Shock tube

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

Turbulent mixing measurements in the Richtmyer-Meshkov instability

Abstract: The Richtmyer-Meshkov instability is experimentally investigated in a vertical shock tube using a new type of broadband initial condition imposed on an interface between a helium-acetone mixture and argon (A = 0.7). The initial condition is created by first setting up a gravitationally stable stagnation plane between the gases and then injecting the same two gases horizontally at the interface to create a shear layer. The perturbations along the shear layer create a statistically repeatable broadband initial condition. The interface is accelerated by a M = 1.6 planar shock wave, and the development of the ensuing turbulent mixing layer is investigated using planar laser induced fluorescence. By the latest experimental time, 2.1 ms after shock acceleration, the layer is shown to be fully turbulent, surpassing both turbulent transition criteria based on the Reynolds number and shear layer scale. Mixing structures are nearly isotropic by the latest time, as seen by the probability density function of gradient angles within the mixing layer. The scalar variance energy spectrum suggests a k−5/3 inertial range by the latest time and an exponential region at higher wavenumbers.

Constrained reaction volume shock tube study of n-heptane oxidation: Ignition delay times and time-histories of multiple species and temperature

Abstract: Ignition delay times of normal heptane have been measured at temperatures ranging from 651 to 823 K and at pressures between 6.1 and 7.4 atm at an equivalence ratio of 0.75 in 15%O 2 /5%CO 2 /Ar and in 15%O 2 /Ar mixtures behind reflected shock waves in a shock tube. Time-history measurements of fuel, OH, aldehydes (mostly CH 2 O), CO 2 , H 2 O, and temperature were also measured under these conditions. These time-histories provide critically needed kinetic targets to test and refine large reaction mechanisms. Measurements were acquired using a novel constrained reaction volume approach, wherein a sliding gate valve confined the reactant mixture to a region near the endwall of the shock tube. A staged-driver gas filling strategy, combined with driver section extensions, driver inserts, and driver gas tailoring, was used to obtain constant-pressure test times of up to 55 ms, allowing observations of the chemistry in the Negative Temperature Coefficient (NTC) region. Experiments with conventional shock tube filling were also performed, showing similar overall ignition behavior. Comparisons between current data and simulations using the Mehl et al. n -Heptane mechanism (2011) are provided, revealing that the mechanism generally under-predicts first-stage ignition delay times in the NTC region, and that at low temperatures it over-predicts the extent of fuel decomposition during first stage ignition.