scholarly journals The effect of different marshalling forms on the aerodynamic performance of the freight train under crosswind

2021 ◽  
Vol 59 (3) ◽  
pp. 57-71
Author(s):  
Zihao Xie ◽  
Zhenfeng Wu ◽  
Longhui Zhu ◽  
Wangcai Ding
Keyword(s):  
Aerodynamic Drag ◽  
Simulation Method ◽  
Lateral Force ◽  
Aerodynamic Performance ◽  
Maximum Difference ◽  
Detached Eddy Simulation ◽  
Freight Train ◽  
Eddy Simulation ◽  
Cavity Structure ◽  
Key Factor

Different types and quantities of freight cars will affect the marshalling forms of freight trains. In order to investi-gate the influence of the marshalling forms on the aerodynamic performance of freight trains under crosswind, three types of freight cars such as box cars, gondola cars and tank cars, were selected to marshal with locomo-tives. This paper used Detached Eddy Simulation method (DES) based on the SST k  ω turbulent model to simulate the aerodynamic performance of the freight train under crosswind. The wind speed, wind angle and train running speed were set as 25m/s, 45° and 100km/h respectively. The influence of different marshalling forms on the aerodynamic performance of the freight train such as aerodynamic drag and lateral force were calculated and compared. The results showed that the marshalling forms have significant effect on the aerody-namic drag and the maximum difference of the aerodynamic drag can reach 20.5%. Furthermore, the variations of the lateral force of the whole train and the locomotive are not apparent. The maximum difference is only 4.3% and 4.1% respectively. However, the changes of marshalling forms have obvious influence on the lateral force of each carriage. The maximum difference of the lateral force of the box car, gondola car and tank car is 17%, 20.1% and 24.1% respectively. The essential reason why the marshalling forms has a significant impact on the aerodynamic performance of the freight train is that there are obvious differences in the volume and shape struc-ture of each railway carriage. The large volume of box cars and the cavity structure of gondola cars make their position a key factor affecting the aerodynamic performance of freight trains. Among the six different marshalling forms selected in this paper, the best marshalling form is: locomotive--gondola car--box car--tank car. Both the aerodynamic drag of the train and the lateral force of the boxcar are the smallest by taking this marshalling form.

scholarly journals Investigation of wheelhouse shapes on the aerodynamic characteristics of a generic car model

2021 ◽  
Vol 13 (12) ◽  
pp. 168781402110668
Author(s):  
Haichao Zhou ◽  
Qingyun Chen ◽  
Runzhi Qin ◽  
Lingxin Zhang ◽  
Huiyun Li
Keyword(s):  
Aerodynamic Drag ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Aerodynamic Performance ◽  
Vehicle Speed ◽  
Cavity Volume ◽  
Detached Eddy Simulation ◽  
Slant Angle ◽  
Drag Coefficients ◽  
Ahmed Body

As vehicle speed increases, the aerodynamic drag reduction becomes increasingly significant. The aim of this paper is to find out the effects of the wheelhouse shapes on the aerodynamics of an Ahmed body with a 35 slant angle. In this paper, based on the detached-eddy simulation method, the effects of the three classic different wheelhouse on the aerodynamic performance and near wake of the Ahmed body are presented. The mesh resolution and methodology are validated against the published test results. The results show that the front wheelhouse has a significant impact on the aerodynamic performance of the Ahmed body, leading to different aerodynamic drag forces and flow fields. Enlarging the wheelhouse cavity volume could result in a gradual increase in aerodynamic drag coefficients, the ratio of the wheelhouse cavity volume increased by 2.9% and 9.8%, the drag coefficients increased by 2.5% and 4.5% respectively. The increase in aerodynamic drag was primarily caused by flow separation in the large cavity volume wheelhouse.

Numerical simulation of the effects of obstacle deflectors on the aerodynamic performance of stationary high-speed trains at two yaw angles

2017 ◽  
Vol 232 (3) ◽  
pp. 913-927 ◽  
Author(s):  
Ji-qiang Niu ◽  
Dan Zhou ◽  
Xi-feng Liang
Keyword(s):  
High Speed ◽  
Simulation Method ◽  
Aerodynamic Performance ◽  
Wake Flow ◽  
Detached Eddy Simulation ◽  
Aerodynamic Forces ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
High Speed Trains ◽  
Yaw Angle

In this study, based on the shear-stress transport κ–ω turbulent model, the improved delayed detached eddy simulation method has been used to simulate the unsteady aerodynamic performance of trains with different obstacle deflectors at two yaw angles (0° and 15°). The numerical algorithm is used and some of the numerical results are verified through wind tunnel tests. By comparing and analysing the obtained results, the effects of the obstacle deflectors on the force of the trains as well as the pressure and flow structure around the trains are elucidated. The results show that the obstacle deflectors primarily affect the flow field at the bottom of the head car as well as the wake flow, and that the internal oblique-type obstacle deflector (IOOD) markedly improves the aerodynamic performance of the trains, by decreasing most of the aerodynamic forces of the train cars and minimising their fluctuations. Further, a nonzero yaw angle weakens or even changes the effect of the IOOD on the aerodynamic forces of the train cars. However, the effect of the IOOD is more on the tail car.

Detached-eddy simulation of the slipstream of an operational freight train

2014 ◽  
Vol 132 ◽  
pp. 1-12 ◽  
Author(s):  
Dominic Flynn ◽  
Hassan Hemida ◽  
David Soper ◽  
Chris Baker
Keyword(s):  
Detached Eddy Simulation ◽  
Freight Train ◽  
Eddy Simulation

Detached Eddy Simulation for Model Hydro Turbine

2006 ◽  
Author(s):  
Xiaojing Wu ◽  
Shuhong Liu ◽  
Yulin Wu
Keyword(s):  
Vortex Motion ◽  
Internal Flow ◽  
Simulation Method ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Hydro Turbine ◽  
Eddy Simulation ◽  
Mesh Density ◽  
Flow Vortex

In this paper, detached eddy simulation method is applied to the numerical simulation for whole passage of a model hydro turbine. The method combines the strong points of Reynolds-averaged Navier-Stokes and Large eddy simulation. In this model, Spalart–Allmaras turbulent model is improved, which reduces to a RANS formulation near a solid surface and to a subgrid model away from the wall. The hexahedron type mesh is used to divide the model, which can decrease the mesh scale and computation cost. In this paper, a unsteady turbulent simulation is done for model hydro turbine with this viscous model. The internal flow, vortex motion and pressure fluctuation inside hydro turbine can be studied from the result, which are also compared with the experiment data. It can be seen that this method can describe the complex flow of the turbine well while the mesh density is not very high.

scholarly journals Hybrid Numerical Simulation of Jet Blast Distance of a Departing Aircraft

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xin He ◽  
Yaqing Chen ◽  
Yilong Ma ◽  
Dengfeng Hu ◽  
Haoran Gao
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Turbulence Model ◽  
Internal Flow ◽  
Aircraft Engine ◽  
Simulation Method ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Numerical Simulation Method

A hybrid numerical simulation method was established by combining the Spalart-Allmaras (SA) turbulence model and detached eddy simulation (DES). Numerical simulations were carried out to model cold and hot spray conditions of a nozzle without considering the internal flow of an engine to determine jet conditions. Analysis results show that the calculated hot spray results more in line with the reality. The jet effect of a typical aircraft engine was simulated numerically to determine the distance influenced by the jet blast from a departing aircraft engine.

scholarly journals Wind turbines in atmospheric flow – FSI simulations with hybrid LES-IDDES turbulence modelling

2020 ◽  
Author(s):  
Christian Grinderslev ◽  
Niels Nørmark Sørensen ◽  
Sergio González Horcas ◽  
Niels Troldborg ◽  
Frederik Zahle
Keyword(s):  
Turbulence Model ◽  
Wind Turbines ◽  
Separated Flow ◽  
Simulation Method ◽  
Turbine Rotor ◽  
Detached Eddy Simulation ◽  
Atmospheric Flow ◽  
Eddy Simulation ◽  
Significant Difference ◽  
The Impact

Abstract. In order to design future large wind turbines, knowledge is needed about the impact of aero-elasticity on the rotor loads and performance, and about the physics of the atmospheric flow surrounding the turbines. The objective of the present work is to study both effects by means of high fidelity rotor-resolved numerical simulations. In particular, unsteady computational fluid dynamics (CFD) simulations of a 2.3 MW wind turbine rotor are conducted, this rotor being the largest design with relevant experimental data available to the authors. Turbulence is modeled with two different approaches. On one hand, the well established improved delayed detached eddy simulation (IDDES) model is employed. An additional set of simulations relies on a novel hybrid turbulence model, developed within the framework of the present work. It consists on the blending of a large eddy simulation (LES) model for atmospheric flow by Deardorff with an IDDES model for the separated flow near the rotor geometry. In the same way, the assessment of the influence of the blade flexibility is performed by comparing two different sets of computations. A first group accounts for a structural multi body dynamic (MBD) model of the blades. The MBD solver was coupled to the CFD solver during run time with a staggered fluid structure interaction (FSI) scheme. The second set of simulations uses the original rotor geometry, without accounting for any structural deflection. The results of the present work show no significant difference between the IDDES and the hybrid turbulence model. However, it is expected that future simulations of more complex stratification and longer domains will benefit from the developed hybrid model. In a similar manner, and due to the fact that the considered rotor was relatively stiff, the loading variation introduced by the blade flexibility was found to be negligible when compared to the influence of inflow turbulence. The simulation method validated here is considered highly relevant for future turbine designs, where the impact of blade elasticity will be significant and the detailed structure of the atmospheric inflow will be important.

Analysis of the pump-turbine S characteristics using the detached eddy simulation method

2014 ◽  
Vol 28 (1) ◽  
pp. 115-122 ◽  
Author(s):  
Hui Sun ◽  
Ruofu Xiao ◽  
Fujun Wang ◽  
Yexiang Xiao ◽  
Weichao Liu
Keyword(s):  
Simulation Method ◽  
Detached Eddy Simulation ◽  
Pump Turbine ◽  
Eddy Simulation

Investigation of effects of tire contour on aerodynamic characteristics and its optimization

2021 ◽  
pp. 095440702110586
Author(s):  
Lingxin Zhang ◽  
Haichao Zhou ◽  
Guolin Wang ◽  
Huiyun Li ◽  
Qingyang Wang
Keyword(s):  
Aerodynamic Drag ◽  
Great Influence ◽  
Wind Tunnel Test ◽  
Aerodynamic Characteristics ◽  
Design Parameters ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Design Variables ◽  
Aerodynamic Drag Coefficient ◽  
Contour Design

Reducing the aerodynamic drag is one of the most important approaches for the development of energy-saving and environment-friendly automobiles. The tire contour has a great influence on the aerodynamic characteristics of automobiles. The aim of this study is to investigate the influence of the tire contour design parameters on the aerodynamic characteristics around a closed wheel, and obtain the optimized tire contour to reduce the automobile aerodynamic drag. A passenger car tire 185/65R14 was selected to conduct the wind tunnel test, and the surface pressure coefficients were used to validate the simulation model established using the detached eddy simulation (DES) model. To decrease tire drag, and taking the upper sidewall height, the tread radii, the tread width, and the transition arc radius of the shoulder as four design variables of contour, a combination of the Latin hypercube experimental design, the Kriging surrogate model, and the adaptive simulated annealing (ASA) algorithm were used to optimize the tire contour design parameters. The changes of flow field around the tire, including the velocity, turbulent kinetic energy, and pressure field were compared and analyzed for further understanding of the drag reduction mechanism. It is found that the aerodynamic drag coefficient of the optimized tire is reduced by 14.5%, and the aerodynamic coefficient drag of the car using the optimized tire is reduced by 7%. The present results are expected to provide useful information for designing new tire structures and improving the aerodynamic performance of the automobile.

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