ANSYS CFX-Mesh Tutorials phần 9 docx

Setting up the Regions Create the 2D Regions: 1. Create a Composite 2D Region called Sparger on the top part of the small hole (the ring sparger). 2. Create a Composite 2D Region called Top on the very top face of the reactor (highest Y-coordinate). 3. Create a Composite 2D Region called Column on the column walls. You need to select five faces: the three parts of the outside wall (highest X-coordinate), the bottom face of the reactor (lowest Y-coordinate) and the bottom part of the small hole which forms the ring sparger. 4. Create a Composite 2D Region called Symmetry1 on the two faces which lie in the XYPlane. 5. Create a Composite 2D Region called Symmetry2 on the two faces which are directly opposite the faces used for Symmetry1. Finally, create a Composite 2D Region on the internal face which will form the draft tube. In order to do this, it is important to understand the difference between faces and 2D Regions when there are multiple solids in the geometry, and how to use the selection rectangles. If you have not already done so, you are advised to work through or at least read the meshing section of Tutorial 6: Butterfly Valve and the meshing section of Tutorial 10: Heating Coil. For the Composite 2D Region which comprises the draft tube, it is appropriate to include only one side of the internal face. When you come to set up the Thin Surface boundary condition in CFX-Pre, the other side of the face will then be automatically identified as the other side of the thin surface. 1. Right-click over Regions in the Tree View and select Insert>Composite 2D Region. Change its name to DraftTube. 2. Click on the cyan ball in the triad at the bottom right of the Model View to put the geometry into a good viewing position for the selection. 3. Place the cursor in the position shown in the picture below and click with the left mouse button. Tutorial 11: Airlift Reactor CFX-Mesh Tutorials . . © SAS IP, Inc. 110 4. The selection rectangles will appear. The 2D Regions they correspond to are (from left to right): outside of the column, draft tube face (outside), draft tube face (inside), face from symmetry plane. Click on the second one down (draft tube face, outside), to select it. 5. Press Apply in the Details View. You should see that the text next to Location now reads 1 2D Region. 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 1.0 cm, and press Enter on the keyboard to set this value. A maximum edge length of 1 cm will produce a coarse grid of about 4000-5000 nodes, suitable only for instruc- tional and demonstrative uses. With the use of such a coarse mesh, the recirculation flow patterns in the reactor cannot be resolved adequately and some difficulties in convergence may be expected. To create a mesh that is appropriate for formal quantitative analysis of the airlift reactor in this tutorial, the maximum edge length should be 0.5 cm or shorter. The resulting mesh will contain significantly more nodes. Because the Default Face Spacing is set to use an Angular Resolution of 30 degrees, the mesh around the sparger is automatically refined since the sparger has a high curvature. 111 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 2: Mesh Generation 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 BubbleColumnMesh.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. If you want to continue by working through the CFX-5 example “Tutorial 16: Gas-Liquid Flow in an Airlift Reactor” 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 BubbleColumnMesh.gtm to open up CFX-Pre. 2. Once CFX-Pre has opened, choose File>Save Simulation As to save the simulation as BubbleColumn. 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 11: Airlift Reactor CFX-Mesh Tutorials . . © SAS IP, Inc. 112 Tutorial 12: Room with Air Conditioning This example creates the geometry and mesh for a room geometry, which can then be used in simulations to determine the effectiveness of an air conditioning system. In the CFD simulation, the air is input through a small vent in the roof of the room. The following geometry and meshing features are illustrated: • Imprint Surfaces, to add surfaces for boundary conditions; • Face Spacing, to refine the mesh on a particular face; and • Inflation. 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 HVAC.wbdb. (“HVAC” is an acronym for Heating, Ventilation and Air Conditioning.) 2. Choose New Geometry to open DesignModeler, specifying the units as meters. Creating the Solid The first step is to create the main solid, which is a simple box. 1. Create a new sketch ( ) based on the XYPlane. 2. Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at the origin and another at X = 3.0 m, Y = 3.0 m CFX-Mesh Tutorials . . © SAS IP, Inc. 3. Select Extrude from the 3D Features Toolbar. 4. Set Base Object to be the new sketch (Sketch1), and set Operation to Add Material. 5. Set Depth to be 2.5 m, and click on Generate to generate the solid. Breaking the Faces to form the Boundary Conditions The solid that you have just created has six rectangular faces. Some of these faces need breaking up, so that the features such as windows, door and vents exist as separate faces of the solid. This can be done by using Extrude with the Imprint Faces option. Using this option requires sketches of the correct dimensions to be created first. However, when the Extrude operation takes place, you cannot choose to have the Imprint Faces action only apply at a specified face; it will apply at all faces between the sketch and the required face. For this reason, the sketches cannot be created on the existing three planes since then they would always affect the faces of the solids which are co-planar with these planes. This means that you need to start by creating a new plane. 1. Create a new plane ( ), based on the XYPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 1 m. 3. Click on Generate to create the plane. 4. Create a new sketch ( ) based on the new plane (Plane4). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at X = 0.05 m, Y = 1.3 m and another at X = 0.15 m, Y = 1.7 m. 5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch (Sketch2), and set Operation to Imprint Faces. 7. Set Type to be To Next, and click on Generate to break the top face. Tutorial 12: Room with Air Conditioning CFX-Mesh Tutorials . . © SAS IP, Inc. 114 Notice that in the figure above, the top face has been selected in order to show that it is in two parts. These operations now need to be repeated to break the faces to form the windows and side vent. 1. Create a new plane ( ), based on the ZXPlane. 2. In the Details View, set Transform 1 to Offset Global Y, and set the Value of the offset to 1 m. 3. Click on Generate to create the plane. 4. Create a new sketch ( ) based on the new plane (Plane5). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at X = 1.25 m, Z = 0.75 m and another at X = 1.75 m, Z = 1.75 m. 5. Use Rectangle from the Draw Toolbox of the Sketching tab to create another rectangle, which has one corner at X = 2.05 m, Z = 0.15 m and another at X = 2.55 m, Z = 0.55 m. 6. Select Extrude from the 3D Features Toolbar. 7. Set Base Object to be the new sketch (Sketch3), and set Operation to Imprint Faces. 8. Set Direction to Reversed, Type to be To Next, and click on Generate to break a side face. 115 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 1: Geometry Creation 1. Create a new plane ( ), based on the YZPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 1 m. 3. Click on Generate to create the plane. 4. Create a new sketch ( ) based on the new plane (Plane6). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at Y = 1.25 m, Z = 0.75 m and another at Y = 1.75 m, Z = 1.75 m. 5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch (Sketch4), and set Operation to Imprint Faces. 7. Set Direction to Reversed and Type to To Next, then click on Generate to break another side face. Tutorial 12: Room with Air Conditioning CFX-Mesh Tutorials . . © SAS IP, Inc. 116 Finally, you need to break one more face to make a face for the door. However, this time, the plane which contains the sketch to be extruded must be outside the geometry. Otherwise, because the door reaches the edge of the room, you will find that the rectangular (unbroken) face which shares an edge with the door will be broken. 1. Create a new plane ( ), based on the YZPlane. 2. In the Details View, set Transform 1 to Offset Z, and set the Value of the offset to 4 m. 3. Click on Generate to create the plane. 4. Create a new sketch ( ) based on the new plane (Plane7). Use Rectangle from the Draw Toolbox of the Sketching tab to create a rectangle which has one corner at Y = 2.3 m, Z = 0.0 m and another at Y = 3.0 m, Z = 2.0 m. 5. Select Extrude from the 3D Features Toolbar. 6. Set Base Object to be the new sketch (Sketch5), and set Operation to Imprint Faces. 7. Set Direction to Reversed and Type to To Next, and click on Generate to break the side face. 117 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 1: Geometry Creation The geometry is now complete. 1. Select File>Save to save the geometry file. 2. Mesh Generation First open CFX-Mesh. 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 2D Regions: 1. Create a Composite 2D Region called Inlet on the vent in the roof (small rectangular face contained in the plane with the highest Z-coordinate. 2. Create a Composite 2D Region called Roof on the remaining part of the roof (highest Z-coordinate). 3. Create a Composite 2D Region called Window1 on the rectangular face which is cut out from the ZXPlane. This plane has two cutout rectangular faces, and you need the one which is taller and located at a higher Z-coordinate. 4. Create a Composite 2D Region called Window2 on the rectangular face which is cut out from the YZPlane. 5. Create a Composite 2D Region called VentOut on the rectangular face which is cut out from the ZXPlane. This plane has two cutout rectangular faces, and you need the one which is smaller and located at a lower Z-coordinate. 6. Create a Composite 2D Region called Floor on the rectangular face which is in the XYPlane. 7. Create a Composite 2D Region called Door on the tall, thin rectangular face which is cut out from the face with the highest X-coordinate. Setting up the Mesh Set the Maximum Spacing: 1. Click on Default Body Spacing in the Tree View, which is contained in Mesh>Spacing. Tutorial 12: Room with Air Conditioning CFX-Mesh Tutorials . . © SAS IP, Inc. 118 2. In the Details View, change Maximum Spacing to 0.25 m, and press Enter on the keyboard to set this value. This is a coarse length scale, suitable only for tutorial purposes. In order to better resolve the flow near the inlet and outlet vents, Face Spacings will be applied to these regions to refine the mesh. 1. Right-click on Spacing and select Insert>Face Spacing. 2. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.04 m. 3. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.3. 4. For Location, select Inlet from the Tree View. 5. Right-click on Spacing and select Insert>Face Spacing, to create another Face Spacing. 6. In the Details View, set Face Spacing Type to Constant, and set the Constant Edge Length to 0.1 m. 7. Set the Radius of Influence to 0.0 m, and Expansion Factor to 1.3. 8. For Location, select VentOut from the Tree View. Setting up Inflation It is a good idea to put inflation on the walls. 1. Click on Inflation in the Tree View. In the Details View, set Number of Inflated Layers to 5. 2. Set Expansion Factor to 1.2. Leave the rest of the parameters as their default values. 3. In the Tree View, right-click on Inflation and select Insert>Inflated Boundary. 4. For Location, select all of the Composite 2D Regions in the Tree View (including the Default 2D Region) except for Inlet and VentOut. The Details View should show 6 Composites after you have made the selection. 5. Set Maximum Thickness to 0.25 m. 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 HVACMesh.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. If you want to continue by working through the CFX-5 example “Tutorial 17: Air Conditioning Simulation” 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 HVACMesh.gtm to open up CFX-Pre. 2. Once CFX-Pre has opened, choose File>Save Simulation As to save the simulation as HVAC. 119 CFX-Mesh Tutorials . . © SAS IP, Inc. Section 2: Mesh Generation [...]... download it here (you will need to use “gunzip” to extract the required Parasolid file) CFX-Mesh Tutorials © SAS IP, Inc Tutorial 13: Can Combustor If you want to skip the geometry part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials 1 Geometry Import Creating the Project 1 Open ANSYS Workbench, and create a new empty project Save it as Combustor.wbdb 2 Choose New... missing out the instructions in the sections “Creating a New Simulation” 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: 1 120 Exit from ANSYS Workbench by selecting File>Exit CFX-Mesh Tutorials © SAS IP, Inc Tutorial 13: Can Combustor This example creates the mesh for a can combustor, which might typically be... save the geometry file 2 Mesh Generation First open CFX-Mesh 1 122 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 CFX-Mesh Tutorials © SAS IP, Inc Section 2: Mesh Generation Setting up the Regions Create the 2D Regions: 1 Create a Composite 2D Region for the fuel inlet called fuelin on the six tiny faces on the... status bar (the bar along the bottom of the ANSYS Workbench window) should change to show that you have selected 5 Bodies Right-click over the Model View and select Form New Part The Tree View should now show that you have 1 Part, 5 Bodies The geometry does not need any further modifications 1 Select File>Save to save the geometry file 2 Mesh Generation First open CFX-Mesh 1 122 Switch from DesignModeler... shown below 3 Create a Composite 2D Region for the secondary air inlet called secairin on the six small circular faces on the main body of the combustor These introduce extra air to aid combustion CFX-Mesh Tutorials © SAS IP, Inc 123 . 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 11: Airlift Reactor CFX-Mesh Tutorials. 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 12: Room with Air Conditioning CFX-Mesh Tutorials. required Parasolid file). CFX-Mesh Tutorials . . © SAS IP, Inc. If you want to skip the geometry part of the tutorial, then see the instructions in Introduction to the CFX-Mesh Tutorials. 1. Geometry