﻿ 空爆冲击波对高速破片绕流效应的仿真
 舰船科学技术  2019, Vol. 41 Issue (1): 33-38 PDF

Research on turbulent flow of blast wave on high-velocity fragments by numerical simulation
ZHENG Hong-wei, CHEN Chang-hai, LI Mao, ZHU Xi, HOU Hai-liang
Department of Naval Architecture Engineering, Naval University of Engineering, Wuhan 430033, China
Abstract: Study is carried on turbulent flow of blast wave on high-velocity fragments and factors which may affect it. By Ansys/LS-DYNA software, simulation model of air blast that prefabricated fragments are affixed to the end of the columnar TNT is built. This research pays attention to describe the characteristic of the turbulent flow process and the influence factors such as fragment clearance, fragment size, fragment mass were discussed by analyzing realistic cases and comparing Numerical Simulation cases. The results show that turbulent flow of blast wave on high-velocity fragments take place at the beginning of the blast because the velocity of air-blast wave is higher than the velocity of fragments. What′s more, it will be easier for blast wave to make a detour, when the fragment is smaller, heavier and the clearance is bigger. Meanwhile, the smaller fragment clearance and bigger fragment size will make the detoured blast wave become weaker. In a word, the blast wave spread ahead of the fragments is turbulent flow of blast wave on high-velocity fragments. This research can provide reference for the study of blast loads propagation characteristic and damage characteristic.
Key words: explosion mechanics     air-blast wave     high-velocity fragment     turbulent flow     numerical simulation
0 引　言

1 模型建立与仿真方法验证 1.1 模型选择及参数设置

 图 1 模型示意图 Fig. 1 Schematic diagram of the model

 $P = A\left( {1 - \frac{\omega }{{{R_1}V}}} \right){e^{ - {R_1}V}} + B\left( {1 - \frac{\omega }{{{R_2}V}}} \right){e^{ - {R_2}V}} + \frac{{\omega {e_0}}}{V}\text{。}$ (1)

 $\begin{split} & P = {C_0} + {C_1}\mu + {C_2}{\mu ^2} + {C_3}{\mu ^3} + \\ & \left( {{C_4} + {C_5}\mu + {C_6}{\mu ^2}} \right){e_0}\text{，} \end{split}$ (2)

 ${\sigma _d} = \left( {{\sigma _0} + \frac{{E{E_h}}}{{E - {E_h}}}{\varepsilon _p}} \right)\left[ {1 + {{\left( {\frac{{\dot \varepsilon }}{D}} \right)}^{1/n}}} \right]\text{，}$ (3)

 ${\sigma _d} = \left( {{\sigma _0} + {E_h}{\varepsilon _p}^{{n_0}}} \right)\left[ {1 + c\ln \frac{{{\varepsilon _p}}}{{{\varepsilon _0}}}} \right]\left[ {1 - {{\left( {\frac{{T - {T_0}}}{{{T_m} - {T_0}}}} \right)}^m}} \right]\text{。}$ (4)

 $\begin{split} & {\varepsilon _f} = \left[ {{D_1} + {D_2}\exp \left( {{D_3}\frac{{{\sigma _h}}}{{{\sigma _{eff}}}}} \right)} \right]\left( {1 + {D_4}\frac{{{\varepsilon _p}}}{{{{\dot \varepsilon }_0}}}} \right) \times\\ & \left[ {1 + {D_5}5{{\left( {\frac{{T - {T_0}}}{{{T_m} - {T_0}}}} \right)}^m}} \right]\text{。} \end{split}$ (5)

1.2 仿真方法验证

 图 2 模型2预制破片布置图 Fig. 2 Placed fragments of model 2

 图 3 试验结果与模型仿真结果 Fig. 3 Experimental and numerical simulation images of damaged steel plate
1.3 冲击波对高速破片绕流作用分析

 图 4 模型冲击波压力云图 Fig. 4 Pressure contours of the model 2/3/4
1.4 计算工况

 图 5 观测点分布 Fig. 5 View point

2 计算结果分析 2.1 破片间隙对冲击波绕流作用影响

 图 6 模型case-2/4/6在35 μs时冲击波压力云图 Fig. 6 Pressure contours of the case-2/4/6 at 35 μs

 图 7 破片间隙对冲击波绕流影响 Fig. 7 Influence of fragment clearance on wave turbulent flow
2.2 破片尺寸对冲击波绕流作用影响

 图 8 模型case-8/13/18在26 μs时冲击波压力云图 Fig. 8 Pressure contours of the case-8/13/18 at 26 μs

 图 9 破片尺寸对冲击波绕流影响 Fig. 9 Influence of fragment size on wave turbulent flow
2.3 破片质量对冲击波绕流作用影响

 图 10 模型case-18/21/23在50 μs时冲击波压力云图 Fig. 10 Pressure contours of the case-18/21/23 at 50 μs

 图 11 破片质量对冲击波绕流影响 Fig. 11 Influence of fragment mass on wave turbulent flow
3 结　语

1）爆炸初期冲击波速度高于破片速度，在对破片加速的过程中，冲击波对高速破片存在绕流作用。

2）当预制破片端为破片群时，冲击波主要透过破片之间间隙，绕流至破片之前碰撞形成新的冲击波向前传播；而对于单一大破片，在破片前传播的冲击波主要是从破片两侧边缘绕流的冲击波在轴线附近碰撞产生，碰撞后对轴线上的冲击波有一定的加强。

3）当预制破片间存在间隙时，随破片间隙的增大，轴线方向的冲击波超压和比冲量增大，其波形和强度都越来越近似于裸药空爆的冲击波。

4）单一预制破片尺寸越大，冲击波对破片的绕流能力越差，绕流产生的冲击波强度随破片尺寸增大而逐渐降低。

5）迎爆面积不变，变化单一预制破片质量对绕流冲击波的波形及强度影响不大，但随破片质量增加，冲击波绕流过破片速度加快。

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