scholarly journals Numerical Analysis of Aerodynamic Characteristics of Hyperloop System

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 518 ◽  
Author(s):  
Jae-Sung Oh ◽  
Taehak Kang ◽  
Seokgyun Ham ◽  
Kwan-Sup Lee ◽  
Yong-Jun Jang ◽  
...  
Keyword(s):  
Mach Number ◽  
Aerodynamic Drag ◽  
Strong Shock ◽  
Aerodynamic Characteristics ◽  
Friction Drag ◽  
Total Drag ◽  
Pressure Drag ◽  
Flow Phenomena ◽  
Pod Length ◽  
Large Parameter Space

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.

Numerical Simulation of Drag Reduction in Microgrooved Substrates Using Lattice-Boltzmann Method

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
H. Asadzadeh ◽  
A. Moosavi ◽  
A. Etemadi
Keyword(s):  
Drag Reduction ◽  
Drag Coefficient ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Groove Depth ◽  
Friction Drag ◽  
Total Drag ◽  
Pressure Drag ◽  
Depth Ratio ◽  
Boltzmann Method

We study drag reduction of a uniform flow over a flat surface due to a series of rectangular microgrooves created on the surface. The results reveal that making grooves on the surface usually leads to the generation of secondary vortices inside the grooves that, in turn, decreases the friction drag force and increases the pressure drag force. By increasing the thickness of the grooves to the thickness of the obstacle, the pressure drag increases due to the enhancement of the generated vortices and the occurrence of separation phenomenon and the friction drag reduces due to a decrease of the velocity gradient on the surface. In addition, by increasing the grooves depth ratio, the pressure drag coefficient decreases and the friction drag coefficient increases. However, the impact of the pressure drag coefficient is higher than that of the friction drag coefficient. From a specific point, increasing the groove depth ratio does not effect on decreasing the total pressure drag of the plate. Therefore, creating the grooves in flat surfaces would reduce the total drag coefficient of the plate if the thickness of the grooves does not exceed a specific size and the depth of the grooves is chosen to be sufficiently large. The lattice-Boltzmann method (LBM) is used and the optimal reduction of the drag coefficient is calculated. It is found that for the width ratio equal to 0.19 and the groove depth ratio equal to 0.2548, about 7% decrease is achieved for the average total drag.

Design of Upswept Aft-Body of Civil Transport Based on CFD

2013 ◽  
Vol 690-693 ◽  
pp. 2722-2725
Author(s):  
Mu Qing Yang ◽  
Dong Li Ma ◽  
Ya Feng Liu ◽  
Wen Yue Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Field ◽  
Aerodynamic Performance ◽  
Design Parameters ◽  
Friction Drag ◽  
Total Drag ◽  
Pressure Drag ◽  
Computational Fluid Dynamics Cfd ◽  
The One

Study on flow field of civil transport upswept aft-body is of much value as the drag coursed by aft-body contributes to about 10 percent of total drag. Currently researches were mostly concerned on clean fuselage, while little emphasis was put on fuse-tail configuration. With interests to exploiting the effect of design parameters on fuselage with empennage, computational fluid dynamics (CFD) was used to simulate the flow field of fuselages with different parameters. Based on studying the aerodynamic performance of clean fuselages, emphases were placed on fuse-tail configurations. Although fairing at root of stabilizer is good for reducing pressure drag, influence on friction drag should be taken into consideration when determine the design of fairing. With stabilizer mounted, drag of axial symmetric fuselage is not the minimum, while the one with some angle upswept is drag optimal.

Aerodynamic Drag on Trains in Tunnels Part 1: Synthesis and Definitions

1996 ◽  
Vol 210 (1) ◽  
pp. 29-38 ◽  
Author(s):  
A E Vardy
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Aerodynamic Drag ◽  
Common Method ◽  
Pressure Waves ◽  
Friction Drag ◽  
Pressure Drag ◽  
Normal Forces ◽  
Wide Range ◽  
Definition Of

Aerodynamic drag on trains in tunnels includes friction drag and pressure drag, which are respectively the algebraic sums of the longitudinal components of all shear and normal forces on the train surfaces. The first of these is broadly similar to its counterpart in the open. The second is shown to include two effects that are usually negligible in the open. It is shown that the overall drag force must be regarded as the sum of individual components, each of which behaves differently from the others. The components can be represented by non-dimensional coefficients whose numerical values are nearly constant for a wide range of train journeys. In contrast, the overall drag coefficient is shown to vary significantly, even during any particular journey. The principal causes of aerodynamic drag in tunnels are also the principal causes of pressure waves that give rise to potential aural discomfort for passengers. It is argued that a common method of analysis is appropriate for the prediction of both of these effects. Ill-defined train areas are shown to be a potentially serious source of confusion in the estimation and interpretation of drag coefficients. The relevant train area is shown to be its aerodynamic area, the definition of which is explained.

scholarly journals Simulation of Gas Flow Over a Micro Cylinder

2009 ◽  
Author(s):  
Yuan Hu ◽  
Quanhua Sun ◽  
Jing Fan
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Drag Coefficient ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Low Reynolds Number ◽  
Pressure Drag ◽  
Low Reynolds ◽  
Rarefied Gas Effect ◽  
Gas Effect

Gas flow over a micro cylinder is simulated using both a compressible Navier-Stokes solver and a hybrid continuum/particle approach. The micro cylinder flow has low Reynolds number because of the small length scale and the low speed, which also indicates that the rarefied gas effect exists in the flow. A cylinder having a diameter of 20 microns is simulated under several flow conditions where the Reynolds number ranges from 2 to 50 and the Mach number varies from 0.1 to 0.8. It is found that the low Reynolds number flow can be compressible even when the Mach number is less than 0.3, and the drag coefficient of the cylinder increases when the Reynolds number decreases. The compressible effect will increase the pressure drag coefficient although the friction coefficient remains nearly unchanged. The rarefied gas effect will reduce both the friction and pressure drag coefficients, and the vortex in the flow may be shrunk or even disappear.

Іmprovement of driving-speed properties improvement of the method for selecting the parameters of the motor-transmission unit car

2021 ◽  
Vol 13 (1) ◽  
pp. 111-117
Author(s):  
Mikhail Podrigalo ◽  
◽  
Volodymyr Krasnokutskyi ◽  
Vitaliy Kashkanov ◽  
Olexander Tkachenko ◽  
...  
Keyword(s):  
Aerodynamic Drag ◽  
Dynamic Properties ◽  
Aerodynamic Characteristics ◽  
Gear Ratio ◽  
Design Stage ◽  
Transmission Unit ◽  
Air Resistance ◽  
Design Speed ◽  
Maximum Design ◽  
Engine Power

Aerodynamic characteristics have a major impact on the energy efficiency and traction and speed properties of the vehicle. In this article, based on previous studies of the aerodynamic characteristics of various car models, we propose an improved method for selecting engine and transmission parameters at the design stage. The aim of the study is to improve the dynamic properties of the car by improving the method of selecting the main parameters of the engine-transmission unit by refining the calculation of aerodynamic drag. To achieve it, the following tasks must be solved: to specify the method of selecting the maximum effective engine power; to specify a technique of definition of the maximum constructive speed of the car; to develop a technique for selecting gear ratios. The aerodynamic resistance to the movement of the vehicle is determined by the frontal coefficient of the specified resistance, the density of the air, the area of the frontal resistance and the speed of the vehicle. It is known from classical works on the aerodynamics of a car that in the range of vehicle speeds from 20 m / s to 80 m / s, taking the law of squares when assessing the force of air resistance, it is necessary to change the coefficient of frontal aerodynamic drag depending on the speed of the car. However, when carrying out calculations, this coefficient is taken constant, which leads to obtaining large values of the air resistance force at high speeds and lower at low speeds. There are two possible ways to improve the dynamic properties and energy efficiency of the car during its modernization (increasing the maximum design speed of the car by reducing the gear ratio in higher gear; reducing the maximum efficiency of the engine while maintaining the previous gear ratio in higher gear). As a result of the study, the method of selection (maximum effective engine power; maximum design speed of the car; gear ratios) at the design stage of the parameters of the motor-transmission unit of the car has been improved.

Aerodynamic optimisation of the rocket plane in subsonic and supersonic flight conditions

2017 ◽  
Vol 231 (12) ◽  
pp. 2266-2281 ◽  
Author(s):  
Marcin Figat ◽  
Agnieszka Kwiek
Keyword(s):  
Mach Number ◽  
Main Part ◽  
Numerical Study ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Design ◽  
Supersonic Speed ◽  
Supersonic Flight ◽  
Special Vehicle ◽  
Speed Regime ◽  
The Impact

This paper presents the results of a numerical study of the aerodynamic shape of the Rocket Plane LEX. The Rocket Plane is a main part of the Modular Airplane System – MAS; a special vehicle devoted to suborbital tourist flights. The Rocket Plane was designed for subsonic and supersonic flight conditions. Therefore, the impact of the Mach number should be considered during the aerodynamic design of the Rocket Plane. The main goal of the investigation was to determine the sensitivity of the Rocket Plane aerodynamic characteristics to the Mach number during the optimisation of the LEX geometry. The paper includes results of the optimisation process for Mach number from the range Ma = 0.5 to Ma = 2.5. These results reveal that the aerodynamic characteristics of models optimised for the subsonic and transonic regime of Mach numbers (up to Ma = 1) were also improved for the supersonic speed regime. However, in the case of models optimised for the supersonic flight regime the aerodynamic characteristics in subsonic flight regime, are inferior compared to the model before the optimisation process.

Influence of Engine Cabin Simplification on Aerodynamic Characteristics of Car

2014 ◽  
Vol 1042 ◽  
pp. 188-193 ◽  
Author(s):  
Xing Jun Hu ◽  
Jing Chang
Keyword(s):  
Numerical Simulation ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Thin Plates ◽  
Average Thickness ◽  
Two Dimensional ◽  
Engine Cooling ◽  
Aerodynamic Drag Coefficient ◽  
Simulation Results ◽  
The Impact

In order to analyze the impact of engine cabin parts on aerodynamic characteristics, the related parts are divided into three categories except the engine cooling components: front thin plates (average thickness of 2mm), bottom-suspension and interior panels. The aerodynamic drag coefficient (Cd) were obtained upon the combination schemes consisting of the three types of parts by numerical simulation. Results show that Cd by simulation is closer to the test value gained by the wind tunnel experiment when front thin plates were simplified to the two-dimensional interface with zero thickness. The error is only 5.23%. Meanwhile this scheme reduces grid numbers, thus decreasing the calculating time. As the front thin plates can guide the flow, there is no difference on the Cd values gained from the model with or without bottom-suspension or interior panels when the engine cabin contains the front thin plates; while only both bottom-suspension and interior panels are removed, the Cd value can be reduced when the cabin doesn’t contain the front thin plates.

scholarly journals Aerodynamic profile drag

2021 ◽  
Author(s):  
Matej Sabo ◽  
◽  
Martin Bugaj
Keyword(s):  
Fluid Dynamics ◽  
Boundary Layer ◽  
European Union ◽  
Laminar Flow ◽  
Friction Drag ◽  
Form Drag ◽  
Basic Principles ◽  
Total Drag ◽  
Laminar Flow Control ◽  
Physical Principles

Higher awareness of aviation sustainability and environmental impact creates more research on profile drag reduction. The basic principles of aerodynamic profile drag are described and its role within the total drag. The boundary layer is defined using mathematical and physical principles of fluid dynamics. There are two types of movement inside the boundary layer: laminar and turbulent. In these, their impact on profile drag is analysed. The profile drag of a wing has two sources: form drag and friction drag. Applications with the most impact, throughout history, on both types of drag reductions were reviewed. Because most of the total drag comes from friction, researchers focus more on it compared to form drag. The significant way of reducing friction drag is postponing the transition of laminar flow into turbulent. The control of laminar flow became crucial for reducing friction drag. In the last two decades, European Union supported multiple projects concerning laminar flow control. These advancements in the field are starting to get implemented and tested on new aircraft by manufactures.

scholarly journals Bearing friction effect on cup anemometer performance modelling

2021 ◽  
Vol 2090 (1) ◽  
pp. 012101
Author(s):  
D Alfonso-Corcuera ◽  
S. Pindado ◽  
M Ogueta-Gutiérrez ◽  
A Sanz-Andrés
Keyword(s):  
Rotation Rate ◽  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Friction Torque ◽  
Performance Modelling ◽  
Friction Forces ◽  
Aerodynamic Drag Coefficient ◽  
Yaw Angle ◽  
Cup Anemometer ◽  
Bearing Friction

Abstract In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

The Effect of Reynolds Number on the Aerodynamic Performance of Micro Radial Flow Fans

2005 ◽  
Author(s):  
K. Hanly ◽  
R. Grimes ◽  
E. Walsh ◽  
B. Rodgers ◽  
J. Punch
Keyword(s):  
Reynolds Number ◽  
Heat Dissipation ◽  
Radial Flow ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Fundamental Change ◽  
Geometric Similarity ◽  
Flow Phenomena ◽  
Conventional Cooling ◽  
High Degree

Elevated heat dissipation and simultaneous reductions in package sizes are well documented for a range of electronics systems. The problem is heightened in portable systems where the space available for the implementation of an active cooling methodology is limited and conventional cooling products are too large. Using micro scale radial flow fans is a potential solution. However, little is known about the aerodynamic effects of reducing the fan scale and therefore Reynolds number to the extent required for typical portable electronic applications. This paper investigates this issue, by quantifying the reduction in aerodynamic performance which accompanies the reductions in scale. To do this, geometrically similar radial flow fans were fabricated with diameters ranging from 80 to 10mm. Measurements of the rotors’ geometries are presented, showing a high degree of geometric similarity between the fans. The aerodynamic performance of each of the fans was measured. Non-dimensional performance of each of the larger fans were almost identical, while the performance plot of the smallest fan differed significantly from the others. The paper tentatively concludes that a fundamental change in flow phenomena has emerged in the smallest scale fan which has altered its aerodynamic characteristics.

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