ansys_cfd流体分析实例

v1.0 可编辑可修改Example on using commercial software“ICEM CFD ”Flow around a circular cylinderTwo Dimensional problemsFlow around a circular cylinderProblem DescriptionAir flows across a cylinder with the uniform velocity 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 .Assumption and Boundary Conditions: 1. 2 dimensional problems 2. Steady state condition 3. The uniform flow velocity 4. 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:OutleWall (SideA)1.Establish geometry model2.Block the parts3.Generation the O grid4.Mesh the model and check quality of mesh5.Extrude the mesh6.Reset the BC’s (boundary conditions)7.Output toCreating Geometry1. Open ICEM CFDDouble Click the “ICEM CFD” Icon, afterwards, you can see the interface of the ICEM CFD.Open File>New 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 pointis createdA tree widget can be seen at left of the screen (A) and (B)A BThe same method creates other points:X=0; Y=, X=-5; Y=5, -5X=20; Y=5, -5 Y=0; X=,B.Draw line (curve)First of all see the tree widget, open Model>Geometry>Points by right buttonSelect Show Point Names and you can see the name ofeach point like the figure showed.Now you can create curvesClick button “Create/Modify Curve”Click button “Create Curve”Note: the left corner of the black screen: Selectlocations with left button, middle=done,right=cancelSelect points by using left button of the mouse.Change the name of the Part with “INLET”:A BSelect and 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 , and , and respectively.We will see the line and the tree widgetDraw the cylinderClick button“Circle or arc from Center point and2 points on plane”.Set the Part with name “CYLINDER”Click button and select points “, , ” withleft button respectively (A).A BDraw the cylinder by middle button (B).See tree widget:Close Points nameUse button to fit the window.1111Set the body and material.Click button “Create Body”Choose button “Material Point”and select “Selected surfaces”in the “By Topology”menu.1212Change the name of the part with “FLUID”; open the Show Point Name of the tree widget and use select and .The same way change the part name with “CYLINDER” and select and .Close Show Point Name and open the tree widget:Open the bodies and you can seeAt last, open the File>Geometry>Save Geometry As…Give it the name with “cylinder_2d”. Click “save”.Now we begin to block the model.Click button “Create Block”1313See the first one , choose the part with“FLUID”, from the pull down menu select “FLUID”And set the Initialize Blocks type with “2DPlanar”Click “Apply” button.A BWe will see that the colors of figure are changed. From (A) to (B)1414See the tree widget: Model>BlockingThen create some assistant points with button“Create Point”{Y=0X=,,,,,,,,, , , , , , , , , }{X=0Y=,,,,,,,,, , , , , , , , , }Now begin to block the regionClick button “Split Block”Then select button “Split Block”1515See the split method, select “Prescribed point”Use the put down menu to select the Prescribedpoint,Use the button firstly select the Edge“INLET” and secondly select the Point “”.We will see the block line in the vertical directionof the INLET.Zoom the fiure.1616The same way we draw other block lines.From the “ to ”See the tree widgetSelect the “Blocking” and select “Index Control”1717Model>Blocking : 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 figureThe same way we set I max =3 , J min=2 , J max=31818And the screen shown thatThe same way block again from “, to ”:(A)(B)(C)A B CAfter block.See the tree widget: Model>Parts>VORFN :using the right button select “Add to Part”.1919Click button “Blocking Material”, Add Blocks to PartUsing select blocking regions and we can seeZoom the block regions (A).A20202121Select 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”ABD CSelect the associate edge to curve “AssociateEdge to Curve”buttonUsing the choose the edge and curveChoosing edge:ASelect curves:22222323Middlebutton:Set O gridClick button “Split Block”Click “Ogird Block ” buttonCBSelect theSee the tree widget: Open Model>Parts>VORFNOpen the VORFN (A)AUsing button to select in or attached the cylinder (B)(C)(D).B C2424D EUsing middle button to click “Apply”(E)Close “VORFN” from the tree widget (F)2525F GClick the “Reset”(G)Mesh the edges2626Click button “Set Curve Mesh Size”Using button to select Curve(s):Choose Method with “Element count”Set the Number with 100 and click Apply.2727See the tree: close the Model>Geometry>points,and the Model>Blocking>edgesUsing right button to selectModel>Geometry>Curves:Curve Node Spacing (by using right button)The same way set the “INLET”and “OUTLET”withnumber 100, the “SIDEA”and “SIDEB”with number 250.Click button “Pre-Mesh Params”Choose Blocking >Pre-Mesh Params2828Click button “Update Sizes” and keepdefault,Then click ApplySee tree open Model>Blocking>Pre_Mesh: Projectfaces (by using right button)And we will see a menuClick Yes.2929Now we will see the mesh of the model.Zoom it see the local partClose Geomery>Points and curves, and Blocking>Edges.Then open File>Mesh>Load from BlockingOpen File>Mesh>Save Mesh As…: and set the name with “cylinder_2d”Open File>Blocking>Save Blocking As…: Save block with the name “cylinder_2d”Check the quality of the mesh3030Click button “Display Mesh Quality”Click ApplyWe can see no negatives mesh.Extrude meshClick button “Extrude Mesh”3131Use to select Elements:Method 1Click button “Select items in a part” and a menu appears:Click “All” and “Accept”3232Method 2A BPut 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 type>spacing with “”, then ApplyCSo the mesh change a height in the Z direction (D)3333DBox ZoomE FClick button “Shaded Full Display”(E)(F)Check the quality of the extrude mesh3434See the tree widget:Close top “TOP” (B) Close “FLUID” (C)AB3535CSet the new boundary conditionsSee the tree widget:Model>Parts: Create Part (by using the rightbutton)Click “Create Part by Selection”buttonFrom the pull down menu of the Part: select the“CYLINDER”Using and left button drag the region36363737Using middle button accepts it, so a new CYLINDER boundary condition has been set (C).The same way set the INLET , OUTLET , SIDEA and SIDEB boundary conditions.INLETThe Whole Boundary ConditionsACAC BAB CSee the tree widget:Open Model>Parts>FLUID(B)AA3838Open Model>Parts>TOP(C)Six kinds of patternsCBC BF EDA3939Click File>Mesh>Save Mesh As…And save the new mesh with name“cylinder_2d_extrude”.Output the mesh file to CFXClick button “Select solver” and choose “CFX-5”Click “Okay”Click button “Write input”4040v1.0 可编辑可修改Keep default and click “Done”Then the Domain selection appearsKeep the Selected domains with “” and click “Done”.Now we will see the created files in working directions:4141v1.0 可编辑可修改From these files, we must note that only the file named “cfx5” can be inputted intomesh is finished.Other examples:4242Example on using commercial software “CFX around a circular cylinder43434444Two Dimensional problemsFlow around a circular cylinderAfter established the geometry model, we begin to use CFX to solve this two dimensional case.1.Processing with CFXDouble click the “CFX” Icon, afterwards, you can see the interface of the CFX.There are three kinds of functions of the CFX:1.CFX-Pre (set the relevant parameters).2.CFX-Solver (solve the case by using established physical model)3.CFX-Post (get the data and figures which we need)4545CFX-Pre step:1.Import the mesh file from ICEM CFD2.Simulation type3.Domain4.BC’s (boundary conditions)5.Initial conditions6.Solver control7.Output file and monitor points8.Write “.def” file and simulationClick button “CFX-Pre and run it.Establish a new simulationOpen File>New Simulation…:4646Select button “General” and give the file name with “cylinder_2d”. Click “Save”Now we can see the interface of the CFX-Pre4747Import mesh fileSee the middle position of the screen, Click button “Import mesh”Open Mesh>Definition>Mesh Format:From the pull down menu select “ICEM CFD”, (see figure below)4848Definition>File: Click button “Browse”Find the working direction and select the file named “cfx5”,Then click “Open”button. And “OK” Note: no other files can be inputted inThen the mesh file has been inputted into the CFX-Pre4949And the left window appears.All of these names were already defined by us in “ICEM CFD”Set the relevant parameters1. Define the simulation type:5050。