An Experimental Investigation On Morphology, Electromyography, Constitutive Relationship Of Crucian Carp For "Digital Fish"

Experimental researches on the biomechanics related to fish swimming are significant and meaningful for both scientific exploration and technical innovation. Recent advances in the diversity, precision and systematization of experimental methods and techniques lead to a general trend in quantitative researches and integrated studies on fish locomotion. Based on the control framework of "Neural Control-Active Contraction of Muscle-Passive Deformation", the morphology, electromyography (EMG), as well as the mechanical properties and constitutive relationship of the skin, muscle, and the body trunk of crucian carp are investigated with experiments, from which a simplified model of "digital fish" is established. The following work has been done in this dissertation.1. The distribution of geometric parameters and weight parameters for a single sample and multiple samples of crucian carp are studied with experiments. The linear relationship between variables, such as head length, total length, body height, et al, and standard length is acquired by the two dimensional records of different crucian carps. By use of shadow Moire method and the three-dimensional coordinate machine, the geometric parameters which characterize the 3D morphology of crucian carp are measured by comparing the experimental results. The distribution of weight parameters of crucian carp is obtained by applying slicing methods. The corresponding power function relationship between standard length and weight is clarified by statistics on different crucian carp samples.2. The electromyography(EMG) experimental technology is introduced to study the muscle activity of crucian carp during swimming, and the related operation procedures are elucidated in details. The EMG signals from red-muscle of crucian carp, which is evolving in the C-start movement, are acquired with a self-designing amplifier, after calibrated and tested by a male ECG experiment. A conclusion is drawn that there is nearly a simultaneous red muscle activity on the ipsilateral side of fish body with nearly a same duration, and the maximal amplitude of EMG locates in the anterior part of the body. Based on the electromyographic results from other fish species during steady swimming, the corresponding conclusions for crucian carp during steady swimming are inferred. Modes of the neural-control during a quick start movement, that Mauthner cell triggers motor neurons synchronously and then motivates muscle synchronous contraction, are evaluated by analyzing the activity patterns of EMG signals. Possible benefits of more muscle tension may be gained considering the special structural characteristic of the intersection between crucian carp's muscle contracting direction and cephalocaudal axis.3. Young's modulus, the reduced relaxation function and the reduced creep function of crucian carp's skin and muscle are determined by failure tests, relaxation tests and creep tests with uniaxial tensile ways, respectively. Viscoelastic models are adopted to deduce the constitutive relationship, and body effective stiffness may be increased with a little energy dissipation according to the viscoelastic nature. The mechanical properties and angular stiffness of different sites on cucian carp's body are obtained from dynamic bending experiments, where a self-designing dynamic bending test machine is employed, and a conclusion is drawn that maximal angular stiffness locates in the anterior part of the body. The conclusion of regarding the body trunk of cucian carp under dynamic bending deformation as an approximate elastomer is also confirmed.4. Based on the above experimental results of the geometric parameters, the activity patterns of muscle, the constitutive relationship of skin and muscle, and the results from dynamic bending tests, generic experimental data are obtained by normalization, and a preliminary "digital fish" model is established. Conclusions are drawn such that the horizontal transection is the overlook configuration of fish, and it is enveloped between NACA0014 and NACA0020 airfoil, and so on. Its applications are attempted on both the fish-body construction model establishment and the 2-D fish shape model related to its fluid dynamic characteristics, which reflects the necessity and significance of "digital fish" studying.