報告時(shí)間：2020年10月24日(周六) 17:00-18:30

報告地點(diǎn)：機械館J3報告廳

報告形式：遠程視頻

報告人：Ekaterina Pavlovskaia

報告人簡(jiǎn)介：

Ekaterina Pavlovskaia是英國阿伯丁大學(xué)首席終身教授、阿伯丁大學(xué)研究生院院長(cháng)(分管研究生教學(xué)，校委會(huì )成員)、英國機械工程師學(xué)會(huì )會(huì )士、國際水下研究工程大學(xué)聯(lián)盟輪值主席、英國阿伯丁大學(xué)水下工程研究生專(zhuān)業(yè)創(chuàng )始人、journal of sound and vibration雜志責任編輯(中國科學(xué)院工程技術(shù)大類(lèi)2區TOP期刊)、International Journal of Nonlinear Mechanics雜志客座編輯(中國科學(xué)院工程技術(shù)大類(lèi)3區)、哈爾濱工業(yè)大學(xué)非線(xiàn)性動(dòng)力學(xué)研究中心特聘顧問(wèn)教授。她的主要研究方向包括：非光滑系統、連續介質(zhì)的線(xiàn)性和非線(xiàn)性動(dòng)力學(xué)、機器和結構以及斷裂力學(xué)，特別是動(dòng)態(tài)（平穩和非平穩）接觸問(wèn)題、沖擊、非均勻介質(zhì)中的波傳播、裂紋擴展、材料的動(dòng)態(tài)測試。Ekaterina Pavlovskaia教授發(fā)起或組織近20余場(chǎng)國際學(xué)術(shù)會(huì )議，受邀在30多所國際研究機構進(jìn)行學(xué)術(shù)報告，發(fā)表論文150余篇。

報告內容簡(jiǎn)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.

機械工程學(xué)院

2020年10月20日