臺灣博碩士論文加值系統

本研究使用泛用計算流體力學FLUENT軟體模擬本研究室現有的試驗渠道流經透水孔隙方塊之流況，藉由軟體模擬明渠通過孔隙方塊三維流場特性，瞭解三維流場分布及孔隙間的流速分佈。在研究中，採用有限體積法(finite volume method)離散控制方程式，以二階上風法離散對流項，重力權重法(body force weighted)離散壓力項，由SIMPLE法耦合速度和壓力，使整個流場符合質量守恆及動量守恆，再由多相流κ-ε紊流模式配合體積分率法處理三維自由液面水流流場，最後再應用孔隙介質流理論模擬孔隙方塊三維流場特性。本研究透過與實驗值比對，模擬自由液面及中心斷面流速剖面發現，驗證結果良好，FLUENT可以成功的模擬出三維明渠通過孔隙方塊所產生的跌水現象。

本研究中網格主要是由六面體網格及四面體網格所組成的混合網格，總網格數約40萬個，研究案例依照入口水深的不同分為三組，結果顯示，FLUENT在發展段的模擬結果良好且可成功獲得在孔隙間的流場分佈，因此可藉由模擬的方式彌補實驗量測的困難。由模擬結果可發現，入口流速為0.397m/s，但在孔隙內的最大流速僅約為0.7倍入口流速，隨著入口水深的減小，孔隙附近的壓力梯度的變化越明顯，其最大流速值則發生在跌水現象產生的位置，流況則由亞臨界流轉為超臨界流。由橫向流速分佈結果得知，在孔隙方塊上層受到自由液面跌水的影響，流速有較大的變動。水流方向在孔隙間並非規則的往下游流動，孔隙間速度有大有小，甚至會產生一微小的回流區域，藉由模擬可以清楚了解孔隙內的流動情況，由FLUENT 軟體模擬，可獲得實驗所不能量測及觀測到的細微流場。在三組案例裡，因水流型式相同，所以在結果顯示上，其趨勢大致相同，僅因流量不同而造成數值上的差異。

In this study, the commercial hydrodynamic software, FLUENT is adopted to construct a model for simulating the free surface flow through porous block. The modules used are the finite volume discretization, the second order upwind scheme, the near wall κ-ε model and the volume of fluid approach. Using GAMBIT preprocessor, a model that has a grid system composed of hexahedron and tetrahedron mixed meshes with total cells number of approximate 400 thousand is generated. The constructed model is verified using mean velocity and free surface profiles from experimental study, and prove that this complex model is capable of simulating the free surface variation, the 3-D turbulence flow field of the concerned problem.

The model is used to compute flows of entrance depths of 24.2cm、20cm、15cm at uniform entrance velocity of 0.397m/s. The computed free surface with noticeable elevation change and air mixture at the upper end of the block, the detail 3-D velocity distribution and pressure distribution in and outside the block, for the three cases, are presented. These results give good understanding to the detail flow structure in the pores of the block which are diffculty to observe using ordinary experimental methods.

中文摘要 I
Abstract II
誌謝 III
目錄 IV
表目錄 VII
圖目錄 VIII
符號說明 XI
第一章 緒論 1
1-1 研究動機 1
1-2 前人研究 1
1-3 研究目的 2
1-4 本文架構 3
第二章 數學模式與模式驗證 4
2-1 三維非穩態基本物理方程 4
(a) 連續方程 4
(b) 動量方程 5
(c) 紊流動能k方程 5
(d) 紊流動能消散率ε方程 5
2-2 孔隙介質控制方程 6
2-3 體積分率法 7
2-4 紊流流動的近壁處理 8
2-5 實驗配置 9
2-6 實驗結果與驗證 10
第三章 數值模擬 12
3-1 數值模擬架構 12
3-2 控制方程式的離散方法 12
3-3 收斂條件 13
3-4 網格設計 13
3-5 邊界條件設定 16
3-6 自由液面邊界 16
3-7 數值模擬設定流程 18
第四章 數值模擬結果 20
4-1 自由液面狀況 20
4-2 不同水深縱向平均流速剖面比較 24
4-3 三維壓力分佈狀況 25
4-4 孔隙方塊內流動情況 29
4-5 橫向速度分佈 35
4-6 不同時間之明渠流場速度變化 40
第五章 結論與建議 47
5-1 結論 47
5-2 建議 48
參考文獻 49

1.Cai Y. H. , J. Hu , H. P. Ma , B. L. Yi , and H. M. Zhang , “Effects of hydrophilic/hydrophobic on the water behavior in the micro-channels of a proton exchange membrane fuel cell” , J. Power Sources , Vol.161 , pp.843-848 , 2006.
2.Ergun, S., “Fluid Flow through Packed Columns,” Chem. Engineering Progress, Vol.48, pp.89-94, 1952.
3.FLUENT，“FLUENT 6.1 User’s Guide”，FLUENT.
4.Guardo A. , M. Coussirat , M. A. Larrayoz, F. Recasens and Egusquiza , “Influence of the turbulence model in CFD modeling of wall-to-fluid heat transfer in packed beds.” , Chemical Engineering Science , Vol.60 , pp.1733-1742 , 2005.
5.Guardo A. , M. Coussirat , F. Recasens , M. A. Larrayoz and X. Escaler , “CFD study on particle-to-fluid heat transfer in fixed bed reactors : Convective heat transfer at low and high pressure.” , Chemical Engineering Science , Vol.61 , pp.4341-4353 , 2006.
6.Herrmann Hans J. , José S. Andrade Jr. , Ascânio D. Araújo and Murilo P. Almeida , “Transport of particles in fluids.” , Physica A , Vol.372 , pp.374-386 , 2006.
7.Hirt , C.W. and Nichols , B.D. , “Volume of Fluid (VOF) method for the dynamics of free surface boundaries.” J. Comput. Phys. , pp.201-225 , 1981.
8.Kang Hyeongsik and Sung-Uk Choi , “Turbulence modeling of compound open-channel flows with and without vegetation on the floodplain using the Reynolds Stress model.” , Advances in Water Resources , Vol.29 , pp.1650-1664 , 2006.
9.Jr. Hite J. E. and W. C. Mih , ‘‘Velocity of air-core vortices at hydraulic intakes.’’ J. Hydraulic Engineering , ASCE , Vol. 120(3) , pp.284–297 , 1994.
10.Li S. , Lai Y. , L. Weber , J.M. Silva and V.C. Patel ,“Validation of a 3D numerical model for water pump intakes.” Journal Hydraulic Research , Vol. 42(3) , pp.282-292 ,2004.
11.Lin Ma , Philip J. Ashworth , James L. Best , Lionel Elliott , Derek B. Ingham and Leslie J. Whitcombe , “Computational fluid dynamics and the physical modeling of an upland urban river.” , Geomorphology , Vol.44 , pp.375-391 , 2002.
12.Mahesh K. , S. G.. Constantinescu , S. Apte , G. Iaccarino , F. Ham and P. Moin “Progress Toward Large Eddy Simulation of Turbulent Reacting and Non-Reacting Flows in Complex Geometries.” Annual Research Briefs 2002 , Center for Turbulence Research, Stanford University , CA , 2002.
13.Mahesh K. , G. Constantinescu , P. Moin , “A numerical method for LES in complex geometries.” , Journal of Computational Physics , Vol. 197(1) , pp. 215-240 , 2004.
14.Mahesh K. , S.G.. Constantinescu and P. Moin , “A Numerical Method for Large Eddy Simulation in Complex Geometries.” , Journal of Computational Physics , Vol. 197(1) , pp.215-240 , 2004.
15.Manoj Kumar , V. Anantha Subramanian , “A numerical and experimental study on tank wall influences in drag estimation.” , Ocean Engineering , Vol.34 , pp.192-205 , 2007.
16.McCoy A. , S.G. Constantinescu and L. Weber (2005a) , “LES simulation of contaminant removal from the embayment area between two vertical groynes in a channel.” , XXXIst International Association Hydraulic Research Congress , Seoul, Korea , September 2005.
17.McCoy A. , S.G. Constantinescu and L. Weber (2005b) ,“Coherent structures and mass exchange processes in channel flow with spanwise obstructions.” , ERCOFTAC International Symposium on Engineering Turbulence Modeling and Measurements , Sardinia , Italy , May 2005.
18.Mousavi M.S. , A. Jafari , S. Yaghmaei , M. Vossoughi and P. Sarkomaa , “Computer simulation of fluid motion in a porous bed using a volume of fluid method : Application in heap leaching.” , Minerals Engineering , Vol.19 , pp.1077-1083 , 2006.
19.Prions , P. , D. Sofialidis , and E. Keramaris , “Turbulent flow over and within a porous bed.” , J. Hydraulic Engineering ,Vol. 129(9) , pp.720-733, 2003.
20.Tarek M. Salaheldin , ASCE ; Jasim Imran, ASCE; and M. Hanif Chaudhry, ASCE﹐“Numerical Modeling of Three-Dimensional Flow Field Around Circular Piers.”﹐ J. Hydraulic Engineering , Vol. 130(2) , pp.91-100 , 2004.
21.Tokyay T. and S.G. Constantinescu (2005a) ,“Large Eddy Simulation and Reynolds Averaged Navier Stokes Simulations of flow in a realistic pump intake: A validation study ,” World Water and Environmental Resources Congress , Alaska, May 2005.
22.Tokyay T. and S.G. Constantinescu, (2005b) ,“Coherent structures in pump intake flows: A Large Eddy Simulation study.” , XXXIst International Association Hydraulic Research Congress , Seoul, Korea , September 2005.
23.Wu W., W. Rodi and T. Wenka ,“3D numerical modeling of flow and sediment transport in open channels.” , J. Hydraulic Engineering , ASCE , Vol. 126 , pp. 4-15 ,2000.
24.Wang X. and L. Cheng , “Three-dimensional simulation of a side discharge into a cross channel flow.” , Computers and fluids , Vol.29 , pp.415-433 , 2000.
25.Yıldırım N. and F. Kocabas , ‘‘Critical submergence for intakes in open channel flow.’’, J. Hydraulic Engineering , ASCE , Vol. 121(12) , pp. 900–905 , 1995.
26.Yildirim Nevzat and Fikret Kocabas ﹐“Critical Submergence for Intakes in Still-Water Reservoir.”﹐J. Hydraulic Engineering , Vol. 124(1) , pp. 103-104 , January 1998.
27.Zeng J., S.G. Constantinescu, and L. Weber (2005a) , “A fully 3D non-hydrostatic models for prediction of flow, sediment transport and bed morphology in open channels.” , XXXIst International Association Hydraulic Research Congress, Seoul , Korea, September 2005.
28.Zeng J., S.G. Constantinescu, and L. Weber (2005b) ,“Validation of a computational model to predict suspended and bed load sediment transport and equilibrium bed morphology in open channels,” River and Coastal Estuarine Morphology Conference, University of Illinois, 2005.
29.林呈、顏光輝、陳謹偉、黃文彥，「人工魚礁周邊之流場特性與沖刷機制之試驗研究」，第二十屆海洋工程研討會論文集，p.p.305-312，1998。
30.林玫珊，「計算生態流體力學在三維度自由液面植栽帶流場之應用研究」，國立台灣大學生物環境系統工程學研究所碩士論文，2005。
31.林明峰，「喇叭型進水口三維流場之模擬」，國立成功大學水利及海洋工程研究所碩士論文，2006。
32.洪健豪，「三維光滑明渠紊流流場之量測與分析」，國立中興大學土木工程研究所博士論文，2003。
33.陳建文，「水流通過橋下保護工之流速分佈探討」，國立成功大學水利及海洋工程學系碩士論文，2001。
34.黃偉哲，「水流通過透水式橋墩保護之流況分析」，國立成功大學水利及海洋工程學系碩士論文，2002。
35.董志昌，「水流通過橋墩保護之流況分析」，國立成功大學水利及海洋工程學系碩士論文，2003。