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1、,單擊此處編輯母版標題樣式,,單擊此處編輯母版文本樣式,,第二級,,第三級,,第四級,,第五級,,,,*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,Nanjing University of Technology,,計算流體動力學,Computational fluid mechanics,機械與動力工程學院,,凌祥,2,To provide the engineer with the understanding and practical experience required to use commercial CFD software for solving real
2、 engineering problems,Aim,3,Objectives,To learn how to solve problems in fluid dynamics using a commercial CFD code,,To understand sufficiently the underlying fluid dynamics to appreciate the scope and limitations of solutions,,To be able to assess the errors involved in CFD simulation,,To be able t
3、o interpret and present the results in an appropriate professional context,4,4,課程背景,Who should learn this course?,,動力工程及工程熱物理、機械工程、暖通、安全工程等專業(yè)研究生,,prerequisite courses for this course,,流體力學、,Pro/E,、高等數(shù)學、數(shù)值計算方法,5,5,教材,H K Versteeg and W Malalasekera.,An Introduction to Computational Fluid Dynamics: th
4、e Finite Volume Method.,Harlow, England: Pearson Eduaction Ltd. (1st Edition, 2000),,Anderson J D.,Computational Fluid Dynamics: The basics with applications.,Mcgraw-Hill Companies, Inc. (1995),,Uses finite difference approach,,Well written text excellent introduction,6,6,6,參考書,Patankar S V.,Numeric
5、al Heat Transfer and Fluid Flow.,NY: Mcgraw-Hill Companies, Inc. (1980),,陶文銓,.,數(shù)值傳熱學,.,西安交通大學出版社,(2004),,陶文銓,.,傳熱與流動問題的多尺度數(shù)值模擬：方法與應(yīng)用，科學出版社,,，,2009,,Ferziger J H and peric M.,Computational Methods for Fluid Dynamics.,Springer 3ed 2001,,—excellent treatise on finite volume method for the mathematics a
6、nd fluids expert,7,7,7,Important websites,Http://scholar.lib.vt.edu/ejournal/JFE/.,Journal of Fluids Engineering,,Http://www.CFD- user manual,8,8,8,8,Important Journals,Transactions of ASME,,Journal of Fluids Engineering,,Journal of Engineering for Gas Turbines,,Journal of Heat Transfer,,AIAA Journa
7、l,,Journal of Fluids Mechanics,,Proceeding of the IMechE,9,9,9,9,9,Available Commercial Codes,Fluent,,CFX,,FIDAP(,基于有限元方法和完全非結(jié)構(gòu)化網(wǎng)格,),,PHOENICS,,AirPak,,STAR-CD,,FLOW3D,,NUMECA,,…,10,10,10,10,10,10,學習與授課,,學,,自學,,動手,,大作業(yè),,考核,,大作業(yè),,期末考試（待定）,教學方式,,教師授課,,學生實踐,,討論,,學生,Presentation,,11,12,13,14,15,16,17,18
8、,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,第一章 計算流體動力學的基本原理,什么是,CFD,,為什么要學習,CFD,,作為研究工具的,CFD,,作為設(shè)計工具的,CFD,,CFD,應(yīng)用實例,,CFD,研究范圍,85,CFD,是英文,Computa
9、tional Fluid Dynamics,（計算流體動力學）的簡稱。,,CFD,是伴隨著計算機技術(shù)、數(shù)值計算技術(shù)的發(fā)展而發(fā)展的。,,CFD,相當于,",虛擬,",地在計算機做實驗，用以模擬仿真實際的流體流動情況。,什么是,CFD,86,CFD,基本原理則是數(shù)值求解控制流體流動的微分方程，得出流體流動的流場在連續(xù)區(qū)域上的離散分布，從而近似模擬流體流動情況?？梢哉J為,CFD,是現(xiàn)代模擬仿真技術(shù)的一種。,,1933,年，英國人,Thom,首次用手搖計算機數(shù)值求解了二維粘性流體偏微分方程，,CFD,由此而生。,,1974,年，丹麥的,Nielsen,首次將,CFD,用于暖通空調(diào)工程領(lǐng)域，對通風房間內(nèi)
10、的空氣流動進行模擬。,什么是,CFD,？,87,CFD,軟件是計算流體力學（,Computational fluid Dynamics,）軟件的簡稱，是專門用來進行流場分析、流場計算、流場預(yù)測的軟件。,,著名的,CFD,處理工具有以下一些：,用于前處理：,Gambit, Tgrid, GridPro, GridGen, ICEM CFD,用于計算分析：,Fluend, FIDAP, POLYFLOW,用于后處理：,Ensight, IBM Open Visulization Explorer, Field View, AVS,提供綜合的處理能力：,Ansys,，,MAYA,特殊領(lǐng)域的應(yīng)用：,I
11、cepak, Airpak, Mixsim,什么是,CFD,？,88,為什么要學習,CFD,流體力學中有些問題采用實驗和理論的方法無法解決,,空天飛機,超聲速燃燒沖壓式噴氣發(fā)動機,,高超聲速（高馬赫數(shù),-25,，,8000m/s,）,,很高的氣流溫度,,沒有風洞能模擬上述兩方面,89,空天飛機是既能航空又能航天的新型飛行器。它像普通飛機一樣起飛，以高超音速在大氣層內(nèi)飛行，加速進入地球軌道后，成為航天飛行器，返回大氣層后，像飛機一樣在機場著陸,,航天飛機返回再入大氣層的空氣動力學問題，曾經(jīng)耗費了科學家們多年的心血，作了約,10,萬小時的風洞試驗?？仗祜w機的空氣動力學問題比航天飛機復(fù)雜得多。因為飛
12、機速度變化大，馬赫數(shù)從,0,變化到,25,；飛行高度變化大，從地面到幾百公里高的外層空間；返回再入大氣層時下行時間長，航天飛機只有十幾分鐘，空天飛機則為,l,～,2,小時。,90,解決空氣動力學問題的基本手段是風洞。目前，就連美國也不具備馬赫數(shù)可以跨越這樣大范圍的試驗風洞。即使有了風洞還需要作上百萬小時的試驗，那意味著就是晝夜不停地試驗，也需要花費,100,多年的時間。,,只能求助于計算機，用,CFD,來解決，對那維爾斯托克斯方程進行求解,91,During the early morning hours, the Tacoma Narrows Bridge began to undulate
13、 violently in 35+ mph winds. After several hours (and luckily after the bridge had been closed by police), the oscillations took the form of a twisting motion that would cause the main section of the bridge to tilt at up to a 45o angle from its original position.,On November 7, 1940, one of the most
14、 spectacular engineering failures of the 20th century occurred in Tacoma, Washington.,92,The Tacoma Narrows Bridge disaster illustrates two main points: 1) that fluid dynamics can play a role in many critical phenomena outside the traditional spheres of aerospace and mechanical engineering and 2) th
15、at analysis of these phenomena during the design phase of a project can potentially save a lot of time and money.,The fundamental design flaw in the Tacoma bridge was a failure to account for the resonance vibrations generated in the structure due to the aerodynamic forces.,,Subsequently, the replac
16、ement bridge design was tested a wind tunnel to measure potential wind effects before being built, and such type of testing became standard for all future bridge designs.,93,The Tacoma Narrows Bridge disaster illustrates two main points:,,that fluid dynamics can play a role in many critical phenomen
17、a outside the traditional spheres of aerospace and mechanical engineering and,,that analysis of these phenomena during the design phase of a project can potentially save a lot of time and money.,94,Bernouli,,(1667-1748),Euler,,(1667-1748),Stokes,,(1819-1903),Navier,,(1785-1836),Archimedes,,(BC287 -
18、BC212),Reynolds,,(1842-1912),Prandtl,,(1875-1953,）,Taylor,,(1886-1975),為什么要學習,CFD,95,為什么要學習,CFD,流體力學的三種研究方法,,17,世紀，實驗流體力學（法國和英國,),,18,和,19,世紀，理論流體力學（歐洲）,,20,世紀,70,年代,,試驗,,CFD,,理論,96,作為研究工具的,CFD,數(shù)值風洞（,Numerical Wind Tunnel,）,,風載荷－圓屋頂（,Smooth and Rough Domes,）,Dome of the Rock > Jerusalem, 684 AD,^ Ta
19、j Mahal, Agra,,India 1631-1641,97,作為研究工具的,CFD,St. Peter’s >,,Rome,,1546-1564,北京國家大劇院,98,Velocity Contours:,,U,max,= 15 m/s,作為研究工具的,CFD,Wind-Tunnel Initial Conditions,,20 m,2 m,1.8 m,Grid: 86,000 cells,,Z = 1m,,Z = 0.8 m,,ASCE 7-98C,,Windtunnel,,99,Grid Systems: One and Two Domes,,,,,,18,000 Cells,,
20、33,000 Cells,,16,400 Cells,,43,000 Cells,100,,12,800 cells,Grid Systems: One and Two Domes,,101,Hemisphere Grids,Boundary layer & Hex Grid,Boundary layer & Tet Grid,102,Single Dome Comparisons: Pressure Profiles,,103,Single Dome Comparisons: Reynolds Number Variation,Reynolds Number = (U H/,?,) = 1
21、85,000,,,Reynolds Number =,(U H/,?,) = 1,440,000,,,Conclusion: No significant difference,,,,,104,Double Dome Comparisons Approach wind at 90,o,,105,Surface Pressures: Angles 0,o,, 45,o,& 90,o,,,,,,,,,106,Cp Contours: numerical,Cp Contours: experimental,,,,,,Pressure Coefficient Contours: Experimen
22、tal vs Numerical:,,Approach wind at 0,o,107,作為設(shè)計工具的,CFD,108,作為設(shè)計工具的,CFD,109,作為設(shè)計工具的,CFD,110,作為設(shè)計工具的,CFD,111,作為設(shè)計工具的,CFD,112,CFD,應(yīng)用實例,-,Automobile,113,CFD,應(yīng)用實例,-,Aerospace,,,114,CFD,應(yīng)用實例,-,Chemical,Furnace Nox Reduction,115,CFD,應(yīng)用實例,–,Civil Engineering,Lower Monumental Dam Forebay,116,CFD,應(yīng)用實例,-,Mult
23、i-scale CFD applications,,Eye ~ 10,-5,m,Turbine Blade ~ 10,-2,m,Aircraft Engine ~ 1m,Oil Reservoir ~ 10,3,m,Ocean Flow ~ 10,5,m,Binary Stars ~ 10,12,m,,,,,,117,計算方法,,高精度、高分辨率的計算方法,,并行算法,,遺傳算法,,無網(wǎng)格算法,CFD,研究范圍,118,CFD,研究范圍,計算,物理,模型,,新的,湍流,模型,,多,相流,模型,,化學非平衡問題,,太陽風問題,,119,CFD,研究范圍,網(wǎng)格技術(shù),,網(wǎng)格與流動特征的相容性,：,對于某些復(fù)雜流動問題, 如果使用傳統(tǒng)的網(wǎng)格技術(shù), 無限加密網(wǎng)格, 就可能使計算結(jié)果失真, 此時就要求有構(gòu)造與特征相適應(yīng)的網(wǎng)格, 例如在渦的周圍鑲嵌錐形網(wǎng)格,。,,分塊網(wǎng)格以及混合網(wǎng)格技術(shù),：,分塊網(wǎng)格主要用于處理復(fù)雜幾何形式, 也用于并行計算,。,,混合網(wǎng)格技術(shù)包括矩形網(wǎng)格和非結(jié)構(gòu)網(wǎng)格的混合使用,。,120,應(yīng)用領(lǐng)域拓展研究,,生物力學、生物醫(yī)藥,,航天航空，環(huán)境污染,,多相流動、微型機械流動,,電子技術(shù),,高速火車,,高速船舶,CFD,研究范圍,
第一章-CFD的基本原理-2010
