为了研究固体火箭发动机在封闭水域中工作时尾流场特性参数变化规律,建立三维空间模型,忽略重浮力等体积力及燃气与水之间的换热传质,采用Realizable k-ε湍流模型与VOF (Volume of fluid)多相流模型,针对试验水箱内固体发动机在不同水深条件下的工作过程进行数值模拟,获得尾流流场燃气射流形貌,以及水箱壁面受力与压强振荡规律。研究结果表明:三维空间模型的仿真结果与试验结果较为符合;燃气泡的形貌结构及尾流场特性参数变化在受限空间内分布呈非轴对称性;射流中心气路内部不稳定的激波运动宏观表现为射流界面的不稳定胀鼓和颈缩位置的后移;深水条件下试验水箱壁面靠近喷管出口位置承受压强幅值更大,高背压环境中水箱壁面更易受到局部低频小幅压强冲击。
A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of the screw dislocation in smectic A is the key to the correct result that we obtained by overcoming a longstanding puzzle. We further use the dislocation pile-up principle and the singular integral equation method to construct the solution of the crack in the phase. From the solution, we can determine the size of the plastic zone at the crack tip and the crack tip opening(tearing)displacement, which are the parameters relevant to the local stability/instability of materials. Our results may be useful for developing soft-matter mechanics.
