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Showing papers on "Shock tube published in 2018"


Journal ArticleDOI
TL;DR: In this article, a pressure-driven shock tube was employed to switch TiO2 nanoparticles from anatase to rutile phase at an applied pressure of about 2.683 MPa.

79 citations


Journal ArticleDOI
TL;DR: In this article, the effects of pre-ignition energy releases on H 2 O 2 mixtures were explored in a shock tube with the aid of high-speed imaging and conventional pressure and emission diagnostics.

64 citations


Journal ArticleDOI
01 Aug 2018
TL;DR: Richtmyer-Meshkov instability is regarded as a central role for understanding the hydrodynamic processes involved in inertial confinement fusion, supersonic combustion and supernova explosion as mentioned in this paper.
Abstract: Richtmyer–Meshkov (RM) instability is regarded as a central role for understanding the hydrodynamic processes involved in inertial confinement fusion, supersonic combustion and supernova explosion....

49 citations


Journal ArticleDOI
TL;DR: In this article, a high-speed imaging setup was utilized to visualize the shock tube cross-section through a transparent quartz end-wall, and the results suggest that premature ignition events are more likely to happen in mixtures containing higher ethanol concentration and that preignition energy release is more pronounced at lower temperatures.

43 citations


Journal ArticleDOI
15 Aug 2018-Fuel
TL;DR: In this paper, the authors measured selected species time-histories during fuel pyrolysis using laser absorption, and ignition delay times using multiple methods behind reflected shock waves in a heated shock tube.

40 citations


Journal ArticleDOI
TL;DR: In this paper, the Richtmyer-Meshkov instability on a three-dimensional single-mode light/heavy interface is experimentally studied in a converging shock tube, and it is quantitatively found that the perturbation amplitude experiences a rapid growth to a maximum value after shock compression and finally drops quickly before the reshock.
Abstract: The Richtmyer–Meshkov instability on a three-dimensional single-mode light/heavy interface is experimentally studied in a converging shock tube. The converging shock tube has a slender test section so that the non-uniform feature of the shocked flow is amply exhibited in a long testing time. A deceleration phenomenon is evident in the unperturbed interface subjected to a converging shock. The single-mode interface presents three-dimensional characteristics because of its minimum surface feature, which leads to the stratified evolution of the shocked interface. For the symmetry interface, it is quantitatively found that the perturbation amplitude experiences a rapid growth to a maximum value after shock compression and finally drops quickly before the reshock. This quick reduction of the interface amplitude is ascribed to a significant Rayleigh–Taylor stabilization effect caused by the deceleration of the light/heavy interface. The long-term effect of the Rayleigh–Taylor stabilization even leads to a phase inversion on the interface before the reshock when the initial interface has sufficiently small perturbations. It is also found that the amplitude growth is strongly suppressed by the three-dimensional effect, which facilitates the occurrence of the phase inversion.

39 citations


Journal ArticleDOI
TL;DR: A robust sharp-interface immersed boundary method for numerically studying high speed flows of compressible and viscous fluids interacting with arbitrarily shaped either stationary or moving rigid solids.

38 citations


Journal ArticleDOI
TL;DR: In this article, an alternative non-destructive approach is proposed and demonstrated for modifying electrical properties of crystal using shock-waves, which is an alternative to the conventional doping process for tailoring dielectric properties of this type of crystal.
Abstract: An alternative non-destructive approach is proposed and demonstrated for modifying electrical properties of crystal using shock-waves. The method alters dielectric properties of a potassium dihydrogen phosphate (KDP) crystal by loading shock-waves generated by a table-top shock tube. The experiment involves launching the shock-waves perpendicular to the (100) plane of the crystal using a pressure driven table-top shock tube with Mach number 1.9. Electrical properties of dielectric constant, dielectric loss, permittivity, impedance, AC conductivity, DC conductivity and capacitance as a function of spectrum of frequency from 1 Hz to 1 MHz are reported for both pre- and post-shock wave loaded conditions of the KDP crystal. The experimental results reveal that dielectric constant of KDP crystal is sensitive to the shock waves such that the value decreases for the shock-loaded KDP sample from 158 to 147. The advantage of the proposed approach is that it is an alternative to the conventional doping process for tailoring dielectric properties of this type of crystal.

37 citations


Journal ArticleDOI
TL;DR: In this article, a grid-convergence approach was proposed to simulate the flow field in a square closed closed shock tube at the Reynolds number of 1000, and the resulting grid is shown to be a gridconverged solution of the problem.
Abstract: The flow in a shock tube is extremely complex with dynamic multi-scale structures of sharp fronts, flow separation, and vortices due to the interaction of the shock wave, the contact surface, and the boundary layer over the side wall of the tube. Prediction and understanding of the complex fluid dynamics are of theoretical and practical importance. It is also an extremely challenging problem for numerical simulation, especially at relatively high Reynolds numbers. Daru and Tenaud [“Evaluation of TVD high resolution schemes for unsteady viscous shocked flows,” Comput. Fluids 30, 89–113 (2001)] proposed a two-dimensional model problem as a numerical test case for high-resolution schemes to simulate the flow field in a square closed shock tube. Though many researchers attempted this problem using a variety of computational methods, there is not yet an agreed-upon grid-converged solution of the problem at the Reynolds number of 1000. This paper presents a rigorous grid-convergence study and the resulting grid...

36 citations


Journal ArticleDOI
TL;DR: In this paper, the Richtmyer-Meshkov instability was investigated in a vertical shock tube using a broadband initial condition imposed on an interface between a helium-acetone mixture and argon (Atwood number when considering both density and velocity effects in planar turbulent kinetic energy (TKE) measurements).
Abstract: The 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 (Atwood number when considering both density and velocity effects in planar turbulent kinetic energy (TKE) measurements.

33 citations


Journal ArticleDOI
TL;DR: In this paper, real gas effects on high-pressure combustion by comparing simulated and experimentally-measured shock tube ignition delay measurements for n-dodecane/O2/N2 mixtures are studied.

Journal ArticleDOI
01 May 2018-Fuel
TL;DR: In this article, a spray environment for injection of liquid fuel sprays into hot air at 1.0, 2.14, and 4.0 MPa was used to characterize relative fuel reactivity, the dependence of reactivity on temperature and pressure, and allow for correlation of reactionivity under spray and homogenous gas phase conditions.

Journal ArticleDOI
TL;DR: The combination of ab initio quantum chemistry PESs and QCT calculations provides an attractive approach for the determination of accurate high-temperature rate coefficients for use in aerothermodynamics modeling.
Abstract: Comparisons are made between potential energy surfaces (PESs) for N2+N and N2+N2 collisions and between rate coefficients for N2 dissociation that were computed using the quasi-classical trajectory...

Journal ArticleDOI
TL;DR: In this article, the authors studied the chemical effects (chaperon effects of CO2 and the effects of reactions containing CO2) and physical effects on the ignition of methane at different pressures and temperatures in detail using a modified model.
Abstract: Pressurized oxy-fuel combustion is regarded as a new generation of oxy-fuel technology. The ignition delay times of methane in an O2/N2 atmosphere (0.21O2 + 0.79N2) and an O2/CO2 atmosphere (0.21O2 + 0.79CO2) were measured in a shock tube at a pressure of 0.8 atm, an equivalence ratio of 0.5, and within a temperature range of 1501–1847 K. The present experimental data and the experimental data of Hargis and Peterson at 1.75 and 10 atm were adopted to evaluate five representative chemical kinetic models. This paper studied the chemical effects (chaperon effects of CO2 and the effects of reactions containing CO2) and physical effects of CO2 on the ignition of methane at different pressures and temperatures in detail using a modified model. Artificial materials X and Y were employed to analyze the chemical and physical effects. The analysis showed that the physical effects of CO2 inhibit the ignition of methane and are not sensitive to the temperature. The chemical effects of CO2 vary greatly with the pressu...

Journal ArticleDOI
12 Jan 2018
TL;DR: In this paper, the cylindrical Richtmyer-Meshkov (RM) instability is studied in a shock tube and the growth rate of this instability does not saturate in the nonlinear regime as it does in the planar geometry.
Abstract: The cylindrical Richtmyer-Meshkov (RM) instability is studied in a shock tube. The growth rate of this instability does not saturate in the nonlinear regime as it does in the planar geometry. Numerical and theoretical studies show that a Rayleigh-Taylor instability superimposes on the RM one and that Bell-Plesset effects enhance the growth of the instability.

Journal ArticleDOI
TL;DR: In this article, the influence of small particle fragmentation on the ignition of real and surrogate fuels was investigated in two Stanford shock tubes, showing that small particles were observed to arrive near the endwalls of the shock tubes approximately 5 milliseconds after reflection of the incident shock wave.
Abstract: Homogeneous and inhomogeneous ignition of real and surrogate fuels were imaged in two Stanford shock tubes, revealing the influence of small particle fragmentation. n-Heptane, iso-octane, and Jet A were studied, each mixed in an oxidizer containing 21% oxygen and ignited at low temperatures (900–1000 K), low pressures (1–2 atm), with an equivalence ratio of 0.5. Visible images (350–1050 nm) were captured through the shock tube endwall using a high-speed camera. Particles were found to arrive near the endwalls of the shock tubes approximately 5 ms after reflection of the incident shock wave. Reflected shock wave experiments using diaphragm materials of Lexan and steel were investigated. Particles collected from the shock tubes after each experiment were found to match the material of the diaphragm burst during the experiment. Following each experiment, the shock tubes were cleaned by scrubbing with cotton cloths soaked with acetone. Particles were observed to fragment after arrival near the endwall, often leading to inhomogeneous ignition of the fuel. Distinctly more particles were observed during experiments using steel diaphragms. In experiments exhibiting inhomogeneous ignition, flames were observed to grow radially until all the fuel within the cross section of the shock tube had been consumed. The influence of diluent gas (argon or helium) was also investigated. The use of He diluent gas was found to suppress the number of particles capable of causing inhomogeneous flames. The use of He thus allowed time history studies of ignition to extend past the test times that would have been limited by inhomogeneous ignition.

Proceedings ArticleDOI
25 Jun 2018
TL;DR: In this paper, the authors used a tunable diode laser to measure the temperature relaxation behind the electric arc shock wave in pure CO at a pressure of 0.25 Torr in the driven section and span a shock velocity range from 3.4-9.5 km/s.
Abstract: Incident shock waves in pure CO have been characterized in the Electric Arc Shock Tube facility at NASA Ames Research Center. Spectrally and spatially resolved emission spectra characterize radiative signatures from CO in the VUV (Vacuum Ultra-Violet) and mid-infrared and atomic carbon and C2 in the visible. CO absorption of a single vibrational line is also measured with a tunable diode laser. The experimental data analyzed here are at a pressure of 0.25 Torr in the driven section and span a shock velocity range from 3.4-9.5 km/s. The emission and absorption signals are analyzed to extract temperature relaxation behind the shock which is used to derive the rate of CO dissociation. The emission spectra are compared to results using different kinetic parameters for CO dissociation and C2 dissociation and exchange. Different rates from the literature are found to match the data from 3.4-6.6 km/s and 6.6-9.5 km/s. Areas for improvement in CO and C2 radiation modeling are suggested on the basis of the analysis.

Journal ArticleDOI
TL;DR: A numerical framework to simulate transcritical and supercritical flows utilising the compressible form of the Navier–Stokes equations coupled with the Perturbed Chain Statistical Associating Fluid Theory equation of state (EoS); both conservative and quasi-conservative formulations have been tested.

Journal ArticleDOI
TL;DR: In this paper, the results of a small scale experimental study of BLEVE overpressure effects were presented, where three parameters were controlled during the experiments: the failing pressure, the weakened length on the tube and the fill level.

Journal ArticleDOI
TL;DR: Behind reflected shock waves, time-resolved measurements of the formation of H atoms using the highly sensitive H-ARAS technique and the depletion of the DMM reactant by high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS) are carried out.
Abstract: Shock-tube experiments have been performed to investigate the thermal decomposition of the oxygenated hydrocarbon dimethoxymethane (DMM; CH3OCH2OCH3) The primary initial reaction channels of DMM decomposition are considered to be the two bond fissions: CH3OCH2OCH3 → CH3O + CH2OCH3 (1) and CH3OCH2OCH3 → CH3 + OCH2OCH3 (2) In the present work, two shock-tube facilities and three different detection techniques have been combined: Behind reflected shock waves, we have carried out time-resolved measurements of (i) the formation of H atoms using the highly sensitive H-ARAS (Atomic Resonance Absorption Spectrometry) technique and (ii) the depletion of the DMM reactant by high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS) In addition, (iii) the temperature-dependent composition of stable reaction products was measured in single-pulse shock-tube experiments via gas chromatography (GC/MS) The experiments span a temperature range of 1100–1430 K, a pressure range of 12–25 bar, and initial reacta

Journal ArticleDOI
TL;DR: In this article, the ignition behavior of undiluted DEE/air mixtures at engine relevant conditions was investigated in a high-pressure shock tube (HPST) under stoichiometric conditions.

Journal ArticleDOI
TL;DR: In this paper, the Coupled Level Set/Volume of Fluid (CLSVOF) interface capturing method was used to capture compressibility effects and phase change in turbulent two-phase flow DNS.

Journal ArticleDOI
TL;DR: In this paper, a review of the literature has revealed that most of the first-stage ignition delay time and species measurement data for normal heptane have been obtained at elevated pressures, rather than at relatively low pressures where many other important experimental techniques such as jet-stirred reactors and flow reactors can provide corroborating results.

Journal ArticleDOI
TL;DR: A conservative interface-interaction method dedicated to simulating multiple compressible fluids with sharp interfaces, suitable for a wide range of complex compressible multi-material flows.

Journal ArticleDOI
Abstract: We report the development of a high-sensitivity laser absorption diagnostic optimized for measurement of the hydroxyl radical (OH) at temperatures relevant to combustion studies, and demonstrated here in shock tube experiments. This diagnostic utilizes a narrow-linewidth CW UV laser that is tunable over the A2Σ – X2Π (0,0) band of the OH rovibronic transitions. First, we identified the strongest absorption transition of OH, over the current temperature range of interest, to be the Q1(5) transition near 308.61 nm. We then measured the OH absorption coefficients behind reflected shock waves over temperatures of 1656–2993 K and pressures of 0.88–4.09 atm, and determined the pressure-broadening and pressure-shifting coefficients in argon bath gas. Compared to the previous diagnostic targeting the OH R1(5) transition, the current diagnostic has approximately 2.2 times the sensitivity. Finally, we demonstrated the excellent sensitivity of the current OH diagnostic in a set of highly-diluted C3H8 oxidation experiments in a shock tube, where a 1 − σ detection limit of less than 0.15 ppm OH was successfully achieved.

Journal ArticleDOI
TL;DR: In this article, shock tube experiments were performed to investigate the blast response of corrugated steel cellular core sandwich panels filled with a silicone-based syntactic foam at room and high temperatures.
Abstract: Shock tube experiments were performed to investigate the blast response of corrugated steel cellular core sandwich panels filled with a silicone based syntactic foam at room and high temperatures. ...

Journal ArticleDOI
TL;DR: In this paper, the authors presented the second part of a study aiming to accurately characterise a Mach 10 scramjet test flow generated using a large free-piston-driven expansion tube.
Abstract: This paper presents the second part of a study aiming to accurately characterise a Mach 10 scramjet test flow generated using a large free-piston-driven expansion tube. Part 1 described the experimental set-up, the quasi-one-dimensional simulation of the full facility, and the hybrid analysis technique used to compute the nozzle exit test flow properties. The second stage of the hybrid analysis applies the computed 1-D shock tube flow history as an inflow to a high-fidelity two-dimensional-axisymmetric analysis of the acceleration tube. The acceleration tube exit flow history is then applied as an inflow to a further refined axisymmetric nozzle model, providing the final nozzle exit test flow properties and thereby completing the analysis. This paper presents the results of the axisymmetric analyses. These simulations are shown to closely reproduce experimentally measured shock speeds and acceleration tube static pressure histories, as well as nozzle centreline static and impact pressure histories. The hybrid scheme less successfully predicts the diameter of the core test flow; however, this property is readily measured through experimental pitot surveys. In combination, the full test flow history can be accurately determined.

Journal ArticleDOI
TL;DR: In this paper, the authors used two sets of specimens: (1) an anthropometric dummy head and (2) a surrogate rodent headform instrumented with pressure sensors and subjected them to blast waves in the interior and at the exit of the shock tube.
Abstract: Dynamic loads on specimens in live-fire conditions as well as at different locations within and outside compressed-gas-driven shock tubes are determined by both static and total blast overpressure–time pressure pulses. The biomechanical loading on the specimen is determined by surface pressures that combine the effects of static, dynamic, and reflected pressures and specimen geometry. Surface pressure is both space and time dependent; it varies as a function of size, shape, and external contour of the specimens. In this work, we used two sets of specimens: (1) anthropometric dummy head and (2) a surrogate rodent headform instrumented with pressure sensors and subjected them to blast waves in the interior and at the exit of the shock tube. We demonstrate in this work that while inside the shock tube the biomechanical loading as determined by various pressure measures closely aligns with live-fire data and shock wave theory, significant deviations are found when tests are performed outside.

Journal ArticleDOI
TL;DR: In this article, real gas effects on combustion and emissions in internal combustion engines were investigated using three-dimensional computational fluid dynamics, and the Peng-Robinson equation of state was implemented.
Abstract: Real gas effects on combustion and emissions in internal combustion engines are investigated using three-dimensional computational fluid dynamics. The Peng–Robinson equation of state is implemented...

Journal ArticleDOI
TL;DR: In this paper, a fourth-order accurate finite-volume method is developed and verified for solving strongly nonlinear, time-dependent, compressible, thermally perfect, and multispecies gaseous flows on mapped grids that are adaptively refined in space and time.