Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session L10: Compressible Flows: Shock Waves and Explosions |
Hide Abstracts |
Chair: Benjamin Emerson, Georgia Tech; Janardhanraj Subburaj, King Abdullah University of Science and Technology (KAUST), Saudi Arabia Room: 137 |
Monday, November 21, 2022 8:00AM - 8:13AM |
L10.00001: Influence of diaphragm opening process on shock tube flow Janardhanraj Subburaj, Miguel Figueroa-Labastida, Aamir Farooq The diaphragm opening process in a shock tube is far from ideal in practical scenarios as it is highly dependent on several factors. A non-ideal diaphragm rupture can result in a three-dimensional flow due to reflections and interactions of secondary waves behind the shock front. The main aim of the present study is to investigate the effects of non-ideal diaphragm rupture on shock tube performance. Experiments are carried out in the Low-Pressure Shock Tube (LPST) at KAUST using argon as driven gas at P5 = 1.33 – 2.06 bar and T5 = 1090 – 2142 K. Optical windows installed in the end walls of the driver and driven sections facilitate high-speed imaging of the diaphragm opening process. The thickness of the cellophane diaphragm used, the location of the diaphragm cutter, and the flow rate of driver gas prior to diaphragm rupture are varied to obtain different diaphragm opening configurations. We will present the results of our investigation on the dependence of the rate of diaphragm opening and the diaphragm opening time on the post-shock pressures and temperatures obtained in the shock tube. The abnormal effects of the slow driver gas filling and asymmetrical diaphragm opening on the pressure profile during the test time will also be presented. |
Monday, November 21, 2022 8:13AM - 8:26AM |
L10.00002: Shock wave characterization using a multi-exposed high-speed camera and high performance fiber optics sensor. Rok Petkovsek, Jaka Mur, Fabian Reuter, Jernej Jan Kocica, Ziga Lokar, Jaka Petelin, Vid Agrez, Claus-Dieter Ohl We will present planar shock wave imaging to determine velocity and pressure that is based on multi exposure of each frame in the high-speed imaging series. The technique is demonstrated using a custom-built illumination source where the illumination pulses are much shorter than the frame exposure time of each frame. The benefit of the presented method is speckle free imaging with the sub nanosecond illumination pulses and a minimal spacing between the pulses of few nanoseconds that can be arbitrary delayed in respect to the event under the investigation. This enables capturing the shock waves right after the emission at multiple time instances. The presented method surpasses previously demonstrated multi-exposure methods by an order of magnitude in time resolution, is suitable for transient events, and is not limited to a homogenous shock wave emission, i.e. extends streak imaging-based techniques. The technique gives detailed insight into the shock wave pressure evolution near its source with the measured shockwave pressure amplitudes reaching 1 GPa. The results from a multi-frame multi-exposure shockwave pressure/velocity measurement technique are verified with a custom-made high-bandwidth high performance fiber optics sensor. |
Monday, November 21, 2022 8:26AM - 8:39AM |
L10.00003: Coupling Traditional Hydrodynamics and Smoothed Particle Hydrodynamics for Increased Performance in 1D Strong Shock Simulations Conner Myers, Camille J Palmer, Todd Palmer, Kyle E Niemeyer We present results from simulations of 1D shock test problems employing a novel scheme coupling traditional hydrodynamics and smoothed particle hydrodynamics. Standard, grid-based hydrodynamics methods typically require high resolution to accurately model the propagation of strong shockwaves due to the large gradients of fluid properties. While adaptive mesh refinement can reduce the number of grids, simulations are still limited to the timestep required for stability by the smallest grid due to the Courant condition. A new method using the meshless Smoothed Particle Hydrodynamics method as a sub-grid model on a coarser Finite Volume is investigated for 1D shock problems. The meshless particles compute interactions directly between each particle and are allowed to flow with the fluid as the shockwave propagates. The hybrid approach shows no speedup for the weaker Sod shock tube problem but demonstrates a speedup of 2.1 and 5.1 times for an acoustic blastwave and Woodward-Collela blastwave problems, respectively. The results from this work will inform the extension of the method to 2D problems and full-scale blast simulations. |
Monday, November 21, 2022 8:39AM - 8:52AM |
L10.00004: RR-MR transition in curved shock wave reflections Sushmitha Janakiram, Subrahmanyam Duvvuri In shock wave reflections, a transition occurs between two reflection types -- regular reflection (RR) and Mach reflection (MR) -- as the flow deflection angle is varied. Experimentally, this transition is commonly induced by varying the angle-of-attack of the shock wave generator. While RR-MR transitions have been extensively studied for planar oblique shock waves, such transitions for curved shock waves have received much lesser attention in the literature. The present work investigates RR-MR transition in a curved shock wave that reflects off a flat surface. Wind tunnel experiments were performed at a free-stream Mach number of 6, with a 2D curved compression ramp as the shock wave generator. The ramp curvature was designed to yield a constant pressure gradient along the compression surface for a Mach 6 inviscid flow at zero angle-of-attack. Schlieren imaging with high temporal resolution allows for detailed visualization of RR-MR transitions as the ramp angle-of-attack is varied continually during experiments. It was observed that the overall flow deflection angle corresponding to the transition point for the curved ramp at Mach 6 was 51.7°, which is significantly higher than the value of 37.8° reported in the literature for planar ramps. |
Monday, November 21, 2022 8:52AM - 9:05AM |
L10.00005: Analysis of ground shock reflections through explosions at various heights of burst Isabella Gatto, Christian R Peterson, Michael J Hargather, Lydia Wermer, Michael Clemenson Spherical explosions were detonated at varying heights above the ground and imaged with high-speed cameras. The high-speed images were processed using natural background oriented schlieren and background subtraction techniques to visualize shock wave propagation and reflection from the ground. Digital streak images were created from the high-speed video frames. Tracking the shock wave became more quantifiable with the streak images, which allowed data such as the shock velocity, shape, and interactions with the fireball to be collected. The images were also analyzed to measure the change in light intensity of the explosive fireball as the reflected ground shock wave passed through the fireball. Correlations between the height of burst, ground shock reflection velocity, and fireball illumination are presented. |
Monday, November 21, 2022 9:05AM - 9:18AM |
L10.00006: The fractal scaling of explosively driven gas clouds Christian R Peterson, Michael J Hargather Characterization of the interface between explosive product gases and ambient air in an explosion is a complicated task due to the turbulent mixing and inherently three-dimensional expansion of the interface. This study aims to quantify the evolution of the interface as a temporally-varying fractal dimension. The Hausdorff or fractal dimension of the two-dimensional slices of an explosively driven gas cloud has been measured from multiple angles for explosions at varying scales. Experimental studies were conducted with explosives from the gram scale to the kilogram scale. Gas cloud profiles are extracted using automated image processing algorithms. The Hausdorff dimension is estimated using boxcounting algorithms on the extracted profiles. Variations in explosive charge mass are used to identify scaling for the Hausdorff dimension. When scaled with time, the fractal dimension evolution as a function of time appears to collapse to a single curve. Following an initial expansion, the fractal dimension tends toward a value of 4/3 before plateauing. Luminous early time fireballs collapse well to this curve, and demonstrate axial symmetry in estimated fractal dimension for symmetric charges. Late time fireballs do not appear to collapse to the same curve, indicating a change in underlying expansion and mixing regime for the product gases. |
Monday, November 21, 2022 9:18AM - 9:31AM |
L10.00007: On the disturbance energy budget for gaseous H2 -Air detonations Hari Priya Rajagopalan, Sai Sandeep Dammati, Vishal Acharya, Alexei Y Poludnenko, Timothy C Lieuwen This study analyzes the wave energetics of gaseous detonations from the standpoint of disturbance energy production and propagation. Contribution of the three canonical forms of disturbances, namely, acoustic vortical and entropic sources are analyzed using data from a stoichiometric 2D Hydrogen air DNS study. Particular attention is paid to the Rayleigh source term, i.e., the product of pressure and heat release terms, which serves as an acoustic source term. Unstable detonative mixtures of hydrogen-air have been compared with the stable H2-O2-Ar mixture from the standpoint of Rayleigh source magnitude. Finally, we compare the magnitude of these source terms relative to the energy flux of the transverse propagating waves. |
Monday, November 21, 2022 9:31AM - 9:44AM |
L10.00008: Optical analysis of a supersonic conical projectile interacting with an explosively-driven shock wave Kailene Strebe, Michael J Hargather, David Morrow Schlieren imaging and optical analysis have previously been used to measure density fields around a supersonic projectile in flight. The same methods are applied here to study shock wave interactions between a supersonic projectile and an external blast wave. Quantitative schlieren and ultra-high-speed digital cameras are used to visualize and quantify the shock wave interaction evolution as a function of time. Quantitative schlieren and symmetry arguments allow the characterization of the density field throughout the flow. The baseline blast wave and projectile flowfields are characterized individually, then the interacting flow field is explored. Differences between the individual flows and the combined interaction are measured. The shock-shock interaction shows changes in the shape of the shock wave on the supersonic projectile and irregular reflections of the blast wave from the cone surface. |
Monday, November 21, 2022 9:44AM - 9:57AM |
L10.00009: Shock structure and equilibrium states of epoxy-spinel and porous Cu-W mixtures employing a new, multi-material continuum mixture model Joshua R Garno, Mark Short, Carlos Chiquete, Stephen J Voelkel A new, Baer-Nunizato type multi-material continuum mixture model is leveraged to explore the shock structure and equilibrium states of epoxy-spinel and copper-tungsten mixtures subjected to plate impact conditions. The theory is symmetric in regard to material appearance and is formulated to handle an arbitrary number of materials in three-dimensions. Based on pairwise interactions of component materials, relaxation parameters controlling the rates of velocity and pressure equilibration are varied to investigate the sensitivity of shock structure and equilibrium states to both momentum and energy exchange and to the evolution in solid volume fraction. Model validation and verification are provided by comparison of simulation results with experimental data and numerical results of Bdzil et al. 2021 for the epoxy-spinel mixture. The capability of the model to predict the effects of porosity on shock equilibrium states is demonstrated for porous copper, porous tungsten, and porous copper-tungsten mixtures, and compared to experimental data. |
Monday, November 21, 2022 9:57AM - 10:10AM |
L10.00010: Measuring viscosity at extreme pressures Jessica Shang, Nitish Acharya, Afreen Syeda, Danae Polsin, J. Ryan Rygg, Hadley Pantell, John J Ruby, David A Chin, Riccardo Betti, Gilbert W Collins, Arianna Gleason, Hussein Aluie Viscosity plays a role in the mixing and transport of fluids at high pressures and temperatures, which can be found in applications ranging from planetary interiors to inertial confinement fusion. Experimental measurements of viscosity of materials at high energy-density (HED) conditions---that is, pressures greater than 100 GPa---are limited in parameter space, and theoretical calculations of viscosity are inconsistent in the warm dense matter regime. Here we present estimates of the dynamic viscosity of epoxy, a proxy for a hydrocarbon, using the acceleration of embedded bluff bodies (Al'tshuler et al., 1986). The epoxy was shock-compressed with laser ablation to a pressure of 240 GPa at the OMEGA laser facility. The sample was embedded with stainless steel microspheres, and the displacement of the spheres was imaged with x-ray radiography. The trajectories of the particles was corroborated with an unsteady forcing model for the shock-particle interaction to estimate the epoxy's dynamic viscosity from the history force. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700