冰孔约束下圆柱体倾斜入水空泡演化与流场特性数值模拟

doi:10.12382/bgxb.2023.0969

摘要/Abstract

摘要：

为研究冰孔约束对圆柱体倾斜入水过程的影响,基于流体体积多相流模型建立冰孔约束下的圆柱体入水数值方法,并通过实验测试,完成数值方法准确性的验证。在此基础上,开展不同冰孔孔径下圆柱体入水运动过程的模拟仿真,分析冰孔约束条件下圆柱体入水过程中的空泡演化特性与运动特性。研究结果表明:冰孔约束改变了自由液面的流动情况,从而影响了表面喷溅方向和形态。另外,由于液体撞击冰孔壁消耗了部分空泡用于扩张的能量,导致空泡扩张受阻,并且撞击后形成反射流,而反射流与空泡扩张方向相反,进一步使空泡受阻,致使背水面空泡壁呈弯曲状。在较小冰孔直径工况下,空泡壁与冰孔发生直接接触,使空泡发生局部变形,并且扩张受阻。而在较大冰孔直径工况下,空泡壁未与冰孔接触,此时反射流成为抑制空泡形态的主要原因;除此之外,冰孔约束下,自由液面处会出现了更大范围的剪切变形区域,并且腔内存在更多大尺度的涡旋,这些涡旋导致腔内的压力梯度增大,从而使空泡受到不同方向的压力,进而抑制自由液面处的空泡形态;冰孔约束导致圆柱体入水载荷峰值增大,并造成圆柱体的速度衰减更快。

关键词: 冰孔约束, 倾斜入水, 空泡演化, 涡旋分布, 运动特性

Abstract:

In order to study the influence of ice hole constraint on the inclined water entry process of a cylinder, a numerical method for a cylinder entering water entry under ice hole constraint is established based on a volume-of-fluid multiphase flow model. The accuracy of the numerical method is verified by experimental tests. On this basis, the process of the cylinder entering water under the condition of different ice hole diameters is simulation, and the cavitaty evolution and motion characteristics of the cylinder entering water under the constraint of ice hole are analyzed. The results show that the ice hole constraint changes the flow of free liquid surface, thus affecting the direction and shape of surface splash. In addition, because the liquid hits the wall of ice hole, it consumes part of the energy of cavity for expansion, which leads to the obstruction of cavity expansion. A reflected flow is formed after impact, and the reflected flow is opposite to the expansion direction of cavity, which further hinders the cavity expansion and causes the cavity wall of the water-away side to be curved. The cavity wall is in direct contact with the ice hole under the condition of small ice hole diameter, which makes the cavity deform locally and hinders its expansion. Under the condition of larger ice hole diameter, the cavity wall does not contact with the ice hole, and the reflected flow becomes the main reason for inhibiting the cavity shape. In addition, under the constraint of ice holes, a wider shear deformation area appears on the free liquid surface, and there are more large-scale vortices in the cavity. The vortices lead to the increase of pressure gradient in the cavity to make the cavity subject to pressure in different directions, thus inhibiting the cavity shape at the free liquid surface. Ice hole constraint causes the increase in the peak value of water-entry load of cylinder, and the faster velocity decay of cylinder.

Key words: ice hole constraint, oblique water-entry, cavity evolution, vortex distribution, motion characteristics

中图分类号:

O383
TJ012.3

杨哲, 鹿麟, 李强, 孙志群, 侯宇. 冰孔约束下圆柱体倾斜入水空泡演化与流场特性数值模拟[J]. 兵工学报, 2024, 45(12): 4539-4553.

YANG Zhe, LU Lin, LI Qiang, SUN Zhiqun, HOU Yu. Numerical Simulation on Cavity Evolution and Flow Field Characteristics of Cylinder Obliquely Entering Water under Ice Hole Constraint[J]. Acta Armamentarii, 2024, 45(12): 4539-4553.

图/表 27

图1 实验系统示意图

Fig.1 Schematic diagram of experimental apparatus

图2 实验现场布置

Fig.2 Experimental installation site layout

图3 实验圆柱体模型

Fig.3 Experimental cylinder model

图4 圆柱体倾斜入水空泡轮廓实验结果(左)与仿真结果(右)对比

Fig.4 Comparison of experimental (left) and numerical (right) cavity shapes in the process of cylinder oblique water-entry

图5 圆柱体速度衰减仿真与实验结果对比

Fig.5 Comparison between simulated and experimental results of cylinder velocity reduction

图6 计算模型

Fig.6 Calculation model

图7 数值模型验证

Fig.7 Validation of the numerical model

图8 计算模型设置

Fig.8 Calculation model settings

图9 入水条件设置

Fig.9 Setting of water entry conditions

图10 整体网格划分

Fig.10 Global grid division

图11 弹丸表面y+值的最小值

Fig.11 The minimum value of y+ on the projectile surface

图12 入水过程中库朗数变化情况

Fig.12 Number of Courant in the water entry process

图13 不同网格密度下速度衰减曲线

Fig.13 Velocity attenuation curves under different grid densities

图14 三维空泡形态演化

Fig.14 Three-dimensional cavitation morphology evolution

图15 入水过程示意图

Fig.15 Schematic diagram of water entry process

图16 碰撞后速度矢量示意图

Fig.16 Schematic diagram of velocity vector after collision

图17 空气流动情况

Fig.17 Air flow distribution

图18 密度云图

Fig.18 Density nephogram

图19 空泡测量方法及结果

Fig.19 The measurement method and measured results of cavity

图20 局部流场矢量

Fig.20 Vector diagram of local flow field

图21 空气相分布情况

Fig.21 Air phase distribution

图22 蒸汽相分布情况

Fig.22 Vapor phase distribution

图23 无冰和Φ=4环境下x=0mm平面上的涡旋分布

Fig.23 Vortex distribution on x=0mm plane in ice-free and Φ=4 environment

图24 速度矢量场

Fig.24 Velocity vector field

图25 腔内压力分布

Fig.25 Pressure distribution in cavity

图26 流场动力特性

Fig.26 Dynamic characteristics of flow field

图27 偏转角

Fig.27 Deflection angle

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