Insights into the shockwave attenuation in miniature shock tubes

TL;DR

This study investigates shockwave formation and attenuation in miniature shock tubes of various sizes, validating models through experiments with nitrogen and helium, revealing how tube size influences shock Mach number and wave behavior.

Contribution

Provides experimental validation and insights into shockwave dynamics in miniature shock tubes, enhancing understanding of size-dependent shock attenuation mechanisms.

Findings

Shock formation region influenced by wave interactions and diaphragm rupture.

Shock attenuation mainly due to wall effects and boundary layers.

Shock Mach number increases with tube diameter.

Abstract

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.