Pressure Load on Rigid Structure Induced by Double Underwater Explosions

2016 ◽  
Author(s):  
Rui Han ◽  
Aman Zhang ◽  
Shiping Wang
Keyword(s):  
Shock Wave ◽  
Underwater Explosion ◽  
Time Difference ◽  
Wave Load ◽  
Underwater Explosions ◽  
Rigid Structure ◽  
Pressure Load ◽  
Adjacent Structures ◽  
Explosive Source ◽  
Source Case

Underwater explosion is a severe threat to nearby ocean structures, such as underwater construction, floating vessels. The pressure load produced by underwater explosion of explosives consists of shock wave load and the explosion bubble pulsation pressure load. After the detonation, there will be a shock wave propagating radially outwards and it’s followed by a large oscillating bubble. The shock wave has the first damaging effect on adjacent structures. Then, the collapse and high-speed jet of oscillating bubbles will cause the second damage to structures. When there are double explosive sources near a rigid structure, the mutual superposition of shock waves and the interaction between two bubbles may improve the explosive damage. If the distance between one explosive source and the rigid structure is fixed, the damage force produced by double underwater explosions is related to many factors, like the detonation time difference and the distance between two explosive sources. At first, the pressure field in single explosive source case is numerically simulated by using the AUTODYN in this paper. Next, pressure fields of underwater explosion detonated by double sources at the same time and with time difference are calculated, respectively. The flow fields in double explosive sources case are compared with that in single explosive source case. The effect of the detonation time difference and the distance between explosive sources on the damage force is investigated and analysed in detail.

scholarly journals The Fluid-Solid Interaction Dynamics between Underwater Explosion Bubble and Corrugated Sandwich Plate

2016 ◽  
Vol 2016 ◽  
pp. 1-21
Author(s):  
Hao Wang ◽  
Yuan Sheng Cheng ◽  
Jun Liu ◽  
Lin Gan
Keyword(s):  
Shock Wave ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Numerical Models ◽  
Near Field ◽  
Three Dimensional ◽  
Underwater Explosion ◽  
Bubble Collapse ◽  
Fe Model ◽  
Wave Load

Lightweight sandwich structures with highly porous 2D cores or 3D (three-dimensional) periodic cores can effectively withstand underwater explosion load. In most of the previous studies of sandwich structure antiblast dynamics, the underwater explosion (UNDEX) bubble phase was neglected. As the UNDEX bubble load is one of the severest damage sources that may lead to structure large plastic deformation and crevasses failure, the failure mechanisms of sandwich structures might not be accurate if only shock wave is considered. In this paper, detailed 3D finite element (FE) numerical models of UNDEX bubble-LCSP (lightweight corrugated sandwich plates) interaction are developed by using MSC.Dytran. Upon the validated FE model, the bubble shape, impact pressure, and fluid field velocities for different stand-off distances are studied. Based on numerical results, the failure modes of LCSP and the whole damage process are obtained. It is demonstrated that the UNDEX bubble collapse jet local load plays a more significant role than the UNDEX shock wave load especially in near-field underwater explosion.

scholarly journals Pressure Load Characteristics of Explosions in an Adjacent Chamber

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chuan-hao Wang ◽  
Shu-shan Wang ◽  
Jing-xiao Zhang ◽  
Feng Ma
Keyword(s):  
Shock Wave ◽  
Classical Model ◽  
Low Frequency ◽  
Reflected Shock Wave ◽  
Main Chamber ◽  
Wave Load ◽  
Pressure Load ◽  
Reflected Shock ◽  
Internal Explosion ◽  
Input Parameters

To learn more about dynamite explosions in confined spaces, we focused on the chamber adjacent to the main chamber, the main chamber being the location of the explosion. We investigated the characteristics of two damaging pressure loads: first reflected shock wave and quasistatic pressure. In this work, we analyzed the characteristics of the first reflected shock wave and the quasistatic pressure formed by the explosion of the chamber charge. Simulated chamber explosion experiments were carried out, where high-frequency piezoelectric sensors were used to measure the first reflected shock wave, and low-frequency piezo-resistive sensors were used to measure the quasistatic pressure. Valid and reasonable experimental data were obtained, and the experimental values of the pressure load were compared with those calculated from the classical model. The results showed that when the main chamber was partially damaged by the explosion load, the adjacent chambers were not subjected to the shock wave load, and the quasistatic pressure load was less than that in the main chamber. The presence of adjacent chambers did not affect the shock wave load in the main chamber. Using the mass of the explosive and the blast distance as input parameters, the internal explosion shock wave load parameters, including those in adjacent chambers, can be calculated. The presence of the adjacent chamber did not affect the theoretically calculated quasistatic overpressure peak in the main chamber. Using the mass of the explosive and the spatial volume of the chamber as input parameters, the quasistatic pressure load parameters of the internal explosion can be calculated, including those in the adjacent chambers.

An Investigation on the Properties of Underwater Shock Waves Generated in Underwater Explosions of High Explosives

1997 ◽  
Vol 119 (4) ◽  
pp. 498-502 ◽  
Author(s):  
S. Itoh ◽  
Z. Liu ◽  
Y. Nadamitsu
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Numerical Simulations ◽  
Underwater Explosion ◽  
High Explosives ◽  
Underwater Shock Wave ◽  
Underwater Explosions ◽  
Expansion Test ◽  
Gas Products ◽  
Underwater Shock

A cylinder expansion test for high explosives was carried out to determine JWL parameters. Using the JWL parameters, we carried out numerical simulations of the underwater shock waves generated by the underwater explosion of the high explosives. Our results showed that the behavior of the underwater shock waves at the vicinity of the explosives differs greatly from that far from the explosives. Especially, the strength of the underwater shock wave nearby the explosive rapidly decreases due to the effect of the expansion of the gas products.

Modeling of the Minehunters Hull Strenght

2014 ◽  
Vol 1036 ◽  
pp. 189-194
Author(s):  
Andrzej Grządziela ◽  
Bogdan Szturomski ◽  
Marcin Kluczyk
Keyword(s):  
Shock Wave ◽  
Theoretical Analysis ◽  
Vibration Spectrum ◽  
Underwater Explosion ◽  
Virtual Model ◽  
Structure Model ◽  
Similar Nature ◽  
Underwater Explosions ◽  
Hull Structure ◽  
Impulse Load

The paper presents problems of modeling the ship’s hull subjected to the load of shock wave associated with non-contact underwater explosion. The article presents equations for describing the parameters of shock wave subjected to an impulse load. The paper presents a proposal of identification of a degree of hazard the ship’s hull forced from underwater explosion. A theoretical analysis was made of influence of changes of hull structure in vicinity of hull. Modeled signals and hull structure were recognized within sensitive symptoms of three sub models: model of hull structure, model of impact and model of propulsion system. All sub models allow testing forces and their responses in vibration spectrum using SIMULINK software and FEM models. The results of testing allowed performing simulations of a similar nature to the actual loads of underwater explosions. Virtual model of the hull of the ship responds in a similar manner to the real impacts.

Experimental investigation on the shock-wave load attenuation by geometrical means

Shock Waves ◽  
2009 ◽  
Vol 20 (1) ◽  
pp. 29-40 ◽  
Author(s):  
Shachar Berger ◽  
Oren Sadot ◽  
Gabi Ben-Dor
Keyword(s):  
Shock Wave ◽  
Experimental Investigation ◽  
Wave Load

EMISSION BY UNDERWATER EXPLOSIONS

Geophysics ◽  
1970 ◽  
Vol 35 (3) ◽  
pp. 419-435 ◽  
Author(s):  
M. Lavergne
Keyword(s):  
Shock Wave ◽  
Frequency Band ◽  
Experimental Investigations ◽  
Water Interface ◽  
Single Charge ◽  
Seismic Effects ◽  
Underwater Explosions ◽  
Seismic Efficiency ◽  
Marine Life ◽  
Air Water Interface

Theoretical and experimental investigations of the seismic effects of underwater explosions of dynamite charges are described. We investigate the acoustic efficiency in a broad frequency band and in the seismic frequency band, the partition of energy between the shock wave and bubble pulses, the seismic effects of cavitation due to ghost reflection at the air‐water interface, and the damage caused to marine life. Results concerning the variation of the seismic efficiency with shot conditions are given: the conclusion is that the seismic efficiency of charges of the order of 100 gm can be considerably increased by dividing the charges and by shooting at depth. Experiments show that two or three properly spaced 50 gm charges of dynamite, shot at a depth of about 12 m, give the same result as a single charge of about 5 to 15 kg shot at a depth of 1 m. CDP marine sections comparing caged charge shooting with conventional shooting in the same area are shown.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
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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