scholarly journals Numerical Investigation of Aerodynamic Drag and Pressure Waves in Hyperloop Systems

Mathematics ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1973
Author(s):  
Thi Thanh Giang Le ◽  
Kyeong Sik Jang ◽  
Kwan-Sup Lee ◽  
Jaiyoung Ryu
Keyword(s):  
Wave Propagation ◽  
Drag Coefficient ◽  
Speed Of Sound ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Propagation Speed ◽  
Pressure Waves ◽  
Wave Propagation Speed ◽  
Pod Length ◽  
Very High

Hyperloop is a new, alternative, very high-speed mode of transport wherein Hyperloop pods (or capsules) transport cargo and passengers at very high speeds in a near-vacuum tube. Such high-speed operations, however, cause a large aerodynamic drag. This study investigates the effects of pod speed, blockage ratio (BR), tube pressure, and pod length on the drag and drag coefficient of a Hyperloop. To study the compressibility of air when the pod is operating in a tube, the effect of pressure waves in terms of propagation speed and magnitude are investigated based on normal shockwave theories. To represent the pod motion and propagation of pressure waves, unsteady simulation using the moving-mesh method was applied under the sheer stress transport k–ω turbulence model. Numerical simulations were performed for different pod speeds from 100 to 350 m/s. The results indicate that the drag coefficient increases with increase in BR, pod speed, and pod length. In the Hyperloop system, the compression wave propagation speed is much higher than the speed of sound and the expansion wave propagation speed that experiences values around the speed of sound.

Dynamic Performance Simulation of Overhead Contact System for over 350km/h High-Speed Rail

2013 ◽  
Vol 706-708 ◽  
pp. 1305-1309 ◽  
Author(s):  
Jie Ruan ◽  
An Li ◽  
Fu Wu Yan ◽  
Hong Mei Li
Keyword(s):  
Wave Propagation ◽  
High Speed ◽  
Dynamic Performance ◽  
Propagation Speed ◽  
Contact System ◽  
Running Speed ◽  
High Speed Rail ◽  
Rail Network ◽  
Infinite Element Method ◽  
Wave Propagation Speed

With full development of 350km/h high-speed rail network in China, further research in the key technology of 380km/h or higher super-speed rail system has become crucial. Applying the simulation of pantograph-catenary interaction based on infinite element method, this paper simulated the dynamic performance of pantograph-catenary system for high-tension overhead contact system at over 350km/h. The research findings showed that wave propagation speed can still serve as a brief computing method for the running speed within the range of 350-400km/h. When the running speed reaches 80% of the wave propagation speed or higher, the current-carrying quality of double-pantograph-catenaries system might not satisfy the standard of EN 50367 all the time.

Influence of the applied pressure of the transducer on the propagation speed of the ultrasonic wave in wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edgar V.M. Carrasco ◽  
Rejane C. Alves ◽  
Mônica A. Smits ◽  
Vinnicius D. Pizzol ◽  
Ana Lucia C. Oliveira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Applied Pressure ◽  
Pressure Gauge ◽  
Eucalyptus Grandis ◽  
Propagation Speed ◽  
Ultrasonic Waves ◽  
Ultrasonic Speed ◽  
Wave Propagation Speed ◽  
Propagation Technique ◽  
Non Destructive

Abstract The non-destructive wave propagation technique is used to estimate the wood’s modulus of elasticity. The propagation speed of ultrasonic waves is influenced by some factors, among them: the type of transducer used in the test, the form of coupling and the sensitivity of the transducers. The objective of the study was to evaluate the influence of the contact pressure of the transducers on the ultrasonic speed. Ninety-eight tests were carried out on specimens of the species Eucalyptus grandis, with dimensions of 120 × 120 × 50 mm. The calibration of the pressure exerted by the transducer was controlled by a pressure gauge using a previously calibrated load cell. The robust statistical analysis allowed to validate the experimental results and to obtain consistent conclusions. The results showed that the wave propagation speed is not influenced by the pressure exerted by the transducer.

scholarly journals К теории рассеяния Мандельштама-Бриллюэна в плазменном слое

2020 ◽  
Vol 128 (1) ◽  
pp. 98
Author(s):  
С.А. Двинин ◽  
Д.К. Солихов ◽  
Ш.С. Нурулхаков
Keyword(s):  
Wave Propagation ◽  
Pump Wave ◽  
Plasma Layer ◽  
Brillouin Scattering ◽  
Propagation Speed ◽  
Local Source ◽  
Arbitrary Angle ◽  
Perturbation Amplitude ◽  
Wave Propagation Speed ◽  
Over Time

The evolution of a perturbation from a local source for Mandel'shtam-Brillouin scattering in a plasma layer with unlimited length is calculated. Perturbation over time in this case can either leave the scattering region through one of the two boundaries, or propagate along the layer at a speed below sound wave propagation speed, with an exponential growth, or a fall in perturbation amplitude. In the particular case of strictly backward scattering (the scattering angle is π), this propagation velocity is zero. The paper calculates the threshold instability fields and the instability increments, taking into account both convective losses and collisional attenuation of waves. It is shown that the instability threshold for scattering at an arbitrary angle can be lower than for strictly backwards scattering and when the threshold is exceeded by the intensity of the pump wave; the scattering increment at an angle can also be higher than the increment for backscattering. When the threshold is greatly exceeded, the convective losses can be neglected, and the largest increment is observed for backward scattering.

Analytical and Optimization Study of Propagation and Reduction of Wave in Granular Sand by DEM Method

2021 ◽  
Author(s):  
Amin Moslemi Petrudi ◽  
Masoud Rahmani
Keyword(s):  
Wave Propagation ◽  
Particle Density ◽  
Propagation Speed ◽  
Granular Soils ◽  
Discrete Elements ◽  
Factors Affecting ◽  
Interparticle Force ◽  
Optimization Study ◽  
Solution Methods ◽  
Wave Propagation Speed

In this research, the discrete element method has been used to analyze wave propagation and to investigate the factors affecting wave reduction in granular soils. The method of discrete elements is important because of the possibility of preparing completely similar specimens and examining the effect of changes in a certain parameter on the Behavior of the specimens. This method also provides an understanding of the changes that have occurred at the micro-scale of granular materials that are not achievable with other laboratory and numerical methods. To model the specimens, a set of disks with specific granulation has been used for two-dimensional studies. PFC 2D software has been used to perform simulations and related analyzes such as interparticle force. The DEM code in MATLAB is used to check the wave depreciation. In this research, the optimization process was performed using experimental data and the Taguchi method using the DEM method. The results of this study show that there is a direct relationship between the number of particle set contacts and the wave propagation speed. Also, material properties such as particle density are the most important parameters affecting wave velocity. The results of the method (DEM) are done with PFC 2D software and a comparison between the results of this method with the solution methods used by other researchers is shown to be a good match.

A new moving model test method for the measurement of aerodynamic drag coefficient of high-speed trains based on machine vision

2017 ◽  
Vol 232 (5) ◽  
pp. 1425-1436 ◽  
Author(s):  
Zhiwei Li ◽  
Mingzhi Yang ◽  
Sha Huang ◽  
Dan Zhou
Keyword(s):  
Machine Vision ◽  
Drag Coefficient ◽  
Model Test ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Full Scale ◽  
Test Method ◽  
Test Accuracy ◽  
Friction Resistance ◽  
Aerodynamic Drag Coefficient

A moving model test method has been proposed to measure the aerodynamic drag coefficient of a high-speed train based on machine vision technology. The total resistance can be expressed as the track friction resistance and the aerodynamic drag according to Davis equation. Cameras are set on one side of the track to capture the pictures of the train, from which the line marks on the side surface of the train are extracted and analyzed to calculate the speed and acceleration of the train. According to Newton’s second law, the aerodynamic drag coefficient can be resolved through multiple tests at different train speeds. Comparisons are carried out with the full-scale coasting test, wind tunnel test, and numerical simulation; good agreement is obtained between the moving model test and the full-scale field coasting test with difference within 1.51%, which verifies that the method proposed in this paper is feasible and reliable. This method can accurately simulate the relative movement between the train, air, and ground. The non-contact measurement characteristic will increase the test accuracy, providing a new experimental method for the aerodynamic measurement.

Axial force measurement for U-bolt using wave propagation speed monitoring

2016 ◽  
Vol 140 (4) ◽  
pp. 3002-3002
Author(s):  
Gyungmin Toh ◽  
Dongki Min ◽  
Jaehong Lee ◽  
Junhong Park
Keyword(s):  
Wave Propagation ◽  
Axial Force ◽  
Force Measurement ◽  
Propagation Speed ◽  
Wave Propagation Speed

Aerodynamic Drag on Vehicles in Tunnels

1969 ◽  
Vol 91 (4) ◽  
pp. 694-706 ◽  
Author(s):  
S. William Gouse ◽  
B. S. Noyes ◽  
J. K. Nwude ◽  
M. C. Swarden
Keyword(s):  
Laminar Flow ◽  
Drag Coefficient ◽  
Surface Area ◽  
Incompressible Flow ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Diameter Ratio ◽  
Infinite Body ◽  
Tunnel Wall ◽  
Wetted Surface Area

The purpose of this study was to investigate the aerodynamic drag on vehicles moving in guideways of varying degrees of enclosure. The reason for this study was that several potential high speed ground transport system concepts involve high speed motion of vehicles in enclosed guideways for significant portions of their travel time. Analytical and experimental investigations have been carried out. The analytical studies developed the solution for the aerodynamic drag on a vehicle in an enclosed guideway in laminar flow. The analysis is based on an analogy between the governing equations for the unsteady flow resulting when an infinite body is started impulsively from rest and the steady flow that results from steady motion of a semi-infinite body. The results of this analysis for laminar flow provided a base from which to begin in turbulent flow and were used to justify the basing of a drag coefficient on the wetted surface area of a vehicle rather than the frontal area of a vehicle. Preliminary experiments were executed using spheres as vehicle models. Final experimental studies were carried out using cylindrical models in circular tunnels of various lengths and various degrees of wall porosity. A drop testing apparatus was employed and results were obtained for Reynolds number of the order of 5 · 105. Results to date indicate that for vehicle length-diameter ratios of the order of 15 and above, with tunnel to vehicle diameter ratios of 1.5 and greater, a drag coefficient based on the wetted surface area of the vehicle is independent of the vehicle length-diameter ratio for incompressible flow. Results also indicate that, for incompressible flow, employing a tunnel model with a closed end simulates a tunnel length-diameter ratio of infinity. Tunnel wall porosity, assuming relatively unobstructed motion of fluid outside the porous wall, has a marked effect on decreasing the aerodynamic drag on vehicles moving in enclosed guideways and that for the range of variables investigated (clearance ratio as low as 1.4) tunnel wall porosity of 20 per cent is adequate for all the significant drag reduction that is possible. Qualitative predictions of loss coefficient analytical modeling and literature on transonic flow wind tunnel testing with porous walls are in agreement with the data presented.

Extension of Campbell's Major Resonance With Experimental Demonstration

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Robert P. Czachor
Keyword(s):  
Wave Propagation ◽  
Rotational Velocity ◽  
Propagation Speed ◽  
Experimental Demonstration ◽  
Adjacent Structure ◽  
Component Test ◽  
Turbine Disc ◽  
Wave Propagation Speed ◽  
Trans Asme ◽  
Classic Paper

The interaction of vibratory traveling waves in rotating and stationary axisymmetric components is examined. In the most general case, a resonance can occur when the wave propagation speed in a first structure is equal in magnitude and direction to the rotational velocity of an adjacent structure. When a backward wave in a rotor appears stationary, a major resonance, as discussed in Wilfred Campbell's classic paper (Campbell, W., 1924, “The Protection of Steam Turbine Disc Wheels from Axial Vibrations,” Trans ASME, 46, pp. 31–160), results. A related resonance has been observed when the wave propagation speed in the stator is equal to the physical speed of the adjacent rotor. A third mechanism is derived for resonance between a wave in rotor 1 and a co- or counter-rotating rotor 2. Description of a component test which demonstrated this final phenomenon is provided.

scholarly journals EXPONENTIAL STABILITY OF LAMINATED BEAM WITH CONSTANT DELAY FEEDBACK

2021 ◽  
Vol 26 (4) ◽  
pp. 566-581
Author(s):  
Kassimu Mpungu ◽  
Tijani A. Apalara
Keyword(s):  
Wave Propagation ◽  
Exponential Stability ◽  
Propagation Speed ◽  
Transverse Displacement ◽  
Structural Damping ◽  
Constant Delay ◽  
Laminated Beams ◽  
Laminated Beam ◽  
Delay Term ◽  
Wave Propagation Speed

In this article, we consider a system of laminated beams with an internal constant delay term in the transverse displacement. We prove that the dissipation through structural damping at the interface is strong enough to exponentially stabilize the system under suitable assumptions on delay feedback and coefficients of wave propagation speed.

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