Fluent一个英文例子.docx

1、Fluent一个英文例子Laminar Pipe FlowProblem SpecificationConsider fluid flowing through a circular pipe of contant cross-section. The pipe diameter D=0.2 m and length L=8 m. The inlet velocity Vin=1 m/ s. Consider the velocity to be constant over the inlet cross-section. The fluid exhausts into the ambient

2、 atmosphere which is at a pressure of 1 atm. Take density =1 kg/ m3 and coefficient of viscosity = 2 x 10-3 kg/(ms). The Reynolds number Re based on the pipe diameter is where Vavg is the average velocity at the inlet, which is 1m/s in this case. Solve this problem using FLUENT. Plot the centerline

3、velocity, wall skin-friction coefficient, and velocity profile at the outlet. Validate your results. Note: The values used for the inlet velocity and flow properties are chosen for convenience rather than to reflect reality. The key parameter value to focus on is the Reynolds no. Preliminary Analysi

4、sWe expect the viscous boundary layer to grow along the pipe starting at the inlet. It will eventually grow to fill the pipe completely (provided that the pipe is long enough). When this happens, the flow becomes fully-developed and there is no variation of the velocity profile in the axial directio

5、n, x (see figure below). One can obtain a closed-form solution to the governing equations in the fully-developed region. You should have seen this in the Introduction to Fluid Mechanics course. We will compare the numerical results in the fully-developed region with the corresponding analytical resu

6、lts. So its a good idea for you to go back to your textbook in the Intro course and review the fully-developed flow analysis. What are the values of centerline velocity and friction factor you expect in the fully-developed region based on the analytical solution? What is the solution for the velocit

7、y profile? Well create the geometry and mesh in GAMBIT which is the preprocessor for FLUENT, and then read the mesh into FLUENT and solve for the flow solution. Go to Step 1: Create Geometry in GAMBITStep 1: Create Geometry in GAMBITStrategy for Creating GeometryIn order to create the rectangle, we

8、will first create the vertices at the four corners. Well then join adjacent vertices by straight lines to form the edges of the rectangle. Lastly, well create a face corresponding to the area enclosed by the edges. In Step 2, well mesh the face i.e. the rectangle. Note that in 3D problems, youll hav

9、e to form a volume from faces. So the hierarchy of geometric objects in GAMBIT is vertices - edges - faces - volumes.Create a Working DirectoryCreate a folder called pipe in a convenient location. Well use this as the working folder in which files created during the session will be stored. Note for

10、ACCEL computer lab users: Each user gets his/her own 100 MB of disk space under S: at ACCEL. You can put your files in S: and itll be accessible from any computer. This is where you should put files that you want to keep and access later on. Start GAMBITStart your command prompt. Start Run In Window

11、s NT/2000/XP: Type cmd and press enter.In Windows 95/98/ME: Type command and press enter. Navigate your way to your working folder. For example, if you created a folder named fluent on drive S: in Windows, type cd S:fluent at the command prompt and press Enter. Start GAMBIT by typing gambit -id pipe

12、 at the command prompt and pressing Enter. If this doesnt work, try typing the full pathname to the GAMBIT executable: c:fluent.incntbinntx86gambit -id pipe This brings up the GAMBIT interface and tells GAMBIT to use pipe as the default prefix for all files created during the session. In Windows, th

13、e Exceed X-server starts up before the GAMBIT interface comes up. Exceed is a third-party application needed to render the interface in Windows (GAMBIT was originally developed under Unix). To make best use of screen real estate, move the windows and resize them so that you approximate this screen a

14、rrangement. This way you can read instructions in the browser window and implement them in GAMBIT. You can resize the text in the browser window to your taste and comfort:In Internet Explorer: Menubar View Text Size, then choose the appropriate font size.In Netscape: Menubar View Increase Font or Me

15、nubar View Decrease Font.The GAMBIT Interface consists of the following: Main Menu Bar: Note that the job name pipe appears after ID: in the title bar of the Utility Menu. Operation Toolpad:Well more or less work our way across the Operation Toolpad as we go through the solution steps. Notice that a

16、s each of the top buttons is selected, a different sub-pad appears. The Geometry sub-pad is shown in the above snaphot. Global Control Toolpad:The Global Control Toolpad has options such as Fit to Screen and Undo that are very handy during the course of geometry and mesh creation. GAMBIT Graphics:Th

17、is is the window where the graphical results of operations are displayed. GAMBIT Description Panel:The Description Panel contains descriptions of buttons or objects that the mouse is pointing to. Move your mouse over some buttons and notice the corresponding text in the Description Panel. GAMBIT Tra

18、nscript Window:This is the window to which output from GAMBIT commands is written and which provides feedback on the actions taken by GAMBIT as you perform operations. If, at some point, you are not sure you clicked the right button or entered a value correctly, this is where to look to figure out w

19、hat you just did. You can click on the arrow button in the upper right hand corner to make the Transcript window full-sized. You can click on the arrow again to return the window to its original size. Go ahead, give this a try.Select SolverSpecify that the mesh to be created is for use with FLUENT 6

20、.0:Main Menu Solver FLUENT 5/6Verify this has been done by looking in the Transcript Window where you should see:The boundary types that youll be able to select in the third step depends on the solver selected.We can assume that the flow is axisymmetric. The problem domain is:where r and x are the r

21、adial and axial coordinates, respectively.Strategy for creating geometryWe will put the origin of the coordinate system at the lower left corner of the rectangle. The coordinates of the corners are shown in the figure below:We will first create four vertices at the four corners and join adjacent ver

22、tices to get the edges of the rectangle. We will then form a face that covers the area of the rectangle.Create VerticesFind the buttons described below by pointing the mouse at each of the buttons and reading the Description Window.Operation Toolpad Geometry Command Button Vertex Command Button Crea

23、te Vertex Notice that the Create Vertex button has already been selected by default. After you select a button under a sub-pad, it becomes the default when you go to a different sub-pad and then come back to the sub-pad.Create the vertex at the lower-left corner of the rectangle:Next to x:, enter va

24、lue 0. Next to y:, enter value 0. Next to z:, enter value 0 (these values should be defaults). Click Apply. This creates the vertex (0,0,0) which is displayed in the graphics window. In the Transcript window, GAMBIT reports that it Created vertex: vertex.1. The vertices are numbered vertex.1, vertex

25、.2 etc. in the order in which they are created. Repeat this process to create three more vertices:Vertex 2: (0,0.1,0)Vertex 3: (8,0.1,0)Vertex 4: (8,0,0)Note that for a 2D problem, the z-coordinate can always be left to the default value of 0. Operation Toolpad Global Control Fit to Window Button Th

26、is fits the four vertices of the rectangle we have created to the size of the Graphics Window. (Click picture for larger image)Create EdgesWell now connect appropriate pairs of vertices to form edges. To select any entity in GAMBIT, hold down the Shift key and click on the entity. Operation Toolpad

27、Geometry Command Button Edge Command Button Create Edge Select two vertices that make up an edge of this rectangle by holding down the Shift button and clicking on the corresponding vertices. As each vertex is picked, it will appear red in the Graphics Window. Then let go of the Shift button. We can

28、 check the selected vertices by clicking on the up-arrow next to Vertices:. This will bring up a window containing the vertices that have been selected. Vertices can be moved from the Available and Picked lists by selecting them and then pressing the left or right arrow buttons. After the correct ve

29、rtices have been selected, click Close, then click Apply in the Create Straight Edge window. Repeat this process to create a rectangle. (Click picture for larger image) Create FaceOperation Toolpad Geometry Command Button Face Command Button Form Face To form a face out of the area enclosed by the f

30、our lines, we need to select the four ledges that enclose this area. This can be done by holding down the Shift key, clicking on each line (notice that the currently selected line appears red), and then releasing the Shift key after all four lines have been selected. Alternatively, an easier way to

31、do this would be to click on the up arrow next to edges:This will bring up the Edge List window. Click on All- to select all of the edges at once. Click Close.Click Apply to create the face.Go to Step 2: Mesh Geometry in GAMBIT Step 2: Mesh Geometry in GAMBITWell now create a mesh on the rectangular

32、 face with 100 divisions in the axial direction and 5 divisions in the radial direction. Well first mesh the four edges and then the face. The desired grid spacing is specified through the edge mesh. Mesh EdgesOperation Toolpad Mesh Command Button Edge Command Button Mesh Edges Shift-click or bring up the Edge List window and select both the vertical lines