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The propulsion mechanism and swimming performance are of great significance to the construction of fish migratory channels. By using computational fluid dynamics method combined with overlapping mesh technology, the two-dimensional fish autonomous swimming was simulated by compiling the UDF program for controlling fish body swing, analyzing the evolution process and parameter changes of fish body pressure field distribution and inverse Carmen vortex street structure, carrying out the changes of fish swimming performance and fish body force under different parameters of tail swing frequency, tail swing amplitude, fish body shape and tail fin size, etc., and revealing the swimming mechanism of fish in the process of autonomous swimming. The results show that: (1) the fish body’s tail fin periodically swings back and forth under the formation of anti-Carmen vortex street, which is the main source of the fish body forward thrust, and with the increase of tail swing frequency and tail swing amplitude, the fish body tail vortex street length and vortex street strength gradually increase, while the effect of tail swing amplitude on the vortex street width is greater; (2) with the increase of swinging frequency and swinging amplitude, the horizontal mean coefficient of synergy and the maximum lateral force coefficient increase, which makes the fish obtain a larger swimming speed, but the increase of mean coefficient of synergy and swimming speed is more obvious when the swinging frequency has been changed, and the increase of maximum lateral force coefficient is more obvious when the swinging amplitude has changed; (3) with the increase of body width index, the horizontal average coefficient of force gradually decreases, and the swimming resistance to be overcome increases, which makes the swimming speed of fish gradually decrease, while the maximum lateral force coefficient gradually increases; (4)and with the increase of caudal fin index, both horizontal mean coefficient of force and maximum lateral force coefficient increase, which leads to the gradual increase of swimming speed of fish. The results of the study can provide a support for fish habitat restoration.
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| 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 |
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