BEE453 Professor Ashim Datta 2005 Cornell University 1Tutorial: Creating and Meshing Basic Geometry in Gambit 2005 Cornell University BEE453, Professor Ashim Datta Authored by Vineet Rakesh Software: GAMBIT 2.1.6/ FIDAP 8.7.2 /Presto 1.2 Tutorial: Creating and Meshing Basic Geometry in Gambit..........................................................................1 Problem Specification................................................................................................................................2 Step 1: Run the software GAMBIT to create the geometry and to mesh it...............................................3 Step 2: Create a Brick ...............................................................................................................................4 Step 3: Create an Elliptical Cylinder..........................................................................................................6 Step 4: Unite the Two Volumes.................................................................................................................8 Step 5: Manipulate the Display................................................................................................................10 Step 6: Mesh the Volume ........................................................................................................................12 Step 7: Examine the Mesh ......................................................................................................................14 Step 8: Remove the mesh from Display..................................................................................................16 Step 9: Define boundaries and continuum ..............................................................................................17 Step 10: Save..........................................................................................................................................21BEE453 Professor Ashim Datta 2005 Cornell University 2Problem Specification The model consists of an intersecting brick and elliptical cylinder. The basic geometry is shown schematically in Figure 1.1 Figure 1.1: Problem specification Strategy This tutorial illustrates some of the basic operations for generating a mesh using GAMBIT. In particular, it demonstrates: ¾ How to build the geometry easily using the "top-down" solid modeling approach ¾ How to create a hexahedral mesh automatically The "top-down" approach means that you will construct the geometry by creating volumes (bricks, cylinders, etc.) and then manipulating them through Boolean operations (unite, subtract, etc.). In this way, you can quickly build complicated shapes without first creating the underlying vertices, edges, and faces. Once you have built a valid geometry model, you can directly and (in many cases) automatically create the mesh. In this example, the Cooper meshing algorithm is used to automatically create an unstructured, hexahedral mesh. More complicated geometries may require some manual decomposition before you can create the mesh. The steps you will follow in this tutorial are listed below: ¾ Create two volumes (a brick and an elliptical cylinder). ¾ Unite the two volumes. ¾ Automatically generate the mesh. ¾ Examine the quality of the resulting mesh.BEE453 Professor Ashim Datta 2005 Cornell University 3Step 1: Run the software GAMBIT to create the geometry and to mesh it In the Command Prompt, type: gambit –id brick brick is the filename Remember: The filename should be at the most 7 characters long. Now Gambit is launched. Click on Solver menu at the top of the Gambit window and choose FIDAP.BEE453 Professor Ashim Datta 2005 Cornell University 4 Step 2: Create a Brick 1) In the Operation toolpad (located in the top right corner of the GAMBIT GUI), select the GEOMETRY command button by clicking on it with the left mouse button. If the Geometry subpad does not appear when you select the GEOMETRY command button, click it again. The name of a command button is displayed in the Description window at the bottom of the GAMBIT GUI when you hold the mouse cursor over the command button. The GEOMETRY command button will appear depressed when it is selected. Selecting the GEOMETRY command button opens the Geometry subpad. Note that when you first start GAMBIT, the GEOMETRY command button is selected by default. 2) Use the left mouse button to select the VOLUME command button in the Geometry subpad. Again, this command button will be depressed when selected. Selecting this command button opens the Geometry/Volume subpad. 3) Use the left mouse button to select the CREATE VOLUME command button in the Geometry/Volume subpad. This command sequence opens the Create Real Brick form.BEE453 Professor Ashim Datta 2005 Cornell University 54) Left-click in the text entry box to the right of Width in the Create Real Brick form, and enter a value of 10 for the Width of the brick. 5) Use the Tab key on the keyboard to move to the Depth text entry box, and enter 6 for the Depth of the brick. 6) Use the Tab key on the keyboard to move to the Height text entry box, and enter 10 for the Height of the brick. The text entry box for Height can be left blank; GAMBIT will set this value to be the same value as the Width by default. 7) Select Centered from the option menu to the right of Direction. Hold down the left mouse button on the option button to the right of Direction until the option menu appears. Select Centered from the list. 8) Click Apply. A message appears in the Transcript window at the bottom left of the GAMBIT GUI to indicate that a volume, called volume.1, was created. The volume will be visible in the graphics window, as shown in Figure 1.2. If you make a mistake at any point in the geometry creation process, you can use the UNDO command button to undo multiple levels of geometry creation. At this point, you have only performed one operation, so you can only undo one operation.BEE453 Professor Ashim Datta 2005 Cornell University 6 Figure 1.2: Rectangular brick volume (side view) Step 3: Create an Elliptical Cylinder 1) Hold down the right mouse button while the cursor is on the CREATE VOLUME command button. 2) Select the CREATE REAL CYLINDER option from the resulting menu. This action opens the Create Real Cylinder form. 3) In the Create Real Cylinder form, enter a Height of 10. 4) Enter a value of 3 for Radius 1. 5) Enter a value of 6 for