Theoretical and numerical analysis of pressure waves and aerodynamic characteristics in Hyperloop system under cracked-tube conditions

Abstract

The Hyperloop system is a new transportation mode in which a maglev capsule travels in a confined sub-vacuum tube at transonic speed. If the sub-vacuum tube is cracked, supersonic flow is induced by the pressure difference with the atmosphere. This flow affects the traveling pod, and the Hyperloop system becomes unstable. In this study, we focused on pressure waves generated by a crack and a pod, and investigated the aerodynamic characteristics. The pressure magnitude and propagation speed of the normal shock wave and the drag were considered in a theoretical approach. In addition, numerical simulations for various crack widths and pod speeds were performed. A highly underexpanded jet develops owing to the crack, which results in a distinct Mach disk. As the crack width increases, a larger oblique shock cell structure is created. The leading shock wave generated in front of the Mach disk propagates as a normal shock wave. The propagation speed and pressure of the normal shock wave increase with increasing crack width. Moreover, the normal shock wave propagates in front of the nose, and the expansion wave propagates behind the tail owing to the pod movement. The drag increases rapidly as the normal shock wave caused by the crack reaches the pod. As the pod moves under the crack, the drag decreases and the negative lift steeply increases owing to the downward flow. The pressure of the normal shock wave and the aerodynamic drag were predicted with the theoretical approach; the predictions agree well with the simulation results.