Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session E39: Flow Instability: Richtmyer-Meshkov II |
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Chair: Peter Vorobieff, University of New Mexico Room: Sheraton Back Bay C |
Sunday, November 22, 2015 4:50PM - 5:03PM |
E39.00001: Flow morphologies after oblique shock acceelration of a cylindrical density interface Patrick Wayne, Dylan Simons, Dell Olmstead, C. Randall Truman, Peter Vorobieff, Sanjay Kumar We present an experimental study of instabilities developing after an oblique shock interaction with a heavy gas column. The heavy gas in our experiments is sulfur hexafluoride infused with 11\% acetone by mass. A misalignment of the pressure and density gradients results in three-dimensional vorticity deposition on the gaseous interface, dtriggering the onset of Richtmyer-Meshkov instability (RMI). Shortly thereafter, other instabilities develop along the interface, including a shear-driven instability that presents itself on the leading (with respect to the shock) and trailing edges of the column. This leads to the development of rows of co-rotating ``cat's eye'' vortices, characteristic of Kelvin-Helmholtz instability (KHI). Characteristics of the KHI, such as growth rate and wavelength, depend on several factors including the Mach number of the shock, the shock tube angle of inclination $\alpha$ (equal to the angle between the axis of the column and the plane of the shock), and the Atwood number. [Preview Abstract] |
Sunday, November 22, 2015 5:03PM - 5:16PM |
E39.00002: Structure functions of passive scalar: evolution in fully 3D shock-driven transition to turbulence Peter Vorobieff, Dell Olmstead, Dylan Simons, Patrick Wayne, C. Randall Truman, Sanjay Kumar Oblique interaction between a planar shock and a cylindrical density interface results in baroclinic vorticity deposition. The character of the evolving flow is thus different from a similar flow produced by planar normal shock acceleration of the same density interface. In the latter case (planar normal shock), vorticity deposited by the shock is predominantly two-dimensional (directed along the axis of the cylinder), while in the case we consider the shock-induced vorticity field is fully three-dimensional. This results in a complex interplay of vortical structures with different orientations. The statistical properties of the flow are analyzed based on images from two orthogonal visualization planes, using second-order structure functions of the intensity maps of fluorescent tracer pre-mixed with the heavy gas. Scalings consistent with fully developed turbulence are observed at late times. The character of the emergence of these scalings is affected by the flow Mach number, Atwood number, and initial geometry. [Preview Abstract] |
Sunday, November 22, 2015 5:16PM - 5:29PM |
E39.00003: Progress on Simultaneous PLIF/PIV Measurements for a Turbulent Complex Fluid Interface David Reilly, Mohammad Mohaghar, John Carter, Jacob McFarland, Devesh Ranjan Experiments were performed at the inclined shock tube facility at Georgia Institute of Technology to study a Richtmyer-Meshkov unstable complex interface. The complex density stratification was achieved by counter flowing N$_{2}$ over CO$_{2}$ in order to create shear and buoyancy effects. The resulting Atwood number is 0.23 with an incident shock strength of Mach 1.55 and an angle of inclination of 80$^{\circ}$. High-resolution, full-field simultaneous Planar Laser-Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) was employed to measure density and velocity statistics, respectively. For the first time with the inclined interface, mixing parameters from the BHR (Besnard-Harlow-Rauenzahn) model, including the density self-correlation and turbulent mass flux, are determined from experiments. Secondary modes added to the interface result in markedly greater mixing compared to the simple inclined interface as measured by mixedness and mixed mass. [Preview Abstract] |
Sunday, November 22, 2015 5:29PM - 5:42PM |
E39.00004: Evaluation of a Two-Length Scale Turbulence Model with Experiments on Shock-Driven Turbulent Mixing John Carter, Rob Gore, Devesh Ranjan A new second moment turbulence model which uses separate transport and decay length scales is used to model the shock-driven instability. The ability of the model to capture the evolution of turbulence statistics and mixing is discussed. Evaluation is based on comparison to the Georgia Tech shock tube experiments. In the experiments a membraneless light-over-heavy interface is created. There is a long-wavelength perturbation which exists due to inclination of the entire shock tube. By limiting calculations to one dimension, there is not a geometric description of the incline, and the ability of the transport length scale alone to capture the effect of the long-wavelength perturbation is tested. [Preview Abstract] |
Sunday, November 22, 2015 5:42PM - 5:55PM |
E39.00005: Shock Wave Interactions in Multi-Phase Particle Systems Characterized by Various Interfaces Wolfgang Black, Nicholas Denissen, Jacob Mcfarland Multi-phase systems have been of interest since the 1800s with Stokes studying flow over a particle, and are still an important field of study today with various applications in propulsion design, astrophysics, refrigeration, fluid instabilities, as well as fusion. Many multi-phase systems experience complex accelerations, such as shock waves, which may drive shear dominated instabilities, increase or dampen mixing between the phases, and even affect a phase change phenomena within the flow. The parameter space to study within these systems is extensive and provides a rich field for research, with hydrodynamic codes allowing new insight into old and recent experiments alike. This talk will discuss early efforts to tap into this parameter space by using high density high energy hydrodynamics codes to investigate simulations of multi-phase systems that experience a shock wave interaction across an interface, for example a particle laden gas cylinder within an unseeded shocked tube environment, and the evolution of these systems. This particular interface will be compared with recent experiments within literature while other turbulent interfaces will be discussed as future experiments to be performed by the University of Missouri Fluid Mixing Shock Tube Laboratory. [Preview Abstract] |
Sunday, November 22, 2015 5:55PM - 6:08PM |
E39.00006: Comparison of hydrodynamic simulations with two-shockwave drive target experiments Varad Karkhanis, Praveen Ramaprabhu, William Buttler We consider hydrodynamic continuum simulations to mimic ejecta generation in two-shockwave target experiments [1], where metallic surface is loaded by two successive shock waves. Time of second shock in simulations is determined to match experimental amplitudes at the arrival of the second shock. The negative Atwood number $\left( {A\to -1} \right)$ of ejecta simulations leads to two successive phase inversions of the interface corresponding to the passage of the shocks from heavy to light media in each instance. Metallic phase of ejecta (solid/liquid) depends on shock loading pressure in the experiment, and we find that hydrodynamic simulations quantify the liquid phase ejecta physics with a fair degree of accuracy, where RM instability is not suppressed by the strength effect. In particular, we find that our results of free surface velocity, maximum ejecta velocity, and maximum ejecta areal density are in excellent agreement with their experimental counterparts, as well as ejecta models [2,3]. We also comment on the parametric space for hydrodynamic simulations in which they can be used to compare with the target experiments. [1] W. T. Buttler et al., J. Appl. Phys., 116 (2014). [2] Guy Dimonte et al., J. Appl. Phys., 113 (2013). [3] W. T. Buttler et al., J. Fluid Mech., 703 (2012). [Preview Abstract] |
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