Setting up Inflation The velocity gradients near the pipe wall surfaces can vary significantly, so it is advisable to apply inflation in these areas. 1. Click on Inflation in the Tree View. 2. In the Details View, check that Number of Inflated Layers is set to 5. 3. Leave the other settings as their default values. 4. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 5. Click on Default 2D Region in the Tree View to select the faces which are in the Default 2D Region for the Inflated Boundary. Click on Apply in the Details View. 6. Leave Maximum Thickness as the default setting. Generating the Volume Mesh Finally, you can generate the volume mesh. 1. Right-click on Mesh in the Tree View and select Generate Volume Mesh. 2. Save the GTM File as InjectMixerMesh.gtm. The mesh is now complete. 1. Select File>Save to save the CFX-Mesh database. 2. Switch to the Project Page using the tabs at the top of the window, and choose File>Save to save the project. Tutorial 3: Process Injection Mixing Pipe CFX-Mesh Tutorials . . © SAS IP, Inc. 40 If you want to continue by working through the CFX-5 example “Tutorial 3: Flow in a Process Injection Mixing Pipe” using the newly-generated mesh, and have CFX-5.7.1 in ANSYS Workbench installed on your machine, then follow these steps: 1. On the Project Page, a new entry will have appeared when you generated the file: Advanced CFD. Under this entry, double-click on InjectMixerMesh.gtm to open up CFX-Pre. 2. Once CFX-Pre has opened, choose File>Save Simulation As to save the simulation as InjectMixer. 3. Work through the CFX-5.7.1 tutorial, missing out the instructions in the sections “Creating a New Simu- lation” and “Importing a Mesh”. If you do not have CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then: 1. Exit from ANSYS Workbench by selecting File>Exit. 41 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 2: Mesh Generation 42 Tutorial 4: Circular Vent This example creates the geometry and mesh for a simple chimney stack. The following geometry and meshing features are illustrated: • Controls, for refining the mesh along a line; • Inflation; and • Preview Groups, for previewing part of the surface mesh. If you want to skip the geometry creation part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials. 1. Geometry Creation Creating the Project 1. Open ANSYS Workbench, and create a new empty project. Save it as CircVent.wbdb. 2. Choose New Geometry to open DesignModeler, specifying the units as meters. Creating the Solid The geometry consists of a cylindrical pipe which is placed in the center of a cylindrical region. 1. Create a new sketch ( ) based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle in the new sketch, centered on the origin and with radius 10 m. If you just extruded this circle, you would get a cylinder which consisted of three faces: circular top, circular bottom and the curved cylindrical face. However, you will need to apply a boundary condition in the CFD simu- lation to just half of the curved cylindrical face. The only way to do that effectively is to create the cylindrical face in two parts. This means that you need to modify the circle before extruding. 1. Select Construction Point at Intersection from the Draw Toolbox. This is located right at the bottom of the list. CFX-Mesh Tutorials . . © SAS IP, Inc. 2. Select the Y-axis and then select the circle somewhere near where it intersects the Y-axis. You should find that a point appears at the intersection. 3. Now select the Y-axis again, and select the circle somewhere near where the other intersection of it and the Y-axis occurs. A second construction point should appear. 4. Select Split from the Modify Toolbox of the Sketching tab. Right-click over the Model View and select Split Edge at All Points. 5. Click on the circle to perform the split. 6. Select Extrude from the 3D Features Toolbar. 7. Set Base Object to be the new sketch (Sketch1), and set Operation to Add Material. Set Depth to be 10 m. 8. Set Merge Topology? to No. This stops DesignModeler from optimizing the surfaces created by com- bining them where possible, which would prevent the splits in the circle from having any effect. 9. Click on Generate to create the cylinder. Now you will cut material from this cylinder to form the vent itself. 1. Create another new sketch ( ) based on the XYPlane. 2. Use Circle from the Draw Toolbox of the Sketching tab to draw a circle in the new sketch, centered on the origin and with radius 1 m. 3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch (Sketch2), and set Operation to Cut Material. 5. Set Depth to be 5 m, and click on Generate to cut the pipe out of the large cylindrical region. The geometry is now complete. 1. Select File>Save to save the geometry file. 2. Mesh Generation First open CFX-Mesh. Tutorial 4: Circular Vent CFX-Mesh Tutorials . . © SAS IP, Inc. 44 1. Switch from DesignModeler to the Project Page using the tabs at the top of the window, and click on Generate CFX Mesh to open CFX-Mesh. Setting up the Regions Create the region for the wind inlet: 1. Create a Composite 2D Region called Wind. 2. Select the large curved face with the lowest X-coordinates. Click on Apply in the Details View. Create the region for the opening to the atmosphere: 1. Create a Composite 2D Region called Atmosphere. 2. Select the other large curved face and the top of the large cylinder (highest Z-coordinate) to apply it to. Create the region for the vent opening to the atmosphere: 1. Create a Composite 2D Region called Vent. 2. Select the small circular face at the top of the vent to apply it to. This can be slightly tricky to select directly since from most viewing positions it is behind another face. Either: • Click over the axes in the bottom right corner of the Model View in the position shown in the picture below. As you move the cursor into this position, the black “-Z”-axis will appear (it is not shown by default). This will put the geometry into a good position for picking the required face. • This viewing position allows you to view the bottom of the geometry and you can look up the vent itself to see the small circular face at the top of the vent without it being behind another face. You can now select it directly. or • Click over the required face even though it is behind another face. The face at the front will be selected and a stack of Selection Rectangles (shown below) will appear at the bottom left of the Model View. Note that exactly how many selection rectangles there are will depend on exactly what the viewing position of your model was when you clicked over the face. • Each rectangle represents a face which was under the cursor when you clicked, with the left-most rectangle representing the front face. You will be able to see from the selection rectangles that this front face is outlined in red, which means that it is currently selected. Click on the rectangle which represents the face which you want. As you click on the rectangle, the corresponding face in the geometry will highlight. You may need to experiment to get the correct face. 45 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 2: Mesh Generation Setting up the Mesh Set the Maximum Spacing: 1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. 2. In the Details View, change Maximum Spacing to 2.0 m, and press Enter on the keyboard to set this value. Create inflated surfaces for the vent and ground surfaces: 1. Click on Inflation in the Tree View. 2. In the Details View, set Number of Inflated Layers to 4. 3. Leave the other settings as their default values. 4. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 5. Select the faces for the boundary. The two surfaces which it should be applied to are the side of the vent and the bottom of the large cylinder (lowest Z-coordinate). 6. Set Maximum Thickness to 0.2 m. Create a Control in the center of the vent to refine the mesh in this region of the simulation. You will use a Line Control, which refines the mesh in the region around a line. Point, Line and Triangle Controls all make use of the Point Spacing object. This defines a set of spacing values, which can be applied to the various Controls as desired. 1. Right-click on Controls in the Tree View, and select Insert>Point Spacing. 2. In the Details View, set Length Scale to 0.33 m. Set Radius of Influence to 1.0 m, and Expansion Factor to 1.15. 3. Right-click on Controls in the Tree View, and select Insert>Line Control. 4. In the Details View, there will now be two buttons, Apply and Cancel. Click on Cancel without selecting anything in the Model View, and then right-click in the same place and choose Edit. Enter 0 0 0 to set the coordinates of the first Point. 5. Set the coordinates of the second Point to be [0 0 4], in the same way. 6. You want the specified Point Spacing to apply to both points, so leave Spacing Definitions set to Uniform. 7. Click in the box next to Spacing, and then click on Point Spacing 1 in the Tree View to select the appro- priate Point Spacing for the Control. Press Apply to complete the selection. 8. In order to better see the inside of the vent, click on Geometry in the Tree View, and in the Details View, set Transparency to 40 %. If you ensure that the new Line Control is selected in the Tree View, and look at the vent in the Model View, you should be able to see where the Control has been created, as shown below. The line itself should be clearly visible, and the two spheres at each end show the Radius of Influence. Tutorial 4: Circular Vent CFX-Mesh Tutorials . . © SAS IP, Inc. 46 Generating the Surface Mesh To get a clear view of how the Control affects the mesh, it is convenient to generate just part of the surface mesh. 1. Right-click over Preview in the Tree View, and select Insert>Preview Group. 2. Change the name of the Preview Group to Ground. 3. For Location, select the large circular face (with a hole in) at the bottom of the geometry (lowest Z-co- ordinate). 4. Now right-click over the Preview Group Ground in the Tree View, and select Generate This Surface Mesh. The surface mesh will be generated on just the corresponding face. Generating the Volume Mesh Finally, you can generate the volume mesh. 1. Right-click on Mesh in the Tree View and select Generate Volume Mesh. 2. Save the GTM File as CircVentMesh.gtm. 47 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 2: Mesh Generation The mesh is now complete. 1. Select File>Save to save the CFX-Mesh database. 2. Switch to the Project Page using the tabs at the top of the window, and choose File>Save to save the project. If you want to continue by working through the CFX-5 example “Tutorial 4: Flow from a Circular Vent” using the newly-generated mesh, and have CFX-5.7.1 in ANSYS Workbench installed on your machine, then follow these steps: 1. On the Project Page, a new entry will have appeared when you generated the file: Advanced CFD. Under this entry, double-click on CircVentMesh.gtm to open up CFX-Pre. 2. Once CFX-Pre has opened, choose File>Save Simulation As to save the simulation as CircVent. 3. Work through the CFX-5.7.1 tutorial, missing out the instructions in the sections “Creating a New Simu- lation” and “Importing a Mesh”. If you do not have CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then: 1. Exit from ANSYS Workbench by selecting File>Exit. Tutorial 4: Circular Vent CFX-Mesh Tutorials . . © SAS IP, Inc. 48 Tutorial 5: Blunt Body This example creates the geometry and mesh for a simulation of flow over a vehicle body shape. Due to the symmetry of both the geometry and the flow pattern, only half of the body needs to be modeled. The following geometry and meshing features are illustrated: • Face Spacing, for refining the mesh on a particular face; • Inflation; • Proximity, for refining the volume mesh where two faces are close together; and • Preview Groups, for previewing part of the surface mesh. If you want to skip the geometry creation part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials. 1. Geometry Creation Creating the Project 1. Open ANSYS Workbench, and create a new empty project. Save it as BluntBody.wbdb. CFX-Mesh Tutorials . . © SAS IP, Inc. [...]... from the Draw Toolbox of the Sketching tab to draw a rectangle as shown below (note the orientation of the axes) The required dimensions are: H1 = 1 .44 m, V2 = 5.22 m Select the top right corner of the geometry to create the chamfer, as shown below CFX-Mesh Tutorials © SAS IP, Inc Section 1: Geometry Creation 7 Use Angle from the Dimensions Toolbox to specify the angle between the chamfer and the top... shown The values required are: V1 = 0.9725 m, R2 = 0.5 m 4 Select 5 Extrude from the 3D Features Toolbar Set Base Object to be the new sketch (Sketch2), and set Operation to Cut Material 6 Set Depth to be 1.5 m, and click on Generate to cut away the material The end of your blunt body should now look the same as in the picture below 52 CFX-Mesh Tutorials © SAS IP, Inc Section 1: Geometry Creation... complete, and can be extruded to form the body 1 Select 2 Extrude from the 3D Features Toolbar Set Base Object to be the new sketch (Sketch1), and set Operation to Add Material Set Direction to Reversed CFX-Mesh Tutorials © SAS IP, Inc 51 Tutorial 5: Blunt Body 3 Set Depth to be 0.9725 m, and click on Generate to create the solid The front end of the blunt body is already rounded; however, some more material... Tools>Freeze from the Menu Toolbar to freeze the body 3 Create a new sketch ( 4 ) based on the ZXPlane Use Rectangle from the Draw Toolbox of the Sketching tab to draw a rectangle as shown below Note that the rectangle extends below the bottom of the body (below the XYPlane) The required dimensions are: V5 = 12.39 m, V6 = 17.61 m, H7 = 4. 75 m, H8 = 0.25 m 5 Select 6 Extrude from the 3D Features Toolbar Set... Type to Fixed Set Depth to be 5.15 m, and click on create the solid Generate to You can now cut out the blunt body from the containing box, to leave just the region of interest for the CFD simulation CFX-Mesh Tutorials © SAS IP, Inc 53 ... body 1 Create a new sketch ( ) based on the ZXPlane 2 3 Select Fillet from the Modify Toolbox of the Sketching tab, and enter 0.5 m for the Radius in the box which opens to the right of the word Fillet 4 Select the two corners of the geometry that are on the Z-axis, to create the two fillets, as shown below 5 Select Chamfer from the Modify Toolbox, and enter 1.11 m for the Length in the box which opens . File>Save to save the geometry file. 2. Mesh Generation First open CFX-Mesh. Tutorial 4: Circular Vent CFX-Mesh Tutorials . . © SAS IP, Inc. 44 1. Switch from DesignModeler to the Project Page using the. not have CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then: 1. Exit from ANSYS Workbench by selecting File>Exit. 41 CFX-Mesh Tutorials . . © SAS IP,. CFX-5.7.1 in ANSYS Workbench installed or do not want to work through the CFX-5 example, then: 1. Exit from ANSYS Workbench by selecting File>Exit. Tutorial 4: Circular Vent CFX-Mesh Tutorials