可压缩介质中细长体高速入水过程流动机理实验方法与数值模拟研究

The prediction of hydrodynamic impact loads in high-speed water entry is of great significance in the design of naval architecture, aeronautical and aerospace structures. The hydrodynamic load during the impact period is characterized by the huge transient pressures, which may potentially damage the structure. In nature, the sound speed of natural seawater is around 100m/s due to the existence of tiny air bubble. The compressible effects became important when the water entry speed approaches the sound speed of air/natural seawater. Compressible effects, strong nonlinear air-water interface deformation and cavitation are the dominant phenomenon during high-speed water entry process.. Toward to understand the compressible effects in the high-speed water entry problem, laboratory experiments will be conducted to investigate the water entry of slender bodies. According to the order analysis, the influence of Mach number, Froude number and Cavitation number will be studied. To decrease the sound speed of fluid and realize the high Mach number flows in laboratory other than high-speed water tunnel, a novel approach will be stablished through the injection of tiny air bubble into the water tank. With the similarity analysis, the experimental results could be convert to real high Mach number flows in high-speed water entry, or the slamming problem involved breaking waves with complex air-water mixture. . To investigate the effects of air cushion, compressible effects, numerical models for high-speed water entry will be developed. Through numerical simulations, the hydrodynamic loads and flow field during the impact and closure process will be studied.

船体砰击、航天器回收以及空投武器都涉及入水问题。自然界含微气泡的海洋表面水体声速仅有100m/s量级。随着工程需求的发展，物体入水速度已与空气和含微气泡水体的声速接近，需要考虑流动介质可压缩性的影响。高速物体入水过程涉及介质可压缩性、自由面大变形、入水空泡和局部空化诸多复杂水动力学问题及相互作用。. 针对高速物体在穿越可压缩水、气介质与水气界面的水动力学问题，开展不同外形细长体垂直入水和斜入水过程流场和水动力机理实验研究，通过对马赫数、傅汝德数和空化数等多个无量纲参数的分析，发展通过改变流动介质声速增强可压缩特征的实验方法，建立常规实验室环境开展高速入水过程机理实验的相似准则和实验原理；发展可压缩多相流动数学模型，通过实验和数值模拟研究气垫效应、水体弱可压缩性对入水撞击阶段水动力抨击作用和入水空泡发展、封闭的影响规律，为高速物体入水机理实验和非定常水动力学载荷预报提供技术手段。

船体砰击、航天器回收以及空投武器都涉及入水问题。高速物体入水过程涉及介质可压缩性、自由面大变形、入水空泡和局部空化诸多复杂水动力学问题及相互作用。.针对高速物体在穿越可压缩水、气介质与水气界面的水动力学问题，发展了水中添加微气泡的途径降低含微气泡水体介质的声速、增强可压缩特征的实验方法研究，建立常规实验室环境高速入水过程机理实验的相似律和实验原理；完成了不同外形细长体垂直入水和斜入水过程流场和水动力机理实验研究，并对马赫数、傅汝德数和空化数等多个无量纲参数的影响进行了分析。. 发展了可压缩多相流动数学模型，开发了基于Godunov格式的两相可压缩求解器，在嵌套网格和贴体网格上实现了基于MUSCL高阶格式的三维问题数值求解，通过实验和数值模拟研究高速物体接触水面前的气垫效应、水体弱可压缩性对入水撞击阶段水动力抨击作用。对回转体三维倾斜入水开展了数值研究，观察了倾斜入水时回转体的空腔演化，讨论了入水角度、入水速度和水中含气率对于砰击载荷的影响。. 针对汽泡在复杂流场中的运动和变形，开展了柱泡在各类漩涡流场中的自由面波动变形、膨胀收缩等动力学模型，分析了局部几何约束、粘性等因素的影响，并通过水洞实验结果验证了这一模型的有效性，显著拓展了泡动力学的研究范围。