报告题目：涡激振动数值模拟
报告时间：2020年10月24日(周六) 17:00-18:30
报告地点：机械馆J3报告厅
报告形式：远程视频
报告人：Ekaterina Pavlovskaia
报告人简介：
Ekaterina Pavlovskaia是英国阿伯丁大学首席终身教授、阿伯丁大学研究生院院长(分管研究生教学，校委会成员)、英国机械工程师学会会士、国际水下研究工程大学联盟轮值主席、英国阿伯丁大学水下工程研究生专业创始人、journal of sound and vibration 杂志责任编辑 (中国科学院工程技术大类2区TOP期刊)、International Journal of Nonlinear Mechanics 杂志客座编辑 (中国科学院工程技术大类3区)、哈尔滨工业大学非线性动力学研究中心特聘顾问教授。她的主要研究方向包括：非光滑系统、连续介质的线性和非线性动力学、机器和结构以及断裂力学，特别是动态（平稳和非平稳）接触问题、冲击、非均匀介质中的波传播、裂纹扩展、材料的动态测试。Ekaterina Pavlovskaia教授发起或组织近20余场国际学术会议，受邀在30多所国际研究机构进行学术报告，发表论文150余篇。
报告内容简介：
Growth of subsea production systems for oil and gas extraction in deep water locations leads to building marine risers and pipelines of increased length. These long and thin structures constantly interact with surrounding water flow in various conditions. Vortices formed in the boundary fluid layer and resulting pressure oscillation cause prolong vibrations of the structure which can lead to a failure or accelerated fatigue. Therefore this work is motivated by the need of industry to predict loads and fatigue damage on such slender structures including riser systems, especially most common Top Tensioned Risers (TTRs) and Steel Catenary Risers (SCRs). Accurate prediction of vortex induced vibrations (VIVs) can help to produce more robust structural design and lead to substantial savings in the offshore applications. Although the problem of vortex-induced vibrations could be addressed by different approaches, which include experimental studies, computational fluid dynamics modelling and analytical models, in present work, we focus on analytical model known as wake oscillator model.
In this work we first consider nonlinearities in the fluid-structure interactions of an elastically supported cylinder moving in the uniform fluid flow. A new two degrees-of-freedom wake oscillator model is utilised to describe vortex-induced vibrations of elastically supported cylinders capable of moving in cross-flow and in-line directions. Experimental data and Computational Fluid Dynamics (CFD) results are used to calibrate the proposed model and to verify the obtained predictions of complex fluid-structure interactions for different mass ratios.
In the second part of the talk, the fluid–structure interactions are considered by investigating a straight but slender pipe vibrating in a uniform water flow. The pipe is modelled as an Euler–Bernoulli beam with flexural stiffness. The external fluid force applied to the structure is the result of the action of sectional vortex-induced drag and lift forces which are modelled using nonlinear oscillator equations where various damping types including Van der Pol and Rayleigh were investigated. The coupled system of nonlinear partial differential equations describing the dynamic behaviour of the system was simplified employing Galerkin–type discretisation to obtain the reduced order model. The resulting ordinary differential equations were solved numerically providing multi-mode approximations of the structure displacement and non-dimensional fluid force coefficients. The proposed models were calibrated with the published experimental data by Sanaati and Kato (2012) and the prediction results were compared. The ongoing study aims to investigate different types of nonlinear damping in fluid oscillators and their role in accuracy of VIV prediction.
