Effects of branched tube on pressure waves in the hyperloop system: An experimental study

Abstract

In this study, we experimentally investigated the aerodynamic characteristics of the Hyperloop with branch tube, an important applicational situation. Experiments were performed considering two velocities (258.6 and 295.8 m/s) and five branched angles (θ = 30°–150°) using 8.75 cm of scaled pod model (blockage ratio = 0.34). The leading shock waves LSW₁ and LSW₂ generated in front of the pod model were measured, and their intensity was analyzed before, on, and after the branching. The intensity of LSW₁ and LSW₂ at the straight tube before branching was the same as that without branching. LSW₁ and LSW₂ were divided by branching and propagated to the branched tube, where their intensity decreased to branched shock waves BSW₁ and BSW₂, respectively. The degree of decrease in BSW₁ was linear as θ increased, whereas BSW₂ decreased as θ and speed of the pod model increased when θ ≤ 90° and was nearly constant at 0.80 when θ ≥ 120°. The pressure characteristics near the branching were non-axisymmetric and became axisymmetric as it moved forward through the branching when $x/l_t$ ≥ 0.66. When LSW₁ and LSW₂ passed through the branching and were propagated as transmitted shock waves TSW₁ and TSW₂ after branching, their intensity decreased to approximately 86% and 91%, respectively, and was not significantly affected by the pod speed and θ.