【作者】 杨焱；

【导师】 童秉纲； 余永亮；

【作者基本信息】 中国科学技术大学 ， 流体力学， 2008， 博士

【摘要】 鱼类在自然选择中形成了丰富多样、各具特色的游动本领,同时仿生机器学蓬勃兴起,迫切要求人们更深入地认识鱼类的机动运动机理。近年来,尽管实验技术进步迅速,但对鱼类机动运动机理的认识仍亟需深入,对鱼类游动运动链的一体化研究成为一大趋势。为此,本论文针对该运动链的末端,即“鱼体-流体”相互作用问题,做了以下新的工作:一、率先提出了鱼体作为变形体的动力学控制方程,以此建立鱼体动力学方程与非定常流体力学方程的一体化求解方法。该方法适用于数值模拟“主动变形动作→流体动力响应→鱼体运动结果”的运动链,为研究鱼的自主机动运动机理构建了一个二维的基础平台。二、运用该二维平台研究了锦鲤的加速-滑行游动。根据锦鲤的跟踪测量实验结果,研究了其自由游动中最常见的形式:加速-滑行游动。加速-滑行属于常规的自由游动,其特点是鱼体动作由摆尾与伸直交替构成,基本沿直线运动,有加速和减速两个阶段。论文通过数值模拟揭示了该游动方式的力学机理和流动物理特征,探索了该游动方式中锦鲤对其运动和力能学性能的主要控制机制。其中力能学的计算发现在相同平均速度的条件下,加速-滑行游动方式与巡游方式相比效率较低,输出功率较高,从而更正了前人从实验估算得到的加速-滑行游动耗能较少的认识。三、研究了锦鲤的常规转弯。实验中发现常规转弯,尤其是单摆尾转弯是锦鲤在自由游动中最常用的转弯方式,也属于常规的自由游动。本文研究了单摆尾转弯和巡游转弯两种转弯模式的非定常流动物理和流体动力学特征;通过比较常规转弯两种方式的机动性能和力能学特性,揭示了常规转弯所共有的动力学和流动控制规律以及两种方式的不同特点。计算结果给出了锦鲤常规转弯中的机动性能和力能学性能的若干重要控制规律,如敏捷性与机动性成正相关的关系,输出功率与转速成良好的线性关系,单摆尾转弯的效率高于巡游转弯。更多还原

【Abstract】 Natural selection provides fishes remarkable and diversified swimming abilities. At the same time, bioinspiration and biomimetics relevant to living fish develop increasingly in last ten years. The communities of researchers interested in fish biomechanics and AUV/UUV begin to come together to explore the mechanism of fish maneuvering more comprehensively, and the multidisciplinary integrated study on fish locomotion becomes a general trend. Aiming to the "body - fluid" interaction, within the mechanical chain of fish locomotion, the following new work has been done in this dissertation.1. We take the lead in putting forward the dynamical equations of a deforming body, as well as a fish body. Based on this, we set up an integrated method solving deforming body dynamics equations and unsteady fluid dynamics equations (Navier-Stokes equations). The coupled method can be used to investigate a part of the mechanical chain of fish locomotion, which consists of active body deforming, fluid dynamical response and fish body movement. This method provides a two-dimensional numerical platform for studying mechanics of freely and self-propelled fish maneuvering.2. Burst-and-coast swimming of koi carp is studied on this platform, according to the detailed kinematics data of tracking measurements. Burst-and-coast is the most common locomotion type in freely routine swimming of koi carps, which consists of a burst phase and a coast phase in each cycle and usually leads to an almost straight-line trajectory. This study reveals the hydrodynamics and flow physics in koi carp burst-and-coast, and explores its main control mechanisms of kinematical and energetic performance. We find that at the same average velocity, burst-and-coast swimming of koi carp has lower efficiency and more cost (total output mechanical power) than its equivalent steady swimming, in contrast to the available empirical conclusion that burst-and-coast costs less than steady swimming.3. Routine turns of koi carp have been investigated, also according to the kinematics data of tracking measurements. Experiments has found that the routine turn, especially single-beat turn, is the most observed turn gait in freely routine swimming of koi carps. This thesis studies the unsteady flow physics, unsteady hydrodynamic and energetic characteristics of single-beat turns and cruising turns, the basic two turning modes. Through comparative studies of the turning maneuverability performance and energetics of above two kinds of turns, their common flow control laws and different features are discovered, such as (1) agility (defined as turning rate) is correlated positively with maneuverability (defined as the reciprocal of the turning radius), (2) the total power appears good linear relation with the turning rate, and (3) single-beat turns are more efficient than cruising turns.更多还原