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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/10302

Title: 以主、被動流動控制方式調制鈍體流場特性及應用---調控桿、柵欄激擾、脈動泵及聲音波激擾
Applications and Analysis of Bluff-Body Flow Fields Using Active and Passive Flow-Modulations Mechanisms---Control Rod, Fence Actuator, Pulsation Pump and Acoustic Excitation
Authors: 閻順昌
Contributors: NTOU:Department of Mechanical and Mechatronic Engineering
國立臺灣海洋大學:機械與機電工程學系
Keywords: 流動控制;調控桿;柵欄激擾;聲波激擾;脈動泵
Flow Control;Control Rod;Fence Actuator;Pulsation Pump;AcousticExcitation
Date: 2008-08
Issue Date: 2011-06-28T07:38:22Z
Publisher: 行政院國家科學委員會
Abstract: 摘要:本計劃書擬議一個系統性的實驗方法,利用主、被動流控制方式調制鈍體的 流場特性,同時將尾流性質回朔給上游的流動控制機構,達到鈍體的氣動力性能 及尾流渦漩性質的「可調控性」,進行科學性及應用性的實驗研究。申請人基於 過去幾年對於鈍體流場的研究與實務經驗,發現利用簡易的被動式流動控制鈍 體,即可使流場的大結構產生變化,進而影響受力大小與尾流渦漩的性質,相關 文章已被國際期刊接受。因此如能以「應用」層面的觀點,利用主、被動流動控 制方式,調控流場達到氣動力性能及尾流渦漩性質的「可調控性」,進而發展出 初步的流量量測機制。則是另一研究的重要課題。 有鑑於此,在此專題研究計畫中;第一年中,進行以調控桿(Control rod)被動 式的調控研究,建立一套可以改變鈍體與調控桿間的旋轉角及相對位置的系統性 幾何配置機構,嘗試在各種不同的幾何配置與雷諾數條件下,調制鈍體流場與尾 流渦漩性質。過程中將以煙線流場可視化技術、PIV 量測系統、拓樸理論的分析 應用、熱線風速儀、壓力掃描器等交互應用,以尋找出最佳化的設計規則與操作 條件,並探討受調控桿所調控的流場行為、幾何配置選取、氣動力性能、紊動特 性、以及非穩態流動與尾流的調制能力。煙線流場可視化技術將用來觀測低雷諾 數下巨觀的流體行為,並界定出最佳化的設計規則與操作條件;PIV 系統以量化 的量測時間相關的非穩態流之演化過程以及與漩渦尾流之交互作用;運用臨界點 理論之拓樸學的分析,確定複雜的流場結構模態;熱線風速儀將用以偵測尾流與 剪流層中的頻率特性及高低頻之間的相關聯;利用壓力掃描器擷取鈍體的表面壓 力,並經由理論的計算,得到升、阻力的分佈。由所有實驗結果的分析與討論中, 期盼得到設施發展與物理探討的雙重益處。 第二年中,以柵欄激擾(Fence actuate)之被動式流動控制方式,調制鈍體的流 場達到尾流渦漩性質的可調性,並同時回饋前一年所得到以調控桿的最佳結果。 過程中以置放不同疏密度的鋼絲網於風洞噴嘴出口和測試段之間,藉以產生不同 的自由流紊流強度。研究方式以油膜觀察鈍體表面流場的特徵模態;及以熱線風 速儀偵測鈍體尾流流場行為,包含由壓力及速度梯度所形成的渦街(Vortex street) 及剪流層不穩定波(Shear layer instability)之間機制的差異。將不同紊流強度的流 體,穿過鈍體時,鈍體的表面流場與尾流行為的關連性做討論。並將尾流性質回 溯給上游的流動控制機構,促使尾流渦漩性質的「可調控性」機制成立。俾利下 一年度計畫,使用聲波激擾及脈動泵主動式流動控制的進行。 第三年中,以聲波激擾(Acoustic excitation),及脈動泵(Pulsation pump)之主動 式流動控制方式,調制鈍體的流場在高、低不同速度操作條件下,達到尾流渦漩 表C011 共4頁第 2頁 性質的可調性,並回饋與彙整前二年所得到的結果。過程中將以函數產生器及功 率放大器,所產生的不同波形、頻率及振幅為驅動訊號。在低速度時於水槽的噴 嘴上游架設可調動式的脈動泵,藉由驅動訊號的帶動,產生不同自由流的擾動性 質。同樣驅動形式亦用於風洞中,在較高速度時以改變聲波源的頻率及振幅,及 聲波源置放的位置,藉以產生不同自由流的擾動性質,包含頻率、壓力波與紊流 強度等特性。實驗量測以壓力掃描器擷取鈍體的表面壓力,並輔以表面油膜流的 流場可視化法,清楚界定鈍體受聲波激擾時表面的分離、再接觸、及分離泡等物 理特性與氣動力的關係;以熱線及熱膜風速儀偵測鈍體尾流區非穩態結構的物理 現象,藉以釐清受脈動泵及聲波激擾下,鈍體尾流的性質。可以預期的,在主動 式流動控制系統所探討出來的細部物理特徵將可回饋至前二年被動式的結果,以 更進一步改善鈍體流動與尾流的調制能力的設計方法與規範,作有系統相關性的 統整與討論。
abstract:This project presents a series of systematical experiment processes to study the active and passive flow control mechanism on the modulation of bluff body flow field. The modulability of aerodynamic performance and wake vortex will be experimentally studied. Applying the results of our previous studies, a simple passive flow-controlled bluff body could modify the global flow structures, and then the aerodynamic loadings and the properties of wake vortex were varied. The previous conclusions of the basic theoretical analysis have been published (or to be published) in some journals. However, the applications of the flow modulation mechanism are another important issue. This project will focus on the applications of the flow modulations and a feedback control system will be designed to response the signals from the wake vortex. In the first year, a study on the flow modulation using a passive control rod will be performed and develop a systematic regulative mechanism to change the rotation angle and relative position between the bluff body and the control rod. Furthermore, the effects of the bluff body geometry and Reynolds number on the flow-field and the wake vortex will be explored. The measurement tools includes the streakline flow field visualization, PIV measurement, topological analysis, hot-wire velocimeter and pressure scanner, etc. to find the optimum design rules and operation conditions. Moreover, the behavior of the modulated flow, geometric configuration of the bluff body, aerodynamic performances, turbulent properties, and the modulation ability of the instable flow will be probed. The streakline flow visualization can be utilized to observe the macroscopic flow behavior and to find the optimum design rules and operation conditions. The evolution process of instable flow and the wake vortex can be visualized using the PIV measurement. Topological analysis can be utilized to verify the flow patterns. The hot-wire velocimeter can be applied to detect the frequency properties in the wake flow and shear layer and to find the connectivity between the high and low frequencies. The pressure scanner can be used to measure the pressure distribution on the bluff body surface, and then compute the lift and drag theoretically. In the second year, a passive fence actuator will be presented to modulate the wake vortex. Furthermore, the data will be compared with the results attained in the first year. The free stream with different turbulent intensity can be produced by installing different metal meshes with distinct spacing between the nozzle jet and test 表C011 共4頁第 4頁 section. The oil-flow visualization will be applied to examine the characteristic flow modes on the bluff body surface. Furthermore, the hot-wire velocimeter can be used to detect the vortex street and shear layer instabilities and their differences. The relationships between the turbulent intensities and the wake behavior will be discussed and proceed to the following researches. Furthermore, a feedback control mechanism will be designed to response the wake vortex properties. In the third year, this project will focus on the study of the active control mechanisms using the acoustic excitation and pulsation pump. The properties of the wake vortex will be adjusted by changing the flow speed. Furthermore, the previous experimental data and results will be incorporated. The experimental instruments include a function generator, power amplifier, and oscilloscope to generate different acoustic frequency, amplitude and monitor the output waveform, respectively. In the low speed regions, a tunable pulsation pump will be installed near the upstream nozzle jet in a water tank. Different turbulent properties of the free stream will be created by altering the driving signals. Furthermore, in the high speed region (that is, in the wind tunnel), different driving frequencies, pressure waves, and turbulent intensities will be produced by varying the source frequencies, amplitudes and the positions of the acoustic sources. The surface pressure will be recorded using a pressure scanner. Moreover, the oil-flow visualization will be utilized to recognize the separation, reattachment and separation bubble and analyze the aerodynamic properties on the bluff-body surfaces. The hot wire and hot film velocimeters will be used to detect the instable configurations in wake regions. The conclusion will center on ascertaining the relations and discussing systematically among the free stream disturbances (the acoustic frequency, acoustic amplitude, and acoustic source position), the surface flow field, unsteady flow structures and aerodynamic parameters in the bluff wake.
Relation: NSC97-2221-E019-039
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/10302
Appears in Collections:[機械與機電工程學系] 研究計畫

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