Modeling of aerodynamic phenomena and drag for vehicles moving through a low-pressure tube in Hyperloop systems.

This article focuses on the aerodynamic analysis of vehicles moving inside a closed low-pressure tube system, such as the Hyperloop, emphasizing shock wave generation and drag characteristics. Using axisymmetric and three-dimensional computational fluid dynamics (CFD) simulations alongside an analytical choking nozzle analogy model, the study investigates how vehicle speed, blockage ratio (the ratio of vehicle cross-sectional area to tube cross-sectional area), and vehicle geometry affect shock wave properties and drag. Results show that beyond certain speeds and blockage ratios, supersonic expansion occurs near the vehicle tail, producing oblique shocks that increase drag, while the nozzle analogy effectively predicts shock behavior at higher speeds and blockage ratios. The three-dimensional simulations reveal additional vortical flow structures in the vehicle tail region and indicate a slight increase in drag compared to axisymmetric models, highlighting the importance of vehicle shape and flow control for drag optimization in Hyperloop systems.