  Miniature shock tubes are finding growing importance in a variety of
interdisciplinary applications. There is a lack of experimental data to
validate the existing shock tube flow models that explain the shockwave
attenuation in pressure-driven miniature shock tubes. This paper gives insights
into the shock formation and shock propagation phenomena in miniature shock
tubes of 2mm, 6mm, and 10mm square cross-sections operated at diaphragm rupture
pressure ratios in the range 5-25 and driven section initially at ambient
conditions. Pressure measurements and visualization studies are carried out in
a new miniature table-top shock tube system using nitrogen and helium as driver
gases. The experimental findings are validated using a shock tube model
explained in terms of two regions; (1) The shock formation region, dominated by
wave interactions due to the diaphragm's finite rupture time. (2) The shock
propagation region, where the shockwave attenuation occurs mainly due to wall
effects and boundary layer growth. Correlations to predict the variation of
shock Mach number in the shock formation region and shock propagation region
work well for the present findings and experimental data reported in the
literature. Similar flow features are observed in the shock tubes at the same
dimensionless time stamps. The formation of the planar shock front scales
proportionally with the diameter of the shock tube. The peak Mach number
attained by the shockwave is higher as the shock tube diameter increases.
