Effects of tail shapes/lengths of Hyperloop pod on aerodynamic characteristics and wave phenomenon

Abstract

This study provides a view of the primary aerodynamic design of Hyperloop pod considering the influence of tail shape and length on aerodynamic forces (drag and lift) and flow behaviors (pressure, Mach number, and temperature). Numerical simulations are performed considering two tail shapes (i.e., upward and downward tails) and five lengths of the downward tail (i.e., 1.725, 3.45, 6.9, 13.35, and 13.8 m). The dynamic overset mesh method utilizing polyhedral meshes is applied to simulate the movement of the pod. A simplified three-dimensional model is simulated using the unsteady Reynolds-averaged Navier–Stokes shear stress transport k–ω turbulence model, compressible ideal gas, and a pod speed of 300 m/s. The results indicate that the two tail shapes only have a minor effect on aerodynamic drag (i.e., the difference between the upward and downward tails is only 0.75%), generating two tendencies of aerodynamic lift (i.e., the upward tail provides negative lift, and the downward tail yields positive lift). When tail length of the pod increases, it effectively reduces the aerodynamic drag (approximately 7%) and pressure on the pod surface. Meanwhile, the variation of lift observes an intriguing tendency (which the lift is maximum at 6.9 m – tail length). When the tail length is increased over 6.9 m, the lift starts to reduce; however, the lift is increased when the tail is shorter than 6.9 m. The flow fields around and behind the pod tail are significantly affected by the change in tail length, particularly when considering the intensity and generation of the first OS. The highest intensity of the first OS is attained when the tail length is 6.9 m. The increase in tail length considerably reduces the pressure on the pod but slightly affects the pod temperature (exhibiting a maximum difference of 0.4% among the five cases).