Influence of vehicle length on the aerothermodynamic environment of the Hyperloop

Abstract

Hyperloop has received much attention as a futuristic mode of transportation because of its energy efficiency and high speed, among other advantages. The length of the capsule vehicle has essentially little influence on the distribution of the aerodynamic environment, but makes significant differences in the evolution of waves and in the fluctuations of pressure and temperature in the aerodynamic environment. This study employs fluid simulation to learn the aerothermodynamic effects of a capsule vehicle traveling in an evacuated tube of Hyperloop. Based on a validation of CFD simulations via wind-tunnel test measurements, a meshing strategy was designed to ensure that errors in the computational results were minimized. An axisymmetric model of the capsule vehicle was used to reduce computational costs. The results show that different capsule vehicle lengths affect the formation of pressure and temperature flow fields, boundary-layer thickness of the capsule-vehicle surface, and interference of shock waves and expansion waves in Hyperloop. As the vehicle length increased, the pressures at the vehicle head and tail gradually decreased, whereas the middle of the vehicle did not undergo this decrease in pressure. Inside the tube, the high temperature and pressure upstream of the vehicle head decreased slightly as the vehicle length increased. The temperature and pressure around the vehicle tended to increase, whereas at the tail of the vehicle, the pressure tended to decrease, and the temperature to increase. For short, medium and long vehicles, the shock waves were 1.06, 1.120, and 1.243 m, respectively, from the top of the tail, from which it is inferred that the flow separation point moved forward as the length of the vehicle increased. The wake widened as the length of the capsule vehicle increased. The boundary layer at the vehicle tail gradually thickened along the contour. Before separation, the maximum difference in boundary-layer thickness was able to reach 50.3 %, after separation, the difference decreased to a minimum of 8.8 %. The interaction (IE1) and reflection (RE2) of the expansion wave led to pressure decreases of 5.86 % and 4.07 %, respectively, whereas the interaction of shock wave (IS1) and reflection of shock wave (RS1) led to pressure decreases of 4.15 % and 3.67 %, respectively. The interaction had a greater effect on the Hyperloop flow field than that of the reflection.