Overview of diagnostic methods used in shock-tube investigations of mixing induced by Richtmyer–Meshkov instability

We present an overview of the diagnostic methods used in shock-tube investigations of mixing induced by Richtmyer–Meshkov instability. The different diagnostic techniques are first briefly presented, and then reviewed in a simple single table, which lists their advantages and disadvantages, their technological characteristics and domain of validity, the physical parameters measured, the laboratory in which they were developed and an assessment of their mean cost. Received 19 November 1997 / Accepted 3 March 1998     

Characterization of adsorbed species on soot formed behind reflected shock waves

The present work addresses the soot formation parameters behind reflected shock waves and the identification of adsorbed species on their surface. Soot induction delay times and yields have been experimentally determined in the case of toluene pyrolysis highly diluted in argon for the following conditions: the initial carbon atoms concentration was kept constant around 1 × 10¹⁸ C atoms cm⁻³, reflected shock pressure and temperature ranges of 1135-1600 kPa and 1470-2230 K, respectively. The decrease of the induction time, as the temperature is raised, was described using an Arrhenius type expression while, for the bell-shaped evolution of the soot yield versus the temperature, a modified Gaussian expression was derived. Using TEM analysis, the mean particle diameter was found to decrease from 35 to 20 nm as the temperature is raised from 1475 to 2135 K. The micro-texture of the soot sample was found to vary as the temperature is raised, leading to a more organised structure. The adsorbed species on these soot were characterized using laser desorption/ionization time of flight mass spectrometer. Results indicate that for temperatures below 1600 K, PAHs in the 178-572 atomic mass units (amu) range were identified. PAHs range was limited to 178-374 amu above 1900 K and they were of benzenoid type above 1600 K. The amount of species adsorbed on the soot surface was found to be inversely proportional to the soot yield with a maximum for the lower temperature domain.     

The development of a shock-tube based characterization technique for air-coupled ultrasonic probes

The present paper proposes a new characterization technique for air-coupled ultrasound probes. The technique is based on a shock tube to generate a controlled pressure wave to calibrate transducers within their operating frequency range. The aim is to generate a high frequency pressure wave (at least up to 200 kHz) with the low energy levels typical of commonly used air-coupled ultrasound probes. A dedicated shock-tube has been designed and tested to assess calibration performances. The sensor transfer function has been measured by using a pressure transducer as reference.