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.

Aerodynamic behavior of a high-speed train with a braking plate mounted in the region of inter-car gap or uniform-car body: A comparative numerical study

2020 ◽  
pp. 095440972096582
Author(s):  
Jiqiang Niu ◽  
Yueming Wang ◽  
Feng Liu ◽  
Rui Li
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Numerical Study ◽  
Aerodynamic Performance ◽  
Body Region ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Continuous Increase ◽  
Car Body

The continuous increase in train speed has brought serious challenges to train braking safety. Aerodynamic braking technology can effectively improve the braking effect of trains at high speeds. In this study, an aerodynamic braking device installed in the inter-car gap region (ICG) of a high-speed train is proposed and the aerodynamic performance of the high-speed train with an aerodynamic braking device is assessed by improved delayed detached eddy simulation (IDDES) based on the κ-ω turbulence model. The results show that the opening of the plate significantly changes the aerodynamic performance of the train, thereby greatly increasing the aerodynamic forces of the train and their fluctuation degree. The effect of the opening of the plate increases the turbulence of the downstream flow field around the tail car. The affected area is mainly concentrated in the flow field around the location of the plate for the pressure field and the whole flow field behind the plate for the velocity field. The effect of the plate mounted on the uniform-car body region (UCG) on increasing the aerodynamic drag is better than that at the ICG, though the aerodynamic fluctuation and the influence on the surrounding flow field will also be great.

A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model

2018 ◽  
Vol 233 (7) ◽  
pp. 715-730 ◽  
Author(s):  
Mingyang Liu ◽  
Jiabin Wang ◽  
Huifen Zhu ◽  
Sinisa Krajnovic ◽  
Guangjun Gao
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Snow Accumulation ◽  
Phase Model ◽  
Detached Eddy Simulation ◽  
Discrete Phase Model ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Mechanisms ◽  
Discrete Phase

A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.

scholarly journals Numerical Study on Aerodynamic Performance of High-Speed Pantograph with Double Strips

2020 ◽  
Vol 16 (1) ◽  
pp. 31-40 ◽  
Author(s):  
Zhiyuan Dai ◽  
Tian Li ◽  
Weihua Zhang ◽  
Jiye Zhang
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Aerodynamic Performance

Numerical investigation of the aerodynamic characteristics of a train subjected to different ground conditions

2018 ◽  
Vol 232 (10) ◽  
pp. 2371-2384 ◽  
Author(s):  
Ji-qiang Niu ◽  
Xi-feng Liang ◽  
Dan Zhou ◽  
Yue-ming Wang
Keyword(s):  
Wind Tunnel ◽  
Boundary Layers ◽  
High Speed ◽  
Rapid Development ◽  
Ground Effect ◽  
Aerodynamic Performance ◽  
Detached Eddy Simulation ◽  
Scaled Model ◽  
Ground Conditions ◽  
Ground Condition

Due to the rapid development of high-speed railways and the increasing speed of trains, the aerodynamic phenomenon caused by moving trains could be affected. Therefore, the scaled model test has been widely used to simulate the aerodynamic performance of the stationary train in wind tunnel. However, it is difficult to disregard the influence of the ground effect on the aerodynamic performance of trains. In this study, the delayed detached eddy simulation based on the shear stress transport κ–ω turbulence model is used to investigate the aerodynamic performance of trains on three ground conditions (stationary floor + stationary ballast, stationary ground + stationary ballast, and stationary ballast). The numerical method used in this paper is verified by a wind tunnel test. The way the three ground conditions influence the flow field around the train is also analyzed. The results show that the ground condition affects the thickness of the ballast boundary layers without a train, thickness of the train boundary layers, train drag, distribution of pressure and velocity along the train, and the size of the wake region; however, the ground condition had a little effect on the flow structures around the train tail. These findings can help in designing the wind tunnel experiment.

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.

scholarly journals Numerical study on the influence of initial ambient temperature on the aerodynamic heating in the tube train system

2020 ◽  
Author(s):  
Shijie Bao ◽  
Xiao Hu ◽  
Jukun Wang ◽  
Yingyu Rao ◽  
Zigang Deng
Keyword(s):  
Low Temperature ◽  
Flow Field ◽  
Ambient Temperature ◽  
Temperature Region ◽  
High Speed ◽  
Numerical Study ◽  
Geometric Model ◽  
Flow Region ◽  
Aerodynamic Heating ◽  
Evacuated Tube Transportation

Abstract The evacuated tube transportation has great potential in the future because of its advantages of energy saving and environmental protection. The train runs in the closed tube at ultra-high speed. Because the heat quantity generated by aerodynamic heating is not easy to spread to external environment and will be accumulate in the tube, the phenomenon that the ambient temperature in the tube will gradually rise will be induced. In this paper, a three-dimensional geometric model and the Shear Stress Transport (SST) κ-ω turbulence model are used to study the influence of initial ambient temperature on the structure of the flow field in the tube. Simulation results show that when the train runs at transonic speed, the supersonic flow region with low temperature and low-pressure is produced in the wake. The structure of the flow field of the wake will change with the initial ambient temperature. And the higher the initial ambient temperature, the shorter the low temperature region in the wake. Considering that the larger temperature difference caused by the low temperature region may increase the temperature stress of the tube and affect the equipment inside the tube. Consequently, the temperature inside the tube can be maintained at a reasonable value to reduce the influence of the low temperature region in the wake on the system.

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