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The Hyperloop system is promising a viable solution for fast, sustainable, and economic travel between cities. This paper investigates the challenging topic of Hyperloop aerodynamics via extensive numerical simulations. The study is divided based on the speed relative to the geometric Kantrowitz limit to manage the computational resources effectively. Below this limit, which marks the transition to choked flow, we conducted a cross-validation among an axisymmetric 2D model, a similar 3D geometry, and a realistic 3D geometry for blockage ratio 0.5 at several speeds. A definitive range for drag was determined, notably low absolute drag values were observed, and the 2D axisymmetric simplification was put into perspective. Above the choked flow condition, we undertook two resource-intensive simulations of the 2D setup, accelerating through several kilometers of tube. This methodology allowed us to shed light on the drag behavior that emerges under transient conditions. The existence of three regimes outlined by literature is corroborated by our study. Nevertheless, distinct variations emerge between the analyses, notably in the configuration of the shock wave structure, the linear increment of drag at a constant velocity, and the influence of the pod's acceleration profile in the flow structure. The study broadens the understanding of Hyperloop aerodynamics and offers realistic drag data for both choked and non-choked flow. • Drag was found to increase linearly at constant speed above choked flow. • A transient simulation setup is presented to analyze and visualize phenomena above choked flow. • The 2D axisymmetric simplification is put into perspective by comparison with a simulation using realistic 3D geometry. • The behavior of the first three aerodynamic regimes was confirmed and further described. [ABSTRACT FROM AUTHOR]

In this study, we experimentally investigated the aerodynamic characteristics of the Hyperloop with branch tube, an important applicational situation. Experiments were performed considering two velocities (258.6 and 295.8 m/s) and five branched angles (θ = 30°–150°) using 8.75 cm of scaled pod model (blockage ratio = 0.34). The leading shock waves LSW 1 and LSW 2 generated in front of the pod model were measured, and their intensity was analyzed before, on, and after the branching. The intensity of LSW 1 and LSW 2 at the straight tube before branching was the same as that without branching. LSW 1 and LSW 2 were divided by branching and propagated to the branched tube, where their intensity decreased to branched shock waves BSW 1 and BSW 2 , respectively. The degree of decrease in BSW 1 was linear as θ increased, whereas BSW 2 decreased as θ and speed of the pod model increased when θ ≤ 90° and was nearly constant at 0.80 when θ ≥ 120°. The pressure characteristics near the branching were non-axisymmetric and became axisymmetric as it moved forward through the branching when x / l t ≥ 0.66. When LSW 1 and LSW 2 passed through the branching and were propagated as transmitted shock waves TSW 1 and TSW 2 after branching, their intensity decreased to approximately 86% and 91%, respectively, and was not significantly affected by the pod speed and θ. [ABSTRACT FROM AUTHOR]

Considering making an efficient and sustainable ecosystem, the futuristic Hyperloop with Pod is considered a significant contributor in the coming years. However, the development and construction of the Hyperloop project is not easy. The research aims to analyze and evaluate the major factors involved in the success or failure of the Hyperloop project using the Interpretive Structural Modeling (ISM) approach and using (Matrice d'Impacts Croisés Multiplication Appliquée á un Classement (cross-impact matrix multiplication applied to classification) MICMAC analysis. This method helped determine the inter-relationship among the factors and identify the key factors affecting the Hyperloop project. The work also explores the subfactors related to each major factor, which helps refine the major factors and understand their complex relationships. The research also includes data from a survey that was conducted to gather public opinion on the Hyperloop project. The survey questions were designed to collect information about factors such as user accessibility, experience, time, cost, convenience, and environmental impact. The collected data was analyzed to conclude public perception and acceptance, which is an important factor in determining the feasibility and viability of the Hyperloop project. The approach provided a holistic view of the project and helped identify potential issues that could arise during the Hyperloop project implementation phase. Geography of the proposed Mumbai-Pune Hyperloop route. [Display omitted] • Feasibility study of energy efficient Hyperloop system is conducted. • Interpretive Structural Modeling (ISM) approach is used for factor analyses. • Survey was conducted to gather public opinion on the hyperloop system. • Highlighted the challenges and opportunities associated with Hyperloop. [ABSTRACT FROM AUTHOR]

This study proposes a novel test method of the air permeability measurement under extreme vacuum condition to examine the performance of materials for Hyperloop tubes. Tests on cement-based materials demonstrated that the developed test setup was effective in measuring air permeability in extreme vacuum conditions. The results show that ultra-high performance concrete (UHPC) has significantly lower air permeability (10–18 m2) in vacuum conditions than other cement-based materials (10–16 m2) due to its dense microstructure and reduced pore size, which were within the range of previous results (10-18-10-16 m2). The measured porosity results had a strong correlation with air permeability (R2 > 0.97), validating the suitability of the proposed method for measuring the air permeability of cement-based materials in vacuum conditions. These findings provide fundamental material properties for the design of Hyperloop tube structures. [ABSTRACT FROM AUTHOR]

Abstract The Hyperloop is a proposed new mode of transport in which passengers or freight would travel in pods through a vacuum tube at very high speeds, enough to cover a hypothetical route between San Francisco and Los Angeles’ metropolitan areas in just 35 minutes. Whereas the “time-space compression” brought by this new technology can have significant impacts in residents’ travel behaviour and household mobility, similar to those documented for high-speed rail, this paper investigates how the proposed California Hyperloop could expand airline passengers’ choice of airports for long-distance domestic trips. Using an established method to determine airport catchment areas based on flight frequencies, access times, and travel costs, we provide an exploratory analysis of how airport competition could change if a Hyperloop service was introduced. Our results clearly show that the California airport network will move towards a single airport system, with significant short-term leakage effects between major airports. These effects should be taken into consideration in the economic assessment of potential Hyperloop routes connecting major cities. Highlights • We explore the short-term impact of a Hyperloop service on airport competition. • We analysed airport catchment areas based on flight frequencies and travel costs. • A Hyperloop would move the Californian network towards a single airport system. • Significant short-term net passenger leakage from North to South California. • LAX, BUR, and OAK airports benefit, while SFO would lose the most passengers. [ABSTRACT FROM AUTHOR]

The Hyperloop is high-speed ground-based transportation system concept; a supersonic train line stretching across the country in airless tubes, which stands as competition for air, train, and car transportation for distances of travel from 200 to 1100 km. This paper concentrates on software - applied in the Hyperloop pod called Goose 3 [1], which was developed by the team from University of Waterloo [2] - Waterloop [3]. This paper is concentrated on roadblocks, that were faced during the design and development process; to be more specific - building a reliable and scalable infrastructure that allows for complete control of the pod throughout the launch. In the pod, electronics and software play a crucial role, as traveling at high velocities requires immediate response to real-time vehicle conditions obtained from sensors on-board, which raises it’s own unique challenges. This paper looks at the work completed by team Waterloop in areas of design of the electrical and software system. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of vehicle length is considered in the simulation. • The effect of vehicle length on shock wave-boundary-layer interactions is compared. • The temperature/pressure distribution in Hyperloop is discussed. 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 (IE 1) and reflection (RE 2) of the expansion wave led to pressure decreases of 5.86 % and 4.07 %, respectively, whereas the interaction of shock wave (IS 1) and reflection of shock wave (RS 1) 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. [ABSTRACT FROM AUTHOR]

In this study, a Hyperloop pod travelling beyond the Kantrowitz limit in a tunnel of finite length was studied using analytical methods and computational fluid dynamics simulations. Impact on a pod of a shock reflected off the tunnel end wall was observed, resulting in an instantaneous 35% increase in drag across a range of blockage ratios. After impact, further reflections of shocks resulted in continuous drag increase to a peak of 230%. The temperature at the tunnel wall was estimated to rise 26.5 K due to the increase in absolute pressure upstream of the pod. Multiple tunnel-end geometries were proposed to dissipate or delay an incident normal shock and to reduce the transient forces on the pod upon reflected shock impact. We found that a short expanded section at the tunnel end reduced the shock pressure rise by 44%, with small improvements demonstrated by a radial baffle-inspired geometry. [ABSTRACT FROM AUTHOR]

A next-generation mass transportation system, consisting of TransPod aerospace vehicles designed to carry passengers at speeds exceeding 1000 km/h, is presented with respect to dynamics considerations. This system is based on electromagnetic propulsion of vehicles within a protected tube guideway, whose air pressure is reduced and controlled for improved performance at high speed. The tube environment is designed for levitation systems, stability systems, and safety support systems, to permit multiple TransPod vehicles to run simultaneously with high-frequency departures. The design of this vehicle and tube structure is aided by analysis of structural dynamics and aerodynamics, presented in this paper with selected novel topics in physical-fourier-amplitude-domain analysis, and machine-learning-based vibration sensing and control. [ABSTRACT FROM AUTHOR]

Hyperloop aerodynamic characteristics (e.g., the pressure wave in front of the pod) are analyzed experimentally and theoretically in this study. A scaled Hyperloop aerodynamic experimental equipment that has a scale of d pod = 8.75 cm, BR = 0.34 and l t = 16 m is developed; it can be used to run experiments in the range from 160–320 m/s of v pod at approximately 1/1,000 atm (p ref = 150 Pa). Further, this experiment has an observed v a , which is not revealed in the analysis of the ideal case. The v a is generated during the pod acceleration process and has a significant effect on v LSW. Three pressure waves (LSW 1 , FEW, and LSW 2) are measured in front of the pod. v LSW 1 , v FEW , and v LSW 2 are similar at v pod <250 m/s, and LSW 1 , FEW, and LSW 2 are located in this order. However, at v pod >250 m/s, the positions of LSW 1 , FEW, and LSW 2 become increasingly close, and LSW 2 eventually catches up to LSW 1 and FEW as v LSW 2 > v LSW 1 > v FEW. v LSW 2 and I LSW 2 are predicted theoretically assuming v a = v pod. The maximum differences in the v LSW 2 and I LSW 2 between the experimental result and theoretical prediction are 5.66% and 7.31%, respectively. I LSW 1 generated by entering the test section decreases because it moves away from the entrance; it decreases more rapidly for a high v pod. I LSW 2 generated by driving the pod in the tube shows a larger value than the theoretically predicted value in the entrance region (x / l t <0.4). At x / l t >0.4, I LSW 2 is close to the theoretically predicted value with a maximum difference of 10.5%. The suggested theoretical model with assumption v a = v pod is in good agreement with the experiment result. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

This study investigated the variations in aerodynamic drag and the pressure wave effects caused by more than two pods operating in a Hyperloop tube. Three speeds, i.e., 100, 200, and 300 m/s, and two distances between two separate pods, i.e., 43 and 86 m, were simulated using SST k-ω turbulence model. The results indicate that drag of single- and multi-pod systems have similar tendencies that increase with increasing pod speed. For pod speed exceeding the critical Mach number, irrespective of the connectedness or separation of the pods, the last pod always experiences the highest drag. Otherwise, at lower speeds, the differences between the drag acting on each of the pods is negligible. The distance between two pods has a minor influence of less than 4% on the drag. The effects of two different pod shapes, i.e. rectangular and semicircular, on the drag of three connected pods are also small. The average drag per pod was calculated, and it was observed that when more pods were operated, the average drag reduced significantly. The operation of the connected-pod system creates a slightly lower drag than that of a separate-pod system. • Multipod operations were simulated for three different pod speeds. • The last pod experiences the highest drag for both connected and separated pods. • The distance between two separated pods has less than 4% influence on drag. • The average drag per pod decreases with increasing number of pods. • The connected pod system has lower average drag than the separated pod system. [ABSTRACT FROM AUTHOR]

With rapid changes in lifestyle patterns and recent technological advancements, there is an increasing demand for efficient, convenient, and eco-friendly transportation systems. The Hyperloop system, which is a tube–train system, was introduced with the aim of catering to the demand for improved transportation facilities. The primary factors of the Hyperloop system such as the point of departure (pod), standstill, and transfer are directly dependent on the change in the cross-sectional area of the tube such as stations. In this study, the effects of sudden expansion and contraction were analyzed though numerical simulations with respect to the blockage ratio (BR), expansion ratio (ER), and contraction ratios (CR). Furthermore, the propagation Mach number and magnitude of pressure waves were predicted through theoretical consideration. Under sudden expansion and contraction of tube, the first leading shock wave (LSW 1), reflected expansion wave (REW), second leading shock wave (LSW 2), reflected shock wave (RSW), and third leading shock wave (LSW 3) are generated in this system. The propagation Mach number and pressure magnitude of LSW 1 increase with an increase in the BR. The Mach number of REW decreases with an increase in the BR. The propagation Mach number of LSW 2 increases with the BR and with a decrease in the ER owing to the pressure behind the shock wave. The propagation Mach number of RSW decreases with an increase in the BR and with a decrease in the CR, and that of LSW 3 increases with an increase in the BR and with a decrease in the CR. The drag coefficient decreases when REW reaches the pod because the expansion wave decreases the pressure of flow field. Owing to the similar minimum drag coefficient, the difference of drag coefficient increases with an increase in the BR. In this study, the predicted Mach number and pressure magnitude under quasi-one-dimensional assumption are in good agreement with the simulation results. Therefore, this study can aid the design of expanded and contracted zones considering the formation of the shock wave. [ABSTRACT FROM AUTHOR]

In the current study, the 3D shape optimization of a hyperloop pod's head and tail is carried out to improve the pod's aerodynamic performance. For shape exploration, a new shape design method called multi-resolution morphing is applied with three baseline hyperloop models, where each has its own aerodynamic characteristics. As a result, an optimal hyperloop pod with a drag value that is 7.5% smaller with respect to the baseline model and optimal pods with well-balanced drag and lift values are obtained. From further investigations, several meaningful results are also discovered. First, the shape of the tail has a greater impact on the drag and lift of the hyperloop pod than the shape of the head, and this difference is more remarkable in the drag than the lift. Second, changing the shape of the head does not elicit a large effect on the aerodynamic performance of the tail and vice versa. Accordingly, the optimization of a hyperloop pod's head and tail can be implemented independently. A high correlation between the strength of the turbulent kinetic energy around the tail and drag is also found from a flow comparison between the optimal models. Finally, the local flow characteristics are similar for the models that are constructed with the same coefficients of the high-degree spherical harmonics. This indicates that it is possible to transfer the local flow characteristics of one model to the other via the multi-resolution morphing method. [Display omitted] • The shape optimization of a hyperloop pod is carried out to improve its aerodynamic performance. • A new design method called multi-resolution is applied for the various hyperloop pod's shape exploration. • Influences of the shapes of the hyperloop pod's head and tail are investigated. • The flow characteristics around baseline and optimal hyperloop models are analyzed. [ABSTRACT FROM AUTHOR]

During recent years several innovative technology systems have been conceived with the purpose to produce ever faster and more efficient transportation systems (TS) such as the Transrapid, Hyperloop and HeliRail that could provide numerous potential benefits over the traditional railways including the High-Speed Railway (HSR) system. These TS are examined from a technical point of view and are compared to each other by cost-benefits analysis. Benefits (B) and Costs (C) taken into consideration both in Financial and Economic analysis are those of each unconventional transportation system (i.e. Transrapid, Hyperloop and HeliRail) with respect to the HSR system. A case study has been considered (line length: 500 km, traffic demand: 15 million passengers for direction). The results demonstrate that from a financial point of view all the innovative TS are worse in comparison with the HSR system. The economic indicators show that the most advantageous system is the HSR because the other ones give rise to values of the Economic Net Present Value (ENPV) < 0. Alternative types of TS in comparison with HSR system are unsustainable since, for each of these, it results ENPV <0 and benefit-cost ratio B/C < 1. Sensitivity analyses of Financial and Economic indicators in function of the traffic demand levels (range 1–21 million passengers/year) and line lengths (range 100–800 km) have been carried out to identify the most appropriate transportation system for given boundary conditions. The outcomes prove that the best mass public transport system is still today the HSR, except in special cases. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Hyperloop is a proposed transportation system in which a high-speed vehicle travels in a near-vacuum tube. High-speed motion of an object (near Mach 1) in a confined space generates choked flow, endangering operational safety. This study investigates the physics and behaviour of choked flow in the Hyperloop system, and the corresponding law and influencing factors are theoretically analysed. A CFD method is used to simulate the compressible flow in the system. The different flow states caused by a pod travelling in the Hyperloop tube are numerically obtained, and the results concurred with the theoretical prediction. The results show that the choking strength gradually increases as the vehicle accelerates, reaching its maximum at Mach 1 and then gradually decreasing. When the blockage ratio reaches 0.4, nearly one-third of air hardly passes through the throat at most owing to the choking. The inflow velocity, choked flow density, and total pressure loss caused by the shock wave jointly affect the mass-flow limitation. In addition, the normal shock wave is the main characteristic of choked flow. The flow transitions from choked to unchoked regimes owing to the supersonic pod and forms a bow shock wave. These findings, including the equations describing the choking mechanism, can benefit various design aspects of the Hyperloop system. [ABSTRACT FROM AUTHOR]

The Hyperloop has been proposed as a high-speed vactrain system for freight and passenger transport. Given that the Hyperloop aims to operate at subsonic to supersonic speeds, the aerodynamic environment within the tube needs to be carefully considered. The shape of a pod is also very important with regard to reduction of aerodynamic drag and lift. Therefore, this study investigates the influence of the nose and tail shape of a Hyperloop pod on its aerodynamic drag, lift, and pitching moment by comparing five pod shapes: symmetrical, downward nose–upward tail (N d T u), upward nose–upward tail (N u T u), downward nose–downward tail (N d T d), and upward nose–downward tail (N u T d). Six pod speeds from 100 to 350 m/s at 50-m/s intervals are simulated under steady-state conditions and the shear-stress transport k- ω model. The shape of the nose and tail has only a slight effect on aerodynamic drag, with minor differences in drag acting on N d T u , N u T u , N d T d , and N u T d. The symmetrical design producing a drag that is 10.7% lower than that of the other designs at a pod speed of 350 m/s. In contrast, aerodynamic lift strongly varies with a change in the shape of the nose and tail, especially for pod speeds of 250 to 350 m/s. A downward tail produces positive lift, while an upward tail experiences negative lift. The lift acting on the tail of the pod accounted for more than 90% of the total lift. Additionally, the upward noses of the pod also produce negative lift. Based on these results, pod designs with an upward nose and tail should be avoided. The results of this study thus provide useful guidelines for the design of pods for the Hyperloop. [ABSTRACT FROM AUTHOR]

The Hyperloop is a form of ultra-high-speed transportation system subject to complex fluid dynamic regimes, such as choked flow. This study investigates the aerothermodynamic behavior of the Hyperloop in a choked flow structure using computational fluid dynamics (CFD). A vehicular movement model of the Hyperloop was constructed to simulate the relative motion of the pod and tube. The CFD algorithm has been previously verified via experiment data and numerical simulation. The flow structure around the Hyperloop pod and the causes of the significant temperature and pressure differences were studied. A series of complex phenomena occur in the choked region, including choked flow, shock waves, and expansion waves. The blockage ratio and pod velocity increase, widening the temperature and pressure differences across the Hyperloop tube and increasing the total temperature and pressure in the tube. The initial pressure of the tube promotes the formation of the aerodynamic environment, but has no significant effect on the temperature. Aerodynamic drag is a key performance characteristic of the Hyperloop, and the influence of three aerodynamic parameters (blockage ratio, Hyperloop pod velocity and initial tube pressure) is positively correlated with drag. With the decrease in initial tube pressure, the decrease in aerodynamic drag decelerates. Engineers could control aerodynamic drag using a low initial tube pressure and minimizing the blockage ratio, which helps improve the Hyperloop's velocity and performance. • Characteristics analysis of flow structure around Hyperloop pod in a choked flow. • Investigate reasons for significant temperature and pressure differences around the Hyperloop pod. • Analysis of variable Hyperloop pod velocity, initial tube pressures, and blockage ratios on aerodynamic environment of Hyperloop. • Simulation of aerodynamic drag and aerodynamic drag coefficient under variable aerodynamic parameters. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of the aerodynamic performance of a Hyperloop pod equipped with an axial compressor using CFD simulation. The compressor is expected to reduce the drag if the operational speed of the pod exceeds the Kantrowitz Limit (KL). To evaluate the effectiveness of the compressor, two types of pod have been designed: those with and those without a compressor. A validation study was undertaken for supersonic flow around a cylindrical body in a wind tunnel. Several combinations of pod Mach number and blockage ratios were examined. The axial compressor was modeled with the fan interface model and our original method, which we call the source terms model. Results are similar, but our model has the advantage that it can be applied to higher pressure ratios without inducing numerical instabilities. The power consumption was reduced owing to the compressor by decreasing the pressure accumulated in front of the pod. The effectiveness of the compressor was shown to be greater for conditions well above the KL, with a maximum power reduction of 47.5%. Simulations performed half-scale, and at a different system pressure, showed that the effectiveness of the compressor was not greatly influenced by these parameters. [Display omitted] • Pods with and without an axial compressor are compared by CFD. • The compressor is modeled by the source term in NS equations. • The pressure upstream of the pod is reduced by the axial compressor. • Maximum power reduction is estimated to be 48%. [ABSTRACT FROM AUTHOR]

In this study, numerical simulations were conducted at various pod speeds (v p o d = 100–350 m/s) using an unsteady, compressible solver with the Reynolds-averaged Navier–Stokes model to analyze the aerodynamic characteristics and pressure wave behavior in the Hyperloop system. Furthermore, the aerodynamic drag and pressure wave behavior were theoretically predicted based on quasi-one-dimensional assumptions. The flow around the pod is classified into three regimes according to the pod speed based on the compressible flow phenomena. In regime 1 (v p o d = 100–170 m/s), the compression waves develop into normal shock waves even without the occurrence of choking at the throat. In regime 2 (v p o d = 180–230 m/s), choking occurs at the throat and an oblique shock wave appears within the pod tail section. In regime 3 (v p o d = 240–350 m/s), a trailing shock wave propagates at the end of the oblique shock wave. Due to fully accelerated flow in this regime, the Mach number of the flow behind the pod in a pod-fixed coordinates remains constant as 2.1, regardless of the pod speed. This constant Mach number causes the drag coefficient to decrease while the pod speed increases. Although non-isentropic conditions such as the formation of a boundary layer and flow separation cause variation between the theoretical prediction and simulation results, the predicted properties of the pressure waves and the aerodynamic drag of the pod concur with the simulation results. Because the boundary layer along the pod is thinner at a higher pod speed, the difference between the theoretical and simulation values of the leading shock pressure decreases from 9.71% to 2.83% and that of the leading shock speed decreases from 4.39% to 1.30% as the pod speed increases from 180 to 350 m/s. Additionally, the theoretically predicted drag of the pod shows good agreement with the simulation results with an error of around 6%. [ABSTRACT FROM AUTHOR]

• Hyperloop is a novel transport mode still in early stages of development. • Safety is essential to any transport mode and must be addressed at all levels. • This study aims to set up a preliminary framework for safety in the Hyperloop. • Safety features in existing modes are used as inspiration. • Based on these, an initial approach for safety in the Hyperloop is proposed. The Hyperloop is a new mode of transport consisting on a pod travelling along a low-pressure tube that relies on greatly reduced friction to significantly decrease energy consumption and associated emissions. This mode is still in early stages of development. On the other hand, safety is a serious concern in any kind of transport system and must be addressed from the very beginning in order to avoid redesigns and delays in development, as well as increasing costs. Within this framework, this article aims to set up the premises to implement safety into the Hyperloop development process, from the beginning and as a foundational criterion. We use a refined SWIFT method to identify the main hazards in the Hyperloop operations. We also propose a first list of measures to eliminate, reduce and control hazards, as well as measures to reduce damage in case of hazardous incidents. These measures are based on existing knowledge related to safety in other more developed and operating modes of transport, specifically commercial aviation and railways, as well as in a more innovative one: unmanned vessels. The paper takes the main lessons found in these three transport modes and articulates a first approach to risk analysis and safety management for the Hyperloop. [ABSTRACT FROM AUTHOR]

• Comprehensive study of key structural aspects of long Hyperloop vacuum tube viaducts. • Elastically restrained (R-Configuration) and free expanding (F-Configuration) tubes were analysed. • Tube thickness values for a range of spans result from stability and stress checking. • Vehicle impact is not a determinant action though resonance speeds have been detected. • Fatigue is not a key concern for 100–200 kN vehicles Hyperloop is an avant-garde idea for high-speed transportation of passengers and freight in a pod or capsule-like vehicle travelling through an hermetically sealed tube with reduced internal pressure. Its maximum envisaged speed is around 1200 km/h, which would be directly comparable to airplane travel and much faster than road and railway transportation. Because the unconventional, ad hoc civil infrastructure required for Hyperloop is still under a conceptual design phase, one of the most important steps to undertake at this stage is to develop analytical models and tools to simulate the mechanical behaviour, so that any potential issue can be anticipated. This article is a novel comprehensive study of the relevant phenomena that influence the design of Hyperloop infrastructure from the structural engineering viewpoint. The aim is to obtain, for the first time, representative values of the main internal forces and stresses leading to a preliminary design of the vacuum tube and, simultaneously, to provide relevant insight into the main phenomena involved. Depending on the longitudinal restrictions implemented at the piers, two basic configurations based on steel tubes are proposed. The strength and stability of the tube have been analysed thoroughly by taking into account the self and dead weight, internal low pressure, wind, thermal and traversing vehicle dynamic effects. Fatigue has also been assessed at potential critical locations. The relevance of each external action has been suitably highlighted, with particular emphasis on the predominant thermal and buckling effects. Estimates of the required tube thickness are provided, and resonance phenomena at some particular speeds are pointed out. Since the Hyperloop concept comprises both vehicle design and structure standardization that strongly relate to each other, their definition must be advanced in parallel. This work represents a starting point for future detailed studies, as the HL technology evolves through subsequent stages when relevant details of vehicle design will be available. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of a hyperloop vehicle with or without channels operating at subsonic speeds in a low-pressure tube were simulated using a scale-adaptive simulation (SAS) method based on the shear-stress transport (SST) κ-ω turbulence model. The aerodynamic behavior of the hyperloop pod, fluid flow, and heat transfer phenomena in the tube were analyzed and evaluated. The grid resolution was analyzed, and the numerical algorithm was validated using a wind tunnel test. The results show that the effects of using channels on the pressure drag of the pod are mainly noticeable at the end of the deceleration stage, and using channels has a great influence on the friction drag relative to the pressure drag, especially during deceleration. The friction drag of such a pod increased with the inclusion of an axial channel in both the acceleration and deceleration stages, whereas it was decreased using a radial gap inside the pod in conjunction with an axial channel during deceleration. The flow field around the pod tail is greatly affected when channels are used relative to other areas around the pod. Using both radial gap and axial channel can effectively reduce the abnormally high temperature in the wake of the pod when the pod surpasses the critical speed. The effects of the radial gap on the flow field in the radial gap are different during different stages of operation, especially in terms of the pressure field. The inclusion of a radial gap is not conducive to improving the surrounding flow field, especially during deceleration. It was also found that the aerodynamic profile design of the channel exit is very important, and the pod speed must be considered. • Effects of the radial gap on the flow field differ between different stages • Flow fields around the pods were affected by the channels, especially the radial gap • Use of channels has a small effect on pressure drag except during deceleration • High temperatures from shockwaves can be reduced using radial and axial channels [ABSTRACT FROM AUTHOR]

• Institutional fragmentation hampers network-of-networks investment opportunities. • Desirable network-of-networks scenarios employ intersectoral infrastructure adaptations. • Finding network-of-networks investment opportunities calls for a common ground. • Participatory foresight enables scenario use in institutionally fragmented contexts. Contemporary infrastructure networks require large investments especially due to aging. Investment opportunities of network-of-networks are often obscured because current scenarios often concern single infrastructure networks. Major barriers to the construction and use of network-of-networks scenarios are institutional fragmentation and the disconnection of scenario-development phases. This paper aims to construct and enhance the use of network-of-networks scenarios through a participatory scenario process. We employed a hybrid-method approach comprising document analysis, Disaggregative Policy Delphi, and futures-oriented workshop for five large national infrastructure administrations in the Netherlands. This approach yielded twelve key infrastructure developments for which 28 infrastructure experts provided future estimates. We constructed seven scenarios through cluster analysis of experts' quantitative estimates, qualitative direct content analysis of the qualitative data, and a futures table. The scenarios are: Infraconomy; Techno-Pessimism; Safety; Technological; Missed Boat; Hyperloop; and Green. Our results stress the importance of collaboration: desired scenarios are improbable when infrastructure administrations maintain their current sectoral perspective, whereas an inter-sectoral perspective may generate more investment opportunities. However, these network-of-networks investment opportunities do not simply emerge from network-of-networks scenarios; reasons include administrators' prevailing conception that sufficient optimization capacity remains within their own networks, and that no common ground exists that helps to overcome institutional fragmentation. [ABSTRACT FROM AUTHOR]