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標題: 週期振盪來流中二維矩柱之受力效應
Effect on a Rectangular Cylinder in Sinusoidally Oscillating Flows with Non-Zero Mean Velocities
作者: 方富民
關鍵字: 應用研究;Sinusoidally oscillating approaching flow, Rectangular cylinder,Morison equation;土木水利工程類;週期振盪來流;矩柱;Morison;方程式
為了要瞭解在平均速度為非零之週期性振盪來流中二維矩柱的受力效應,本研究擬配合風洞試驗量測並應用數值模擬的方法系統化地探討其中之變化與機制。問題中涉及的重要影響因子包括了週期振盪來流中相應之庫利根.卡本特數以及速度振幅比(即來流速度振幅與平均速度之比值)。在高雷諾數的情況下,研究中擬針對幾個典型深寬比的柱體,藉來流情況之改變(即改變庫利根.卡本特數與速度振幅比),綜合性地研究在非恆定來流作用下柱體之受力行為,進而比較其與恆定來流情況之不同處並尋求其間之影響機制。此外,研究中在分析柱體承受之阻力與升力之變化時,將以Morison 方程式作為描述之基準。本研究預計以數值模擬與風洞試驗量測兩個方法並行的方式完成。其中,前者係以微可壓縮流的方法為基礎,並配合以動態次網格紊流模型,以期正確地預測出柱體附近之非恆定紊流流場。另一方面,風洞試驗之量測結果將作為數值模擬結果驗證之依據。本研究擬以兩階段(年)完成。其中,在第一年的工作中將專注於方柱情況之探討,並期建構出一套分析問題之程序。本階段工作首先擬於風洞中進行方柱阻力與升力之量測,藉結果之驗證以確立數值模式預測之精確度,繼而應用數值模擬進行方柱之系統化分析。在第二年中,研究之對象則將擴展至矩柱情況。本階段擬針對幾個典型的短柱與長柱,綜合探討矩柱在週期振盪來流中受力行為並整合出整體性的結果。

The unsteady forces on a rectangular cylinder in sinusoidally oscillatingflows with non-zero mean velocities are investigated in a two-dimensionalsense. The major parameters involved in the analysis are theKeulegan-Carpenter number (KC) as well as the ratio (AR) between thevariation and the mean of the approaching-flow velocities. The resultingunsteady forces on the rectangular cylinder with certain selected aspect ratiosat various KC and AR values are analyzed systematically to examine the floweffect of the cylinder. Based on the numerical results, additionally, Morisonequation is used as a basis to describe the variations of resulting drag and lift.The proposed study includes the execution of numerical simulations andwind tunnel measurements. To predict the unsteady turbulent flow around thecylinder, the former adopts a weakly-compressible-flow method together witha dynamic subgrid-scale turbulence model. The results from the wind tunnelmeasurements, on the other hand, will be used to confirm the results ofnumerical predictions.The proposed project is planed to be carried out in two stages (years). Inthe first year, the study will concentrate on the analysis in the square cylindercase. Measurements of the histories of drag and lift on the cylinder will bemade. The results will be used to guide and confirm the development of thenumerical model and allow for systematic analyses on the square cylinder case.In the second year, the analyses will be then extended to the cases ofrectangular cylinders. Finally, the results will be integrated to provideadditional insight for the assessment of the flow effects of the cylinders in asinusoidally oscillating flow field.
其他識別: NSC96-2221-E005-107
Appears in Collections:土木工程學系所

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