LES study of the influence of the nose shape and yaw angles on flow structures around trains

Hemida, Hassan; Krajnović, Siniša

doi:10.1016/j.jweia.2009.08.012

Cited by 169 publications

(99 citation statements)

References 15 publications

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“…At t = 33.8t C , a quasi-steady situation seems to be reached in our simulations. This observation is in agreement with [8], where it was found by LES that unsteadiness of the vortex system should not be expected below a distance of five train heights in the direction of train length, measured from the train nose.…”

Section: Unsteady Flow Simulationssupporting

confidence: 92%

“…From the URANS simulations it is verified that the vortex system on the leeward side of the train attains a steady-state after about 50 convective timescales, which was already argued by previous authors [8] and gives some justification for using RANS based methods in the first place. Once a steady state is achieved, there is virtually no major difference in terms of force coefficients between the incompressible URANS and RANS computations.…”

Section: Discussionsupporting

confidence: 73%

“…While the lower vortex is quickly destroyed by interaction with the front bogie sections, the upper vortex stays somewhat attached to the vehicle at the roof/leeward side interface for about 3-4 characteristic length scales, cf. Hemida & Krajnovic [8]. Since the front car has a length of ≤ 5H, the stationarity of this vortex system justifies to some extend the use of the RANS methodology in predicting force coefficients on the front car.…”

Section: Steady Flow Simulationsmentioning

confidence: 99%

“…Numerical studies with RANS based models have been reported by Diedrichs [6] and Khier et al [7]. Hemida & Krajnovic [8,9] used the large eddy simulation (LES) approach to study the influence of varying yaw angle and nose shape on flow structures around a simplified train model without inter-cap gaps and wheel bogies. Similar to the flow over a cylinder, they found that vortex shedding is induced by the shear layer instability at the periphery of the re-circulation region.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Comparison of Industrial and Scientific CFD Approaches for predicting Cross Wind Stability of the NGT2 Model Train Geometry

Fragner¹,

Weinman²,

Deiterding³

et al. 2015

Int J Railw Tech

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Safety assessments of cross-wind influence on high-speed train operation require a detailed investigation of the aerodynamic forces acting on a vehicle. European norm 14067-6 permits the derivation of required integral force and moment coefficients by experiments as well as by numerical simulation. Utilizing the DLR's Next Generation Train 2 model geometry, we have performed a case study comparing simulations with varying turbulence modeling assumptions. Because of its relevance for actual design, a focus lies on steady RANS computations, but more expensive unsteady RANS (URANS) and delayed detached eddy simulations (DDES) have also been carried out for comparison. Validation data for the exact same model configuration and moderate Reynolds numbers 250,000 and 450,000 is provided by side wind tunnel experiments. Particular emphasis is laid on simulating a yaw angle of 30• , for which a major vortex system on the leeward side of the train leads to sizeable uncertainties in predicted integral coefficients. At small to intermediate wind angles the flow remains attached and absolute errors in integral quantities decline with decreasing yaw angles. However, a consistent relative difference to the experimental results greater than 10% raises doubts about the general reliability of CFD methods, that are not capable of capturing laminar-turbulent transition, which is observed for scaled models in industry type wind tunnel experiments.1

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Section: Unsteady Flow Simulationssupporting

confidence: 92%

Section: Discussionsupporting

confidence: 73%

Section: Steady Flow Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Comparison of Industrial and Scientific CFD Approaches for predicting Cross Wind Stability of the NGT2 Model Train Geometry

Fragner¹,

Weinman²,

Deiterding³

et al. 2015

Int J Railw Tech

View full text Add to dashboard Cite

show abstract

“…In this paper, a kind of A-type vehicle model of 6-car marshalling is adopted .The paper simplifications the shape of the metro train [12] , ignoring the influence of the bogie and the pantograph [11] . Fig.2 shows the model of the A-type train of 6-car marshalling.…”

Section: Models and Arrangement Of Measureing Pointsmentioning

confidence: 99%

Study of the Change of the Shaft Shape on the Influence to Aerodynamics Effect of the High-Speed Metro Tunnel

Ran¹,

Xiong²

2017

dtetr

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When a metro train passes through the shaft, it will lead to severe pressure fluctuations on surfaces of tunnel and train due to the sudden change of tunnel cross section. Based on the three-dimensional, compressible and unsteady N-S equation method, this paper simulates aerodynamic problems caused by trains when they pass through the airshafts at the speed of 140 km/h by the means of constructing four middle shaft models, one is the real shaft, the other three are the simplifications. Time delays generated on trains' surfaces after trains pass through shafts in the three simplifications' model, but on tunnels' surfaces from entering portals for the different corridor sizes. The tendency of max pressure, min pressure and pressure amplitude at trains' and tunnels' surfaces is consistent in four kinds of models. But the different area of shafts' corridor sizes cause the most used model gets the maximum pressure amplitude, the real model gets the minimum pressure amplitude, and the two simplifications' are the middle.

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A Hybridized Triboelectric‐Electromagnetic Nanogenerator as a Power Supply of Monitoring Sensors for the Ventilation System

Zheng

Zhou

et al. 2022

Advanced Energy Materials

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To ensure the regular operation of the machine, there are so many decentralized monitoring sensors and control equipment used. However, complicated wiring for their power supply and signal transmission makes the assembly and maintenance of the ventilation system significantly more complex. [4][5][6] Fortunately, a promising solution is using energy harvesting devices to convert wind energy from the ventilation system into electricity. [7][8][9][10][11] Current approaches are using conventional wind energy harvesters based on wind turbines with complex mechanical structures. [12,13] However, these designs are complicated and costly, which limits them to be used conveniently in the ventilation system. [14][15][16] Triboelectric nanogenerator (TENG), based on triboelectrification and electrostatic induction, has merits of simple structure, light weight, low cost, and diverse material selection. [17][18][19][20][21] A more important feature is that the TENG is a viable technology to harvest wind energy and an applicable solution for self-powered sensing systems. [22][23][24][25][26][27][28][29] Under the same mechanical input, the TENG and the conventional electromagnetic generator (EMG)With the improvement of the airtightness of modern buildings, installing ventilation systems indoors is becoming increasingly important, which works for a long time continuously and needs to be monitored in real-time. However, the complex wiring of monitoring sensors makes assembly and maintenance more difficult. This work reports a hybridized triboelectric-electromagnetic nanogenerator (HNG) as a power supply of a self-powered wireless monitoring system for ventilation systems. The HNG integrates an air inlet cover, a stator with coils and interdigitated copper electrodes, a rotor with magnets, fluorinated ethylene propylene films, and optimized built-in wind blades. The HNG scavenges wind energy from a ventilation system and serves as a power supply for electric applications. Under the wind speed of 6.5 m s −1 in the ventilation system, the maximum stabilized voltage and maximum instantaneous current of the HNG are 177.5 V and 0.049 A, which can charge smartphones and light up a bulb. Furthermore, the HNG realizes the self-powered wireless transmission of temperature and humidity sensing nodes. This work demonstrates an effective wind energy harvester, providing an innovative strategy for monitoring the condition of the ventilation system and broadening the thoughts of prospective energy harvesting.

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LES study of the influence of the nose shape and yaw angles on flow structures around trains

Cited by 169 publications

References 15 publications

Comparison of Industrial and Scientific CFD Approaches for predicting Cross Wind Stability of the NGT2 Model Train Geometry

Comparison of Industrial and Scientific CFD Approaches for predicting Cross Wind Stability of the NGT2 Model Train Geometry

Study of the Change of the Shaft Shape on the Influence to Aerodynamics Effect of the High-Speed Metro Tunnel

A Hybridized Triboelectric‐Electromagnetic Nanogenerator as a Power Supply of Monitoring Sensors for the Ventilation System

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