Fluid‐Structure Interaction Mechanisms for Close‐In Explosions

Wardlaw, A.; Luton, J. Alan

doi:10.1155/2000/141934

Cited by 85 publications

(84 citation statements)

References 6 publications

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“…The mass exchange inside the cavitation region has to be introduced and a proper model has yet to be developed [10]. Although the cavitation zone may be simply treated by assuming a constant-pressure zone [4,11], this may result in inaccurate ow physics since subsequent wave cannot propagate through the said region and furthermore conservation laws are not maintained. In the present work, the simulation is carried out until the ow exhibits and sustains a pressure ÿeld slightly below the critical pressure (SVP of water), which indicates the likely presence of a cavitating region.…”

Section: Introductionmentioning

confidence: 99%

Underwater shock‐free surface–structure interaction

Liu¹,

Khoo²,

Yeo³

et al. 2003

Numerical Meth Engineering

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SUMMARYA recently developed numerical method has been employed to evaluate the in uence of free surface on shock loading in a cylindrical underwater explosion carried out near to both a free surface and a cylindrical rigid structure. In the usual simulation of underwater shock-structure interaction, the shock loading tends to accelerate=move the (rigid) structure only in the resultant force direction. The presence of a free surface and explosion bubble suggests the existence of a reverse loading and provides an additional torque (rotational moment) on the loaded structure. The numerical results also demonstrate the possible existence of a cavitation zone=region in the immediate vicinity of the free surface due to the near-surface underwater explosion.

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Section: Introductionmentioning

confidence: 99%

Underwater shock‐free surface–structure interaction

Liu¹,

Khoo²,

Yeo³

et al. 2003

Numerical Meth Engineering

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“…Further indications supporting this explanation can be seen in the following section where t shift is found to become larger as the size of the field bubbles increases and as the natural period of oscillation of the bubble increases. This finding cannot be captured by methods assuming homogeneous medium, e.g., (Wardlaw & Luton, 2000, Wardlaw & Luton, 2003 and the analytical Gilmore equation (Gilmore, 1952). This highlights the importance of considering the individual bubble dynamics in the dispersed phase for high fidelity modeling.…”

Section: Pressure and Density Variations In The Neighborhood Of The Pmentioning

confidence: 99%

“…Eulerian-Lagrangian approaches are more appropriate for higher void fractions (Spelt & Biesheuvel, 1997, Balachandar & Eaton, 2010, Raju et al, 2011, Shams et al, 2011. In a recent work by Raju et al (2011) comparing a continuum homogeneous model (Gilmore, 1952) , an Eulerian multicomponents model (Wardlaw & Luton, 2000, Wardlaw & Luton, 2003, and an Eulerian-Lagrangian model , Chahine, 2009, Hsiao et al, 2013b it was found that high-frequency local fluctuations were only captured when an Eulerian viscous solver was coupled with a Lagrangian discrete bubble dynamics and when the microscale behavior of the field bubbles was well resolved. Continuum models, on the other hand, captured well the average low-frequency behavior.…”

Section: Introductionmentioning

confidence: 99%

Spherical bubble dynamics in a bubbly medium using an Euler–Lagrange model

Chahine

Hsiao

2015

Chemical Engineering Science

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For applications involving large bubble volume changes such as in cavitating flows and in bubbly two-phase flows involving shock and pressure wave propagation, the dynamics, relative motion, deformation, and interaction of bubbles with the surrounding medium play crucial roles and require accurate modeling. We present in this paper a fundamental study of the dynamic oscillations of a 'primary' bubble in a bubbly mixture using a two-way coupled Euler-Lagrange model. It addresses a simplified spherical configuration while using the full three-dimensional code. A main objective of the study is to investigate how the dynamics of a 'primary' bubble is affected by the presence of a surrounding bubbly medium and how it differs from its behavior in a pure liquid. This The simulations clearly indicate that the surrounding microbubbles absorb energy emitted from the primary bubble during its oscillations. This results in a reduction of the maximum radius and the period of oscillations of the primary bubble as compared to the dynamics in the pure liquid. Also, accounting for the dynamics of the field bubbles brings out the presence in the two-phase medium of a phase shift between density and pressure distributions. Such a shift is not captured by two-phase homogeneous medium models. These effects increase with increase in the mixture void fraction and in the initial bubble sizes in the mixture. The numerical observations are found to be in good qualitative agreements with previously published experimental data (Jayaprakash et al., 2011) investigating spark generated bubble dynamics in a bubbly medium.

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“…The pressure fields in the fluid and at the specimen-water interface following detonation of an explosive sheet were calculated using a fully coupled Euler-Lagrange finite element hydrocode [Wardlaw and Luton 2000;Wardlaw et al 2003]. The code allowed the analysis of shock propagation through a fluid medium using an Eulerian solver and then coupled it to the structural response of the solid target using a Lagrange code.…”

mentioning

confidence: 99%

“…The Euler run was started with 0.2 mm cells in the explosive sheet thickness direction and 0.4 mm divisions in the other two directions (in the plane parallel to the explosive sheet). The explosive sheet was specified by its geometry, the explosive's material properties, and by the detonation velocity using the Jones-Wilkins-Lee equations of state for shock calculations [Wardlaw and Luton 2000;Wardlaw et al 2003]. The pressure loading on a rigid wall, representing the front surface of the solid cylinder, was calculated at four locations along the radial direction measured from the shortest distance of impact of the blast wave.…”

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confidence: 99%

Dynamic compression of square honeycomb structures during underwater impulsive loading

Wadley

Dharmasena

Queheillalt

et al. 2007

JOMMS

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Significant reductions in the fluid structure interaction regulated transfer of impulse occur when sandwich panels with thin (light) front faces are impulsively loaded in water. A combined experimental and computational simulation approach has been used to investigate this phenomenon during the compression of honeycomb core sandwich panels. Square cell honeycomb panels with a core relative density of 5% have been fabricated from 304 stainless steel. Back supported panels have been dynamically loaded in through thickness compression using an explosive sheet to create a plane wave impulse in water. As the impulse was increased, the ratio of transmitted to incident momentum decreased from the Taylor limit of 2, for impulses that only elastically deformed the core, to a value of 1.5, when the peak incident pressure caused inelastic core crushing. This reduction in transmitted impulse was slightly less than that previously observed in similar experiments with a lower strength pyramidal lattice core and, in both cases, was well above the ratio of 0.35 predicted for an unsupported front face. Core collapse was found to occur by plastic buckling under both quasistatic and dynamic conditions. The buckling occurred first at the stationary side of the core, and, in the dynamic case, was initiated by reflection of a plastic wave at the (rigid) back face sheet-web interface. The transmitted stress through the back face sheet during impulse loading depended upon the velocity of the front face, which was determined by the face sheet thickness, the magnitude of the impulse, and the core strength. When the impulse was sufficient to cause web buckling, the dynamic core strength increased with front face velocity. It rose from about 2 times the quasistatic value at a front face initial velocity of 35 m/s to almost 3 times the quasistatic value for an initial front face velocity of 104 m/s. The simulations indicate that this core hardening arises from inertial stabilization of the webs, which delays the onset of their buckling. The simulations also indicate that the peak pressure transmitted to a support structure from the water can be controlled by varying the core relative density. Pressure mitigation factors of more than an order of magnitude appear feasible using low relative density cores. The study reveals that for light front face sandwich panels the core strength has a large effect upon impulse transfer and the loading history applied to support structures.

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Fluid‐Structure Interaction Mechanisms for Close‐In Explosions

Cited by 85 publications

References 6 publications

Underwater shock‐free surface–structure interaction

Underwater shock‐free surface–structure interaction

Spherical bubble dynamics in a bubbly medium using an Euler–Lagrange model

Dynamic compression of square honeycomb structures during underwater impulsive loading

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