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A discrete approach to modelling helicopter blade sailing.

機譯：建模直升機葉片航行的離散方法。

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Blade sailing is an aeroelastic phenomenon which can occur during the engage and disengage phases of shipboard operations. This phenomenon is characterized by large blade deflections which are known to occur mainly at low rotor rotational speeds in high wind and sea conditions. Proper examination of this phenomenon requires adequate modelling of many contributing factors, including system dynamics, ship motion, airwake modelling, and aerodynamics. The research encompassed in this thesis sought to achieve a greater understanding of the factors that affect the blade sailing phenomenon through numerical modelling of the system as a whole.;Novel models for system dynamics and ship airwake were developed under this research programme. The dynamic model is comprised of a series of rigid segments, which allows the analyst to completely define the parameters of the system, including number of blades and blade segments. The model also allows the inclusion of coupled stiffness terms, and a method for calculating the equivalent lumped stiffnesses from continuous coupled stiffness distributions. The numerical model was shown to capture non-linear, coupled, flexible beam bending behaviour through validation against published experimental data and analytical models.;The airwake model is based on experimental data, and incorporates changing mean and turbulent flow characteristics over the flight deck in space, time, and with ship deck roll angle. The experimental research showed that ship motion changes the airwake significantly. A novel approach to the modelling of spatially- and temporally-correlated turbulence was developed, which recreates the time history of turbulent velocity fluctuations as experienced by a specific point on the rotating blade.;Using these and previously developed models for ship motion and for blade aerodynamics, a comprehensive model of the system was developed and validated in combined blade sailing-like conditions through experiment. The results of the experiment support the claims that the developed numerical tools capture the important aspects of the blade sailing environment, and that the interplay between the contributors to blade sailing motion is very complex.;The goals of this research, to study the contributors to the blade sailing phenomenon, and to develop validated modelling tools for this purpose, were achieved through this research.
機譯：葉片航行是一種空氣彈性現(xiàn)象，可能會在艦船操作的接合和脫離階段發(fā)生。這種現(xiàn)象的特征在于葉片偏轉(zhuǎn)大，已知該偏轉(zhuǎn)主要在高風和海況下以低轉(zhuǎn)子轉(zhuǎn)速發(fā)生。對這種現(xiàn)象的正確檢查需要對許多影響因素進行適當?shù)慕?，包括系統(tǒng)動力學，船舶運動，空中喚醒模型和空氣動力學。本論文所涉及的研究旨在通過對整個系統(tǒng)的數(shù)值模擬來更深入地了解影響葉片航行現(xiàn)象的因素。；在該研究計劃下，開發(fā)了用于系統(tǒng)動力學和船舶航行的新穎模型。動態(tài)模型由一系列剛性段組成，這使分析人員可以完全定義系統(tǒng)參數(shù)，包括葉片數(shù)量和葉片段。該模型還允許包含耦合剛度項，以及一種用于從連續(xù)耦合剛度分布中計算等效集總剛度的方法。數(shù)值模型顯示出通過針對已發(fā)布的實驗數(shù)據(jù)和分析模型進行驗證來捕獲非線性，耦合的柔性梁彎曲行為;空中喚醒模型基于實驗數(shù)據(jù)，并結(jié)合了駕駛艙內(nèi)變化的平均和湍流特性空間，時間以及與船甲板側(cè)傾角的關(guān)系。實驗研究表明，船舶運動顯著改變了尾流。開發(fā)了一種新穎的方法來對空間和時間相關(guān)的湍流進行建模，該方法可以重新創(chuàng)建旋轉(zhuǎn)葉片上特定點所經(jīng)歷的湍流速度波動的時間歷史;使用這些模型以及先前開發(fā)的船舶運動和葉片模型空氣動力學方面，開發(fā)了系統(tǒng)的綜合模型，并通過實驗在類似葉片航行的條件下進行了驗證。實驗結(jié)果支持以下觀點：已開發(fā)的數(shù)值工具捕捉了葉片航行環(huán)境的重要方面，并且對葉片航行運動的貢獻者之間的相互作用非常復雜。通過這項研究實現(xiàn)了葉片航行現(xiàn)象，并為此目的開發(fā)了經(jīng)過驗證的建模工具。

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