Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session F05: Compressible Flow: Shock Waves and Explosions (3:55pm - 4:40pm CST)Interactive On Demand
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F05.00001: Examining unsteady drag of shocked micro-droplets with narrow particle size distribution Kyle Hughes, Adam Martinez, John Charonko, Kathy Prestridge Previous experiments of shock-accelerated micro-droplets suffered from a wide range of sizes that prevented an accurate measurement of the drag coefficient. The experimental setup has since been improved to provide a narrow range of micro-droplets that are more suitable to statistical averaging. An eight-pulse particle tracking diagnostic measures individual particle positions, and a shadowgraph system measures shock location, with pressure transducers providing shock speed at the test section. These diagnostics give us detailed measurements of particle positions versus time for Mach 1.2, 1.3 and 1.4 experiments, allowing us to calculate accelerations and drag. [Preview Abstract] |
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F05.00002: Particle Resolved Direct Numerical Simulations to Study Shock-Particle Cloud Interaction Yash Mehta, Jonathan D. Regele, Fady M. Najjar Thus far, the numerical study of shock-particle cloud interactions has been confined to either using sub-grid scale models (Euler-Lagrange or Euler-Euler) or particle resolved simulations neglecting the effect of viscosity and/or particle motion due to high computational costs. With the recent development of scalable and accurate solvers along with the availability of exascale computing resources, it's now possible to perform particle resolved direct numerical simulations of shock waves interacting with a cloud of particles. In the present study, capabilities of PAWCM (Parallel Adaptive Wavelet Collocation Method) code that can solve the Navier-Stokes equations with moving colliding particles is first demonstrated. After that validation and grid resolution studies for the case of shock interacting with a single cylinder are discussed. Finally, the late-term (viscous) drag experienced by a curtain of particles after an incident-shock propagates over them is presented. Importance of fluctuating terms, which appear in the average governing equations that can be used to obtain closure models for Euler-Lagrange or Euler-Euler studies of shock-particle cloud interaction is investigated. \begin{flushright} LA-UR-20-25495 \end{flushright} \begin{flushright} LLNL-ABS-812985 \end{flushright} [Preview Abstract] |
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F05.00003: Stability of expanding accretion shocks for an arbitrary equation of state César Huete, Alexander L. Velikovich, Daniel Martínez-Ruiz Stagnation of a cold material streaming to the center or axis of symmetry via an expanding accretion shock wave is a phenomenon of paramount importance in high-energy-density physics. The examples range from plasma flows in x-ray-generating Z pinches, impact ignition in ICF and Astrophysics, where stellar collapse may result in the formation of a high-density compressed core and a shock that propagates outwards through the infalling matter. We present a theoretical analysis for the case of stagnation that does not involve a rarefaction wave behind the expanding shock front. The dispersion equation that determines the eigenvalues of the problem and the explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented for an arbitrary equations of state (EoS) and finite-strength shocks. The stagnated flow has been demonstrated to be stable for ideal gases and simple metals, with initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. Unstable behavior is found possible when certain conditions associated to the shape of the Rankine-Hugoniot curve are met, as those present in gases governed by van de Waals EoS, in resemblance to the D'yakov-Kontorovich instability of planar shocks. [Preview Abstract] |
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F05.00004: Analysis of unsteady strong shocks Michael Wadas, Eric Johnsen From supernovae to inertial confinement fusion, strong, unsteady shock waves occur in a variety of flows encountered in high-energy-density (HED) science. The unique feature of such flows that inhibits their analytical treatment is the development of entropy gradients behind the shock front that result from a variable shock strength, significantly complicating the analysis of HED experiments involving laser-driven shocks. Our objective is to develop a semi-analytical theory for solving these flows that accounts for the effect of this variable-entropy region and apply it to the analysis of HED experiments. The theory extends the method of characteristics by imposing a unique boundary condition on entropy discontinuities in a framework that prevents the unbounded generation of additional characteristics that would otherwise lead to an intractable problem. It is found that the method correctly calculates key flow features present in laser-driven compression experiments including the shape of the entropy profile and the variable strength of the shock. The solutions obtained using our theory are compared to simulations performed using an in-house, high-order accurate discontinuous-Galerkin code. [Preview Abstract] |
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F05.00005: Blast wave simulations on adaptively refined meshes: evaluating strategies for shock tube noise mitigation Ashwath Sethu Venkataraman, Logan Kunka, Nathan Gaddis, Elaine Oran The large-scale blast and detonation research facility now being developed at Texas A\&M University is centered on a 2m in diameter, 200 m long shock tube. One particular issue is that the noise level generated when the tube is fired must be low enough so that local residents are not disturbed. Here, we describe development of a new multidimensional, fully compressible, numerical model that will be used to compute sound levels and evaluate methods of sound mitigation. The model is based on the previously well tested flux-corrected transport algorithm for high-fidelity fluid dynamics calculations coupled with the AMReX software framework for block-structured adaptive mesh refinement. Results from the simulations are compared with other models and actual scale experiments. In particular, the results are compared with noise levels generated from simulations of a detonation tube and actual sound measurements generated by a modified 3-inch M1902 field gun. [Preview Abstract] |
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F05.00006: High-order Extension of Roe's Solver for Unsteady Compressible Multi-Component Real Gas Flows Luc Lecointre, Etienne Studer, Sergey Kudriakov, Ronan Vicquelin, Christian Tenaud In applications such as detonation phenomenon or atmospheric reentry, compressible effects are associated with important variations of temperature. In order to obtain accurate results, the nonlinear variation of the internal energy with the temperature must be taken into account while maintaining shock capturing with low numerical diffusion. For this purpose, a numerical strategy based on a high-order one-step shock-capturing scheme is considered using an extension of the Roe’s approximate Riemann solver for multicomponent real gas flows. This scheme minimizes numerical diffusion and presents accurate results around contact discontinuities and shockwaves, which feature strong variations in real gas properties. The method remains high-order in smooth regions. The scheme is coupled with the second-order Strang splitting procedure to consider viscous, diffusive, and combustion phenomena with the adapted numerical scheme. Adaptive mesh refinement is finally used to resolve the most relevant scales of the flow with gains on the CPU time and memory usage. The approach is validated with customized numerical test-cases with compressible effects on multicomponent flows. A 2D case of a flame acceleration phenomenon is then presented. [Preview Abstract] |
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F05.00007: A Simple Method for Detecting and Computing Shock Speeds on the Fly Tanner Nielsen, Jonathan Regele Tracking the motion and speed of shocks as they propagate throughout the computational domain during hydrodynamic calculations remains a challenging unsolved problem. We present a straight-forward approach to tracking shocks and computing their speeds in an arbitrary Lagrangian-Eulerian (ALE) framework that uses artificial viscosity for the handling of shocks. The method consists of two parts: shock detection, followed by the calculation of the shock speed. The shock detection algorithm operates with a cell-based tracking of a shock profile, which is based on the ratio of shock work to material work (i.e. large near shocks and near zero otherwise). During this process, the pre-shock and post-shock density and pressure are stored, which are then used to compute the shock speed based on a simple relation derived from the Hugoniot condition. Preliminary results show that this approach computes 1D normal shock speeds within ~1% accuracy on the fly (i.e. without post-processing). Multi-dimensional test problems will also be presented. [Preview Abstract] |
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F05.00008: Level Set Modeling of Liquid Breakup by a Supersonic Flow Abdullahalmut Sharfuddin, Foluso Ladeinde The modeling of liquid breakup by an incompressible gas flow is a well-known problem with numerous applications. However, the high-speed analog of this problem, wherein the liquid is in contact with a gas or gas mixture that flows in the supersonic regime, has not received enough attention, despite the obvious applications in, for example, aerospace propulsion. An algorithm is being developed and tested in our work, for simulating the breakup of bulk liquids in supersonic airflows, wherein the interface is tracked by applying the level set method. In order to handle the hyperbolic character of the gas flow and the presence of shock waves, a special version of the level set approach is being developed to work with the method of characteristics. Results from canonical, but fundamental, applications of the method will be presented. [Preview Abstract] |
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F05.00009: Standing Shock Regulates Sparks in Explosive Flows Jens Von Der Linden, Clare Kimblin, Ian McKenna, Skyler Bagley, Ryan Houim, Chris Kueny, Allen Kuhl, Dave Grote, Mark Converse, Caron Vossen, Soenke Stern, Corrado Cimarelli, Jason Sears Recent observations of explosive events in nature [1] and decompression experiments [2] indicate that explosive flows may alter electrical discharge processes, suppressing parts of the hierarchy of the discharge phenomena, such as leaders. In the experiments, a shock tube ejects a flow of gas and particles into an expansion chamber. We imaged an illuminated plume from a decompression of argon and a small amount of diamond particles and performed simulations. The discharges occur below the sharp boundary of a condensation cloud that agrees closely with a Mach disk shock in shape and height. This represents direct evidence that the spatial and temporal scale of the discharges transmit an impression of the shock tube flow, a connection that could enable novel instrumentation to diagnose currently inaccessible supersonic granular phenomena. [1] Behnke, S. A., et al. (2018). J. Geophys. Res. Atmos., 123(8). [2] Méndez-Harper, J. S. et al. (2018). Geophys. Res. Lett., 45(14). [Preview Abstract] |
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