Study on Aerodynamic Performance of Maglev Train Passing by Each Other at Constant Speed

2021 ◽  
Vol 10 (02) ◽  
pp. 107-115
Author(s):  
淼 于
Keyword(s):  
Aerodynamic Performance ◽  
Constant Speed ◽  
Maglev Train

scholarly journals Aerodynamic Optimization Design of a Multistage Centrifugal Steam Turbine and Its Off-Design Performance Analysis

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Hui Li ◽  
Dian-Gui Huang
Keyword(s):  
Steam Turbine ◽  
Mass Flow ◽  
Pressure Ratio ◽  
Aerodynamic Performance ◽  
Constant Speed ◽  
Medium Size ◽  
Aerodynamic Design ◽  
One Dimensional ◽  
Design Program ◽  
The One

Centrifugal turbine which has less land occupation, simple structure, and high aerodynamic efficiency is suitable to be used as small to medium size steam turbines or waste heat recovery plant. In this paper, one-dimensional design of a multistage centrifugal steam turbine was performed by using in-house one-dimensional aerodynamic design program. In addition, three-dimensional numerical simulation was also performed in order to analyze design and off-design aerodynamic performance of the proposed centrifugal steam turbine. The results exhibit reasonable flow field and smooth streamline; the aerodynamic performance of the designed turbine meets our initial expectations. These results indicate that the one-dimensional aerodynamic design program is reliable and effective. The off-design aerodynamic performance of centrifugal steam turbine was analyzed, and the results show that the mass flow increases with the decrease of the pressure ratio at a constant speed, until the critical mass flow is reached. The efficiency curve with the pressure ratio has an optimum efficiency point. And the pressure ratio of the optimum efficiency agrees well with that of the one-dimensional design. The shaft power decreases as the pressure ratio increases at a constant speed. Overall, the centrifugal turbine has a wide range and good off-design aerodynamic performance.

scholarly journals Unsteady Aerodynamic Performance of a Maglev Train: The Effect of the Ground Condition

2021 ◽  
Author(s):  
Shi Meng ◽  
Guang Chen ◽  
Dan Zhou ◽  
Shuang Meng
Keyword(s):  
Vortex Structure ◽  
Aerodynamic Force ◽  
Simulation Method ◽  
Aerodynamic Performance ◽  
Detached Eddy Simulation ◽  
Maglev Train ◽  
Unsteady Aerodynamic ◽  
Ground Conditions ◽  
Ground Condition ◽  
Main Vortex

Abstract The effect of the ground condition on unsteady aerodynamic performance of maglev train was numerically investigated with an IDDES (Improved Delayed Detached Eddy Simulation) method. The accuracy of the numerical method has been validated by wind tunnel experiments. The flow structure, slipstream and aerodynamic force around the train under stationary and moving ground conditions were compared. Compared with the stationary ground condition, the vortex structure under the condition of moving ground generated by the wake region is narrower and higher because of the track. Near the nose point of the head and tail vehicles, the peak value of slipstream under the condition of moving ground is slightly higher than that under stationary ground. In the wake area, the effect of the main vortex structure on both sides of the tail vehicle and the track makes the vortex structure in the wake area stronger than that under moving ground, the slipstream peak is larger and the locus thereof is further forward. Under the two ground conditions, the vortex structure is periodically shed from both sides of the train into the wake area, and the shedding frequency of the main vortex under the moving ground condition is lower than that under the stationary ground condition. Moving ground can increase the resistance of the maglev train, reduce the lift of the maglev train, and decrease the standard deviation of the maglev train’s aerodynamic force.

scholarly journals Influence of the Topological Structures of the Nose of High-Speed Maglev Train on Aerodynamic Performances

2021 ◽  
Author(s):  
Yeteng Wang ◽  
Zhenxu Sun
Keyword(s):  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Force ◽  
Design Method ◽  
Aerodynamic Performance ◽  
Superior Performance ◽  
Maglev Train ◽  
Topological Structures ◽  
Aerodynamic Shape ◽  
Vehicle Modeling Function

Abstract In the past few years, considerable attention has been paid to high-speed maglev train in the field of rail transit. The design speed of the high-speed maglev train is 600km/h, which is significantly higher than that of the high-speed train. With the increase in operating speed, high-speed maglev trains have higher requirements for aerodynamic shape. Superior performance, the beautiful aerodynamic shape is an important direction for the development of high-speed maglev trains. Based on the Vehicle Modeling Function (VMF) method, the current research has developed a parametric shape design method suitable for the aerodynamic shape of the maglev train’s nose. This method can obtain different topological structures of the high-speed maglev train’s nose. The current research uses this method to generate four maglev train noses with large appearance differences and uses these train noses to construct four simplified high-speed maglev models. Then this study numerically analyzes the flow fields of different train models and compares the differences in aerodynamic performance including aerodynamic drag, aerodynamic lift and wake characteristics. The Q-criterion is used to study the vortex structure and mechanism of different train wake regions, and the vortex propagation process is studied by turbulence kinetic energy (TKE). Studying the difference in the aerodynamic force of different topological shapes will help to improve the aerodynamic performance of high-speed maglev trains.

Numerical Study on Unsteady Wake Characteristics of an Urban Maglev Train

2019 ◽  
Author(s):  
Zhenxu Sun ◽  
Yongfang Yao ◽  
Fanbing Kong ◽  
Guowei Yang
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Vortex Structures ◽  
Detached Eddy Simulation ◽  
Maglev Train ◽  
Aerodynamic Loads ◽  
Shed Light ◽  
Wake Characteristics

Abstract As the running speed increases, the aerodynamic loads become dominant for high-speed ground vehicles. Meanwhile, the aerodynamic lift of the trailing car becomes crucial at higher speed, which may lead to security and comfort problems. Flow field details are the root to the aerodynamic loads. Study on the wake characteristics of the train could shed light to learn the mechanism of their aerodynamic loads and know how to improve their aerodynamic performance. In the present paper, the urban maglev train with a design speed of 200 km/h is mainly focused on. Numerical investigation is adopted for current study. The Improved Delayed Detached Eddy Simulation (IDDES) numerical approach is utilized to count for unsteady flow details. To characterize the vortex structures, the iso-surface of Q for urban maglev train is obtained and compared. Due to the existence of guide way, the streamline of maglev trains is much more influenced by the guide way. The ground effect for maglev trains is more obvious. The streamlined shape is quite essential to the flow phenomena, and as a result, the vortex structures for urban maglev trains are also different. Guide way could lead to more vortices, which is common for maglev trains. However, lateral vortex could be observed for urban maglev trains, which is unique and is a result of the flat shape of the trailing nose. Meanwhile, the slipstream in the wake of the train is also compared. The streamlined shape of urban maglev trains is the bluntest, which induces the relatively biggest train wind. Based on the above analysis, the unsteady characteristics of flow field for urban maglev train are obtained and the main vortex structures are characterized. Based on the unsteady analysis of flow field, the relationships between aerodynamic loads of the trailing car and different kinds of trailing vortices are obtained. Current study could shed light on the understanding of mechanism of aerodynamic performance of a train and how to design the streamlined shape for trains with certain operational speed.

How to speed up to be in time: Action-judgment dissociations in children and adults

2004 ◽  
Vol 63 (1) ◽  
pp. 17-29 ◽  
Author(s):  
Friedrich Wilkening ◽  
Claudia Martin
Keyword(s):  
Rating Scale ◽  
Constant Speed ◽  
Linear Condition ◽  
Speed Up ◽  
Nonlinear Condition ◽  
Speed Change ◽  
Catch Up ◽  
Normative Rule ◽  
Judgment Condition ◽  
Time Linear

Children 6 and 10 years of age and adults were asked how fast a toy car had to be to catch up with another car, the latter moving with a constant speed throughout. The speed change was required either after half of the time (linear condition) or half of the distance (nonlinear condition), and responses were given either on a rating scale (judgment condition) or by actually producing the motion (action condition). In the linear condition, the data patterns for both judgments and actions were in accordance with the normative rule at all ages. This was not true for the nonlinear condition, where children’s and adults’ judgment and also children’s action patterns were linear, and only adults’ action patterns were in line with the nonlinearity principle. Discussing the reasons for the misconceptions and for the action-judgment dissociations, a claim is made for a new view on the development of children’s concepts of time and speed.

Effects of stator splitter blades on aerodynamic performance of a single-stage transonic axial compressor

2020 ◽  
Vol 14 (4) ◽  
pp. 7369-7378
Author(s):  
Ky-Quang Pham ◽  
Xuan-Truong Le ◽  
Cong-Truong Dinh
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Aerodynamic Performance ◽  
Numerical Results ◽  
Single Stage ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Operating Stability ◽  
Length Coverage

Splitter blades located between stator blades in a single-stage axial compressor were proposed and investigated in this work to find their effects on aerodynamic performance and operating stability. Aerodynamic performance of the compressor was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations using the k-e turbulence model with a scalable wall function. The numerical results for the typical performance parameters without stator splitter blades were validated in comparison with experimental data. The numerical results of a parametric study using four geometric parameters (chord length, coverage angle, height and position) of the stator splitter blades showed that the operational stability of the single-stage axial compressor enhances remarkably using the stator splitter blades. The splitters were effective in suppressing flow separation in the stator domain of the compressor at near-stall condition which affects considerably the aerodynamic performance of the compressor.

Study on Correlation between Geometrical Correction and Aerodynamic Performance of Microscale Supersonic Wind Tunnel

2018 ◽  
Vol 138 (4) ◽  
pp. 145-152
Author(s):  
Naoki Murai ◽  
Ryouto Yamamoto ◽  
Kouhei Rikuno ◽  
Toshiyuki Toriyama
Keyword(s):  
Wind Tunnel ◽  
Aerodynamic Performance ◽  
Supersonic Wind Tunnel
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