Investigation of shock waves reflected at the end of a Hyperloop tube

In this study, a Hyperloop pod travelling beyond the Kantrowitz limit in a tunnel of finite length was studied using analytical methods and computational fluid dynamics simulations. Impact on a pod of a shock reflected off the tunnel end wall was observed, resulting in an instantaneous 35% increase in drag across a range of blockage ratios. After impact, further reflections of shocks resulted in continuous drag increase to a peak of 230%. The temperature at the tunnel wall was estimated to rise 26.5 K due to the increase in absolute pressure upstream of the pod. Multiple tunnel-end geometries were proposed to dissipate or delay an incident normal shock and to reduce the transient forces on the pod upon reflected shock impact. We found that a short expanded section at the tunnel end reduced the shock pressure rise by 44%, with small improvements demonstrated by a radial baffle-inspired geometry.