Shock tube study of particles' motion behind a planar shock wave

In order to shed light on the initial mechanism of dust entrainment behind a moving shock wave, the particles' motion behind a planar shock wave was investigated using horizontally placed shock tubes and a direct photographic technique synchronized with the shock wave motion. The drag coefficient measurement of an accelerating spherical particle (0.3-5.57 mm in diameter) was performed. The obtained drag coefficients were found to be higher than those from the standard drag curve. On average, the difference was about 20% for a relative Reynolds number from 10³ and 10⁵. The initial motion of a particle just lifted-up from the wall was also examined using the other shock tube. The results indicated that the velocity and speed of rotation of particles were strongly affected by the floor conditions. It was also found that the particle's initial rotation does not play a major role in the particle rise.