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RISS 인기검색어
- 검색키워드
- 저자 : Haili Zhou (검색결과 3 건)
- 무료
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Li, Zhiguo,Zhou, Qiang,Liao, Haili,Ma, Cunming Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.26 No.5
A numerical study based on a delayed detached eddy simulation (DDES) is conducted to investigate the aerodynamic mechanism behind the suppression of vortex-induced vibrations (VIVs) of twin box girders by central grids, which have an inhibition effect on VIVs, as evidenced by the results of section model wind tunnel tests. The mean aerodynamic force coefficients with different attack angles are compared with experimental results to validate the numerical method. Next, the flow structures around the deck and the aerodynamic forces on the deck are analyzed to enhance the understanding of the occurrence of VIVs and the suppression of VIVs by the application of central grids. The results show that shear layers are separated from the upper railings and lower overhaul track of the upstream girder and induce large-scale vortices in the gap that cause periodical lift forces of large amplitude acting on the downstream girder, resulting in VIVs of the bridge deck. However, the VIVs are apparently suppressed by the central grids because the vortices in the central gap are reduced into smaller vortices and become weaker, causing slightly fluctuating lift forces on the deck. In addition, the mean lift force on the deck is mainly caused by the upstream girder, whereas the fluctuating lift force is mainly caused by the downstream girder.
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Numerical study of wake and aerodynamic forces on a twin-box bridge deck with different gap ratios
Jingmiao Shang,Qiang Zhou,Haili Liao,Allan Larsen,Jin Wang,Mingshui Li 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.4
Two-dimensional Delayed Detached Eddy Simulation (DDES) was carried out to investigate the uniform flow over a twin-box bridge deck (TBBD) with various gap ratios of L/C=5.1%, 12.8%, 25.6%, 38.5%, 73.3% and 108.2% (L: the gap-width between two girders, C: the chord length of a single girder) at Reynolds number, Re=4×104. The aerodynamic coefficients of the prototype deck with gap ratio of 73.3% obtained from the present simulation were compared with the previous experimental and numerical data for different attack angles to validate the present numerical method. Particular attention is devoted to the fluctuating pressure distribution and forces, shear layer reattachment position, wake velocity and flow pattern in order to understand the effects of gap ratio on dynamic flow interaction with the twin-box bridge deck. The flow structure is sensitive to the gap, thus a change in L/C thus leads to single-side shedding regime at L/C≤25.6%, and co-shedding regime at L/C≥35.8% distinguished by drastic changes in flow structure and vortex shedding. The gap-ratio-dependent Strouhal number gradually increases from 0.12 to 0.27, though the domain frequencies of vortices shedding from two girders are identical. The mean and fluctuating pressure distributions is significantly influenced by the flow pattern, and thus the fluctuating lift force on two girders increases or decreases with increasing of L/C in the single-side shedding and co-shedding regime, respectively. In addition, the flow mechanisms for the variation in aerodynamic performance with respect to gap ratios are discussed in detail.
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Jiangang Liu,Zhipeng Tong,Gao-Hong Yu,Xiong Zhao,Haili Zhou 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5
Non-circular gears with small curvature radius pitch curve are often used in the mechanical transmission of special motion path, but this kind of non-circular gear produces serious undercutting. Therefore, this research presented a kind of variable-involute and variable-cycloid composite tooth profile (VIVC-CTF). A transmission ratio curve of non-circular gear was designed by using Fourier function. The tooth profile equation of VIVC-CTF and its conjugate tooth profile equation were constructed on the basis of the normal and envelope methods. The influence of slip coefficient and ellipse eccentricity on the VIVC-CTF was investigated, and the variation of slip coefficient and eccentricity on the meshing line length, theoretical contact ratio, and pressure angle at pitch curve was analyzed. The meshing experiment of the VIVCCTF non-circular gear transmission mechanism was carried out on the basis of high-speed camera technology. The theoretical results of the transmission ratio were consistent with the experimental results.
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