Relation between Actual Mass and Simulation Mass of Far-Field Underwater Explosion

The far-filed underwater explosive shock wave pressure and impulse is simulated by the FEM code LS-DYNA, and the simulation results are found having rapid decay characteristic through compared with the empirical results. Based on this phenomenon, the relations, whose validity is verified through a computation instance, between simulation mass and actual mass under given initial conditional is obtained by using curve fitting. Using those equations, the accuracy of LS-DYNA to simulate far-field underwater explosive can significantly be increased, thus the ability of this code to simulate far-field underwater explosion is enhanced.

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A Lab-Scale Experiment Approach to the Measurement of Wall Pressure from Near-Field under Water Explosions by a Hopkinson Bar

Shock and Vibration ◽

10.1155/2018/8273469 ◽

2018 ◽

Vol 2018 ◽

pp. 1-15 ◽

Cited By ~ 4

Author(s):

Xiongwei Cui ◽

Xiongliang Yao ◽

Yingyu Chen

Keyword(s):

Shock Wave ◽

Near Field ◽

Underwater Explosion ◽

Experimental System ◽

Hopkinson Bar ◽

Wall Pressure ◽

Pressure Loading ◽

Target Plate ◽

Wave Pressure ◽

Shock Wave Pressure

Direct measurement of the wall pressure loading subjected to the near-field underwater explosion is of great difficulty. In this article, an improved methodology and a lab-scale experimental system are proposed and manufactured to assess the wall pressure loading. In the methodology, a Hopkinson bar (HPB), used as the sensing element, is inserted through the hole drilled on the target plate and the bar’s end face lies flush with the loaded face of the target plate to detect and record the pressure loading. Furthermore, two improvements have been made on this methodology to measure the wall pressure loading from a near-field underwater explosion. The first one is some waterproof units added to make it suitable for the underwater environment. The second one is a hard rubber cylinder placed at the distal end, and a pair of ropes taped on the HPB is used to pull the HPB against the cylinder hard to ensure the HPB’s end face flushes with loaded face of the target plate during the bubble collapse. To validate the pressure measurement technique based on the HPB, an underwater explosion between two parallelly mounted circular target plates is used as the validating system. Based on the assumption that the shock wave pressure profiles at the two points on the two plates which are symmetrical to each other about the middle plane of symmetry are the same, it was found that the pressure obtained by the HPB was in excellent agreement with pressure transducer measurements, thus validating the proposed technique. To verify the capability of this improved methodology and experimental system, a series of minicharge underwater explosion experiments are conducted. From the recorded pressure-time profiles coupled with the underwater explosion evolution images captured by the HSV camera, the shock wave pressure loading and bubble-jet pressure loadings are captured in detail at 5 mm, 10 mm, …, 30 mm stand-off distances. Part of the pressure loading of the experiment at 35 mm stand-off distance is recorded, which is still of great help and significance for engineers. Especially, the peak pressure of the shock wave is captured.

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Dynamic Responses of a Cylindrical Shell Subjected to Shock Wave Induced by Underwater Explosion

Volume 1D: 16th Biennial Conference on Mechanical Vibration and Noise ◽

10.1115/detc97/vib-3923 ◽

1997 ◽

Author(s):

Zhong Weifang ◽

Liu Zhongzu

Keyword(s):

Shock Wave ◽

Cylindrical Shell ◽

Underwater Explosion ◽

Dynamic Responses ◽

Equilibrium Equations ◽

Wave Pressure ◽

Coupled Equations ◽

Shock Wave Pressure ◽

Wave Induced ◽

Interaction Problem

Abstract The dynamic responses of a finite length cylindrical shell submerged in an infinite, inviscid, irrotational, incompressible fluid and subjected to shock waves induced to underwater explosion due to a spherical charge, are investigated in the view of method of modal superposition. Effects of shock wave pressure and hydrodynamic force are considered in shell equilibrium equations. By expanding distribution function of shock wave pressure into Fourier series and using method of Galerkin, the coupled equations of fluid-structure interaction problem are solved numerically. Finally, displacement re sponse of the shell is obtained.

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