Bulletin of the American Physical Society
2006 59th Annual Meeting of the APS Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida
Session AN: Richtmyer-Meshkov/Rayleigh Taylor Instabilitities I* |
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Chair: Katherine Prestridge, Los Alamos National Laboratory Room: Tampa Marriott Waterside Hotel and Marina Meeting Room 9 |
Sunday, November 19, 2006 8:00AM - 8:13AM |
AN.00001: Incompressible Richtmyer-Meshkov Scaling D.L. Cotrell, A.W. Cook We consider the Richtmyer-Meshkov instability of incompressible fluids and show that using appropriate time and length scales, one can get fairly good collapse of growth rate curves for a wide range of initial density disturbances. Thus, given good collapse of the growth rate curves one can get a fairly accurate curve fit and then back out a universal model for the mixing layer thickness. [Preview Abstract] |
Sunday, November 19, 2006 8:13AM - 8:26AM |
AN.00002: Richtmyer-Meshkov instability and turbulence in a reshocked gas curtain Balakumar Balasubramaniam, Greg Orlicz, Christopher Tomkins, Katherine Prestridge We present new velocity and density field measurements of a curtain of SF6 impacted by a Mach 1.2 shock and then reshocked by the reflected shock approximately 600 $\mu$s after the initial shock impact. The initial conditions are those of a diffuse curtain of SF6 surrounded by air, and the interface is perturbed with a large-scale, single-mode, varicose perturbation. Statistical data are collected from multiple experiments by quantitatively correlating repeatable initial conditions within a specified level of variation. We present density field images of both the instantaneous, time-averaged, and fluctuating evolution of the curtain in time, as well as selected mean and fluctuating velocity fields and their correlations. [Preview Abstract] |
Sunday, November 19, 2006 8:26AM - 8:39AM |
AN.00003: K-L turbulence model for the self-similar growth of the Rayleigh-Taylor and Richtmyer-Meshkov instabilities Guy Dimonte, Robert Tipton A turbulence model is developed to described the self-similar growth of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities. The model describes the dominant eddies in the mixing zone with evolutionary equations for their characteristic dimension L and energy per unit mass K $\equiv $ V$^{2}$/2. The equations are based on the successful buoyancy-drag models for RT and RM flows, but constructed only with local parameters so that it can be applied to multi-dimensional flows with multiple shells of materials. The model has several unknown coefficients that are determined by comparing analytical and numerical solutions with RT and RM experiments. [Preview Abstract] |
Sunday, November 19, 2006 8:39AM - 8:52AM |
AN.00004: Numerical Study of Multiple Shock-Bubble Interactions Xiaolin Li, Vadim Gamezo, Elaine Oran, Anne Staples, Lingling Wu We have performed numerical simulations of interactions of a low-density bubble with multiple shocks, including a planar incident shock and subsequent shocks reflected from channel walls. The compressible fluid dynamics is described by Euler and Navier-Stokes equations solved by a high-order method combined with a front-tracking algorithm to maintain the sharp interface between the bubble and the background gas. Simulation results were interpreted using Fourier analysis of vorticity and kinetic energy. The analysis shows that the Richtmyer- Meshkov instability resulting from repeated shock-interface interactions generates vorticity on multiple scales. Vorticity and energy spectra for the high-speed flow dominated by shock- interface interaction are very different from those expected for an equilibrium Kolmogorov-type turbulence. These results can also be extended to high-speed turbulent combustion dominated by shock-flame interactions. [Preview Abstract] |
Sunday, November 19, 2006 8:52AM - 9:05AM |
AN.00005: High resolution simulations of the single-wavelength Richtmyer-Meshkov flow Praveen Ramaprabhu, Guy Dimonte The single-mode Richtmyer-Meshkov (RM) instability was investigated in three dimensions, using the compressible FLASH code, with Adaptive Mesh Refinement with effective resolution of up to 256 zones/$\lambda$, where $\lambda$ is the wavelength of perturbation. The massively parallel capability of this code permitted investigation of this flow in computationally difficult regimes: Mach numbers up to 15, small initial amplitudes to ensure linearity of perturbations, and fluids with starkly different compressibilities. Linear and nonlinear theories of RM were evaluated under these conditions, and our findings will be presented. Other effects such as dimensionality, and Atwood number dependence were also studied. [Preview Abstract] |
Sunday, November 19, 2006 9:05AM - 9:18AM |
AN.00006: A Mach number study of Richtmyer-Meshkov instability and growth rates of a shocked gas column Gregory Orlicz, Balakumar Balasubramaniam, Christopher Tomkins, Katherine Prestridge Presented are density field measurements of a column of SF6 impacted by shocks of varying Mach number greater than and equal to Mach 1.2. This has been made possible through a new capacity of the shock-tube to utilize steel diaphragms for shock generation. The initial conditions are those of a diffuse column of SF6 surrounded by air. Both the initial conditions and the evolution of the structure following shock impact are imaged via planar laser induced fluorescence (PLIF). We present a preliminary study of integral growth rates and their dependence on Mach number. [Preview Abstract] |
Sunday, November 19, 2006 9:18AM - 9:31AM |
AN.00007: PIV measurements of the single-mode Richtmyer-Meshkov instability. Roger Aure, Jeff Jacobs Experiments will be presented where a system of two gases of different densities ($A = 0.66$) is impulsively accelerated to produce Richtmeyer-Meshkov (RM) instability. An interface is created by filling the driven section of a 9.8 meter long vertical shock tube with opposing gas flows of air and Sulfur Hexafluoride (SF$_{6}$). The interface forms in the top of the Plexiglas test section where the two gasses meet and exit through two slots. The gases are seeded with $0.3 \mu$m polystyrene Latex spheres. An initial 2-D perturbation in the form of a standing wave of sinusoidal shape is created by oscillating the driven section in the horizontal direction. The interface between the gases is impulsively accelerated by an $M=1.2$ shockwave. One image per experiment is captured with a cooled CCD camera. The image is doubly exposed by a double-pulsed ND-YAG laser and is analyzed using autocorrelation PIV techniques. Results will be presented showing velocity and vorticity distribution in the RM flow. [Preview Abstract] |
Sunday, November 19, 2006 9:31AM - 9:44AM |
AN.00008: Progress with High Ma Richtmyer-Meshkov Experiments Malcolm Andrews, Robert Gore, Hill Larry, Merrill Frank, Katherine Prestridge We describe our progress with a new experiment to investigate Ma $>$ 4 shock driven Richtmyer-Meshkov (RM) instability, with application to Inertial Confined Fusion (ICF). The experiment comprises a three inch diameter shock tube filled with Xe and He (Atwood=0.95), separated by a Aluminium mesh that supports microfilm. High explosive (HE) is used to drive a projectile, that in-turn generates a plane shock that can range from 4 $<$ Ma $<$ 12 according to the amount of HE. The shock travels down the tube and drives the RM. As diagnostic we have installed the equipment in the Los Alamos pRad (proton radiation) facility, and seek measurements of RM mixing width and density profiles. This is an on-going program and so we shall describe the experiment in detail, its design, and results obtained. [Preview Abstract] |
Sunday, November 19, 2006 9:44AM - 9:57AM |
AN.00009: Experimental and numerical study of 3D Richtmyer-Meshkov instability at an Air-SF$_{6}$ interface. Chris Long, Vitaliy Krivets, Jeff Jacobs, Jeff Greenough Experiments have been conducted in a vertical shock tube with a shock wave Mach number of 1.2. The two gases (air and SF$_{6}$ with $A = 0.66$) are filled separately from the top and bottom ends of the shock tube, respectively. The gases then flow out of the tube through holes in the test section walls forming a slightly diffuse flat interface. Oscillating the flow inside of the tube generates a single-mode three- dimensional standing wave perturbation on the interface. PLIF is used to visualize the flow. The Eulerian Adaptive Mesh Refinement (AMR) code Raptor, which uses a multifluid Godunov method to solve the governing equations, has been used to simulate the entire shock tube length including driver, driven and test sections. This provides a natural mechanism for producing reflected shocks and rarefactions. Comparison between experiment and numerical simulation is presented. [Preview Abstract] |
Sunday, November 19, 2006 9:57AM - 10:10AM |
AN.00010: Analysis of gradient-diffusion modeling of Rayleigh-Taylor and Richtmyer-Meshkov instability-induced mixing Oleg Schilling, Nicholas Mueschke, Marco Latini, Wai Sun Don, Malcolm Andrews Gradient-diffusion models of turbulent transport in Rayleigh- Taylor and Richtmyer-Meshkov instability-induced mixing are assessed using direct numerical simulation (DNS) and implicit large-eddy simulation (ILES) data. Mean and fluctuating fields, defined from spatial averages over the periodic directions of the DNS, are used to construct the unclosed terms in the turbulent kinetic energy transport equation. These terms are then compared a priori with the corresponding terms modeled using the gradient-diffusion approximation to assess the validity of this approximation for these buoyancy- and shock- driven flows. Implications for two-equation turbulence modeling of Rayleigh-Taylor and Richtmyer-Meshkov instability-induced mixing are discussed. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. This research was also sponsored by the National Nuclear Security Administration under the Stewardship Science Academic Alliances Program through DOE Research Grant No. DE-FG03- 02NA00060. UCRL-ABS-223369 [Preview Abstract] |
Sunday, November 19, 2006 10:10AM - 10:23AM |
AN.00011: Computational Analysis for Secondary Vorticity and Non-Axisymmetric Features in the Shock-Bubble Interaction John Niederhaus, Devesh Ranjan, Bradley Motl, Jason Oakley, Mark Anderson, Riccardo Bonazza, Jeffrey Greenough Computations for the shock-bubble interaction are performed using the 3D Eulerian AMR code \textit{Raptor}. In the simulations, performed in 3D at a fine-grid resolution of 128 grid points per bubble radius, a planar shock wave of specified strength accelerates a spherical gas bubble embedded in an otherwise uniform air or nitrogen medium. The computed solutions clearly resolve the development of distinctive features observed in previous experiments (Haas and Sturtevant, \textit{J. Fluid. Mech.}, 1987) and simulations (Zabusky and Zeng, \textit{J. Fluid. Mech.}, 1998), including jets, secondary shocks, vortex rings, and turbulent mixing. Using both flow visualizations and quantitative diagnostics, the non-axisymmetric and turbulent features developing in the flow are characterized. Local fluctuating quantities are defined with respect to an azimuthal mean, and mechanisms are identified for the post-shock origin and growth of secondary vortices and turbulent features. [Preview Abstract] |
Sunday, November 19, 2006 10:23AM - 10:36AM |
AN.00012: Experimental Study of Shock-Induced Compression and Vortex Generation in the Shock-Bubble Interaction Devesh Ranjan, Bradley Motl, John Niederhaus, Jason Oakley, Mark Anderson, Riccardo Bonazza, Jeffrey Greenough Results are presented from experiments studying the interaction of a planar
shock wave of strength 1.4 $ |
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