钝体结构软驰振非定常效应及发生机理研究

Soft galloping known as VIV-galloping, is a kind of large-amplitude self-excited vibration caused by the combined effect of VIV and galloping. It has both the feature of low onset wind speed (VIV) and unstable vibration (Galloping), and greatly affects the safety of structures. To address the problem that the classic quasi-steady theory is unable to predict soft galloping of structures and the mechanism of soft galloping remains unclear, this project applies an integrated method of theoretical analysis, wind tunnel test, and computational fluid dynamics (CFD) to investigate the mechanism of soft galloping, to analyze the ‘unsteady effect’ of soft galloping force, to develop a mathematical model for unsteady soft galloping force and to propose a simplified method for calculating the critical wind speed of soft galloping. The projects will pay much attention to scientific problems on the mechanism of soft galloping, the characteristics and unsteady effect of soft galloping force, the mechanism of the combined effect of VIV and galloping, and the shortcomings of the quasi-steady theory in predicting soft galloping instabilities of structures. This study will reveal the mechanism of soft galloping and provide conditions that soft galloping takes place, understand the unsteady effect of soft galloping force, establish mathematical model for soft galloping force, propose a simplified method for calculating the onset wind speed of soft galloping, aiming to provide a theory and method for structural wind-resistant design of soft galloping.

软驰振也称为涡振-驰振，是在涡振和驰振耦合状态下发生的大幅度的自激振动。它既具有涡振起振风速低的特点，又具有驰振发散振动的特点，严重威胁结构的安全。针对软驰振发生机理不明确、经典驰振理论不能准确预测结构软驰振响应的问题，本项目以钝体结构为研究对象，以揭示软驰振理论、准确预测结构软驰振响应、指导钝体结构软驰振抗风设计为目标，采用理论分析、风洞试验和数值模拟相结合的研究手段，基于软驰振自激力的非定常效应研究钝体结构软驰振发生机理，建立非定常软驰振自激力模型，寻求软驰振临界风速简化计算方法。项目着重解决钝体结构软驰振发生及自激力形成机理、软驰振自激力非定常效应、涡激振动与驰振的耦合关系等关键科学问题。项目预期将阐明钝体结构软驰振发生机理和发生条件，揭示软驰振自激力的非定常效应、明确非定常软驰振自激力的数理特征、提出软驰振临界风速简化计算方法，为钝体结构软驰振抗风设计提供理论支撑。

软驰振是一种大振幅的自激振动，既具有涡振起振风速低的特点，又具有经典驰振发散振动的特点，软驰振的出现严重威胁结构的安全。针对软驰振发生机理不明确、经典驰振理论不能准确预测结构软驰振响应的问题，本项目围绕软驰振自激力的非定常效应和发生机理等关键科学问题开展了研究，形成了钝体结构软驰振理论，指导结构软驰振的抗风设计。主要研究成果包括：（1）揭示了钝体结构软驰振发生及软驰振自激力形成机理。通过开展新型气弹-测压和强迫振动-测压以及CFD动网格数值模拟研究，探明了不同振动区域流体的变化和结构振动规律，明确了钝体结构软驰振发生的条件，从双向流固耦合的角度研究软驰振发生的内在机理。（2）建立了钝体结构非定常软驰振自激力精细化模型。基于改进的小波变换算法，精确识别了非定常软驰振自激力，结合湍流度、Scruton数、截面形状和尺寸等参数对软驰振自激力的影响规律，建立钝体结构非定常软驰振自激力精细化模型，用以准确预测钝体结构软驰振响应。（3）提出了钝体结构软驰振临界风速简化计算方法。在明确经典驰振理论和现有模型不能预测钝体结构软驰振响应的内在原因后，在建立的钝体结构软驰振自激力精细化模型基础上，确定钝体结构软驰振临界风速的简化计算方法，通过风洞试验检验其有效性。