Based on the immersed boundary-multiple relaxation-lattice Boltzmann method, a numerical simulation of the flow around three cylinders in equilateral triangle arrangement was conducted at Re=100, the influence of two key parameters, the spacing ratio (Kd) and incoming flow angle (α), on fluid force coefficient and flow field characteristics was analyzed, and several flow mechanisms were revealed. The calculation results show that the wake pattern in different flow fields is divided into single vortex, single vortex to double vortex, irregular double vortex, regular double vortex, double vortex to triple vortex, irregular triple vortex and regular triple vortex pattern, and that the downstream vortex street is more regular and the wake pattern changes faster at α=30°. The time-averaged fluid force coefficient of three cylinders is greatly affected by the gap flow velocity, and the changing trend with the spacing ratio (except for the small spacing ratio) at each incoming flow angle is nearly identical. The transition of the wake pattern will change the root mean square value of three cylinders’ fluid force coefficient significantly. When Kd≥3.5, the root mean square value of upstream cylinder’s fluid force coefficient fluctuates greatly. Except for α=0°, the vortex shedding frequency of the midstream cylinder is less affected by α and Kd when Kd≥2.5, which is relatively stable.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |