柱体绕流涡激振动的机理研究及其在压电俘能应用中的关键技术研究

以柱体为代表的钝体绕流基础研究具有重要科学意义。流体沿柱体表面生成边界层，因逆压梯度产生流动分离形成尾迹涡，引发涡激振动(VIV)。本项目拟对低Mach数柱体绕流流固耦合进行研究，具体内容包括：1）不同Reynolds数下柱体绕流的复杂非定常流场计算，特别是转捩流态及高Reynolds数流动分析；2）VIV的理论、数值及实验研究：研究折合速度、质量比和阻尼比对VIV的影响，分析‘锁定’发生机理，研究有限长度柱体端部涡、Karman涡与柱体振动的相互作用。重点研究‘驰振’现象，并基于尾迹振子Van der Pol方程进行流固耦合非线性动力系统建模及稳定性分析；3）VIV压电俘能流—固—电耦合数学建模及分析，研究一种基于VIV的自激励压电俘能器的俘能特性。项目研究有助于钝体绕流及VIV压电能量收集的系统综合认知，为多柱体绕流VIV以及多振动稳态俘能器等更深入研究做准备，具有较高学术及应用价值。

Flow past a cylinder, as a canonical example of bluff body flow, is of great scientific importance for basic understanding of aerodynamics and aeroelastic instability. A boundary layer, containing a significant amount of vorticity, forms over the cylinder when flow passes it, and will separate due to the adverse pressure gradient imposed by the divergent geometry of the flow environment at the rear side of the cylinder, resulting vortex shedding in the wake region which can induce the cylinder to vibrate, i.e. the vortex induced vibration (VIV). This project intends to study the fluid-structure interactions (FSI) of the flow past a cylinder in the low Mach number regime, and the specific researches are as follows: 1) To compute the complex unsteady flow fields at different Reynolds number, especially the critical flow regimes (the lower and upper transitions) and the high Reynolds number cases. 2) To perform the theoretical, numerical and experimental studies of the FSI related to the flow past a cylinder. This includes to study the effects on the VIV of reduced velocity, the mass ratio and the damping ratio in order to analyze the mechanism of the ‘lock-in’ phenomenon, to study the interactions among the tip vortices, the Karman vortices and the cylinder vibration of flow past a finite length cylinder. Special attention will be paid to the ‘gallop’ of a noncircular cross-section cylinder, where the Van der Pol equation of the wake oscillator model will be employed to modelling the self-excited vibration and the system stability will be analyzed. 3）To model and analyze piezoaeroelastic energy harvesters, and to study of the performance of a self-excited fluidic energy harvester based on flow past a cylinder. This project systematically and comprehensively investigate the flow around bluff bodies and the VIV piezoelectric energy harvesting, and prepare for the further study of VIV of flow past multiple cylinders and piezoelectric energy harvesting with multi-stable vibrations; therefor it has high academic as well as applied values.