Blast tube design: How shape and size influence the resultant shock wave

Shock tubes and tunnels are often used in research settings as a way of producing high pressure shock waves in a smaller footprint or without the use of explosives. However, there is no standard geometric design across laboratories. Peak pressure is a significant parameter for characterizing a shock wave. However, different tube configurations could also affect parameters such as impulse and duration, yet no research has investigated how the scale of the tube affects the overall waveform shape. To understand the implications of shock tube design, tubes with a constant length to diameter ratio were evaluated to determine how tube scaling affects the shock parameters. Larger tubes with a greater length and diameter produced more intense, shorter-duration shocks, resulting in higher pressure/duration ratios and up to a 20.9% reduction in impulse. Analysis of the pressure vs time profiles showed that square tubes have a more consistent self-similar relationship in peak pressure. Square tubes also exhibit a more pronounced negative phase than circle tubes of the same length-to-diameter (L/D) ratio. Increasing the diameter of constant length tubes from 0.5 to 1 cm increases the incident pressure by 90.94%, although this also leads to shorter shock wave durations. Conversely, increasing the length of constant diameter tubes results in a 2.4% reduction in incident pressure. These findings show that while peak pressure is important, the duration and impulse of the shock wave are crucial for determining the overall energy applied.