Abstract

This paper introduces a modified method of characteristics and its application in forward and inversion simulations of underwater explosion. Compared with standard method of characteristics which is appropriate to homoentripic flow problem, the modified method can be also used to deal with isentropic flow problem such as underwater explosion. Underwater explosion of spherical TNT and composition B explosives are simulated by using the modified method, respectively. Peak pressures and flow field pressures are obtained, and they are coincident with those from empirical formulas. The comparison demonstrates the modified is feasible and reliable in underwater explosion simulation. Based on the modified method, inverse difference schemes and inverse method are introduced. Combined with the modified, the inverse schemes can be used to deal with gas-water interface inversion of underwater explosion. Inversion simulations of underwater explosion of the explosives are performed in water, and equation of state (EOS) of detonation product is not needed. The peak pressures from the forward simulations are provided as boundary conditions in the inversion simulations. Inversion interfaces are obtained and they are mainly in good agreement with those from the forward simulations in near field. The comparison indicates the inverse method and the inverse difference schemes are reliable and reasonable in interface inversion simulation.

Highlights

  • Gas bubble pulsation is an important research subject in underwater explosion of spherical explosive, and it has been widely studied

  • This paper introduces a modified method of characteristics and its application in forward and inversion simulations of underwater explosion

  • This paper introduces forward simulations of underwater explosion of spherical TNT and composition B explosives first

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Summary

INTRODUCTION

Gas bubble pulsation is an important research subject in underwater explosion of spherical explosive, and it has been widely studied. Corresponding simulated results including properties of shock wave, bubble and flow field can be obtained and some of them are difficult to be measured in experiment. Many researchers have performed underwater explosion simulations to study bubble pulsation.[5,6,7,8] Most underwater explosion simulations base on forward problem, and detonation product EOS parameters are of importance and necessity in the forward simulations.[9,10,11,12] Standard method of characteristics is a classical calculation method and has clear physical significance. Because detonation product EOS is not used in inversion simulation, the inverse schemes can be combined with parameters of shock wave measured in experiment to confirm gas-water interface properties for explosive whose detonation parameters are unknown

BASIC EQUATIONS OF THE MODIFIED METHOD OF CHARACTERISTICS
EQUATIONS FOR ONE-DIMENSIONAL SPHERICAL SYMMETRIC UNDERWATER EXPLOSION
Basic characteristics equations for underwater explosion
Equation of state for products
FORWARD SIMULATIONS OF UNDERWATER EXPLOSION OF SPHERICAL EXPLOSIVE
Difference schemes in forward simulation
Solid wall boundary and gas-water interface in simulation
Empirical formula of composition B explosive
Empirical formula of TNT explosive
Forward simulations and result discussions
Underwater explosion simulations from AUTODYN software
Simulations of composition B explosive
Simulations of TNT explosive
APPLICATIONS OF THE MODIFIED METHOD IN INVERSE PROBLEM
Inverse difference schemes for inversion simulation
Boundary condition in inversion simulation
Inversion simulations and discussions
Findings
CONCLUSIONS
Full Text
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