StarCCM+ Pipe Flow Tutorial

Transcription

1 2/1/12 5:54:46 PM Star-CCM+ Pipe Flow Tutorial page: 1 I. Plan the Analysis A. Physical Model D V L 1. Laminar flow of air 2. Dimensions: D = 3 cm, L =? 3. Boundary conditions (a) Choose inlet velocity to guarantee laminar flow Inlet boundary condition can be specified as uniform velocity or inlet mass flow rate. What are the values of the mean velocity or the mass flow rate? (b) Choose pressure outlet Pressure outlet imposes the least constraint Where to locate the outlet? How long should the pipe be? B. Mesh resolution 1. What is the desired dimension of the cells in the center of the domain? 2. What surfaces are important for engineering analysis? What mesh resolution should be imposed on those surfaces C. What computational results are desirable? 1. Flow field rendered as vectors and velocity profile 2. Pressure distribution rendered as surface plot, contour plot on center plane, and line plot D. How can the model be simplified The flow is two-dimensional and axisymmetric. We will solve this problem with a 3D model even though it is computational wasteful II. Start a New Simulation A. Launch CCM+ B. From the File Menu, select "New Simulation" C. In the dialog box, make sure the "Serial" button (in upper left corner) is selected, and click OK This will create a new Simulation Tree named "Star 1" in the explorer pane. The Star 1 tree has "Continua" and "Tools" nodes D. Orientation to the User Interface See "Using the Star-CCM+ Workspace", in the Using Star-CCM+ chapter, p. 351 of the User Guide See also "Changing a Three-Dimensional Visualization Display" on page 527 of the User Guide: Using Star-CCM+" --> "Using the Star-CCM+ Workspace" --> "Using the Graphics Window" --> "Changing a Three-Dimensional Visualization Display" 1. Pan with right mouse button 2. Zoom with middle mouse button or scroll wheel 3. Rotate with left mouse button 4. Align with Axis by... (a) Right click on the object (b) Select "Align View to Surface Normal" from the pop-up (c) Alternative: Use the properties of the Scene node Geometry Scene --> Parts -->... select the part, right click, and select "Align to Part Normal" E. Where to find help

2 page 2 III. Build the geometry of the model A. Click to expand the geometry node B. Right click 3D-CAD models, select New C. Select XY plane (any will do) under the features node, Right click "Create Sketch" D. Set grid scale for CAD drawing E. Sketch a circle and extrude it to create a cylinder 1. Select circle tool (circle from center) 2. Draw circle with radius m 3. Click OK 4. Right-click on sketch1 (the circle) and select Create Extrude from pop-up

3 page 3 5. enter 0.45m for the DIstance, and click OK F. Label the surfaces This will make it easier to identify boundaries of the Regions later in the model setup 1. Rotate the model so that the inlet (or outlet) end is visible 2. Right-click on the face, and select "Rename" from the pop-up menu 3. Change the name of the surface to "inlet" (or "outlet") 4. Repeat the preceding steps to label the outlet (or inlet) and the pipe walls G. Save the current file as laminar_pipe.sim H. Close the 3D-CAD model, and return to the Simulation Pane Notice that the view of the part shows up as a Geometry Scene IV. Create a Geometry Part from the 3D CAD Model To use a 3D-CAD model in a simulation it must first be used to create geometry parts. A. You can rename the 3D CAD model (or not). I suggest "Pipe fluid" or similar name for the part B. Expand the Bodies node C. Select Body 1 (or whatever you named the pipe object) D. Right click and select New Geometry Part Notice that a new Part is created under the Parts node Also note that the names assigned in the CAD tool (Inlet, Outlet and Walls) have been propagated to the nodes of the Parts tree V. Create a Mesh Continuum A. Select Surface Remesher

4 page 4 2. Polyhedral Mesher 3. Prism Layer Mesher B. Set the Base size 1. Expand the Reference Values node 2. Select Base Size and set it to m VI. Create a Physics Continua Refer to Modeling Physics on page 2174 of the User Guide A. Select Three Dimensional 2. Steady 3. Gas 4. Constant Density 5. Segregated flow 6. Laminar VII. Create a Region that contains the pipe object From the Star-CCM+ User's Guide: "Regions are volume domains (or areas in a two-dimensional case) in space that are completely surrounded by boundaries. They are not necessarily contiguous, and are discretized by a conformal mesh consisting of connected faces, cells and vertices." Translation: A region is a volume of material with the same physical properties and the same meshing model. For the pipe flow tutorial, there is only one Region. The boundaries of the region are used to impose boundary conditions on the model A. Right click on the Region node and select New B. Select the Geometric Parts for the region 1. In the Properties pane, click in the area to the right of "Parts" 2. Expand the Parts node in the pop-up window 3. Select the Pipe Fluid region (or Body 1 if you didn't name the Part) 4. Click OK C. Create Boundaries of the region 1. Right click on Boundaries and select New 2. Select the new boundary, right-click and select Rename. Change the name to Inlet (a) With the Inlet boundary (under the Region node) selected, Click on Part Surfaces Expand the nodes and click on the inlet

5 page 5 Click OK

6 page 6 (b) Set the boundary type to inlet with a prescribed velocity Select the Type characteristic in the inlet property pane Select Velocity Inlet from the pop-up menu Expand the Physics Values node and select Constant Set the Value to 0.24 m/s 3. Repeat creation of boundary for the Outlet (a) Click on Part Surfaces (b) Expand the nodes and click on outlet (c) Click OK (d) Set the Type to Pressure outlet 4. Select the remaining boundary, and make sure that only the walls are selected. Change the name from Default to Wall

7 page 7 VIII. Generate the mesh A. Click Generate Surface Mesh on the main menu bar B. Create a scene to view the mesh 1. Scroll down to the Scene node, Right click, select New Scene -> Mesh 2. Expand the mesh node (a) In the C. IX. Solve the flow field A. Open the "Stopping Criteria" Node B. Change the Maximum Steps property to 200 C. Open a Scalar Scene to visualize the solution as it is happening OPTIONAL 1. Right-click the Scene node and select New Scenes -> Scalar 2. Open the Displayers Node 3. Select Scalar 1 (a) Click on the Scalar Field node (b) In the Properties panel, click on the "Function" pop-up and (scroll down to) select "pressure" D. Create reports to monitor the maximum and minimum pressure OPTIONAL 1. Right-click "Reports" and select New Report -> Maximum 2. Click on the "Maximum 1" node that was just created (a) Rename the report to "Maximum Pressure" (b) Click on the "Scalar" Property and select "Pressure" from the pop-up menu for scalar Properties (c) Click on the "[ ]" value for the Parts Property A dialog box opens Select the "pipe" in the "Select From" (left-hand) list of objects and click the > icon to move the pipe ot the "Selected" (right-hand) list of objects Click CLOSE 3. Right-click on "Reports" and select "New Report" -> Minimu 4. Repeat the steps for the maximum pressure report, but this time the minimum value will be reported. E. Make the Monitor Plot visible 1. Select the Plots -> Maximum Pressure Plots node in the Simulation Tree F. Run the simulation

8 page 8 X. Inspect the solution A. Residual Plot. B. Monitory Plot -- Maximum Pressure.

9 page 9 C. Scalar plot -- pressure on pipe wall 1. Select the "Scalar Scene 1" 2. Open the "Displayers" node and select the "Scalar 1" node 3. Expand the "Parts" node (a) Make the Pipe wall visible In the "Parts" property, click on the "[ ]" value Select "wall" and click the > icon to move the wall from the "Select From" list to the "Selected" list Click close (b) Select "Scalar Field" node in the Scalar 1 scene. The result should be a shaded surface plot of the pressure on the pipe wal

10 page 10 D. Velocity Vector Plot 1. Scenes -> New Scene -> Geometry 2. Derived Parts -> Plane Section (a) Leave defaults for Plane Parameters (or adjust as necessary to put the plane through the center) (b) Select "New Vector Displayer" from the Display box (c) Click Create 3. Modify vector length (a) Under the Geometry Scene 2 node (b) Open the Displayers (c) Select Section Vectors (d) Select Relative Length In the properties pane, set the Glyph Length (%) to a new value, say 2 E. Velocity Profile plot F. Pressure along pipe axis XI. Modify the model and rerun it A. Change the inlet BC from uniform velocity to a mass flow rate