Large Eddy Simulations of Side Flow Past a Generic Model of a High-Speed Train

Three-dimensional Large Eddy Simulations (LES) with Smagorinsky subgrid scale model have been performed for the flow past two free-spanning marine pipelines in tandem placed in the vicinity of a plane wall at a very small gap ratio, namely G/D = 0.1, 0.3 and 0.5. The ratio of cylinder center-to-center distance to cylinder diameter, or pitch ratio, L/D, considered in the simulations is taken as L/D = 2 and 5. This work serves as an extension of Abrahamsen Prsic et al. (2015) [1]. In essence, six sets of simulations have been performed in the subcritical Reynolds number regime at Re = 1.31 × 104. Our major findings can be summarized as follows. (1) At both pitch ratios, the wall proximity has a decreasing effect on the mean drag coefficient of the upstream cylinder. At L/D = 2, the mean drag coefficient of the downstream cylinder is negative since it is located within the drag inversion separation distance. (2) At L/D = 2, a squarish cavity-like flow exists between the tandem cylinders and flow circulates within the cavity. A long lee-wake recirculation zone is found behind the downstream cylinder at G/D = 0.1. However, a much smaller lee-wake recirculation zone is noticed at L/D = 5 with G/D = 0.1. (3) At L/D = 2, the reattachment is biased to the bottom shear layer due towards the deflection from the plane wall, which leads to the formation of the slanted squarish cavity-like flow where the flow circulates between the tandem cylinders.

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Large-Eddy Simulations of the Flow past Bluff Bodies: State-of-the Art.

JSME International Journal Series B ◽

10.1299/jsmeb.41.361 ◽

1998 ◽

Vol 41 (2) ◽

pp. 361-374 ◽

Cited By ~ 17

Author(s):

Wolfgang RODI

Keyword(s):

State Of The Art ◽

Large Eddy Simulations ◽

Bluff Bodies ◽

Flow Past ◽

Large Eddy

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Large-Eddy Simulations and Measurements of a Small-Scale High-Speed Coflowing Jet

AIAA Journal ◽

10.2514/1.44534 ◽

2010 ◽

Vol 48 (5) ◽

pp. 963-974 ◽

Cited By ~ 22

Author(s):

Simon Eastwood ◽

Paul Tucker ◽

Hao Xia ◽

Paul Dunkley ◽

Peter Carpenter

Keyword(s):

High Speed ◽

Large Eddy Simulations ◽

Small Scale ◽

Large Eddy

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A Parametric Study of Turbulent Flow Past a Circular Cylinder Using Large Eddy Simulation

Journal of Fluids Engineering ◽

10.1115/1.4030380 ◽

2015 ◽

Vol 137 (9) ◽

Cited By ~ 16

Author(s):

W. Sidebottom ◽

A. Ooi ◽

D. Jones

Keyword(s):

Reynolds Number ◽

Finite Difference ◽

Circular Cylinder ◽

Stokes Equations ◽

Finite Difference Methods ◽

Large Eddy Simulations ◽

Near Wake ◽

Flow Past ◽

Large Eddy ◽

Difference Methods

Flow over a circular cylinder at a Reynolds number of 3900 is investigated using large eddy simulations (LES) to assess the affect of four numerical parameters on the resulting flow-field. These parameters are subgrid scale (SGS) turbulence models, wall models, discretization of the advective terms in the governing equations, and grid resolution. A finite volume method is employed to solve the incompressible Navier–Stokes equations (NSE) on a structured grid. Results are compared to the experiments of Ong and Wallace (1996, “The Velocity Field of the Turbulent Very Near Wake of a Circular Cylinder,” Exp. Fluids, 20(6), pp. 441–453) and Lourenco and Shih (1993, “Characteristics of the Plane Turbulent Near Wake of a Circular Cylinder: A Particle Image Velocimetry Study,” private communication (taken from Ref. [2]); and the numerical results of Beaudan and Moin (1994, “Numerical Experiments on the Flow Past a Circular Cylinder at Sub-Critical Reynolds Number,” Technical Report No. TF-62), Kravchenko and Moin (2000, “Numerical Studies of Flow Over a Circular Cylinder at ReD = 3900,” Phys. Fluids, 12(2), pp. 403–417), and Breuer (1998, “Numerical and Modelling Influences on Large Eddy Simulations for the Flow Past a Circular Cylinder,” Int. J. Heat Fluid Flow, 19(5), pp. 512–521). It is concluded that the effect of the SGS models is not significant; results with and without a wall model are inconsistent; nondissipative discretization schemes, such as central finite difference methods, are preferred over dissipative methods, such as upwind finite difference methods; and it is necessary to properly resolve the boundary layer in the vicinity of the cylinder in order to accurately model the complex flow phenomena in the cylinder wake. These conclusions are based on the analysis of bulk flow parameters and the distribution of mean and fluctuating quantities throughout the domain. In general, results show good agreement with the experimental and numerical data used for comparison.

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Large-eddy simulations of flow past a square cylinder using structured and unstructured grids

Computers & Fluids ◽

10.1016/j.compfluid.2016.07.013 ◽

2016 ◽

Vol 137 ◽

pp. 36-54 ◽

Cited By ~ 35

Author(s):

Yong Cao ◽

Tetsuro Tamura

Keyword(s):

Unstructured Grids ◽

Large Eddy Simulations ◽

Square Cylinder ◽

Flow Past ◽

Large Eddy

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Aerodynamic Noise Reduction Analysis in High-Speed Train Cab

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1049-1050.1022 ◽

2014 ◽

Vol 1049-1050 ◽

pp. 1022-1025

Author(s):

Xiao Feng Zhang ◽

You Gang Xiao ◽

Liang Sun ◽

Yu Shi

Keyword(s):

High Speed ◽

Power Flow ◽

Simulation Method ◽

Aerodynamic Noise ◽

High Speed Train ◽

Interior Decoration ◽

Eddy Simulation ◽

Head Surface ◽

Large Eddy ◽

Fluctuation Pressure

In order to reduce aerodynamic noise in high-speed train cab,the SEA model of cab is established. The fluctuation pressures from train head surface are calculated by large eddy simulation method. Using fluctuation pressure as excitation force, power flow caused by airflow among sub-systems of SEA model of cab is obtained. Two schemes are put forward to reduce the aerodynamic noise in cab, namely interior decoration modification and windowpane thickness increase. The results show that when a layer of splint with 0.01 m thickness, 0.5 loss factor is added to the original decoration in cab, the overall sound pressure level (SPL) at driver head location will reduce 1.23 dB(A). When the cab windowpane thickness is increased to 5 mm from 4 mm, the overall SPL at the driver head location will reduce 0.87 dB(A).

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Shape Optimization of High-Speed Train Pantograph Insulators for Low Aerodynamic Noise

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.249-250.646 ◽

2012 ◽

Vol 249-250 ◽

pp. 646-651

Author(s):

Xiao Yan Yang ◽

You Gang Xiao ◽

Yu Shi

Keyword(s):

Shape Optimization ◽

Sound Pressure Level ◽

High Speed ◽

Sound Pressure ◽

Pressure Level ◽

Aerodynamic Noise ◽

High Speed Train ◽

Eddy Simulation ◽

Large Eddy ◽

Elliptical Section

With large eddy simulation(LES) and Lighthill-Curle acoustic theory, the aerodynamic noises radiated from pantograph insulators with rectangular, circular, elliptical section were calculated, and the optimal pantograph insulator shape was obtained. The results show that in the same model, the sound pressure level (SPL) spectrum at different monitoring points are basically the same, but the amplitude is different. In different models, the SPL spectrum are different. As for rectangular, circular, elliptical section insulators, the frequency with maximum SPL reduces gradually. For reducing aerodynamic noise, the elliptical section insulator is optimal, and the long elliptical axis should be consistent with air flow. The pantograph with bigger and less components is helpful to reduce the aerodynamic noise.

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