scholarly journals Scalar Power Spectra and Scalar Structure Function Evolution in the Richtmyer–Meshkov Instability Upon Reshock

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Christopher D. Noble ◽  
Josh M. Herzog ◽  
David A. Rothamer ◽  
Alex M. Ames ◽  
Jason Oakley ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Shock Tube ◽  
High Speed ◽  
Power Spectra ◽  
Laser Induced Fluorescence ◽  
Initial Condition ◽  
Nominal Strength ◽  
Planar Laser ◽  
Scalar Structure ◽  
End Wall

Abstract The Richtmyer–Meshkov instability of a twice-shocked gas interface is studied using high-speed planar laser-induced fluorescence in the Wisconsin Shock Tube Laboratory's vertical shock tube. The initial condition is a shear layer with broadband diffuse perturbations at the interface between a helium–acetone mixture and argon. This initial condition is accelerated by a shock of nominal strength M = 1.9, and then accelerated again by the transmitted shock that reflects off the end wall of the tube. Three individual experiments are analyzed, the energy spectrum and the structure functions of the light gas mole fraction field are calculated and compared.

scholarly journals An experimental investigation of the turbulent mixing transition in the Richtmyer–Meshkov instability

2014 ◽  
Vol 748 ◽  
pp. 457-487 ◽  
Author(s):  
Christopher R. Weber ◽  
Nicholas S. Haehn ◽  
Jason G. Oakley ◽  
David A. Rothamer ◽  
Riccardo Bonazza
Keyword(s):  
Shock Tube ◽  
Mole Fraction ◽  
Turbulent Mixing ◽  
Mixing Layer ◽  
Initial Condition ◽  
Planar Laser ◽  
Interface Location ◽  
Scalar Variance ◽  
Fraction Distribution ◽  
Stagnation Plane

AbstractThe Richtmyer–Meshkov instability (RMI) is experimentally investigated in a vertical shock tube using a broadband initial condition imposed on an interface between a helium–acetone mixture and argon ($A\approx 0.7$). The interface is created without the use of a membrane by first setting up a flat, gravitationally stable stagnation plane, where the gases are injected from the ends of the shock tube and exit through horizontal slots at the interface location. Following this, the interface is perturbed by injecting gas within the plane of the interface. Perturbations form in the lower portion of this layer due to the shear between this injected stream and the surrounding gas. This shear layer serves as a statistically repeatable broadband initial condition to the RMI. The interface is accelerated by either a$M= 1.6 $or$M= 2.2 $planar shock wave, and the development of the ensuing mixing layer is investigated using planar laser-induced fluorescence (PLIF). The PLIF images are processed to reveal the light-gas mole fraction by accounting for laser absorption and laser-steering effects. The images suggest a transition to turbulent mixing occurring during the experiment. An analysis of the mole-fraction distribution confirms this transition, showing the gases begin to homogenize at later times. The scalar variance energy spectra exhibits a near$k^{-5/3}$inertial range, providing further evidence for turbulent mixing. Measurements of the Batchelor and Taylor microscales are made from the mole-fraction images, giving${\sim }150\ \mu \mathrm{m}$and 4 mm, respectively, by the latest times. The ratio of these scales implies an outer-scale Reynolds number of$6\text {--}7\times 10^4$.

scholarly journals High-Speed Imaging and Measurements of Ignition Delay Times in Oxy-Syngas Mixtures With High CO2 Dilution in a Shock Tube

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Samuel Barak ◽  
Owen Pryor ◽  
Joseph Lopez ◽  
Erik Ninnemann ◽  
Subith Vasu ◽  
...  
Keyword(s):  
Shock Tube ◽  
Ignition Delay ◽  
Delay Time ◽  
High Speed ◽  
Ignition Delay Time ◽  
High Speed Imaging ◽  
Ignition Delay Times ◽  
Delay Times ◽  
Syngas Combustion ◽  
End Wall

In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2 cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% to 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (ϕ), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (θ), hydrogen to carbon monoxide, from 0.25, 1.0, and 4.0. The study was performed at 1.61–1.77 atm and a temperature range of 1006–1162 K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed nonhomogeneous combustion in the system; however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.

Planar laser-induced fluorescence imaging in shock tube flows

2010 ◽  
Vol 49 (4) ◽  
pp. 751-759 ◽  
Author(s):  
J. Yoo ◽  
D. Mitchell ◽  
D. F. Davidson ◽  
R. K. Hanson
Keyword(s):  
Shock Tube ◽  
Fluorescence Imaging ◽  
Laser Induced Fluorescence ◽  
Planar Laser Induced Fluorescence ◽  
Planar Laser

Near-wall imaging using toluene-based planar laser-induced fluorescence in shock tube flow

Shock Waves ◽  
2011 ◽  
Vol 21 (6) ◽  
pp. 523-532 ◽  
Author(s):  
J. Yoo ◽  
D. Mitchell ◽  
D. F. Davidson ◽  
R. K. Hanson
Keyword(s):  
Shock Tube ◽  
Laser Induced Fluorescence ◽  
Tube Flow ◽  
Planar Laser Induced Fluorescence ◽  
Planar Laser ◽  
Wall Imaging ◽  
Near Wall
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