ANSYSCFD管道流体分析算例Fluid

1、Introduction: In this example you will model fluid flow in a channelPhysical Problem: Compute and plot the velocity distribution within the elbow. Assume that the flow is uniform at both the inlet and the outlet sections and that the elbow has uniform depth.Problem Description:The channel has dimens

2、ions as shown in the figureThe flow velocity as the inlet is 10 cm/sUse the continuity equation to compute the flow velocity at exitObjective:To plot the velocity profile in the channel To plot the velocity profile across the elbow You are required to hand in print outs for the aboveFigure:IMPORTANT

3、: Convert all dimensions and forces into SI unitsSTARTING ANSYSClick on ANSYS in the programs menu.Select Interactive.The following menu comes up. Enter the working directory. All your files will be stored in this directory. Also under Use Default Memory Modelmake sure the values 64 for Total Worksp

4、ace, and 32 for Database are entered. To change these values unclick Use Default Memory ModelMODELING THE STRUCTUREGo to the ANSYS Utility Menu (the top bar)Click WorkplaneWP SettingsThe following window comes up:o Check the Cartesian and Grid Only buttonso Enter the values shown in the figure above

5、 Go to the ANSYS Main Menu (on the left hand side of the screen) and clickPreprocessorModelingCreateKeypointsOn Working PlaneCreate keypoints corresponding to the vertices in the figure. The keypoints look like below.Now create lines joining these key points. ModelingCreateLinesLinesStraight lineThe

6、 model looks like the one below.Now create fillets between lines L4-L5 and L1-L2.Click ModelingCreateLinesLine Fillet. A pop-up window will now appear. Select lines 4 and 5. Click OK. The following window will appear:This window assigns the fillet radius. Set this value to m.Repeat this process of f

7、illeting for Lines 1 and 2.The model should look like this now:Now make an area enclosed by these lines. ModelingCreateAreasArbitraryBy LinesSelect all the lines and click OK. The model looks like the followingThe modeling of the problem is done.ELEMENT PROPERTIESSELECTING ELEMENT TYPE: Click Prepro

8、cessorElement TypeAdd/Edit/Delete. In the Element Types window that opens click on Add. The following window opens. Type 1 in the Element type reference number. Click on Flotran CFD and select 2D Flotran 141. Click OK. Close the Element types window. So now we have selected Element type 1 to be solv

9、ed using Flotran, the computational fluid dynamics portion of ANSYS. This finishes the selection of element type.DEFINE THE FLUID PROPERTIES: Go to PreprocessorFlotran Set UpFluid Properties. On the box, shown below, set the first two input fields as Air-SI, and then click on OK. Another box will ap

10、pear. Accept the default values by clicking OK. Now were ready to define the Material PropertiesMATERIAL PROPERTIESWe will model the fluid flow problem as a thermal conduction problem. The flow corresponds to heat flux, pressure corresponds to temperature difference and permeability corresponds to c

11、onductance.Go to the ANSYS Main MenuClick PreprocessorMaterial PropsMaterial Models. The following window will appearAs displayed, choose CFDDensity. The following window appears.Fill in 1.23 to set the density of Air. Click OK. Now choose CFDViscosity. The following window appears:Now the Material

12、1 has the properties defined in the above table so the Material Models window may be closed.MESHING:DIVIDING THE CHANNEL INTO ELEMENTS:Go to PreprocessorMeshingSize CntrlsManualSizeLinesAll Lines. In the window that comes up type in the field for Element edge length.Now Click OK.Now go to Preprocess

13、orMeshingMeshAreasFree. Click the area and the OK. The mesh will look like the following.BOUNDARY CONDITIONS AND CONSTRAINTSGo to PreprocessorLoadsDefine LoadsApplyFluid CFDVelocityOn lines. Pick the left edge of the outer block and Click OK. The following window comes up.Enter 0.1 in the VX value f

14、ield and click OK. The 0.1 corresponds to the velocity of 0.1 meter per second of air flowing from the left side.Repeat the above and set the Velocity to ZERO for the air along all of the edges of the pipe. (VX=VY=0 for all sides)Once they have been applied, the pipe will look like this: Go to Main

15、MenuPreprocessorLoadsDefine LoadsApplyFluid CFDPressure DOFOn Lines. Pick the outlet line. (The horizontal line at the top of the area) Click OK. Enter 0 for the Pressure value. Now the Modeling of the problem is done.SOLUTIONGo to ANSYS Main MenuSolutionFlotran Set UpExecution Ctrl. The following w

16、indow appears. Change the first input field value to 300, as shown. No other changes are needed. Click OK. Go to SolutionRun FLOTRAN.Wait for ANSYS to solve the problem.Click on OK and close the Information window.POST-PROCESSINGPlotting the velocity distributionGo to GeneralPostprocRead ResultsLast

17、 Set. Then go to GeneralPostprocPlot ResultsContour PlotNodal Solution. The following window appears: Select DOF Solution and Velocity VSUM and Click OK. This is what the solution should look like: Next, go toMain MenuGeneral PostprocPlot ResultsVector PlotPredefined.The following window will appear

18、: Select OK to accept the defaults. This will display the vector plot to compare to the solution of the same tutorial solved using the Heat Flux analogy. Note: This analysis is FAR more precise as shown by the following solution: Go to Main MenuGeneral PostprocPath OperationsDefine PathBy Nodes Pick points at the ends of the elbow as shown. We will graph the velocity distribution along the line joining these two points. The following window comes u