Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session E27: Supersonic and Hypersonic Flows: Shock Capturing and Focusing |
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Chair: Veronica Eliasson, University of Southern California Room: Spirit of Pittsburgh Ballroom A |
Sunday, November 24, 2013 4:45PM - 4:58PM |
E27.00001: Shock Wave Mitigation Using Lessons Learned from Shock Focusing Techniques Qian Wan, Veronica Eliasson Shock wave mitigation in channels has been a topic of much attention in the shock wave community. One approach is to use obstacles of various geometries arranged in different patterns to attenuate an incident shock wave. Following the numerical work of A. Chaudhuri et al. (2012), which used cylinders, squares and triangles placed in staggered and non-staggered subsequent columns, we present simulations using a different obstacle pattern that more efficiently attenuates shock waves. Instead of using a matrix of obstacles, we have investigated square-shaped obstacles placed along a logarithmic spiral curve inspired by our previous work on shock focusing using logarithmic spirals. Results indicate that a logarithmic spiral could be an efficient way to collect and reflect the main part of the incident shock wave, thus improving techniques of shock wave attenuation in channels. [Preview Abstract] |
Sunday, November 24, 2013 4:58PM - 5:11PM |
E27.00002: Shock focusing using multiple micro-blast waves Shi Qiu, Zijie Zhang, Veronica Eliasson Numerical simulations have been used to study shock focusing effects from multiple micro-blast waves and to determine shock front amplification mechanisms as the wave converges. Overture, a partial differential equation solver, was used to solve the Euler equations with a second-order accurate Godunov algorithm. Adaptive mesh refinement was used to improve the accuracy and reduce the computational time. The early stage of each micro-blast wave was initialized using Taylor's similarity laws. The total energy of the blast waves was kept constant, but the number of blast waves and their respective size were varied from case to case. Results show that through careful geometrical arrangement and timing of the initialization of the charge, multiple micro-blast waves can be combined to yield more extreme thermodynamic conditions at the focal area than compared to a large blast wave with the same total initial energy. [Preview Abstract] |
Sunday, November 24, 2013 5:11PM - 5:24PM |
E27.00003: Experiments and simulations of shock focusing in thin water-filled convergent structures Veronica Eliasson, Chuanxi Wang, Shi Qiu A shock wave generated by an underwater explosion will impact any nearby surrounding structure and the fluid-structure interaction during the shock impact has to be understood to keep the structure safe from damage. Extremely high pressures will be generated, and the time of impact is on the order of a few milliseconds. In this work, the fluid-structure interaction during shock wave impact on water-filled convergent structures is studied extensively to assess the strength and dynamical response of the surrounding structure to lead to viable future design considerations to minimize or avoid damage. The response of light-weight composite materials are compared to that of steel structures. Experiments using high-speed non-invasive schlieren techniques and finite element numerical simulations have been performed. Results show that the fluid-structure interaction during shock impact is highly dependent on the thickness and material properties of the surrounding convergent structure. Precursor waves in the water ahead of the incident shock wave behave differently from case to case, and will be addressed in this presentation. [Preview Abstract] |
Sunday, November 24, 2013 5:24PM - 5:37PM |
E27.00004: Effects of Heat Conduction on Artificial Viscosity Methods for Shock Capturing Andrew Cook We investigate the efficacy of artificial thermal conductivity for shock capturing. The conductivity model is derived from artificial bulk and shear viscosities, such that stagnation enthalpy remains constant across shocks. By thus fixing the Prandtl number, more physical shock profiles are obtained, only on a larger scale. The conductivity model does not contain any empirical constants. It increases the net dissipation of a computational algorithm but is found to better preserve symmetry and produce more robust solutions for strong-shock problems. [Preview Abstract] |
Sunday, November 24, 2013 5:37PM - 5:50PM |
E27.00005: Numerical simulations of blast/shock wave propagations after nuclear explosions Seungho Song, Jung-il Choi, Yibao Li, Changhoon Lee Pressure waves develop immediately after nuclear explosions and start to move outward from the fireball. The most of initial damages are caused by the blast waves. We performed the blast wave propagations by solving two-dimensional and axisymmetric Euler equations. For shock capturing, inviscid fluxes are discretized using a variant of the piecewise parabolic method (PPM) and an approximate Riemann solver based on Roe's method is used. A clean air burst of fireball above the ground zero is considered. The initial condition of fireball is given at the point of breakaway that shock waves are appeared on the surface of the fireball. The growth of fireball is also calculated by solving one-dimensional radiation hydrodynamics (RHD) equation from point explosion. Characteristics of the blast wave propagations due to the various heights of burst and amount of the nuclear detonations are investigated. The results of parametric studies will be shown in the final presentation. [Preview Abstract] |
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