Study Of Swimming Speed Of Typical Fish In The Upper Yangtze River Based On Hydrodynamic Mechanism

The swimming ability or swimming speed of fish affects the design of engineering practice,while swimming ability is an important factor in evaluating the behavioral patterns of fish in various activities.Therefore,this paper focuses on the correlation between fish swimming speed and various fish movement parameters（i.e.tail swing frequency and tail swing amplitude）through a combination of analysis of the hydrodynamic mechanism of fish swimming,indoor flume test and Fluent numerical simulation,in order to have a systematic understanding of the interaction between them.The results of the study are as follows:（1）When the fish and the current are in relative motion and the flow pattern of the relative motion of the current is laminar,the relationship between the swimming Reynolds number Re,which is related to the swimming speed,and the swimming oscillation number Sw,which is related to the swinging tail frequency and swinging tail amplitude,is Re=k₁ Sw⁴3,k₁（29）0,also （?）;When the fish and the current are in relative motion and the flow pattern of the relative motion of the current is turbulent, （?）,also （?）.（2）The relationship between cyprinid body length and tail swing frequency is basically linear and decreases with the increase of cyprinid body length,with a negative linear correlation.The relationship between cyprinid body length and tail swing amplitude is basically linear and increases with the increase of cyprinid body length,with a positive linear correlation.The relationship between the induced flow velocity and body length of cyprinid is basically linear and increases with the increase of body length of cyprinid,which is positively and linearly correlated,and the fitted curve relationship is as follows:U_ind=1.56L-0.014.The critical swimming speed of cyprinid and body length are basically linear and with the increase of cyprinid body length,the critical swimming speed increases and is positively linearly correlated,and the fitted curve relationship equation is （?）.（3）For a certain body length range of cyprinid under laminar flow conditions,Re and Sw fitted curves are related by Re=0.01Sw^{1.3 2},The relationship between swimming speed and kinematic parameters is （?）.The relationship between the fitted curves of cyprinid Re and Sw for turbulent flow conditions is given by Re=0.47Sw^1.02.The relationship between swimming speed of cyprinid and movement parameters is （?）.The relationship between the fitted curves of Re and Sw for the tetrahymena under turbulence is given by Re=4.26Sw^{0.8 5}.The relationship between swimming speed and kinematic parameters is （?）.The fitted curve relationship between Re and Sw for typical fish in the upper Yangtze River under turbulent flow conditions is given byRe=2.44Sw^0.89.The relationship between swimming speed and kinematic parameters is （?）.（4）Based on the numerical simulation results,it can be seen that overall,the changes of kinematic physical quantities and mechanical coefficients in fish swimming motion are closely related to the tail swing frequency of fish,and the fast and slow tail swing frequency will affect the fluctuation frequency and wavelength of both,while the magnitude of both fluctuations may be related to the tail swing amplitude.