Computational Technology Resources - CCP

Keywords: embankment scenario, wind tunnel tests, cross wind, railway vehicles, force aerodynamic coefficients, computational fluid dynamics calculation.

Summary

The embankment is a typical scenario for railway infrastructures but its modelling within wind tunnel tests presents some drawbacks and open points.

the model scale is penalised as a result of the need to satisfy the requirement that the blockage ratio should be lower than 15% (TSI HS RST) with a consequent reduction of the Reynolds number;
the flow around the embankment, simulated in a wind tunnel, is significantly influenced by unrealistic finite length of the design model and by the finite boundary conditions of the simulated wind flow associated with the intrinsic limited characteristics of the wind tunnel.

This paper deals with the analysis of the effects of the boundary conditions in the evaluation of the aerodynamic coefficients of railway vehicles with the embankment design through wind tunnel tests on a scale model. Using a preliminary analysis based on computational fluid dynamics (CFD) simulation, the distance has been found for which the flow, at the top of the embankment, arising from the nose, is undisturbed. Starting from the CFD study, different finite length embankment configurations have been tested using wind tunnel tests on a scale model and a comparison with the standard wall-to-wall configuration was carried out in terms of the force aerodynamic coefficients.

Tests have been performed on a 1:45 scaled model of the ETR500 train with the 6m-high embankment described in the TSI standard, with wind speeds ranging between 10-55 m/s (Re_max=2.5x10⁵). In particular, two boundary conditions have been simulated: a finite length embankment, equipped by end-noses characterised by different slopes, and a "pseudo-infinite" embankment, reproduced by the extension wall-to-wall of the design. This configuration is considered as the reference one because it represents the most similar model to the real infinite length embankment condition. It has been found that the embankment configuration with the nose, positioned, according to the CFD results, at a distance of 5m from the train, can be considered as a good alternative to the wall-to-wall configuration.

The future goal of this work is to establish a CFD numerical model, validated by the experimental data obtained from these wind tunnel tests, that is able to simulate 1:1 scale real conditions, in order to establish the validity of wind tunnel tests on the embankment for the determination of aerodynamic coefficients.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £110 +P&P)

	Computational & Technology Resources an online resource for computational, engineering & technology publications
	not logged in - login
Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 98 PROCEEDINGS OF THE FIRST INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 154 An Investigation on the Effects of Embankment Design on Railway Vehicle Aerodynamic Coefficients F. Cheli, F. Galli, S. Giappino, P. Schito and G. Tomasini Department of Mechanical Engineering, Politecnico di Milano, Italy doi:10.4203/ccp.98.154 purchase the full-text of this paper Full Bibliographic Reference for this paper F. Cheli, F. Galli, S. Giappino, P. Schito, G. Tomasini, "An Investigation on the Effects of Embankment Design on Railway Vehicle Aerodynamic Coefficients", in J. Pombo, (Editor), "Proceedings of the First International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 154, 2012. doi:10.4203/ccp.98.154 Keywords: embankment scenario, wind tunnel tests, cross wind, railway vehicles, force aerodynamic coefficients, computational fluid dynamics calculation. Summary The embankment is a typical scenario for railway infrastructures but its modelling within wind tunnel tests presents some drawbacks and open points. the model scale is penalised as a result of the need to satisfy the requirement that the blockage ratio should be lower than 15% (TSI HS RST) with a consequent reduction of the Reynolds number; the flow around the embankment, simulated in a wind tunnel, is significantly influenced by unrealistic finite length of the design model and by the finite boundary conditions of the simulated wind flow associated with the intrinsic limited characteristics of the wind tunnel. This paper deals with the analysis of the effects of the boundary conditions in the evaluation of the aerodynamic coefficients of railway vehicles with the embankment design through wind tunnel tests on a scale model. Using a preliminary analysis based on computational fluid dynamics (CFD) simulation, the distance has been found for which the flow, at the top of the embankment, arising from the nose, is undisturbed. Starting from the CFD study, different finite length embankment configurations have been tested using wind tunnel tests on a scale model and a comparison with the standard wall-to-wall configuration was carried out in terms of the force aerodynamic coefficients. Tests have been performed on a 1:45 scaled model of the ETR500 train with the 6m-high embankment described in the TSI standard, with wind speeds ranging between 10-55 m/s (Re_max=2.5x10⁵). In particular, two boundary conditions have been simulated: a finite length embankment, equipped by end-noses characterised by different slopes, and a "pseudo-infinite" embankment, reproduced by the extension wall-to-wall of the design. This configuration is considered as the reference one because it represents the most similar model to the real infinite length embankment condition. It has been found that the embankment configuration with the nose, positioned, according to the CFD results, at a distance of 5m from the train, can be considered as a good alternative to the wall-to-wall configuration. The future goal of this work is to establish a CFD numerical model, validated by the experimental data obtained from these wind tunnel tests, that is able to simulate 1:1 scale real conditions, in order to establish the validity of wind tunnel tests on the embankment for the determination of aerodynamic coefficients. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £110 +P&P)
Back to top	©Civil-Comp Limited 2023 - terms & conditions