ICEM-圆柱扰流.doc

Example on using commercial softwareFlow around a circular cylinderY.F.LinTwo Dimensional problemsFlow around a circular cylinderProblem DescriptionAir flows across a cylinder with the uniform velocity 0.003m/s in the wind tunnel. The length of the wind tunnel (fluid domain) has 25m long and 10 m height. The diameter of cylinder is 1m.Wall (SideA)InletOutlet5DCylinderWall (SideB)Fluid domain5D20DAssumption and Boundary Conditions:1. 2 dimensional problems2. Steady state condition3. The uniform flow velocity4. No Heat transfer5. Neglect the gravitational force6. Constant air densityPre-processing stageIn this stage, we implement the “ICEM CFD” to perform the pre-processing work. The basic steps as follow:1. Establish geometry model2. Block the parts3. Generation the O grid4. Mesh the model and check quality of mesh5. Extrude the mesh6. Reset the BCs (boundary conditions)7. Output to CFX5.7.1 Creating Geometry1. Open ICEM CFDDouble Click the “ICEM CFD” Icon, afterwards, you can see the interface of the ICEM CFD.Open FileNew Project: Set the name with “cylinder_2d”, and Click “Save”2. Creating Geometry:A. PointsClick button “Create Point” and then click button “Explicit Coordinates”Set the points in Cartesian coordinate system(X, Y, Z) with ( X=0, Y=0, Z=0 ) respectively.Click “Apply” button and see the screen: a point is created A tree widget can be seen at left of the screen (A) and (B) The same method creates other points:X=0; Y=0.5, -0.5 X=-5; Y=5, -5X=20; Y=5, -5 Y=0; X=0.5,-0.5 B. Draw line (curve)First of all see the tree widget, open ModelGeo-55metryPoints by right buttonSelect Show Point Names and you can see the name of each point like the figure showed.Now you can create curves Click button “Create/Modify Curve” Click button “Create Curve” Note: the left corner of the black screen: Select locations with left button, middle=done, right=cancelSelect points by using left button of the mouse.Change the name of the Part with “INLET”: Select PONITS.05 and POINTS.06 with left button (A),And draw a line with middle button “done” (B) and the INLET part is created in the tree widget.The same steps draw the curves named “OUTLET, SIDEA, SIDEB” with the POINTS.07and POINTS.08, POINTS.06 and POINTS.07, POINTS.05 and POINTS.08 respectively.We will see the line and the tree widget Draw the cylinderClick button “Circle or arc from Center point and 2 points on plane”. Set the Part with name “CYLINDER”Click button and select points “POINTS.00, POINTS.01, POINTS.03” with left button respectively (A). Draw the cylinder by middle button (B).See tree widget:Close Points nameUse button to fit the window.Set the body and material. Click button “Create Body”Choose button “Material Point” and select “Selected surfaces” in the “By Topology” menu.Change the name of the part with “FLUID”; open the Show Point Name of the tree widget and use select POINTS.06 and POINTS.08.The same way change the part name with “CYLINDER” and select POINTS.01 and POINTS.02.Close Show Point Name and open the tree widget:Open the bodies and you can seeAt last, open the FileGeometrySave Geometry AsGive it the name with “cylinder_2d”. Click “save”. Now we begin to block the model. Click button “Create Block”See the first one , choose the part with “FLUID”, from the pull down menu select “FLUID”And set the Initialize Blocks type with “2D Planar” Click “Apply” button. We will see that the colors of figure are changed. From (A) to (B)See the tree widget: ModelBlockingThen create some assistant points with button “Create Point”Y=0 X=-0.45,-0.4,-0.35,-0.3,-0.25,-0.2,-0.15,-0.1,-0.5, 0.5, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45X=0 Y=-0.45,-0.4,-0.35,-0.3,-0.25,-0.2,-0.15,-0.1,-0.5, 0.5, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45Now begin to block the region Click button “Split Block” Then select button “Split Block” See the split method, select “Prescribed point”Use the put down menu to select the Prescribed point, Use the button firstly select the Edge “INLET” and secondly select the Point “POINTS.03”.We will see the block line in the vertical direction of the INLET.Zoom the fiure.The same way we draw other block lines.From the “POINTS.01 to POINTS.04” See the tree widgetSelect the “Blocking” and select “Index Control” ModelBlocking: Index Control (using right button of the mouse)We can see at the right corner of the screenBy using button and we set I min=2 and see the figure The same way we set I max =3 , J min=2 , J max=3And the screen shown that The same way block again from “POINTS.00, POINTS.09 to POINTS.44”:(A)(B)(C) After block.See the tree widget: ModelPartsVORFN :using the right button select “Add to Part”. Click button “Blocking Material”, Add Blocks to PartUsing select blocking regions and we can see Zoom the block regions (A).Select the blocks in the cylinder or attached the cylinder (B)(C). Using the middle button to set it OK, and you can see blow (D). Click button “Associate” Select the associate edge to curve “Associate Edge to Curve” buttonUsing the choose the edge and curveChoosing edge:Select curves: Middle button:Set O grid Click button “Split Block” Click “Ogird Block” buttonSelect the See the tree widget: Open ModelPartsVORFNOpen the VORFN (A)Using button to select in or attached the cylinder (B)(C)(D). Using middle button to click “Apply” (E)Close “VORFN” from the tree widget (F) Click the “Reset”(G)Mesh the edges Click button “Set Curve Mesh Size” Using button to select Curve(s): Choose Method with “Element count” Set the Number with 100 and click Apply.See the tree: close the ModelGeometrypoints, and the ModelBlockingedgesUsing right button to select ModelGeometryCurves: Curve Node Spacing (by using right button)The same way set the “INLET” and “OUTLET” with number 100, the “SIDEA” and “SIDEB” with number 250. Click button “Pre-Mesh Params”Choose Blocking Pre-Mesh ParamsClick button “Update Sizes” and keep default, Then click ApplySee tree open ModelBlockingPre_Mesh: Project faces (by using right button)And we will see a menu Click Yes.Now we will see the mesh of the model.Zoom it see the local part Close GeomeryPoints and curves, and BlockingEdges.Then open FileMeshLoad from BlockingOpen FileMeshSave Mesh As: and set the name with “cylinder_2d”Open FileBlockingSave Blocking As: Save block with the name “cylinder_2d”Check the quality of the mesh Click button “Display Mesh Quality” Click ApplyWe can see no negatives mesh.Extrude meshClick button “Extrude Mesh” Use to select Elements:Method 1Click button “Select items in a part” and a menu appears:Click “All” and “Accept”Method 2 Put the left button and drag it to select all the regions (A)(C). Click middle button to accept (B)Give the New volume part name “FLUID2D”, new side part name “SIDE”, new top par name “TOP”And set the Spacing typespacing with “0.1”, then ApplySo the mesh change a height 0.1 in the Z direction (D)Box Zoom Click button “Shaded Full Display”(E)(F)Check the quality of the extrude meshSee the tree widget:Close top “TOP” (B)Close “FLUID” (C)Set the new boundary conditionsSee the tree widget:ModelParts: Create Part (by using the right button) Click “Create Part by Selection” button From the pull down menu of the Part: select the “CYLINDER”Using and left button drag