Topic
Overpressure
About: Overpressure is a research topic. Over the lifetime, 3236 publications have been published within this topic receiving 34648 citations.
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TL;DR: In this paper, small-scale vented hydrogen-air explosions were performed in a transparent cubic enclosure with a volume of 3375 cm3, and the flame propagation was followed with a high speed camera and the overpressure inside the enclosure was recorded using high frequency piezoelectric transmitters.
81 citations
TL;DR: In this article, a free-lagrange numerical method is implemented to simulate the axisymmetric jetting collapse of air bubbles in water, which is performed for both lithotripter shock-induced collapses of initially stable bubbles and for free-running cases where the bubble initially contains an overpressure.
Abstract: A free-Lagrange numerical method is implemented to simulate the axisymmetric jetting collapse of air bubbles in water. This is performed for both lithotripter shock-induced collapses of initially stable bubbles, and for free-running cases where the bubble initially contains an overpressure. The code is validated using two test problems (shock-induced bubble collapse using a step shock, and shock–water column interaction) and the results are compared to numerical and experimental results. For the free-running cases, simulations are conducted for a bubble of initial radius 0.3 mm located near a rigid boundary and near an aluminium layer (planar and notched surfaces). The simulations suggest that the boundary and its distance from the bubble influence the flow dynamics, inducing bubble elongation and jetting. They also indicate stress concentration in the aluminium and the likelihood of aluminium deformation associated with bubble collapse events. For the shock-induced collapse, a lithotripter shock, consisting of 56 MPa compressive and ?10 MPa tensile waves, interacts with a bubble of initial radius 0.04 mm located in a free field (case 1) and near a rigid boundary (case 2). The interaction of the shock with the bubble causes it to involute and a liquid jet is formed that achieves a velocity exceeding 1.2 km s?1 for case 1 and 2.6 km s?1 for case 2. The impact of the jet on the downstream wall of the bubble generates a blast wave with peak overpressure exceeding 1 GPa and 1.75 GPa for cases 1 and 2, respectively. The results show that the simulation technique retains sharply resolved gas/liquid interfaces regardless of the degree of geometric deformation, and reveal details of the dynamics of bubble collapse. The effects of compressibility are included for both liquid and gas phases, whereas stress distributions can be predicted within elastic–plastic solid surfaces (both planar and notched) in proximity to cavitation events. There is a movie with the online version of the paper.
80 citations
TL;DR: In this article, the authors investigated the effect of turbulence on the explosion process of a methane-air mixture under standard conditions, and the effect on explosion parameters, i.e., pmax, τe, and (dp/dt)max, was investigated by the turbulence produced by three different inert additives.
80 citations
TL;DR: In this article, the authors present a theoretical investigation of slug overpressure based on magma-static and geometric considerations and develop a set of equations that can be used to calculate the overpressure in a slug when it bursts, slug length at burst, and the depth at which the burst process begins.
Abstract: Strombolian eruptions, common at basaltic volcanoes, are mildly explosive events that are driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting at the surface. Gas overpressure within the bursting slug governs explosion dynamics and vigor and is the main factor controlling associated acoustic and seismic signals. We present a theoretical investigation of slug overpressure based on magma-static and geometric considerations and develop a set of equations that can be used to calculate the overpressure in a slug when it bursts, slug length at burst, and the depth at which the burst process begins. We find that burst overpressure is controlled by two dimensionless parameters: V', which represents the amount of gas in the slug, and A', which represents the thickness of the film of magma that falls around the rising slug. Burst overpressure increases nonlinearly as V' and A' increase. We consider two eruptive scenarios: (1) the "standard model," in which magma remains confined to the vent during slug expansion, and (2) the " overflow model," in which slug expansion is associated with lava effusion, as occasionally observed in the field. We find that slug overpressure is higher for the overflow model by a factor of 1.2-2.4. Applying our model to typical Strombolian eruptions at Stromboli, we find that the transition from passive degassing to explosive bursting occurs for slugs with volume >24-230 m(3), depending on magma viscosity and conduit diameter, and that at burst, a typical Strombolian slug (with a volume of 100-1000 m(3)) has an internal gas pressure of 1-5 bars and a length of 13-120 m. We compare model predictions with field data from Stromboli for low-energy " puffers," mildly explosive Strombolian eruptions, and the violently explosive 5 April 2003 paroxysm. We find that model predictions are consistent with field observations across this broad spectrum of eruptive styles, suggesting a common slug-driven mechanism; we propose that paroxysms are driven by unusually large slugs (large V').
79 citations
TL;DR: In this article, the authors derived the trajectory and overpressure of the intermediate strength blast wave (10 < Δp/p0 ⪝ 0.02) for spherical, cylindrical, and plane blasts.
Abstract: Equations for the trajectory and overpressure of the shock front of the intermediate strength blast wave (10 < Δp/p0 ⪝ 0.02) are developed for spherical, cylindrical, and plane blasts. These equations are based on the correct limit method that provided the trajectory of the blast wave from the inverse pinch to velocities below Mach number 1.16 (Δp/p0 = 0.4). The correct limit equations are an extension of the strong shock similarity solution of G. I. Taylor for the spherical blast and A. Sakurai and S. C. Lin for the cylindrical case. It is now possible, given the energy and ambient gas conditions, to trace the shock front trajectory and overpressure from the very strong through the very weak regimes. Conversely, the shock wave energy can be found from measurement of overpressure or arrival time. Comparisons with experimental data as well as the calculations of H. L. Brode verify the validity of the correct limit equations.
79 citations