Numerical simulation and analysis of aerodynamic drag on a subsonic train in evacuated tube transportation

Zhang, Yaoping

doi:10.1007/bf03325776

Cited by 43 publications

(26 citation statements)

References 4 publications

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“…In designing of a Hyperloop system, aerodynamic limitations such as drag become critical issues. Drag is one of the most important parameters in the analysis of objects moving at very high speed, especially within confined tubes [4,5]. Lower drag in a Hyperloop system not only drastically reduces construction and operation cost, but also minimizes the energy load of propulsion system.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Kang

Ham

et al. 2019

Energies

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The Hyperloop system is a new concept that allows a train to travel through a near-vacuum tunnel at transonic speeds. Aerodynamic drag is one of the most important factors in analyzing such systems. The blockage ratio (BR), pod speed/length, tube pressure, and temperature affect the aerodynamic drag, but the specific relationships between the drag and these parameters have not yet been comprehensively examined. In this study, we investigated the flow phenomena of a Hyperloop system, focusing on the effects of changes in the above parameters. Two-dimensional axisymmetric simulations were performed in a large parameter space covering various BR values (0.25, 0.36), pod lengths (10.75–86 m), pod speeds (50–350 m/s), tube pressures (~100–1000 Pa), and tube temperatures (275–325 K). As BR increased, the pressure drag was significantly affected. This is because of the smaller critical Mach number for a larger BR. As the pod length increased, the total drag and pressure drag did not change significantly, but there was a considerable influence on the friction drag. As the pod speed increased, strong shock waves occurred near the end of the pod. At this point, the flows around the pod were severely choked at both BR values, and the ratio of the pressure drag to the total drag converged to its saturation level. At tube pressures above 500 Pa, the friction drag increased significantly under the rapidly increased turbulence intensity near the pod surface. High tube temperatures increase the speed of sound, and this reduces the Mach number for the same pod speed, consequently delaying the onset of choking and reducing the aerodynamic drag. The results presented in this study are applicable to the fundamental design of the proposed Hyperloop system.

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Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Kang

Ham

et al. 2019

Energies

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“…The aerodynamics of a train/pod in a partially vacuumed tube has been studied by several research groups by using CFD. Zhang presented a CFD simulation for a subsonic train in an evacuated tube [10], in which axisymmetric, incompressible flow computations were performed for a train running at a speed of 50-300 m/s under a system pressure of 10-10,000 Pa. The influence of the blockage ratio (BR) on the drag is evaluated in this study.…”

Section: Introductionmentioning

confidence: 99%

“…However, mainly because of the short length of the Hyperloop pod, the Reynolds number is of the order of 10 6 for the subsonic case, and thus, the transition may play important role with respect to the drag. Nonetheless, the CFD studies mentioned above [10][11][12]14] assumed that the whole computational domain is fully turbulent and the laminar flow and the transition were neglected. Only Opgenoord and Caplan [13] paid attention to the transition.…”

Section: Introductionmentioning

confidence: 99%

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

Nick

Sato

2020

Rail. Eng. Science

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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.

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“…Hence, aerodynamics of the HTS Maglev-ETT system is a new subject needed further research. Many groups have simulated aerodynamics of the vacuum tube train and analyzed the effect of the vehicle speed, blockage ratio, and air pressures [9,10] . Nonetheless, due to the lack of experimental facilities, there is little work on the related experiments.…”

Section: Introductionmentioning

confidence: 99%

Preliminary Study of Aerodynamic Characteristics of High Temperature Superconducting Maglev-Evacuated Tube Transport System

Bao¹,

Wang²,

Zhang³

et al. 2017

dtetr

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In the high temperature superconducting maglev-evacuated tube transport (HTS Maglev-ETT) system, the air drag is the most principal resistance to the speed improvement and energy conservation. Considering the aerodynamic performance of the HTS Maglev-ETT system has great significance in practical application. As the first step, we experimentally explored the influence of velocity, blockage ratio and airshaft on the air drag of a running maglev vehicle at atmospheric pressure (95.6 kPa in Chengdu), coupled with the simulation by using the ANSYS-FLUENT software. The results preliminarily confirmed the feasibility of the aerodynamic experiments on the HTS maglev-ETT test system, as the drag is proportional to the blockage ratio and the square of velocity respectively. Moreover, airshafts are suggested to be added in the future design of the HTS Maglev-ETT system, aimed at its good relief on the air drag displayed in the experiment and simulation.

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Numerical simulation and analysis of aerodynamic drag on a subsonic train in evacuated tube transportation

Cited by 43 publications

References 4 publications

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

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

Preliminary Study of Aerodynamic Characteristics of High Temperature Superconducting Maglev-Evacuated Tube Transport System

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