Static Mixer: Geometry and Mesh Workshop 4.1 Static Mixer: Geometry and Mesh

Workshop 4.1: Static Mixer This workshop will take you through the process of creating a geometry in DesignModeler and using Automatic meshing method to create a simple mesh for that geometry in Meshing. The basic steps involved in creating a CFD mesh are: 1. Create the Geometry (DesignModeler). 2. Define Named Selections for some 2D regions (DesignModeler). 3. Create surface and volume mesh (Meshing). This workshop is intended to give you a feel for the geometry and mesh creation process from start to finish. The methods used and the steps you follow will be discussed and explained in later lectures.

Workshop 4.1: Static Mixer 1. Launch ANSYS Workbench and start new geometry Click Start > Programs > ANSYS 11.0 > ANSYS Workbench 2. Launch DesignModeler and start new geometry Left click New Geometry After new window pops up, select Meter for length unit, then click OK

Workshop 4.1: Static Mixer

Workshop 4.1: Static Mixer You will begin by creating a sketch of the main body profile which you will revolve about the Y-axis to create the main body of the mixer Modeling: > ZXPlane Selecting ZXPlane on the tree displays the sketch plane on the Model View. Click on the Look-At icon to orient the view normal to the plane. Modeling: Sketching tab Selecting the Sketching tab after selecting a plane creates a new sketch and toggles to Sketching mode Sketching: Settings > Grid This is a simple geometry characterized by dimensions of 2.0 m, 1.0 m, & 0.5 m. A grid can be displayed and snapped to to simplify the assignment of the proper dimensions to features that you sketch. Toggle on Show in 2D and Snap to Grid. Click on Major Grid Spacing and set it to 1.0 m Click on Minor-Steps per Major and set it to 2 Zoom in on the Model View (click and drag with the right mouse button) so that the area displayed is centered about the origin with six major steps in the x- and z-directions.

Workshop 4.1: Static Mixer 4. You will now draw the outline of the main body profile as a closed-ended polyline Sketching: > Draw > Polyline The profile of the polyline is shown in the picture at right. Its left edge lies on the X-axis. The main portion is a square with a height and width of two. A tapered section reduces the width to 0.5 over a vertical distance of 1.0. The 0.5 width is maintained for a vertical distance of 1.0 and then the profile is closed as shown. Left-click on the sketch to define each end point of the various line segments in turn. When you arrive back at the starting point, right click and select Closed End from the menu that pops up. You have now completed Sketch1. You will now revolve this sketch by 360 degrees about the X-axis to create the main body of the mixer. X-axis

Workshop 4.1: Static Mixer 5. You will revolve Sketch1 by 360 degrees about the X-axis to create the main body of the mixer. Click on the Revolve icon on the menu bar to bring up the Details view for the revolve 3D operation. The view will switch to the Modeling view In the Details view, the Axis box should have Apply and Cancel tabs. If these are shown, left- click on the X-axis and then left-click on Apply. If the Axis box, shows Not Selected, you must left-click in it first to bring up the Apply/Cancel tabs. Set the Angle to 360 degrees and leave the other settings at their default values. Click on Generate on the main toolbar. You should see the solid geometry created by revolving Sketch1 through a full circle about the X-axis.

Workshop 4.1: Static Mixer

Workshop 4.1: Static Mixer 6. You will now create a new sketch on the Z-X plane to draw the profile of the first-side pipe. The body you’ve already created may make it difficult to see the sketch clearly. In the Tree View, left-click on the + sign next to the last entry which shows 1 Part, 1 Body to expand it. Right click on the Solid, select Hide Body and left-click with the mouse. The body should disappear from the Model View. In the Tree View, left-click on the ZXPlane and then click on the New Sketch icon to create Sketch2 Sketching: > Draw > Circle Click on the Look-At icon to orient the view normal to the ZXPlane. Draw a circle centered at (X=1,Z=1) with a radius of 0.5 m. You can snap to the grid by left-clicking with the mouse. This completes Sketch2. Sketch 2

Workshop 4.1: Static Mixer 7. You will extrude Sketch2 by 3 m in the direction normal to the ZXPlane to create the first side pipe. Click on the Extrude icon on the menu bar to bring up the Details view for the extrude 3D operation. The view will switch to the Modeling View In the Details view, you can see that Sketch2 is already selected as the sketch for the extrude operation. By default, if you click on a 3D operation icon from an active sketch, that sketch will be selected. This selection can always be edited before or after you click Generate. Change the Depth in the Details view to 3 m. With the Type set to Fixed and the Direction to Normal, this will extrude Sketch2 3.0 m in the normal direction to the ZXPlane (this is in the Y direction as you can see from the plane normal vector). Leave all other settings at their default values and click Generate.

Workshop 4.1: Static Mixer If you look at the Tree View, you will see that you still have 1 part and 1 body. When you add material to an existing model using a 3D operation such as revolve or extrude, DesignModeler will, by default, “melt” the solids together to create a single solid. You can control this by freezing individual solids or using the Add Frozen operation. Left click on the solid in the Tree View, you can see the solid shown as right. Highlight the ZXPlane in the Tree View and click on the New Sketch icon. You will next draw the circle which you will use to define the second side pipe. Since the two otherwise identical side pipes are 180 degrees apart, Sketch3 will just be the mirror image of Sketch2 relative to the z=0 plane.

Workshop 4.1: Static Mixer 8. The circle for the second side pipe will also have a radius of 0.5 m, but will be centered at an (X,Z) location of (1,-1) Sketching: > Draw > Circle Click on the Look-At icon or the -Y-axis on the display triad to orient the view normal to the ZXPlane. Sketch 1 Sketch 3 Sketch 2 Draw a circle centered at (X=1,Z=-1) with a radius of 0.5 m. You can snap to the grid by left-clicking with the mouse. This completes Sketch3. 9. Click on the Extrude icon. In the Details View, make sure that Sketch3 is selected and that the Depth is set to 3 m. Change the Direction to Reversed. This will extrude the sketch in the direction opposite to the plane normal (or in the -Y direction). Click Generate. Right-click on the solid in the Tree View and unhide it (Show Body) to see the completed geometry.

Workshop 4.1: Static Mixer 10. Now we need to give specific names for some 2D regions so that later we can use them to create different boundaries. Click Tools>Named Selection, and left click Named Selection In Details View window, set Named Selection to in1, and select one end surface of side pipe at +y location click Apply Click Generate

Workshop 4.1: Static Mixer 11. Following the same procedure as step 10 to create Named Selection in2 on the other side pipe end at –y location and Named Selection out on the bottom pipe end at –x location. in1 in2 out

Workshop 4.1: Static Mixer The geometry is now complete. Click on File>Save to save the DesignModeler database. A new window Save As will pop up. Change the folder to your working directory, set the File name to StaticMixer.agdb, and click Save. Click on the Project tab in the top left corner of the screen to change to the Project page.

Workshop 4.1: Static Mixer With the DesignModeler database highlighted at right as shown below, you will now see a New Mesh entry in the DesignModeler tasks list. Make sure in Default Geometry Options section, check the box for Named Selections and clear anything entered in the entry box. Then left-click on the New Mesh task entry to bring up the Meshing workbench module.

Workshop 4.1: Static Mixer In Details of “Mesh” window, make sure that Physics Preference is set to CFD, and Relevance Center is set to Medium Right click Mesh and left click Generate Mesh

Workshop 4.1: Static Mixer The final mesh is shown as following Click File>Save to save StaticMixer.cmdb file

Workshop B.2 Static Mixer: Basic Settings, Mesh Controls and Inflation

Goals This workshop will take you through the process of meshing a Static Mixer geometry with CFX-Mesh. Line mesh controls and inflation layers will be added to better refine the mesh The basic steps involved in this workshop are: 1. Start a new instance of the ANSYS Meshing Application and open the geometry file to be meshed 2. Set the Mesh Method to CFX-Mesh and edit the Method 3. Define any desired composite regions 4. Set global mesh spacings (Body Spacing and Face Spacing) 5. Preview the initial surface mesh 6. Define Point Spacings and Line Mesh Controls 7. Define Inflation Boundaries 8. Generate the Volume Mesh and save the meshing database

Starting the Meshing Application Copy the file staticmixer.agdb to your working directory Launch ANSYS Workbench Double click on Mesh under component systems. This will create a ‘Mesh component’ in the Project Schematic area. Right click on and “Import Geometry” and click on “Browse…”. Locate and open the file staticmixer.agdb. Once the geometry is loaded double click on to open the meshing application.

Meshing Options Form When the Meshing Application comes up, go to the Meshing Options Panel which appears at the right of the screen Set the Physics Preference to CFD Set the Mesh Method to CFX-Mesh Make sure that Set Meshing Defaults toggle is enabled Click OK

CFX-Mesh Note that the model is now displayed in the CFX meshing environment.

Making the Model Transparent In CFX-Mesh, click on the Geometry entry in the Tree View. In the Details View and move the Transparency slider to 50% to make the model partially transparent This makes it easier to see hidden faces in the model

Defining Composite Region in1 Right-click on Regions in the Tree View and select Insert Composite Region Create a Composite Region named in1 at the side pipe inlet as shown

Defining Composite Region in2 Create a Composite Region named in2 at the other side pipe inlet as shown

Defining Composite Region out Create a Composite Region named out at the bottom pipe outlet as shown

Setting the Global Body Spacing Click on the + sign next to the Spacing entry in the Tree View to expand it Set the Default Body Spacing to 0.20 m Note the mesh size preview icon in the viewport

Setting the Global Face Spacing Set the Default Face Spacing Option to Angular Resolution with a setting of 18° Set the Minimum Edge Length to 0.015 m and the Maximum to 0.20 m Again note the mesh size preview icon

Initial Mesh Preview Click on the + sign next to Preview in the Tree View to expand it Right-click on the Default Preview Group and select Generate Surface Meshes

Generating a Volume Mesh The initial mesh is rather coarse for CFD purposes although it illustrates the basics steps involved in generating a tetrahedral mesh. Right-click the Mesh entry in the Tree View and select Generate Volume Mesh CFX-Mesh will create the volume mesh The information panel at the bottom right will display the node and element count for the mesh

Mesh Refinement The first part of this tutorial resulted in a rather coarse mesh with no resolution of the boundary layer near walls Although a better quality mesh for CFD purposes could be generated by defining finer global mesh spacings, the global mesh spacings will be left as they are Instead, a mesh control will be defined to refine the mesh in the area of the two pipe inlets. Also, an inflation layer will be added to the all walls in the geometry to better resolve the boundary layer

Mesh Control: Point Spacing In the tree view right click on Controls under the Mesh listing and Insert a Point Spacing In the Details View for the Point Spacing enter the following: Length Scale = 0.1 Radius of Influence = 0.5 Expansion Factor = 1.2 This defines a point spacing which describes the element size and the region of influence over which it will be applied

In the white text box, clear None and type in 1,-3,-1 Line Control 1 Right-click on Controls in the Tree View, and select Insert > Line Control In the Details View for the Line Control, click on Cancel in the box next to the first Point. Right-click the red bar in the box next to the first Point and select Edit in the pop-up menu In the white text box, clear None and type in 1,-3,-1 You can hit Enter from the keyboard or click in the model view to finish Units are entered automatically Similarly set the coordinates of the second Point to 1,-1,-1 Leave the Option as Uniform Click in the empty Spacing box and select Point Spacing 1 from the Tree View and then click Apply

Line Control 2 and Inflation In the Tree View, right-click on Controls under the Mesh listing and Insert another Line Control For Line Control 2: Enter 1, 3 ,1 for the first Point Enter 1, 1 , 1 for the second Point Select Point Spacing 1 as the Spacing In the Tree View right-click on Inflation and Insert an Inflated Boundary In the Details View for Inflated Boundary 1, click in the Location box marked None, select Default 2D Region from the Tree View as the Location and click Apply This will inflate from all walls in the model Set the Maximum Thickness for the inflated boundary to 0.2 m

Mesh Preview for Refined Mesh Right-click on Preview > Default Preview Group and select Generate This Surface Mesh Notice the finer mesh in the two side pipes You can modify the Length Scale of Point Spacing 1 to refine the mesh further Also note the quad faces on the faces normal to the inflated boundary

Final Volume Mesh You are now ready to create and save the volume mesh: Select Tools > Options > CFX-Mesh Options Check that Volume Mesh Output is set to Add to CMDB File Click OK Click on the Generate Volume Mesh icon on the task bar When the process finishes, save your CFX-Mesh database (File > Save) The volume mesh is now stored in the Meshing Application cmdb file Note the change in the node and element count in the Information window and the addition of prisms from inflation