Direct numerical simulation of the thermal effects in plasma/turbulence interaction
08 Jan 2007-pp 12041-12055
TL;DR: In this article, the thermal effects of laser-induced plasma on isotropic turbulence were studied using direct numerical simulation, where a tear-drop shaped blast wave propagates into the background becoming spherical in time.
Abstract: The thermal effects of laser–induced plasma on isotropic turbulence are studied using direct numerical simulation. Laminar and turbulent simulations are conducted. For the laminar simulations, a tear–drop shaped blast wave propagates into the background becoming spherical in time. Shock radius and jumps in fluid properties at the shock front are compared to experiment. Both short and long time behavior of the plasma is studied. At short times, baroclinic vorticity is generated as a consequence of propagation of the curved shock through the domain. At long times, the flow field forms toroidal vortex rings, as observed in experiments. For the turbulent simulations, turbulence levels get enhanced in regions of compression across the blast wave and suppressed in regions of expansion in the plasma core.
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07 Jan 2008
TL;DR: In this article, numerical simulations of laser energy deposition in quiescent air and in isotropic turbulence are conducted and the flow field is classified into three phases: shock formation, shock propagation and subsequent collapse of the plasma core.
Abstract: Numerical simulations of laser energy deposition in quiescent air and in isotropic turbulence are conducted. The flow field is classified into three phases: shock formation, shock propagation and subsequent collapse of the plasma core. Each phase is studied in detail. Vorticity is found to be generated in the flow at short times due to baroclinic effects and at long times due to rolling up of the plasma core. An explanation is presented for the roll up process. Scaling analysis is performed for different amounts of laser energy deposited and different Reynolds number of the flow. Simulations are conducted using three different models for air based on different levels of physical complexity. The impact of these models on the evolution of the flow field is discussed.
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01 Sep 1981
TL;DR: In this article, the results of simulations for irrotational strain (plane and axisymmetric), shear, rotation, and relaxation toward isotropy in an incompressible fluid subjected to uniform deformation or rotation are compared with linear theory and experimental data.
Abstract: The direct simulation methods developed by Orszag and Patternson (1972) for isotropic turbulence were extended to homogeneous turbulence in an incompressible fluid subjected to uniform deformation or rotation. The results of simulations for irrotational strain (plane and axisymmetric), shear, rotation, and relaxation toward isotropy following axisymmetric strain are compared with linear theory and experimental data. Emphasis is placed on the shear flow because of its importance and because of the availability of accurate and detailed experimental data. The computed results are used to assess the accuracy of two popular models used in the closure of the Reynolds-stress equations. Data from a variety of the computed fields and the details of the numerical methods used in the simulation are also presented.
993 citations
TL;DR: In this paper, an approach which closely maintains the non-dissipative nature of classical fourth or higher-order spatial differencing away from shock waves and steep gradient regions while being capable of accurately capturing discontinuities, steep gradient, and fine scale turbulent structures in a stable and efficient manner is described.
626 citations
"Direct numerical simulation of the ..." refers methods in this paper
...The Fourier spectral method is therefore combined with a shock capturing scheme proposed by Yee et al (1999), to avoid resolution of the shock thickness....
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...The elements of φ? are denoted by φl? and are given by φl?i+1/2,j,k = κθ l i+1/2,j,kφ l i+1/2,j,k (15) The parameter κ is problem dependent and lies between 0.03 and 2 (Yee et al 1999). κ = 1.0 has been used in the simulations....
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...The formulation used for φli+1/2,j,k is given by the Harten–Yee upwind TVD form (Yee et al 1999)....
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TL;DR: In this article, the von Neumann-Richtmyer artificial viscosity was employed to avoid shock discontinuities, and the solutions were carried from two thousand atmospheres to less than one-tenth atmospheres peak overpressure.
Abstract: The strong‐shock, point‐source solution and spherical isothermal distributions were used as initial conditions for a numerical integration of the differential equations of gas motion in Lagrangean form. The von Neumann‐Richtmyer artificial viscosity was employed to avoid shock discontinuities. The solutions were carried from two thousand atmospheres to less than one‐tenth atmospheres peak overpressure. Results include overpressure, density, particle velocity, and position as functions of time and space. The dynamic pressure, the positive and negative impulses of both dynamic pressure and static overpressure, positive and negative durations of pressure and velocity, and shock values of all quantities are also described for various times and radial distances. Analytical approximations to the numerical results are provided.
484 citations
"Direct numerical simulation of the ..." refers methods in this paper
...Brode (1955) performed a numerical simulation of the blast wave and concluded that the ideal gas assumption was reasonable for shock pressures less than 10 atmospheres in air....
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TL;DR: In this paper, the effects of atmospheric dissociation on the airflow, and hence on the drag, stability and aerodynamic heating of such projectiles, are investigated. But this paper is intended mainly as a source of ideas for later, more comprehensive investigations.
Abstract: Atmospheric dissociation will be appreciable in the neighbourhood of projectiles travelling at speeds greater than 2 km/sec. This introductory paper on possible effects of dissociation on the airflow, and hence on the drag, stability and aerodynamic heating of such projectiles, is intended mainly as a source of ideas for later, more comprehensive investigations.
381 citations
"Direct numerical simulation of the ..." refers background in this paper
...It is well known that shock waves with varying strength and curvature generate vorticity in the flow (Truesdell 1952, Lighthill 1957, Hayes 1957, Berndt 1966, Kevlahan 1997)....
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TL;DR: In this article, the authors presented a new computational method for the calculation of discontinuous solutions of hyperbolic systems of conservation laws, which deal effectively with both shock and contact discontinuities.
Abstract: This paper presents a new computational method for the calculation of discontinuous solutions of hyperbolic systems of conservation laws, which deal effectively with both shock and contact discontinuities. The method consists of two stages: in the first stage a standard finite-difference scheme is hybridized with a nonoscillatory first order accurate method to provide for the monotonic variation of the solution near discontinuities, and in the second stage artificial compression is applied to sharpen transitions at discontinuities. This modification of a standard finite-difference method results in a scheme which preserves the order of truncation error of the original method and yet yields a sharp and oscillation free transition for both shocks and contact discontinuities. The modification can be easily implemented in existing computer codes.
283 citations