【作者】 许伟；

【导师】 蔡健；

【作者基本信息】 华南理工大学 ， 结构工程， 2018， 博士

【摘要】 圆柱或矩形柱等钝体结构或构件是实际工程中常见的结构形式,处于风和水流中的钝体绕流是涉及流动分离、再附和旋涡脱落等特性的经典流体力学问题。钝体绕流及旋涡脱落诱发的流体动力荷载和结构振动,常见于许多实际工程中并成为导致结构失稳或疲劳破坏的主要因素。因此,消除钝体绕流的振荡尾流,进而抑制钝体的涡致振动具有重要的科学意义和工程应用前景。本文采用基于计算流体动力学(Computational Fluid Dynamic,CFD)的数值模拟方法,研究方柱和圆柱等典型钝体的绕流尾流和涡致振动特性,进而研究动波壁(Dynamic Wave Wall,DWW)流动控制方法对方柱和圆柱的尾流与涡致振动抑制效果,并揭示该流动控制方法的物理机理。本文主要开展了以下几个方面的研究工作:(1)基于CFD通用商业软件平台Fluent,完成了不同长宽比截面矩形柱的绕流特性,得到气动力和尾流涡脱模式随长宽比的变化;并完成了方柱与风场间的双向流固耦合模拟,分析了不同质量比和折合阻尼参数下方柱发生涡致振动的气动力和振动响应特性,揭示方柱振动响应与尾流涡脱模式的相互关系。(2)以方柱为研究对象,通过CFD数值模拟方法在方柱表面生成运动的行波,重点研究动波壁的波速、波幅和波数等关键控制参数对方柱气动力和尾流涡脱模式的控制效果。通过与标准方柱绕流结果对比,得到对方柱尾流控制效果较好的动波壁控制参数。(3)采用动波壁方法对固定圆柱绕流的尾迹抑制效果进行研究,重点研究动波壁的关键控制参数对尾流控制效果的影响,完成了从固定圆柱绕流到动波壁控制整个过程的模拟,从各阶段气动力和涡脱特性揭示该方法对圆柱绕流尾流的抑制效果。(4)研究动波壁方法对弹性支撑圆柱涡致振动响应的抑制效果,分析无控圆柱的涡致振动特性和有控动波壁圆柱顺风向和横风向的振动响应特性,完成从圆柱绕流到涡致振动、再到动波壁控制全过程的数值模拟,着重分析各阶段圆柱的气动力、振动响应和尾流涡脱模式的演变规律。(5)以圆柱绕流尾流和涡致振动的动波壁流动控制结果为基础,通过圆柱柔性壁面上的边界涡量流的演变规律、边界涡量的变化规律、相对流场和3D动波壁圆柱尾流的展向空间相关性等揭示方法的控制机理。更多还原

【Abstract】 Circular and square cylinders are common blunt bodies used in structures of practical engineering.Flow around blunt bodies in wind or water is a classical hydrodynamic problem involving flow separation,reattachment and vortex shedding.The dynamic load acting on the structure and vibration induced by flow around bluff body and vortex shedding become the main factors leading to structural instability or fatigue failure.Therefore,eliminating the oscillating wake and suppressing the vortex-induced vibration of the bluff body have important scientific significance and application prospects in engineering.A numerical simulation method based on computational fluid dynamics(CFD)is used to study the wake and vortex-induced vibration characteristics of typical bluff bodies such as circular and square cylinders in this research.Then the effects of flow control method with dynamic wave wall(DWW)on the wake and vortex-induced vibration suppression of square and circular cylinders are analysed.Further on,the physical mechanism of the flow control method is also revealed.The main work are carried out as follows.(1)Based on software platform Fluent,the flow characteristics of rectangular cylinders with different aspect ratios are analysed,and the variation of aerodynamic and wake vortex shedding modes with aspect ratios is obtained.Also,the fluid-structure interaction between square cylinder and flow field is simulated.And the aerodynamic and vibration response characteristics of square cylinder under different mass ratios and reduced damping parameters are analyzed to reveal the relationship between vibration response of square cylinder and wake vortex shedding mode.(2)Flow around the square cylinder with dynamic wave traveling on the side surfaces are simulated.Comparing with the results of flow around the standard squarecylinder,the control parameters of the dynamic wave wall with better control effect on the wake of the square cylinder are obtained.(3)The dynamic wave wall method is used to study the effect of wake suppression on the flow around a fixed circular cylinder.The influence of the key control parameters of the dynamic wave wall on the wake control effect is studied.And,the whole process from the flow around a fixed cylinder to the control of the moving wave wall is simulated.(4)The suppressing effect of dynamic wave wall method on vortex induced vibration of an elastic supported circular cylinder is studied.The vortex-induced vibration characteristics along and across the flow direction of both an uncontrolled cylinder and a controlled cylinder with DWW are analyzed.The numerical simulation of the whole process from the flow around the cylinder to the vortex-induced vibration,and then to the control of the moving wave wall is completed.The evolution of the aerodynamic force,vibration response and wake vortex shedding mode of the cylinder at various stages are emphatically analyzed.(5)Based on the control results of the wake flow around a cylinder with DWW,the mechanism of the method is analyzed according to the evolution law of the boundary vorticity flow,the relative flow field and the spatio-temporal correlation of the wake flow around a 3D cylinder.更多还原