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1 – 10 of 193Rainald Löhner, Lingquan Li, Orlando Antonio Soto and Joseph David Baum
This study aims to evaluate blast loads on and the response of submerged structures.
Abstract
Purpose
This study aims to evaluate blast loads on and the response of submerged structures.
Design/methodology/approach
An arbitrary Lagrangian–Eulerian method is developed to model fluid–structure interaction (FSI) problems of close-in underwater explosions (UNDEX). The “fluid” part provides the loads for the structure considers air, water and high explosive materials. The spatial discretization for the fluid domain is performed with a second-order vertex-based finite volume scheme with a tangent of hyperbola interface capturing technique. The temporal discretization is based on explicit Runge–Kutta methods. The structure is described by a large-deformation Lagrangian formulation and discretized via finite elements. First, one-dimensional test cases are given to show that the numerical method is free of mesh movement effects. Thereafter, three-dimensional FSI problems of close-in UNDEX are studied. Finally, the computation of UNDEX near a ship compartment is performed.
Findings
The difference in the flow mechanisms between rigid targets and deforming targets is quantified and evaluated.
Research limitations/implications
Cavitation is modeled only approximately and may require further refinement/modeling.
Practical implications
The results demonstrate that the proposed numerical method is accurate, robust and versatile for practical use.
Social implications
Better design of naval infrastructure [such as bridges, ports, etc.].
Originality/value
To the best of the authors’ knowledge, this study has been conducted for the first time.
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Zongduo Wu, Zhi Zong and Lei Sun
– The purpose of this paper is to provide an improved Mie-Grüneisen mixture model to simulate underwater explosion (UNDEX).
Abstract
Purpose
The purpose of this paper is to provide an improved Mie-Grüneisen mixture model to simulate underwater explosion (UNDEX).
Design/methodology/approach
By using Mie-Grüneisen equations of state (EOS) to model explosive charge, liquid water and solid structure, the whole fluid field is considered as a multi-phases mixture under Mie-Grüneisen EOS. Then by introducing auxiliary variables in Eulerian model and using mass fraction to establish a diffusion balance, a new improved Mie-Grüneisen mixture model is presented here. For the new reconstructed mixture model, a second order MUSCL scheme with TVD limiter is employed to solve the multi-phase Riemann problem.
Findings
Numerical examples show that the results obtained by Mie-Grüneisen mixture model are quite closed to theoretical and empirical data. The model can be also used in 2-D fluid-structure problem of UNDEX effectively and it is proved that the deformation of structure can be clearly described by mass fraction.
Research limitations/implications
The FVM model based on mass fraction can only describe the motion of compressible material under impact. Material failure or large deformation needs a modification about the EOS or implementations of other models (i.e. FEM model).
Originality/value
An improved non-oscillation Mie-Grüneisen mixture model, which based on mass fraction, is given in the present paper. The present Mie-Grüneisen mixture model provides a simplified and efficient way to simulate UNDEX. The feasibility of this model to simulate the detonation impacts on different mediums, including water and other metal mediums, is tested and verified here. Then the model is applied to the simulation of underwater contact explosion problem. In the simulation, deformation of structure under explosion loads, as well as second shock wave, are studied here.
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The Comprehensive Nuclear Test‐Ban Treaty prohibits the testing of nuclear weapons and establishes an international monitoring system to collect data for international…
Abstract
The Comprehensive Nuclear Test‐Ban Treaty prohibits the testing of nuclear weapons and establishes an international monitoring system to collect data for international verification of the treaty. The objective of verification is to discriminate between nuclear explosions and all other events detected by the monitoring system. Monitoring is performed through a network of seismological, radionuclide, hydroacoustic and infrasound stations. The data will be collected and analyzed at the International Data Center in Vienna, and the results of the analyses will be used to verify compliance or detect non‐compliance. For all the simplicity of the concept, there are questions about the effective operation of the international verification regime. The treaty establishes an elaborate system for collecting and processing the data from the monitoring stations, but it is ambiguous on the decision‐making process for ascertaining non‐compliance. This paper describes the objectives and architecture of the International Monitoring System and its relationship to the verification goals of the treaty.
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This paper reviews engineering work developed for blast analysis and design of industrial/residential and ammunition storage facilities. The review also covers work done for…
Abstract
Purpose
This paper reviews engineering work developed for blast analysis and design of industrial/residential and ammunition storage facilities. The review also covers work done for progressive collapse analysis and blast deflectors.
Design/methodology/approach
The first part of the paper describes characteristics of various types of explosions. Empirical and numerical models that were developed to estimate structural capacity are reviewed. The structural idealization, theoretical basis, and merits of various methods are also described. The influence of various parameters affecting the structural performance is discussed.
Findings
The material of the paper captures recent engineering developments that can be used by practitioners for blast analysis and design for industrial and residential buildings. Little emphasis was given in the published literature to develop simplified analytical models that can be used in practice to compute the dynamic response of buildings subject to accidental explosions. Furthermore, analytical expressions are required to compute the reduction in the stiffness due to impact loading.
Originality/value
Current building codes address conventional live, dead, wind and earthquake loads. Very few guidelines are available in practice for design of buildings subject to blast loading. The objective of this paper is to review and piece together recent engineering work developed for blast analysis and design of industrial/residential buildings and ammunition facilities. The paper provides useful resource material for the engineers in practice using recent techniques to design these structures. The review covers past three decades that can be used as a baseline for future developments.
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F. H. Hamdan and P. J. Dowling
This paper, which is concerned with fluid‐structure interactionanalysis, is a sequel to our earlier paper which gave an introduction to thenumerical treatment of such systems. The…
Abstract
This paper, which is concerned with fluid‐structure interaction analysis, is a sequel to our earlier paper which gave an introduction to the numerical treatment of such systems. The paper is divided into five main sections. In the first two, a state‐of‐the‐art review on near‐field and far‐field fluid structure interaction is presented. In attempting to highlight where current research should be directed, only the most widely used computer codes are reviewed in the third section. Conclusions are presented in the fourth section.
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Abstract
Purpose
The purpose of this paper is to investigate the formation process of linear‐shaped charge jet using the smoothed particle hydrodynamics (SPH). Different material yield models are embed to test the performance of SPH method in the simulation of explosive driven metal liner. The effects of different ignition model to the formation of metal jet have also been studied.
Design/methodology/approach
The SPH method is used with the correction of artificial viscosity and penalty force to simulate the formation process of linear‐shaped charge jet, which includes the process of explosion and interaction between explosive gas and metal liner. The numerical results which got by SPH method are compared with these obtained by mesh‐based method. Different material yield models are implemented in the numerical examples to show the effect of material model to the formation process of metal jet. The single point and two point ignition models are used to study the effect of ignition models to the process of explosion and formation of metal jet.
Findings
Compared with the original mesh‐based method, the SPH method can simulate the physical process of linear‐shaped charge jet naturally, as well as the capturing of explosive wave propagation. The implementation of different material yields models to obtain the same formation tendency of metal jet, but some numerical difference exists. In two‐point ignition model the explosive pressure is superimposed at the location that two detonation waves intersect. Compared with two ignition models, the two point ignition model can form the metal jet faster and get the higher velocity metal jet.
Originality/value
There are a few references that address the application of SPH to simulate shaped charge explosion process. The feasibility of the SPH method to simulate the formation process of linear shaped charged jet is tested and verified in this paper. From the results which compared with mesh‐based method, it is shown that the SPH method has the advantage in tracking the large deformation of material and capturing the explosive wave propagation. The SPH method can be selected as a good alternative to traditional mesh‐based numerical methods in simulating similar explosively driven metal material problems which can be referenced from this paper.
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Timothy C. Weiskel and Richard A. Gray
The ecological decline of ancient Near Eastern civilizations and the violent and explosive characteristics of post‐Columbian colonial ecologies might well remain comfortably…
Abstract
The ecological decline of ancient Near Eastern civilizations and the violent and explosive characteristics of post‐Columbian colonial ecologies might well remain comfortably remote from us in our twentieth century world were it not for the disturbing parallels that such case histories seem to evoke as we consider our contemporary global circumstance. Just as in ancient times and in the age of colonial expansion, it is in the “remote environments,” usually quite distant from the centers of power, that the crucial indicators of environmental catastrophe first become apparent within the system as a whole. These regions are frequently characterized by weak economies and highly vulnerable ecosystems in our time, just as they were in the past. Accordingly, the environmental circumstances in these regions constitute for the modern world a kind of monitoring device that can provide early warnings of ecological instabilities in the global ecosystem.
The paper aims to review recent developments for analysis of deteriorating stiffened panels subjected to static and explosive forces.
Abstract
Purpose
The paper aims to review recent developments for analysis of deteriorating stiffened panels subjected to static and explosive forces.
Design/methodology/approach
The first part reviews numerical procedures developed for stiffened panels subjected to explosive forces. The structural idealization, the theoretical basis, and the merits of these methods are discussed. The second part reviews the probabilistic procedures developed for analysis of deteriorating stiffened panels. The third part reviews recent work developed in several finite element modelling philosophies for analysis of stiffened panels. The influence of various parameters affecting the structural performance, such as geometric and material imperfections, corrosion, residual stresses, etc. is discussed. The fourth part reviews hybrid procedures developed to provide approximate solutions for the designers. Numerical procedure is presented using combination of energy formulations and mathematical programming techniques to model the interaction between the box girder components.
Findings
Localized damage largely affects the performance of stiffened panels and must be accounted for in the design phase. Little emphasis was given in the published literature to developing simplified analytical models that can be used in practice to compute the residual strength of the stiffened panels under these types of loadings. Furthermore, analytical expressions are required to compute the reduction in the stiffness induced due to the structural or material defects. These expressions must be dependent on the type of damage. It must be noted that some of this damages is localized in nature and must be accounted for by using specialized functions to assess the structural defect accurately. Research work is required in this direction.
Practical implications
The paper provides useful resource material for the engineers in practice regarding recent techniques developed to assess damaged stiffened panels subject to static and explosive loadings. The paper reviews work developed over the past 20 years that can be used as a baseline for future developments.
Originality/value
Very limited literature dealt with the ultimate strength of damaged stiffened structure under static and explosive forces. No guidelines are available in current design codes to assess the damage in predicting the strength of deteriorating stiffened panels.
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Fang Ji, Xiongliang Yao and Aman Zhang
The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation…
Abstract
Purpose
The structure‐borne sound generated by power equipment can be isolated effectively through vibration absorber under hull base structures. The practical vibration isolation performance is limited due to the weight, size and cost. The dramatic attenuating wave propagation characteristic of hull base without adding weight is essential to the vessel acoustic stealth.
Design/methodology/approach
The characteristics of vibration wave propagated from typical shape base link structures have been investigated according to impedance mismatch and wave conversion in non‐homogeneous structure. The hull base is simplified to three degrees of freedom damped system through the mechanical impedance method. The influence of blocking mass weight, as well as location properties to the base vibration isolation performance have been discussed. Furthermore, the structure‐borne sound design of a typical hull base is carried out.
Findings
The impedance mismatch of the hull base is further increased by the comprehensive use of high transmission loss base link structures, blocking mass as well as damping layer. The effectiveness of structure‐borne sound design is verified through numerical calculation together with underwater model test. The test data show that the noise has been reduced larger than 3 dB.
Originality/value
The paper describes what is believed to be the first application of the high transmission loss base in hull structures based on the literature survey. The method of structure‐borne sound design of a typical hull base can be applied in different types of vessels.
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Fang Ji, Xiongliang Yao, Aman Zhang and Xi Ye
Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite…
Abstract
Purpose
Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite stiffened double cylindrical shell with separate‐sound and decoupled tile is carried out with the aim of finding out the most effective laying condition.
Design/methodology/approach
The segmentation power function interpolation method and vertex extreme value envelope continuation method are introduced into basic theory of empirical mode decomposition (EMD). The original measured sound pressure signals are decomposed to intrinsic mode function (IMF) group through EMD, and the high‐frequency components are filtered out. Because the mechanical noise of submarine is mainly at low frequency, the IMFs in low frequency are researched through power spectrum analysis. The noise reduction effects of different separate‐sound and decoupled tile laying conditions are compared.
Findings
The sound pressure signal components' amplitudes, periods and phases are obtained through EMD. The test data show that the double cylindrical shell entirely covered with separate‐sound and decoupled tile is the most effective laying condition in noise reduction.
Originality/value
With reference to the case study, this is believed to be the first application of the EMD in sound radiation time‐frequency characteristics of double cylindrical shell. The evaluation of separate‐sound and decoupled tile laying conditions is of great importance in engineering applications.
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