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Y. Wang^1,2, Z. Sun¹, S. Ju¹, D. Guo¹, B. Yin¹ and G. Yang¹

¹Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China
²School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China

doi:10.4203/ccc.7.3.13

Y. Wang, Z. Sun, S. Ju, D. Guo, B. Yin, G. Yang, "Large Eddy Simulation of Micro-Riblet Performance Under Upstream Flow Separation", in J. Pombo, (Editor), "Proceedings of the Sixth International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Edinburgh, UK, Online volume: CCC 7, Paper 3.13, 2024, doi:10.4203/ccc.7.3.13

Keywords: high speed train, flow control, aerodynamic drag, turbulent boundary layer, micro structures, computational fluid dynamics.

Abstract

Micro-riblets are effective for reducing drag in turbulent layers. Flow separation is a prevalent flow phenomenon in transport. However, the precise drag reduction performance of riblets downstream of a flow separation remains unclear. An inclined forward step model is proposed to investigate the interaction between riblet and upstream flow separation. The large eddy simulation method is applied to simulate the flow over geometries with different step angles and riblet positions. The results show that the riblet downstream of a flow separation still reduce drag and have two characteristics, with two distinct behaviours. Firstly, drag reduction rises with separation intensity, a step angle increase from 0 to 30 degree boosts drag reduction from 9.5% to 12.6%. This is due to intensified Q2 motions enhancing riblet effects. Secondly, the position of the riblets has a significant impact on the pressure drag. Riblets close to the point of separation enhance flow separation, altering the surface pressure distribution and thus increasing the resistance. The precise performance of riblets under complex flow conditions is are important for their practical engineering application on the train.

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Front Page Browse CCC CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Conferences ISSN 2753-3239 CCC: 7 PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON RAILWAY TECHNOLOGY: RESEARCH, DEVELOPMENT AND MAINTENANCE Edited by: J. Pombo Paper 3.13 Large Eddy Simulation of Micro-Riblet Performance Under Upstream Flow Separation Y. Wang^1,2, Z. Sun¹, S. Ju¹, D. Guo¹, B. Yin¹ and G. Yang¹ ¹Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Institute of Mechanics, Chinese Academy of Sciences, Beijing, China ²School of Engineering Science, University of Chinese Academy of Sciences, Beijing, China doi:10.4203/ccc.7.3.13 Full Bibliographic Reference for this paper Y. Wang, Z. Sun, S. Ju, D. Guo, B. Yin, G. Yang, "Large Eddy Simulation of Micro-Riblet Performance Under Upstream Flow Separation", in J. Pombo, (Editor), "Proceedings of the Sixth International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Edinburgh, UK, Online volume: CCC 7, Paper 3.13, 2024, doi:10.4203/ccc.7.3.13 Keywords: high speed train, flow control, aerodynamic drag, turbulent boundary layer, micro structures, computational fluid dynamics. Abstract Micro-riblets are effective for reducing drag in turbulent layers. Flow separation is a prevalent flow phenomenon in transport. However, the precise drag reduction performance of riblets downstream of a flow separation remains unclear. An inclined forward step model is proposed to investigate the interaction between riblet and upstream flow separation. The large eddy simulation method is applied to simulate the flow over geometries with different step angles and riblet positions. The results show that the riblet downstream of a flow separation still reduce drag and have two characteristics, with two distinct behaviours. Firstly, drag reduction rises with separation intensity, a step angle increase from 0 to 30 degree boosts drag reduction from 9.5% to 12.6%. This is due to intensified Q2 motions enhancing riblet effects. Secondly, the position of the riblets has a significant impact on the pressure drag. Riblets close to the point of separation enhance flow separation, altering the surface pressure distribution and thus increasing the resistance. The precise performance of riblets under complex flow conditions is are important for their practical engineering application on the train. download the full-text of this paper (PDF, 18 pages, 1168 Kb) go to the previous paper go to the next paper return to the table of contents return to the volume description
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