Computational fluid dynamics simulation of Hyperloop pod predicting laminar–turbulent transition

Abstract

Three-dimensional compressible flow simulations were conducted to develop a Hyperloop pod. The novelty is the usage of Gamma transition model, in which the transition from laminar to turbulent flow can be predicted. First, a mesh dependency study was undertaken, showing second-order convergence with respect to the mesh refinement. Second, an aerodynamic analysis for two designs, short and optimized, was conducted with the traveling speed 125 m/s at the system pressure 0.15 bar. The concept of the short model was to delay the transition to decrease the frictional drag; meanwhile that of the optimized design was to minimize the pressure drag by decreasing the frontal area and introduce the transition more toward the front of the pod. The computed results show that the transition of the short model occurred more on the rear side due to the pod shape, which resulted in 8% smaller frictional drag coefficient than that for the optimized model. The pressure drag for the optimized design was 24% smaller than that for the short design, half of which is due to the decrease in the frontal area, and the other half is due to the smoothed rear-end shape. The total drag for the optimized model was 14% smaller than that for the short model. Finally, the influence of the system pressure was investigated. As the system pressure and the Reynolds number increase, the frictional drag coefficient increases, and the transition point moves toward the front, which are the typical phenomena observed in the transition regime.

The Hyperloop System and Stakeholders: A Review and Future Directions

“…The frontal surface and shape of the pod may affect the aerodynamic drag and the tube's operational energy consumption [5,14,28,31,36,39,51]. The Kantrowitz limit, the blockage ratio, the drag coefficient, and the pod's length are certain factors for optimizing the aerodynamic performance and pod speeds [5,18,22,24,26,27,34,41,43,51,60].…”

“…The tube provides a low-pressure travel-guideway environment and protects the pod from all external conditions [20]. It is airtight to maintain the low-pressure environment [10,11,16,19,20,85,95,106,111], strong enough to prevent failures [11,16,17,19,20,25,61,80,89,102] and designed according to the geometry of the pod and the aerodynamic requirements [16,[18][19][20]23,27,31,34,42,44,59,61,71]. Tube geometry depends on the operational pressure level of the system [18,20,31,34,42,60,61,109].…”

Numerical Investigation of Aerodynamic Characteristics of Hyperloop System Using Optimized Capsule Design

“…In addition to a flow regime, low Reynolds number compressible aerodynamics are numerically predicted by Desert et al [15]. Capsule size consideration got important when Nick and Sato [16] used the Gamma transition model to determine aerodynamics and Fomin and Nalivaychenko [17] tried to estimate the range of possible values of drag force, possible values of lift force, and aerodynamic heating. Wave creation in high-speed transport is a common phenomenon [18]- [20]; following this, Le et al [21] investigated the aerodynamic drag and pressure waves in different Hyperloop systems.…”

High-Speed Vehicles in Low-Pressure Tunnels—Influence of Choked Flows

“…The same cannot safely be said for vehicles travelling at high speeds in tunnels that have been evacuated to very low pressures, notwithstanding the existence of studies providing valuable guidance (e.g., Kauzinyte et al 2019 [2]). No operational systems of this type currently exist, although extensive effort continues to be devoted to assessing many aspects of them-e.g., Bizzozero, et al (2021) [3], Museros, et al (2021) [4], Nick and Sato (2020) [5], Tudor and Paolone (2021) [6]. Also, whereas various authors have addressed the aerodynamic behaviour in detail, most focus on flows local to the vehicle itself, usually with the primary purpose of reducing "form" drag-e.g., Braun et al (2017) [7], Chen et al (2012) [8], Opgenoord and Caplan (2018) [9] and Zhang (2012) [10].…”