Shock tube

About: Shock tube is a research topic. Over the lifetime, 6963 publications have been published within this topic receiving 99372 citations.

Navier-Stokes computations in micro shock tubes

Abstract: Micro shock tube flows were simulated using unsteady 2D Navier–Stokes equations combined with boundary slip velocities and temperature jumps conditions. These simulations were performed using the parallel version of a multi-block finite-volume home code. Different initial low pressures and shock tube diameters allow to have the scaling ratio ReD/4L vary. The numerical results show a strong attenuation of the shock wave strength with a decrease of the hot flow values along the tube. When the scaling ratio decreases the shock waves can transform into compression waves. Comparison to the existing 1D models also shows the limit of these models.

Nonequilibrium Radiation Intensity Measurements in Simulated Titan Atmospheres

Abstract: This paper details the experimental work conducted at the University of Queensland to measure the nonequilibrium radiation intensity behind a shock in simulated Titan atmospheres, as would be seen during planetary entry. Radiation during Titan entry is more important at lower speeds (about 5-6 km/s) than other planetary entries due to the formation of cyanogen in above equilibrium concentrations in the shock layer, which is a highly radiative species. The experiments were focused on measuring the nonequilibrium radiation emitted from cyanogen between the wavelength range of 310-450 nm. This paper includes experimental results for radiation and spectra found in the postshock region of the flow. Experiments have been conducted at various ambient pressures, shock speeds, and chemical compositions. This leads to a comprehensive benchmark data set for Titan entry, which will be useful for validation of theoretical models. Spectra were recorded at various axial locations behind the shock, enabling the construction of radiation profiles for Titan entry. Furthermore, wavelength profiles can also be constructed to identify various radiating species, in this case, predominately cyanogen violet. Furthermore, this paper includes comparisons with experiments performed at NASA Ames Research Center on their electric arc-driven shock tube in Titan compositions. Excellent quantitative agreement has been obtained between the two facilities.

Shock tube ignition delay time measurements in propane/O2/argon mixtures at near-constant-volume conditions

Abstract: Shock tube measurements of ignition delay times with high activation energies are strongly sensitive to variations in reflected shock temperatures. At longer shock tube test times, as are needed at low reaction temperatures, small gradual increases in pressure (and simultaneous increases in temperature) that result from incident shock wave attenuation and boundary layer growth can significantly shorten measured ignition delay times. To obviate this pressure increase, we made use of a recently developed driver-insert method of Hong et al. [8] that allows generation of near-constant-volume test conditions for reflected shock measurements. Using this method, we have measured propane ignition delay times in a lean mixture (0.8% C 3 H 8 /8% O 2 /Ar) over temperatures between 980 and 1400 K and nominal pressures of 6, 24 and 60 atm, under both conventional shock tube operation (with post-shock fractional pressure variation d P 5 /d t ∼ 1–7%/ms) and near-constant-volume operation (with d P 5 /d t ∼ 0%/ms). The near-constant-volume ignition delay times provide a database for low-temperature propane model development that is independent of non-ideal fluid flow and heat transfer effects. Comparisons of these near-constant-volume measurements with predictions using the JetSurF v1.0 mechanism of Sirjean et al. [10] and the Curran et al. mechanism of NUI Galway [5] were performed. Ignition delay times measured with d P 5 /d t ∼ 1–7%/ms were found to be significantly shorter (about 1/3 of the near-constant-volume values) at the lowest temperatures and highest pressures studied. However, these ignition times are successfully simulated using the JetSurF v1.0 mechanism when an appropriate gasdynamic model that accounts for changes in pressure and temperature is used.

Shock tube measurements of rate coefficients of elementary gas reactions

Abstract: The primary objective of this paper is to review the current status of rate coefficient determinations of elementary gas reactions using modern shock tube measurement technques. The major inaccuracies in these determinations arise from uncertainties in reaction conditions due to gas dynamic effects, uncertainties introduced by interfering rate processes such as vibrational relaxation, competing reactions, or reactions involving impurities, and uncertainties introduced by the diagnostics. Some new diagnostics and experimental methods which can improve accuracy of shock tube rate coefficient measurements are discussed. Included among these are tunable laser absorption spectroscopy for species concentration and temperature measurements, digital data recording, new techniques for controlled generation of radical species, and computer optimization of experimental conditions. Currently attainable levels of accuracy of shock tube rate coefficient determinations of elementary gas reactions are illustrated for several classes of reactions including unimolecular decomposition reactions, bimolecular atom--molecule exchange reactions, and termolecular recombination reactions. 5 figures, 1 table.

Operating Characteristics of a 60- and 10-cm Electric Arc-Driven Shock Tube-Part 11: The Driven Section

Abstract: This is the second part of a two-part paper describing the operating characteristics of the electric arc-driven shock-tube facilities at NASA Ames Research Center. This part discusses the performance of the driven sections when the facility is used as a tool to produce a low-density nonequilibrium flow and when used as a shock tunnel. Specifically, the paper discusses the cleanliness of the driven flow at low densities, and the deviation from the equilibrium conditions at the test section of the shock-tunnel flow.