| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學系暨研究所 === 91 === Abstract
Ecological engineering should be designed by the view of living organisms, especially for the freshwater snails which are at the basic layer of the food chains, and they are sensitive to the environment. This paper discusses the response and the adapt ability of the freshwater snails by different water velocity in view of bio-fluid mechanism, to provide some data for ecological engineering design.
This study focus on three species of freshwater snail which are not rare in nature (Sinotaia quadratus, Semisulcospira libertine, Tarebia granifera). As a result, we found that each species is different with regard to the shell shape and behaviors for adapting fluid dynamics. Consequently, we can explain why they have different distributions with different water velocity. The lift coefficient and drag coefficient of the snails in different water velocity can be obtained by experiment. When Reynolds number is 500, the respective drag coefficient of three species is 15.97, 14.76, 10.56; and the respective lift coefficient is 19.26, 17.57, 18.23. When Reynolds number is 5000, the respective drag coefficient of three species is 1.79, 1.30, 0.91; and the respective lift coefficient is 0.91, 0.46, 0.39. Therefore, the lower the ratio of shell length to shell width and the ratio of shell eccentric distance to shell height, or the higher the ratio of the diameter of shell cavity to shell height, which means the shell shape is nearly streamlining and the lower lift coefficient and drag coefficient will be.
By the flume experiment, we found that the maximum velocity that fifty percent are not to be dislodged is 76cm/sec, 105 cm/sec, 165 cm/sec respectively for Tarebia granifera, Sinotaia quadratus, Semisulcospira libertine. Various water velocity and channel section should be maintained in engineering designing, to provide multiple habitat for different aquatics species.
Key words：freshwater snails, bio-fluid mechanism, ecological engineering
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