡轮动态特性的主要因素。计算结果表明 :涡轮前容积对涡轮入口压力和出口背压的过渡过程均有显著的影响 ,涡轮后容积对涡轮入口压力的过渡过程影响不大 ,对涡轮出口背压的影响显著。     

间接边界元法模拟含裂纹介质中弹性波的传播

介绍了间接边界元法的基本理论,利用二维弹性动力边界积分方程解决了地震波在含裂纹介质中的散射问题。编写了地震波在二维非均匀介质中传播的数值模拟程序,模拟了爆炸点源在含裂纹介质中的传播情况,分析了裂纹的分布及填充物对波传播的影响。结果表明,边界元法是研究含裂纹介质中弹性波传播的有效工具。     

激波诱导惰性堆积粉尘运动的建模及数值模拟

基于空间平均的双流体模型 ,引入描述颗粒脉动速度的粒化温度 ,建立颗粒相的本构方程 ,将粒化温度模型推广到解决高速流动问题。采用AUSM+ 有限差分法 ,数值模拟激波在一定厚度的惰性粉尘床中传播及诱导粉尘颗粒运动的过程。结果表明 ,粒化温度模型较好地描述了这一过程 ,证实了此模型在处理稠密颗粒高速流动和流场存在强间断中的可行性     

复合材料层合圆柱壳的动力响应与层间应力

采用分层壳理论和厚度方向的二次插值函数推导出正交铺设层合圆柱壳的动力响应方程,并得出简支层合圆柱壳自由振动问题的解.对于给定算例,计算出的自振频率与三维分析的结果吻合良好,说明所推导的二维解具有足够精度.计算了前四阶模态对应的壳中应力.计算结果说明,对于高阶模态,层间应力相对于面内应力的比值远高于低阶模态的对应比值,高的层间正应力是高阶模态导致脱层破坏的主要原因.     

惰性气体中电爆丝爆炸激励冲击波的理论分析

建立了惰性气体中电爆丝爆炸激励的冲击波模型。对于冲击波马赫数与光辐射强度的关系、惰性气体种类对冲击波强度的影响以及电爆丝根数对冲击波强度的影响,进行了理论计算与分析,所得结论对红外脉冲强光辐射源的研究有重要作用。