著者

長谷川 雄太 青木 尊之 小林 宏充 白﨑 啓太

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.85, no.870, pp.18-00441, 2019 (Released:2019-02-25)

参考文献数

18

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We implement and perform large-scale LES analysis for running groups of cyclists. The mesh-refined lattice Boltzmann method (LBM) and coherent-structure Smagorinsky model (CSM) are adopted for the simulations to achieve a high performance computing on the recent GPU supercomputer. In the simulation with 16 cyclists, the mesh spacing around cyclists is 4 mm, and the total number of the mesh is up to 8.1×108 and the number of GPUs utilized is up to 64. Each calculation took 4 or 5 days for the 8~11 seconds of physical duration. The flow around 16 cyclists in various arrangement is calculated, and the results show that the in-line arrangement is more effective than the rhomboid arrangement in the viewpoint of the total aerodynamic drag of the group; however, a specific person in rhomboid arrangement can obtain larger drag reduction and save the endurance. Results on two groups also suggest that the frontal group in rhomboid arrangement will be exploited as the wind protection of the backward groups.

著者

長谷川 雄太 青木 尊之 小林 宏充 白﨑 啓太

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

pp.18-00441, (Released:2019-02-07)

参考文献数

18

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We implement and perform large-scale LES analysis for running groups of cyclists. The mesh-refined lattice Boltzmann method (LBM) and coherent-structure Smagorinsky model (CSM) are adopted for the simulations to achieve a high performance computing on the recent GPU supercomputer. In the simulation with 16 cyclists, the mesh spacing around cyclists is 4 mm, and the total number of the mesh is up to 8.1×108 and the number of GPUs utilized is up to 64. Each calculation took 4 or 5 days for the 8~11 seconds of physical duration. The flow around 16 cyclists in various arrangement is calculated, and the results show that the in-line arrangement is more effective than the rhomboid arrangement in the viewpoint of the total aerodynamic drag of the group; however, a specific person in rhomboid arrangement can obtain larger drag reduction and save the endurance. Results on two groups also suggest that the frontal group in rhomboid arrangement will be exploited as the wind protection of the backward groups.

著者

白﨑 啓太 山辺 芳 明石 啓太 高嶋 渉

出版者

一般社団法人 日本体育・スポーツ・健康学会

雑誌

体育学研究 (ISSN:04846710)

巻号頁・発行日

vol.64, no.2, pp.637-645, 2019-12-16 (Released:2019-12-20)

参考文献数

15

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In when riding in a group during cycling competitions, cyclists may become located side-by-side during positioning, rotation, and overtaking. The primary objective of this study was to analyze aerodynamic variation with differences in the number of riders (1 and 3) while cycling in parallel. It was assumed that the last cyclist would be riding in parallel with the immediate leading cyclist in the group. Wind tunnel experiments were implemented using a static mannequin and athletes as participants. A floor-mounted 6-component force balance was employed for conducting the measurements, and the athlete sat on a bicycle mounted on a bicycle stand. Experiments were subsequently conducted on groups comprising 2 riders (2R) and 4 riders (4R). The aerodynamic drag of the last rider (i.e., the mannequin) was measured for a wind speed of 16.67 m/s and for various relative spatial positions with respect to the front end of the immediate leading rider’s front wheel as the origin (longitudinal distance X = -1.38 m–0.07 m, lateral distance Y = 0.25 m–0.90 m; X = -1.38 m was applied solely when Y = 0.90 m for the case of 2R). The results indicated that at Y = 0.75 m–0.90 m, the drag of the last rider for both the 2R and 4R cases was equal to or higher than that for the single state. At Y = 0.50 m, the drag in the 2R case was equal to or higher than that for the single state (maximum value, 108.5% of the single state), whereas the drag in the 4R case was less (87.8–95.1%). It was also found that when a parallel cyclist approached a riding group comprising 3 or more cyclists, it was possible to decrease the drag to a value less than for the single state by riding in a position strictly adjacent to the riding group.