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

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.