Shock tube

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

Reaction kinetics of NH in the shock tube pyrolysis of HNCO

Abstract: The high temperature kinetics of NH in the pyrolysis of isocyanic acid (HNCO) have been studied in reflected shock wave experiments. Time histories of the NH(X3Σ−) radical were measured using a cw, narrow-linewidth laser absorption diagnostic at 336 nm. The second-order rate coefficients of the reactions: (1) were determined to be: cm3−mol−1−s−1, where f and F define the lower and upper uncertainty limits, respectively. The data for k1a are somewhat better fit by:

Flowfield Around Spike-Tipped Bodies for High Attack Angles at Mach 4.5

Abstract: The requirements for the design of a new short-range high-velocity missile are both the drag reduction and the correct information acquisition for the optoelectronic sensors embedded in the hemispherical nose. High anglesof attack must be studied to fulfill the maneuverability requirements of present and future missiles. A supersonic missile generates a bow shock around its blunt nose, which causes rather high surface pressure and temperature and, as a result, the development of high drag and damage of embedded sensors. The pressure and the temperature on the hemispherical nose surface can be substantially reduced if an oblique shock is generated by a forward-facing spike. Both the experiments and the computations are carried out to study the flowfield around three-dimensional blunt bodies equipped with forward-facing spikes for a large range of attack angles at a Mach number of 4.5. A blunt body, a classical disk-tip spike, a sphere-tip spike, and a biconical-tip spike are studied. The experiments involve high-pressure shock tunnel investigations using a shock tube facility. The differential interferometry technique is applied to visualize the flowfield around the different missile spike geometries. The differential interferogram pictures as well as surface pressure measurements are compared with numerical results. Numerical simulations based on steady-state three-dimensional Navier-Stokes computations are performed to predict the drag, the lift, and the pitching moment for the blunt body and for each spike-tipped missile. The computations allow one to bring out the advantages of each spike geometry in comparison to the blunt body.

Chemical kinetic simulations behind reflected shock waves

Abstract: Chemical kinetic simulations that more accurately consider reaction conditions behind reflected shock waves in a high pressure shock tube have been conducted by accounting for (1) time-dependent temperature and pressure variations in contrast to assuming constant temperature and pressure, (2) the inclusion of reactions during quenching by cooling in contrast to the assumption of zero kinetic contributions, and (3) real gas behaviors in contrast to assuming ideal gas conditions. The primary objective of the current work is to assess the degree of uncertainty associated with assuming constant temperature and pressure and that no reactions occur during the finite time of quenching and prefect gas behavior. The assessment of the subsequent effect of the uncertainty on chemical kinetic modeling is evaluated by conducting extensive comparative studies. In order to achieve this purpose, available CHEMKIN II and CHEMKIN Real Gas codes were utilized and modified to adopt the proposed approaches. From our computational experiments, it is found: (1) For shock tube experiment with less than a 15% endwall pressure increase, the conventional assumptions lead to reasonable accuracy in predicting stable species; (2) during reaction quenching, the consumption of radical species occurs efficiently and is nearly complete once the pressure drops to 50% of its highest value, but concentrations of stable species are insignificantly perturbed by reactions occurring during quenching; and (3) at elevated pressures, the real gas effects, which are a combination of nonideal P–V–T (state variables), thermodynamic, and kinetic behaviors, affect kinetics by speeding the reaction progress up slightly and do not significantly influence the development or validation of a detailed kinetic model from shock tube data that are obtained in a wide temperature range. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 75–97, 2006

Shock tube investigation of hydrodynamic issues related to inertial confinement fusion

Abstract: A shock tube investigation of two hydrodynamic issues related to inertial confinement fusion (ICF) is undertaken. ICF is a promising source of energy for the future. There has been a considerable increase in the interest in ICF with the development of the National Ignition Facility (NIF). However, much remains to be investigated before a useful yield is obtained from a fusion reaction for power generation. The physics involved in carrying out a fusion reaction combines hydrodynamics, plasma physics and radiation effects superimposed on each other, at extremely small scales, making the problem very complex. One such phenomenon occurring in the deuterium-tritium pellet implosion is the Richtmyer-Meshkov instability occuring at each layer of the fuel which results in the mixing of the ablator with the fuel. This causes dilution of the fuel and reduces the yield of the reaction. Another issue is the impulsive loading of ICF reactor cooling tubes due to the shock wave produced as a result of the fusion reaction. These tubes must withstand the impulse of the shock wave. A shock tube provides an ideal environment to study these issues at large geometric scales with the isolation of hydrodynamics from other effects. A new vertical, square shock tube has been designed specifically for the purpose of studying these fluid flow phenomena from a fundamental point of view. The shock tube is vertical, with a large square inner cross-section and is designed to allow for the release of a $M=5$ shock into air at atmospheric pressure. In this paper, we describe the new shock tube and related instrumentation in detail and present a few preliminary results on the Richtmyer-Meshkov instability and shock-cylinder interactions.