A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized s...A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.展开更多
冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Media...冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Median Volume Diameter,MVD)、总含水量(Total Water Content,TWC)以及相对湿度的情况下,粒子温度、液态水占总含水量的比例(Liquid Water Content/Total Water Content,LWC/TWC)、MVD以及流场温度等粒子和流场参数的沿程变化规律。结果表明:粒子运动速度受MVD、TWC和相对湿度的影响均不大;粒子温度变化受相对湿度影响较大,TWC的增加增大了粒子与流场整体的热交换;风洞出口MVD的大小受初始MVD大小、TWC以及相对湿度的影响均较大;受风洞收缩型构型以及粒子在风洞中的换热影响,空气温度沿流程是降低的,相对湿度沿程是增加的。初始TWC、MVD和相对湿度的变化均对风洞沿程的流场温度和相对湿度造成影响;增大TWC、增加MVD以及增大相对湿度,均有利于在风洞出口形成冰晶。展开更多
基金This work was supported by the National Natural Science Foundation of China(No.11372139)the China Postdoctoral Science Foundation(2020M681596).
文摘A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.
文摘冰晶结冰是威胁航空飞行安全的重要因素之一,研究冰风洞的结冰机理是研究高空冰晶结冰的重要基础。采用基于欧拉方法的数值模拟,实现冰风洞流场与粒子参数的双向耦合,以NRC大尺寸冰风洞为模型,计算分析了风洞进口不同平均体积直径(Median Volume Diameter,MVD)、总含水量(Total Water Content,TWC)以及相对湿度的情况下,粒子温度、液态水占总含水量的比例(Liquid Water Content/Total Water Content,LWC/TWC)、MVD以及流场温度等粒子和流场参数的沿程变化规律。结果表明:粒子运动速度受MVD、TWC和相对湿度的影响均不大;粒子温度变化受相对湿度影响较大,TWC的增加增大了粒子与流场整体的热交换;风洞出口MVD的大小受初始MVD大小、TWC以及相对湿度的影响均较大;受风洞收缩型构型以及粒子在风洞中的换热影响,空气温度沿流程是降低的,相对湿度沿程是增加的。初始TWC、MVD和相对湿度的变化均对风洞沿程的流场温度和相对湿度造成影响;增大TWC、增加MVD以及增大相对湿度,均有利于在风洞出口形成冰晶。
