激波驱动下密实填充颗粒的初始运动机制研究

Explosive dispersal technology which is widely used in the military and civilian areas has important academic and application value. The researches on this problem are mainly focused on the overall effect of the explosive dispersal, while the study on the cloud concentration formed after the explosive dispersal is not deep enough to restrict the application of the explosive dispersal. The fundamental solution to this problem is the precise controlling of the temporal and spatial distribution of the cloud concentration from the initial movement of the densely-packed particles. The detailed investigation of the loading and movement of the particles under the blast or shock wave were mainly carried out in shock tubes, and mainly around the single particle, dilute particles, and dense particles. In this project, the densely-packed particles, which is more similar to the actual explosive dispersal, are impacted by planar shock waves in the shock tube to investigate the mechanism of the initial movement of the densely-packed particles..In this project, the densely-packed particles layers are impacted by low-strength and high-strength incident shock waves in the compressed gas and the detonation driving shock tube cooperated with the high-speed schlieren imaging system, pressure measurement system and particle concentration measurement system. The research details include: i) study the complex wave structures and energy attenuation in the process of the interaction between shock wave and densely-packed particles, and obtain the pressure gradient of the internal flow field in the densely-packed particles; ii) study the movement positions of the upstream and downstream interfaces of the densely-packed particle layer and the internal concentration distribution at the initial moving stage of the particle layer; iii) investigate the initial motion physical mechanism of the densely-packed particles, and establish the motion model of the densely-packed particles which are transformed into the dense gas-particle flow. The researches of the project are beneficial to deep understanding of the explosive dispersal mechanism and cloud concentration controlling of the dispersal.

爆炸抛撒技术在军事和民用领域都有广泛应用，具有重要的学术和应用价值。目前研究主要集中在抛撒整体效果上，对云雾浓度的研究还不够深入，制约了它的应用和发展。这需要从被抛撒颗粒的初始运动开始，精确控制抛撒过程中云雾浓度的时空分布。目前颗粒在冲击流场中受力和运动的细致研究主要在激波管中进行，且主要集中在单颗粒、稀疏颗粒群以及稠密颗粒群上，本项目以更接近爆炸抛撒实际的密实填充颗粒为研究对象，在激波管中进行加载实验，借助多种瞬态测量技术，研究密实填充颗粒的初始运动机制。主要内容包括：（1）研究激波与密实填充颗粒层相互作用过程中的复杂波系结构和能量衰减；（2）研究激波驱动下密实填充颗粒在开始运动初期的边界运动及浓度分布；（3）研究密实颗粒在激波驱动下逐步开始运动的物理机制，建立密实填充颗粒向稠密颗粒流转化的密实颗粒运动模型。本项目研究有利于深入理解爆炸抛撒的物理机制，为抛撒云雾场的浓度控制提供理论指导。

大量密实颗粒在爆炸、冲击荷载作用下，初期的膨胀、射流等特殊现象，决定着远场的颗粒分布，制约着爆炸抛撒技术在军事和民用领域的精确应用。本项目对密实颗粒在激波驱动初期的受力状态、运动状态、演化过程、运动机制等进行了实验和数值研究。1）建立了激波/密实颗粒层相互作用实验系统，将可压缩气粒两相流的激波管实验研究，从加载稠密颗粒云团拓展到了加载密实填充颗粒，捕获到激波驱动下密实颗粒初始运动阶段的界面运动特征和内部浓度特征。2）将激波驱动密实颗粒层初始运动过程划分为准静态和加速两阶段，在准静态阶段（数十微秒），激波完成在密实颗粒层上的入射、反射和透射，颗粒层被进一步压缩和重新排列，颗粒骨架上建立起向下游传播应力波，颗粒层获得每秒几米量级的不可识别的轴向速度。在加速阶段，由于渗透气流的携带作用，下游颗粒获得每秒几十米量级的可识别的轴向速度。3）发现本实验中的微米颗粒填充颗粒层对激波的能量衰减不能用现有的颗粒层激波衰减模型来描述，对现有模型进行了修正，可以统一描述毫米颗粒和微米颗粒填充颗粒层的激波衰减性能，也揭示了影响流场压力梯度的决定因素是颗粒骨架间孔隙率而非颗粒粒径。4）基于上述密实颗粒受力、运动状况的实验观测和模拟分析，以及颗粒层激波衰减模型，应用气体非定常膨胀理论和非达西渗流理论，考虑气体渗流及颗粒层质量损失，建立了密实颗粒层上、下游界面在激波诱导高速气流驱动下活塞式推进膨胀的颗粒运动模型，揭示了激波驱动下密实填充颗粒的阻塞-渗透双重物理机制。5）另外，采用欧拉-拉格朗日框架，开发了一种可压缩-稠密颗粒三维四向耦合的多相流求解程序，并采用Wanger et al.经典激波驱动颗粒幕膨胀实验和本实验进行了验证，程序用于爆炸冲击波驱动下颗粒抛撒流场的计算和设计。

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