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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/30723

Title: 波與流環境對射流場之影響研究(II)
Waves and Currents Interaction with a Submerged Jet Flow (Ii)
Authors: 黃榮鑑;謝志敏
Contributors: NTOU:Department of Systems Engineering and Naval Architecture
國立臺灣海洋大學:系統工程暨造船學系
Keywords: 射流;雷諾平均方程式;流體體積法;波流交互作用
Jet;RANS;Volume of Fluid;Wave-current interaction
Date: 2011
Issue Date: 2012-04-13T01:21:17Z
Publisher: 行政院國家科學委員會
Abstract: 水環境污染問題是當今世界各國普遍所關注的重大問題,由於經濟的發展以及人民生活水平的提 高,城市污水、電廠廢水、廠礦煙氣等的排放量逐漸增加,這些排放過程都跟射流的流動有關。海洋 放流是現代沿海城市污水處置的發展方向,但是將波浪作爲主要動力因素,用紊流模式對污染物的擴 散輸運作數值模擬的研究還不多見。且海洋放流的課題勢必要有良好的管控,才不致使海洋蒙受污染 的威脅情況;而要達到良好的放流管控,則須輔以學理的探討,使海洋放流能成污水處理的經濟有效 的工具。海洋放流通常以射流的形式排放到海洋之中,若能有系統的對波浪與流環境中之射流特性的 基礎性研究,不僅可以加深對紊流的認識,而且能夠爲射流在工程應用中提供更加完善的理論基礎, 有著重要的科學價值和實際意義。故而本計畫擬對波浪與流環境對射流場之影響為課題,發展適切的 數值模式並模擬探討,以提供政府及業界參考引用。 本計畫擬從數值模擬方面對波與流環境中射流特性,包括射流的流態、射流擴展範圍以及污染物 濃度場分布等特性進行研究。特別是在環境水體爲波浪時,對波流要素的改變影響射流特性的規律進 行了深入的探討。本計畫將在主持人以往的研究成果為基礎,擬以RANS 方程式爲基本控制方程式, 用 k − ε 紊流模式來模擬紊流效應和流體體積法模擬自由液面的紊動射流之二維數學模式和三維數 學模式。 本計畫為三年計畫,第一年主要工作發展數值模式探討垂直射流在二維波與流環境作用下之流場 特性,目前進度已經發展出波浪射流數值模式,今年度為第二個執行年度,第二年利用第一年發展之 波浪射流數值模式探討在不同方向、位置之射流對二維波與流環境中之流場影響研究;第三年探討射 流在三維波與流環境作用下之流場特性。本文擬設計模擬了不同水深、射流速度、波高和週期組合的 案例,基於紊流模式的數值計算,研究了波浪和波流環境中擴散係數和各影響因素的關係。本計畫擬 對靜水、波浪和波流環境中的射流作了模擬分析。靜水環境中重點分析了自由面分布、軸線速度和濃 度的衰減和水平分布規律;擬在波環境中波浪週期和波高對射流濃度場分布的影響;擬在波流環境中 分析了自由液面分布、濃度場分布、軌跡線、渦形結構的發展過程及底邊界和自由液面對它們的影響。 其研究成果可提供工程單位設計海洋放流之參考。
Water pollution problem has been becoming more and more attention in our environment. Due to the rapid development of economy and the improvement of living standard, the discharge quantities of city sewage, power plant waste water, and factories exhaust gases increase rapidly. Most of the waste desposal is the jet type discharge. The discharge process is concerned with dynamics of a jet flow. A marine outflall system is the main tendency for a modern coastal city to dispose wasterwater. Studies in mixing and advection of pollutants in a wave environment are using a turbulence model. The design of the ocean outfall must focus on how to let it undertake under the good management and prevent the ocean suffering the threat situation of pollution. In order to reach good control of the ocean outfall, it is important to understand the mechanism of ocean outfall and then an ocean outfall can become an economic and effective tool for the sewage disposal. A marine outflall is designed to discharge flows into rivers and sea by jets. A systemic study of characteristics of a jet in the waves and currents not only provides the fundamental knowledge on a turbulent flow, but also supplies more insight for applications of jets in engineering. Thus the purpose of this project is concerned with waves and currents interaction with a submerged jet flow using numerical simulations. Those results can then be references for government policy and industry investment. Based on PI’s past research work, the Reynolds Averaged Navier-Stokes Equations (RANS) coupled with a modified k − ε turbulence model will be used in the study. In order to update the free surface configuration at each time step, the Volume of Fluid (VOF) method will be implemented. Based on RANS equations the 2D and 3D numerical models for a turbulent jet will be established by the k − ε turbulence model and VOF method. The study will take three years to undertake the project. In the first year, we developed the numerical model to simulate the behavior of vertical jet under waves. Up to the present, the numerical model is extended to include jet discharged into a regular wave field. In the second year, a numerical simulation will be conducted for the 2D waves and currents interaction with a submerged jet flow. In the third year, numerical simulations will be conducted for 3D waves and currents interaction with a submerged jet flow. The diffusion coefficients in wave and wave-current will be studied under a variety of water depth, jet speed, wave height, and wave period. Jets in still water, wave, current and wave-current environments will be simulated and analyzed. In a still environment, the distributions of velocity, concentration, and free surface will be analyzed. The effects of wave period and wave height on the distribution of concentration will be explored when a jet is submerged under a travelling wave train. The distributions of free surface, velocity and concentration, the jet trajectory, the development of the vortices will be investigated and analyzed when a jet undergoes a travelling wave train and current. The established model will be utilized for simulations of a marine outfall. Researchers and coastal engineers would obtain the whole picture of evolution of a marine outflall from this project.
Relation: NSC100-2221-E019-003
URI: http://ntour.ntou.edu.tw/handle/987654321/30723
Appears in Collections:[系統工程暨造船學系] 研究計畫

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