ANSYS, Inc. Proprietary © 2009 ANSYS, Inc. All rights reserved. WS5-1 April 28, 2009 Inventory #002599 Workshop 5 Cavitating Centrifugal Pump Introduction

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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. WS5-1 April 28, 2009 Inventory #002599 Workshop 5 Cavitating Centrifugal Pump Introduction to CFX Pardad Petrodanesh.Co Lecturer: Ehsan Saadati ehsan.saadati@gmail.com www.petrodanesh.ir
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-2 April 28, 2009 Inventory #002599 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 working 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.
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-3 April 28, 2009 Inventory #002599 1.Start Workbench and save the project as centrifugalpump.wbpj 2.Drag CFX into the Project Schematic from the Component Systems toolbox 3.Start CFX-Pre by double clicking Setup 4.When CFX-Pre opens, import the mesh by right-clicking on Mesh and selecting Import Mesh > ICEM CFD 5.Browse to pump.cfx5 6.Keep Mesh units in m 7.Click Open Workbench
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-4 April 28, 2009 Inventory #002599 Modifying the material properties: 1.Expand Materials in the Outline tree 2.Double-click Water 3.On the Material Properties tab change Density to 1000 [kg/m 3 ] 4.Change Dynamic Viscosity to 0.001 [kg m^-1 s^-1] under Transport Properties 5.Click OK Creating Working Fluids
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-5 April 28, 2009 Inventory #002599 Setting up the Fluid Domain 1.Double-click on Default Domain 2.Under Fluid and Particle Definitions, delete Fluid 1 and then create a new Fluid named Water Liquid 3.Set Material to Water 4.Create another new Fluid named Water Vapour 5.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 Water Data object Click OK 6.Back in the Material panel, select Water Vapour at 25 C Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-6 April 28, 2009 Inventory #002599 Setting up the Fluid Domain 7.Set the Reference Pressure to 0 [Pa] 8.Set Domain Motion to Rotating 9.Set Angular Velocity to 2160 [rev min^-1] 10.Switch on Alternate Rotation Model 11.Make sure Rotation Axis under Axis Definition is set to Global Z 11.Switch to the Fluid Models tab, and set the following: 12.Turn on Homogeneous Model in the Multiphase section 13.Under Heat Transfer set the Option to Isothermal, with a Temperature of 25 C 14.Set Turbulence Option to Shear Stress Transport 15.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-7 April 28, 2009 Inventory #002599 Inlet Boundary Condition 1.Insert a boundary condition named Inlet 2.On the Basic Settings tab, set Boundary Type to Inlet 3.Set Location to INLET 4.Set Frame Type to Stationary 5.Switch to the Boundary Details tab 6.Specify Mass and Momentum with a Normal Speed of 7.0455 [m/s] 7.Switch to the Fluid Values tab 8.For Water Liquid, set the Volume Fraction to a Value of 1 9.For Water Vapour, set the Volume Fraction to a Value of 0 10.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-8 April 28, 2009 Inventory #002599 Outlet Boundary Condition 1.Inset a boundary condition named Outlet 2.On the Basic Settings tab, set Boundary Type to Opening 3.Set Location to OUT 4.Set Frame Type to Stationary 5.Switch to the Boundary Details tab 6.Specify Mass and Momentum using Entrainment, and enter a Relative Pressure of 600,000 [Pa] 7.Enable the Pressure Option and set it to Opening Pressure 8.Set Turbulence Option to Zero Gradient 9.Switch to the Fluid Values tab 10.For Water Liquid, set the Volume Fraction to a Value of 1 11.For Water Vapour, set the Volume Fraction to a Value of 0 12.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-9 April 28, 2009 Inventory #002599 Periodic Interface 1.Click to create an Interface, and name it Periodic 2.Set the Interface Type to Fluid Fluid 3.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) 4.For Interface Side 2, set the Region List to DOMAIN INTERFACE 1 SIDE 2 and DOMAIN INTERFACE 2 SIDE 2 5.Set the Interface Models option to Rotational Periodicity 6.Under Axis Definition, select Global Z 7.Set Mesh Connection Option to 1:1 8.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-10 April 28, 2009 Inventory #002599 Wall Boundary Conditions 1.Insert a boundary condition named Stationary 2.Set it to be a Wall, using the STATIONARY location 3.On the Boundary Details tab, enable a Wall Velocity and set it to Counter Rotating Wall 4.Click OK 5.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 with the rotating domain, so there is nothing that needs to be set
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-11 April 28, 2009 Inventory #002599 Initialization 1.Click to initialize the solution 2.On the Fluid Settings form, set Water Liquid Volume Fraction to Automatic with Value, and set the Volume Fraction to 1 3.Set Water Vapour Volume Fraction to Automatic with Value, and set the Volume Fraction to 0 4.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-12 April 28, 2009 Inventory #002599 Solver Control 1.Double click Solver Control in the Outline tree 2.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 from this. In this case, 2/omega will be used to achieve faster convergence. 3.Enter the following expression in the Physical Timescale box: 1/(pi*2160 [min^-1]) 4.Set Residual Target to 1e-5 5.On the Advanced Options tab, turn on Multiphase Control, then turn on Volume Fraction Coupling and set the Option to Coupled 6.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-13 April 28, 2009 Inventory #002599 Output Control 1.Double Click on Output Control in the Outline tree 2.On the Monitor tab, turn on Monitor Options 3.Under Monitor Points and Expressions, create a new object and call it InletPTotalAbs 4.Set Option to Expression 5.Specify the following expression: massFlowAve(Total Pressure in Stn Frame )@Inlet 6.Create a new object called InletPStatic, and set Option to Expression 7.Specify the following expression: areaAve(Pressure )@Inlet 8.Click OK
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-14 April 28, 2009 Inventory #002599 Solver 1.Close CFX-Pre and switch to the Workbench Project window 2.Save the project 3.Now double click on Solution in the Project Schematic to start the Solver Manager 4.When the Solver Manager opens, click Start Run 5.When the solution has completed, close the Solver Manager and return to the Project window 6.Save the project
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-15 April 28, 2009 Inventory #002599 Post-processing 1.View the results in CFD-Post by double clicking Results in the Project Schematic 2.Insert a Contour by clicking 3.For the Location, click, expand Regions and then select BLADE 4.Set Variable to Absolute Pressure from the extended list 5.Set Range to Global 6.On the Render tab switch off Lighting and Show contour Lines 7.Click Apply
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump WS5-16 April 28, 2009 Inventory #002599 Post-processing 9.Insert another Contour on the HUB location, using the variable Absolute Pressure coloured by Local Range. Turn off Lighting and Show Contour Lines. 10.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 Water here. In the next step, the outlet pressure will be reduced enough to initiate Cavitation.
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  • ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. Workshop Supplement WS5: Cavitating Centrifugal Pump

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