NUMERICAL CALCULATION OF PROPULSIVE CHARACTERISTIC OF FISH'S SWIMMING
Cheng Jianyu Zhuang Lixian Tong Binggang (Department of Modern Mechanics, University of Science and Technology of China)
Based on the unified three-dimensional waving plate model, an optimum motion theory is developed in this paper. The caudal fin propulsion of fish using carangiform mode is discussed, and the morphological adaptation of caudal fin is tentatively elucidated. When the caudal fin is evaluated with middle aspect ratio, the theoretical analysis shows that good tail shape should be similar to a triangle with adequately rearward or forward slanted trailing edge, and effective tail undulations should have their lateral amplitude increased mainly in the narrow necking region, immediately anterior to the caudal fin, to a large and approximately uniform value over the fin itself. This is confirmed by observations. Fish with good drag-reducing devices are also examined. The important morphological adaptation is that their caudal fins are developed to arrow-like shape, typical to the configuration of carangiform swimmers. Using observation data and theoresi-cal methods, the swimming performance of a trout is estimated, giving satisfactory results.