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Keywords: train aerodynamics, cross-wind stability, drag prediction, computational fluid dynamics, experiments, vortex shedding, RANS.

Summary

Safety assessments of cross-wind influence on high-speed train operation requires 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. Utilising the DLR's Next Generation Train 2 model geometry, we have performed a case study using incompressible steady RANS simulations from the OpenFOAM fluid dynamics solver software. Validation data for the exact same model configuration and moderate Reynolds numbers 250,000 and 450,000 is provided by side wind tunnel experiments. Highly resolved cross verification computations with the compressible DLR TAU code confirm that yaw angles >= 30° create major vortex systems on the leeward side of the train leading to sizeable uncertainties in predicted integral coefficients. At low to intermediate wind angles the flow remains attached and absolute errors in integral quantities decline with decreasing yaw angles. A consistent relative difference to the experimental results greater than 10%, however, raises doubts about the suitability of the RANS approach for accurately assessing such configurations in general and indicates that such comparably inexpensive simulations, presently performed by routine in industry, will typically not be sufficient to satisfy the accuracy requirements of EN 14067-6.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 104 PROCEEDINGS OF THE SECOND INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 24 Numerical and Experimental Studies of Train Geometries Subject to Cross Winds M.M. Fragner¹, K.A. Weinman¹, R. Deiterding¹, U. Fey¹ and C. Wagner^1,2 ¹Department Fluid Systems, German Aerospace Center, Göttingen, Germany ²Institute of Thermodynamics and Fluid Mechanics, Ilmenau University of Technology, Ilmenau, Germany doi:10.4203/ccp.104.24 purchase the full-text of this paper Full Bibliographic Reference for this paper M.M. Fragner, K.A. Weinman, R. Deiterding, U. Fey, C. Wagner, "Numerical and Experimental Studies of Train Geometries Subject to Cross Winds", in J. Pombo, (Editor), "Proceedings of the Second International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 24, 2014. doi:10.4203/ccp.104.24 Keywords: train aerodynamics, cross-wind stability, drag prediction, computational fluid dynamics, experiments, vortex shedding, RANS. Summary Safety assessments of cross-wind influence on high-speed train operation requires 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. Utilising the DLR's Next Generation Train 2 model geometry, we have performed a case study using incompressible steady RANS simulations from the OpenFOAM fluid dynamics solver software. Validation data for the exact same model configuration and moderate Reynolds numbers 250,000 and 450,000 is provided by side wind tunnel experiments. Highly resolved cross verification computations with the compressible DLR TAU code confirm that yaw angles >= 30° create major vortex systems on the leeward side of the train leading to sizeable uncertainties in predicted integral coefficients. At low to intermediate wind angles the flow remains attached and absolute errors in integral quantities decline with decreasing yaw angles. A consistent relative difference to the experimental results greater than 10%, however, raises doubts about the suitability of the RANS approach for accurately assessing such configurations in general and indicates that such comparably inexpensive simulations, presently performed by routine in industry, will typically not be sufficient to satisfy the accuracy requirements of EN 14067-6. 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 £65 +P&P)
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