CFX-离心泵算例p

1、Workshop 5Cavitating Centrifugal Pump,Introduction to CFX,Introduction,The Purpose of the tutorial is to model cavitation in a centrifugal pump, which involves the use of a rotation domain and the cavitation model. The problem consists of a five blade centrifugal pump operating at 2160 rpm. The work

2、ing fluid is water and flow is assumed to be steady and incompressible. Due to rotational periodicity a single blade passage will be modeled. The initial flow-field will be solved without cavitation. It will be turned on later.,Start Workbench and save the project as centrifugalpump.wbpj Drag CFX in

3、to the Project Schematic from the Component Systems toolbox Start CFX-Pre by double clicking Setup When CFX-Pre opens, import the mesh by right-clicking on Mesh and selecting Import Mesh ICEM CFD Browse to pump.cfx5 Keep Mesh units in m Click Open,Workbench,Modifying the material properties: Expand

4、Materials in the Outline tree Double-click Water On the Material Properties tab change Density to 1000 kg/m3 Change Dynamic Viscosity to 0.001 kg m-1 s-1 under Transport Properties Click OK,Creating Working Fluids,Setting up the Fluid Domain,Double-click on Default Domain Under Fluid and Particle De

5、finitions, delete Fluid 1 and then create a new Fluid named Water Liquid Set Material to Water Create another new Fluid named Water Vapour Next to the Material drop-down list, click the “” icon, then the Import Library Data icon (on the right of the form), and select Water Vapour at 25 C under the W

6、ater Data object Click OK Back in the Material panel, select Water Vapour at 25 C Click OK,Setting up the Fluid Domain,Set the Reference Pressure to 0 Pa Set Domain Motion to Rotating Set Angular Velocity to 2160 rev min-1 Switch on Alternate Rotation Model Make sure Rotation Axis under Axis Definit

7、ion is set to Global Z Switch to the Fluid Models tab, and set the following: Turn on Homogeneous Model in the Multiphase section Under Heat Transfer set the Option to Isothermal, with a Temperature of 25 C Set Turbulence Option to Shear Stress Transport Click OK,Inlet Boundary Condition,Insert a bo

8、undary condition named Inlet On the Basic Settings tab, set Boundary Type to Inlet Set Location to INLET Set Frame Type to Stationary Switch to the Boundary Details tab Specify Mass and Momentum with a Normal Speed of 7.0455 m/s Switch to the Fluid Values tab For Water Liquid, set the Volume Fractio

9、n to a Value of 1 For Water Vapour, set the Volume Fraction to a Value of 0 Click OK,Outlet Boundary Condition,Inset a boundary condition named Outlet On the Basic Settings tab, set Boundary Type to Opening Set Location to OUT Set Frame Type to Stationary Switch to the Boundary Details tab Specify M

10、ass and Momentum using Entrainment, and enter a Relative Pressure of 600,000 Pa Enable the Pressure Option and set it to Opening Pressure Set Turbulence Option to Zero Gradient Switch to the Fluid Values tab For Water Liquid, set the Volume Fraction to a Value of 1 For Water Vapour, set the Volume F

11、raction to a Value of 0 Click OK,Periodic Interface,Click to create an Interface, and name it Periodic Set the Interface Type to Fluid Fluid For Interface Side 1, set the Region List to DOMAIN INTERFACE 1 SIDE 1 and DOMAIN INTERFACE 2 SIDE 1 (use the “” icon and the Ctrl key) For Interface Side 2, s

12、et the Region List to DOMAIN INTERFACE 1 SIDE 2 and DOMAIN INTERFACE 2 SIDE 2 Set the Interface Models option to Rotational Periodicity Under Axis Definition, select Global Z Set Mesh Connection Option to 1:1 Click OK,Wall Boundary Conditions,Insert a boundary condition named Stationary Set it to be

13、 a Wall, using the STATIONARY location On the Boundary Details tab, enable a Wall Velocity and set it to Counter Rotating Wall Click OK In the Outline Tree, right-click on the Default Domain Default boundary and rename it to Moving The default behavior for the Moving boundary condition is to move wi

14、th the rotating domain, so there is nothing that needs to be set,Initialization,Click to initialize the solution On the Fluid Settings form, set Water Liquid Volume Fraction to Automatic with Value, and set the Volume Fraction to 1 Set Water Vapour Volume Fraction to Automatic with Value, and set th

15、e Volume Fraction to 0 Click OK,Solver Control,Double click Solver Control in the Outline tree Set Timescale Control to Physical timescale A commonly used timescale in turbomachinery is 1/omega, where omega is the rotation rate in radians per second. You can use an expression to determine a timestep

16、 from this. In this case, 2/omega will be used to achieve faster convergence. Enter the following expression in the Physical Timescale box:1/(pi*2160 min-1) Set Residual Target to 1e-5 On the Advanced Options tab, turn on Multiphase Control, then turn on Volume Fraction Coupling and set the Option t

17、o Coupled Click OK,Output Control,Double Click on Output Control in the Outline tree On the Monitor tab, turn on Monitor Options Under Monitor Points and Expressions, create a new object and call it InletPTotalAbs Set Option to Expression Specify the following expression: massFlowAve(Total Pressure

18、in Stn Frame )Inlet Create a new object called InletPStatic, and set Option to Expression Specify the following expression:areaAve(Pressure )Inlet Click OK,Solver,Close CFX-Pre and switch to the Workbench Project window Save the project Now double click on Solution in the Project Schematic to start

19、the Solver Manager When the Solver Manager opens, click Start Run When the solution has completed, close the Solver Manager and return to the Project window Save the project,Post-processing,View the results in CFD-Post by double clicking Results in the Project Schematic Insert a Contour by clicking

20、For the Location, click , expand Regions and then select BLADE Set Variable to Absolute Pressure from the extended list Set Range to Global On the Render tab switch off Lighting and Show contour Lines Click Apply,Post-processing,Insert another Contour on the HUB location, using the variable Absolute

21、 Pressure coloured by Local Range. Turn off Lighting and Show Contour Lines. Insert another Contour on the SHROUD location, using the variable Absolute Pressure coloured by Local Range. Turn off Lighting and Show Contour Lines. The minimum pressure is above the Saturation Pressure of 2650 Pa for Wat

22、er here. In the next step, the outlet pressure will be reduced enough to initiate Cavitation.,Adding another Analysis,Close CFD-Post and return to the Project Schematic Click the arrow next to the A cell and select Duplicate A new CFX project is created as a copy of the first Change the name of the

23、new Simulation to Cavitation Use the arrow next to the A cell to Rename it to No Cavitation Save the Project Double-click Setup for the Cavitation simulation to open CFX-Pre,Physics Modifications,Edit the Default Domain On the Fluid Pair Models tab set Mass Transfer to Cavitation Set Option to Rayle

24、igh Plesset Turn on Saturation Pressure Set a Saturation Pressure of 2650 Pa Click OK Edit the Outlet Boundary Condition On the Boundary Details tab, set the Relative Pressure to 300,000 Pa Click OK,Physics Modifications,Edit Solver Control Set the Max. Iterations to 150 Set the Residual Target to 1

25、e-4 Click OK Close CFX-Pre and save the project In the Project Schematic, drag cell A3 onto cell B3 The non-cavitating solution will be used as the initial guess for the cavitating solution Double-click Solution for the Cavitation system In the Solver Manager note that the initial conditions have be

26、en provided from the project schematic Click Start Run,Cavitation Solution,There is a significant spike in residuals, in part due to the outlet pressure difference, but also due to the fact that the absolute pressure is low enough to induce cavitation. When the run completes, close the Solver Manage

27、r and return to the Project Schematic Save the project Double-click Results for the Cavitation project to openCFD-Post,Post-processing,If it is not enabled, turn on visibility for the Wireframe and turn off visibility for any User Locations and Plots Create an XY Plane at Z = 0.01 m Colour it by Abs

28、olute Pressure (the variable is available in the Extended List by clicking ). Use a Global Range The minimum absolute pressure is equivalent to the Saturation Pressure specified earlier, which is a strong hint that some cavitation has occurred Change the Colour Variable to Water Vapour.Volume Fraction Change the Colour Map to Blue to White,Post-processing,Turn off visibility for Plane 1 Create a Volume using the Isovolume method Set the Variable to Water Vapou