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CFX-5 Tutorials

Tutorial 12Flow in an Axial Rotor/StatorArrangement

Page 363 CFX-5.5.1

CFX-5 TutorialsFlow in an Axial Rotor/Stator

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Introduction

The following tutorial demonstrates the versatility of GGI and MFR inCFX-Build by combining two dissimilar meshes. The first mesh to beimported (the rotor) was created in CFX-TurboGrid. This is combinedwith a second mesh (the stator) which was created using CFX-Build.

The geometry to be modelled consists of a single stator blade passageand two rotor blade passages, as shown in Figure 12.1 below. Therotor rotates about the z-axis while the stator is stationary. Periodicboundaries are used to allow only a small section of the full geometryto be modelled.

Figure 12.1.

Hub

Shroud

Inflow

Outflow

Rotor Blade

Stator Blade

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At the change in reference frame between the rotor and stator, twodifferent interface models are considered. First a solution is obtainedusing a frozen-rotor model. After viewing the results from thissimulation, the CFX-Build database is modified to use a transient rotor-stator interface model. The frozen rotor solution is used as an initialguess for the transient rotor-stator simulation.

The full geometry contains 60 stator blades and 113 rotor blades. Tohelp you visualise how the modelled geometry fits into the fullgeometry, Figure 12.2 shows approximately half of the full geometry.The Inflow and Outflow labels show the location of the modelledsection in Figure 12.1.

Figure 12.2.

The modelled geometry contains 2 rotor blades and 1 stator blade, thisis an approximation to the full geometry since the ratio of rotor bladesto stator blades is close but not exactly 2:1. In the stator blade passagea 6o section is being modelled (360o/60 blades), while in the rotor bladepassage a 6.372o section is being modelled (2*360o/113 blades). Thisproduces a pitch ratio at the interface between the stator and rotor of0.942, where the pitch ratio is the area of side 1 divided by the area of

Inflow

Outflow

Axis of Rotation

65 Introduction CFX-5.5.1



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side 2. As the flow crosses the interface it is scaled to allow this type ofgeometry to be modelled. This results in an approximation of the inflowto the rotor passage. Furthermore, the flow across the interface will notappear continuous due to the scaling applied.

The periodic boundary conditions will introduce an additionalapproximation since they cannot be periodic when a pitch changeoccurs.

You should always try to obtain a pitch ratio as close to 1 as possiblein your model to minimise approximations, but this must be weighedagainst computational resources. A full machine analysis can beperformed (modelling all rotor and stator blades) which will alwayseliminate any pitch change, but will require significant computationaltime. For this rotor/stator geometry, a 1/4 machine section (28 rotorblades, 15 stator blades) would produce a pitch change of 1.009, butthis would still be about 15 times larger than this tutorial example.

If you have already completed the frozen rotor part of this tutorial youcan continue from Setting up the Transient Rotor-StatorCalculation (p. 383) . Note that a converged results file from the frozenrotor section is required as an initial guess. You can use your ownsolution or use the results file provided in the examples directory.Further details are given in Obtaining a Solution to the TransientRotor-Stator Model (p. 387) . You must make sure that the boundarynames used in the initial results file exactly match those used in thetransient rotor-stator definition file.

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Problem Definition for the Frozen-Rotor Calculation

FeaturesThe first part of this tutorial demonstrates the following features ofCFX-5:

• Volume Mesh Import.

• Multiple Frames of Reference.

• Generalised Grid Interface.

• Frozen Rotor interface condition.

Session FileYou can create the frozen-rotor model step by step by following theinstructions below. However, as an alternative to this, you can play aCFX-Build session file to complete the preprocessing of the frozen-rotor part of this tutorial. To do this, select Tools > Examples... fromthe Main Menu, and then use the Playback action and select the fileAxialIni.ses .

If you use the session file to create the model, you can continue withthis tutorial from Obtaining a Solution to the Frozen Rotor Model(p. 376).

Creating a New Database• Start CFX-Build from the CFX-5 Launcher.

When CFX-Build is loaded, select File > New... from the Main Menu.

• Create a new database called AxialIni .

When the New Model Preferences form appears:

• Select Import Mesh as the Meshing Mode , leaving the rest of thesettings at their default values.

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Importing the MeshesThe first step will involve importing the two different mesh files. The firstfile contains the rotor mesh in a CFX-TASCflow “grd” file.

First, you will need to copy the mesh files from the examples directory.

• Select Tools > Examples... from the Main Menu, and then use theCopy action.

• Select Any as the file type and select the file rotor.grd. Click OKand the file will be copied to your local directory. The form closes.

• Copy the file stator.def in the same way.

• Click on the Import (Imported Mesh on UNIX) button in the mainmenu bar.

Create

Mesh Group

• Enter rotor in the Name box.

• Set the Source to CFX-TASCflow v2 .

• Click on the File... button.

• Select the file rotor.grd and then click OK.

• Click on the Advanced Options... button.

• Set the Retain BlockOffs toggle to OFF and click Close . Anexplanation of when this toggle should be ON, and further detailsabout importing CFX-TASCflow “grd” files is given in CFX-TASCflow v2 (p. 956 in CFX-Build: Chapter 2) .

• Click -Apply- .

When the Import Mesh message appears, note the extent of the gridby examining the size of the Bounding Box. If any of the Bounding Boxlengths (∆x, ∆y or ∆z) are less than the Global Model Tolerance, thegrid will "collapse on itself" and fail in the solver.

• Click OK to dismiss the message.

• Next enter stator in the Name box.




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• Set the Source to CFX-5 Def/Res file .

• Click on the File... button.

• Select the file stator.def . Click OK.

• Click -Apply- .

• Note the extents of the grid when the Import Mesh messageappears. Click OK to dismiss the message.

• Select the Left side view and then the Fit view icons to view themodel.

Creating the DomainIn this section the domain properties will be set. Air will be consideredas an Ideal Gas and the Total Energy equation will be used.

Rotor domain

• Click on the Domains button on the Main Window to open theDomains panel. Select:

Create

Fluid Domain

New

• Enter rotor in the Name box.

• Click on the Domain Options... button to open the DomainOptions panel.

• Enter a reference pressure of 0.25 bar .

• Set the Simulation Type to Steady State .• Set the Domain Motion to be Rotating .• Make sure that the Axis of Rotation is set to Coord 0.3 .• Enter an Angular velocity of 523.6 radian s^-1 .

Important: Please note that the units of pressure are bars and thatthis is not the default. You must set the units for reference pressureto bars.




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• Close the Domain Options panel to return to the Domainspanel.

• Select the fluid as Air Ideal Gas and then set the followingparameters on the Fluid Models... form.

• Turbulence Model to k-epsilon.• Turbulent wall functions to Scalable.• Heat Transfer Model to Total Energy. Make sure that Include

Viscous Work Term is NOT checked.• Buoyancy Model to Non -Buoyant .• Thermal Radiation Model to No Radiation.• Close the Fluid Models panel to return to the Domains panel.

• In the Mesh Groups window make sure that rotor is highlighted.

• Click on -Apply- to complete the creation of the fluid domain.

Stator Domain

• Select:

Create

Fluid Domain

Copy

and enter stator in the Name box.

• Click on the Domain Options... button to open the DomainOptions panel.

• Set the Domain Motion to be Stationary .• Close the Domain Options panel.

• In the Mesh Groups window highlight stator .

• Click on -Apply- to create the second fluid domain.

Setting Boundary Conditions• Click on the BCs (Windows) or Boundary Conditions (UNIX)

button to open the boundary condition specification form.




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• Select:

Create

Fluid Boundary

New

Inlet

• In the Domains list select stator and then enter inlet as the Name.

• Make sure that Type is set to Inlet .

• Click the Values... button to open up the Boundary ConditionValues form.

• Set Mass and Momentum to Stat. Frame Total Pressure andenter a Relative Pressure of 0 Pa.

• Leave the Flow Direction unchanged.• Set the Turbulence option to Default Intensity and

Autocompute Length Scale .• Enter a Static Temperature of 340 K for the Heat Transfer

setting.• Click Close on the Boundary Condition Values form.

• In the 2D Regions window select in . The mesh on this region willbe shown in the Viewer

• Click -Apply- to create the Boundary Condition.

Outlet

• Select rotor from the Domains list and enter outlet as the Name.

• Make sure that Type is set to Outlet , and Frame is set to Rotating .

• Click the Values... button to open up the Boundary ConditionValues form.

• Set Mass and Momentum to Mass Flow Rate and enter a valueof 0.06 kg s^-1 .

• Click Close on the Boundary Condition Values form.

• In the 2D Regions list highlight OUTFLOW.




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Wall Boundary Conditions

You will define the two shroud surfaces as separate walls. This willcreate extra regions that will prove useful during post-processing.

• Select rotor from the Domains list and enter Rotor Shroud as theName.

• Set Type to Wall and Frame to Rotating .

• There is no need to open the Values... form as the default No Slip,Smooth, Adiabatic Wall will be accepted.

• In the 2D Regions list highlight SHROUD.


Now create the second wall boundary:

• In the Domains list highlight stator and then enter Stator Shroudas the Name.

• Make sure that Type is set to Wall .

• There is no need to open the Values... form as the default No Slip,Smooth, Adiabatic Wall will be accepted.

• In the 2D Regions list click on shroud .


Interfaces• Click on the Interfaces (Domain Interfaces on UNIX) button.

Here you will set up appropriate Periodic Interfaces on the rotor andstator. These are required since you are only modelling a small sectionof the true geometry. Periodic Boundary Conditions (set from theBoundary Conditions panel) achieve the same result and should beused when ever possible. However, they impose the limitation that




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identical surface meshes must exist on both periodic faces. A PeriodicInterface uses the GGI capability of CFX-5 and can therefore beapplied more generally. See Periodic Interfaces (p. 1174 inCFX-Build: Chapter 7) for more details.

• Select:

Create

Domain Interface

• Enter Rotor Periodic as the Name.

• Set the Type to Periodic and then the Option to Rotation .

• Make sure that the Axis of Rotation is set to Coord 0.3 .

• In Boundary List 1 , select rotor/PER1 and in Boundary List 2select rotor/PER2 .

• Click -Apply- .

Create

Domain Interface

• Now enter Stator Periodic as the Name.

• Use the same Type , Option and Axis of Rotation settings.

• In Boundary List 1 , select stator/periodic1 and in Boundary List2 select stator/periodic2 .

• Click -Apply- .

The next step is to create a Frozen Rotor interface between the statoroutlet and the rotor inlet.

Create

Domain Interface

• Enter Interface as the Name.

• Select the Type as Fluid-Fluid .

• Select the Frame Change as Frozen Rotor and theTransformation Type as Automatic .




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• Select stator/out from Boundary List 1 , and rotor/INFLOW fromBoundary List 2 .

• Click -Apply- .

Initial Conditions• Click on the Init. Cond. (Initial Guess on UNIX) button.

Set

Domain Initial Cond.

• Check that both rotor and stator are highlighted in the ExistingDomain(s) list to set the initial conditions for both domains.

Next, you will specify an initial guess for the Cartesian VelocityComponents individually.

• Select Set Individually as the Variables option.

• Click on the Variables... button.

• For Cartesian Velocity Components, select Automatic withValue .

• For U enter 0 m/s .• For V enter 0 m/s .• For W enter 100 m/s .• Leave all other settings as they are and Close the form.

• Click -Apply- to set the initial values.

Solver Control• Click on the Solver (Solver Control on UNIX) button.

Set

Solver Parameters

• On the Convergence Control form:

• Set a Physical Timestep of 0.002 s applied to All EquationClasses . This value is approximately equal to 1 / ω which isusually appropriate for rotating machinery applications.




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• Close the form.

• Click on Convergence Criteria...

• Select RMS Norm for Residuals and use the default value of1E-4 for the Target Residual .

• Close the form.

• Click on Advection Scheme... , select 2nd Order High Resolutionand then Close the form.

• Click on Options... :

• Set Smart Start to No.• Close the form.

• Click -Apply- to set the Solver Parameters.

Writing the Definition FileSelect the Definition File button.

Write

• Leave the default File Name for the Definition File.

• Set the Shutdown CFX-Build toggle ON.

• Leave the Start Solver Manager option menu set as it is.

• Press Apply to write the Definition File.




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Obtaining a Solution to the Frozen Rotor Model

Compared to previous tutorials, the mesh for this tutorial containsmany more nodes (although it is still too coarse to perform a highquality CFD simulation). This will result in a corresponding increase insolution time for this problem. We therefore recommend solving thisproblem in parallel (on more than one processor). We recommend thatyour machine has a minimum of 256MB of memory to run this tutorial.

• If you do not have a license to run CFX-5 in parallel you can run inserial by clicking the Start Run button when CFX-5 Solver Managerhas opened up. Solution time in serial is approximately 2 hours ona 450MHz P2 processor.

Instructions are provided below to run this tutorial in parallel. Thistutorial assumes that you are already set up to run in parallel. Moredetailed information about setting up CFX-5 to run in parallel isprovided in Tutorial 5 and in Setting Up and Running a Parallel Run(p. 52 in CFX-5 Solver and Solver Manager) .

You can solve this example using either Local Parallel or DistributedParallel; guidance is provided for both.

Local Parallel Solution

To run in Local Parallel, the machine that you are currently logged intomust have more than one processor.

• On the Define Run panel, set the Run Mode to Local Parallel .

• Check that the Processes option is set to 2.

• Click on the Start Run button.

When the Solver has finished:

• Click on the Post-Process Results button to view the results.

• Exit from the Solver Manager.

Distributed Parallel Solution

• On the Define Run panel, set the Run Mode to Distributed Parallel .

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• Click the New icon to specify new parallel hosts.

• In the Select Parallel Hosts panel, click on the Host Name of themachine that you are currently logged into to highlight it. Highlightanother Host Name (this should be a machine that you know youcan log into using the same user name). Press Add and then Close .

The names of the two machines you selected should appear in theHost Name column in the Define Run panel.

• Click on the Start Run button.

Notice that the pitch ratio is written near to the start of the OUT file:

+--------------------------------------------------------------------+| Total Number of Nodes, Elements, and Faces |+--------------------------------------------------------------------+......

Domain Interface Name : Interface

Non-overlap area fraction on side 1 = 0.1 % Non-overlap area fraction on side 2 = 0.0 % Pitch ratio: (area side 1)/(area side 2) = 0.942




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Viewing the Results

When CFX-Post opens there will be 12 Boundary objects alreadycreated. You created 4 of these as named boundaries in CFX-Build. Inaddition there are 2 Default Walls (one for each Fluid Domains), 4Periodic Interfaces, and 2 Domain Interfaces.

• Experiment with the Edge Angle setting for the Wireframe objectand the various rotation and zoom features to put the geometry intoa sensible position.

• If you are unsure about where any of the Boundary objects arelocated, make each one visible.

• Create a YZ Slice Plane at an X value of 0.41, coloured by Pressure.

• Next you will inspect the GGI interface region. Make the plot ofPressure invisible.

• Create a vector plot with the following settings:

• Location as the plane you just created.• Variable as Velocity .• Symbol Size as 0.2.• Use the default settings for the remaining options.

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• Zoom in on the area where the stator meets the rotor. Make theWireframe invisible to view the plot more easily.

You can see that the velocity vectors appear very different across theinterface. The difference is due to the different frames of reference.Velocity is measured relative to its local reference frame, so you arelooking at the velocity vectors in a stationary frame for the stator and inthe rotating frame for the rotor.

• Click on the icon next to the Variable box in the Object Editor.Select Velocity in Stn. Frame from the list of variables thatappears, then click OK. Click Apply to modify the Vector plot.




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The velocity vectors are now all plotted relative to a stationaryreference frame and the flow pattern now appears continuous throughthe interface.

Next, you will use an Instancing Transformation to show three bladepassages for the stator and six blade passages for the rotor. By plottingpressure on the blade surfaces and along the inner walls, you can gaina deeper understanding of the process occurring. The rotor and statorshrouds were both explicitly defined as walls during preprocessing.This now allows you to produce plots on only these walls in CFX-Post.You can also produce plots on the default walls excluding the shroud.

• Make all objects invisible by turning the relevant toggles off in theObject Selector.

• Make the Default Boundary visible and colour it by Pressure .

• Repeat the last step for the Location Default 1 .




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The name Default 1 was assigned to the boundary when the definitionfile was created. CFX-Build assigns the name Default to any boundarythat does not have a boundary condition applied to it. Since twodomains were created, a different name was assigned to the defaultboundary condition for the stator domain.

Creating Instancing Transformations

You will now create the instancing transformation:

• Click on the icon or select Create > Instance Transform .

• Accept the default name Instance Transform 1 .

• Enter 3 as the # of Copies .

• Make sure that Apply Rotation is checked, Principal Axis isselected as the Method , and that Z is chosen as the Axis .

• Toggle Full Circle OFF and enter a value of 6 degrees into theAngle box (This is because there are 60 blade passages in the fullgeometry: 360 / 60 = 6 degrees.).

• Click Apply .

• Create another transform called Instance Transform 2 , using thesame settings, except this time enter an Angle of 6.372 degrees.(There are 113 blade passages in the full geometry: 360 /113 = 3.186 degrees. However, you have modelled two blade

passages so you need to double this angle).

Next, you need to modify the default wall boundaries to use thesetransformations.

• Edit the Default object to use the Transform Instance Transform 2(located at the bottom of the Render tab panel).

• Edit the Default 1 object to use the Transform InstanceTransform 1 .

• You may wish to plot a Legend using either of the default walls asthe Plot, to gain an idea of pressure values through the domain.




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• Try plotting the surface mesh on Interface Interface A1 andInterface Interface B1 . You will need to disable the Draw Facestoggle, enable the Draw Lines toggle, and set a different Line Colourfor each interface.

• When you have finished looking at the results close CFX-Post.

This completes the frozen-rotor part of the tutorial. The next sectiondescribes how to use the solution you have obtained to set up atransient rotor-stator calculation.




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Setting up the Transient Rotor-Stator Calculation

FeaturesThe second part to this tutorial demonstrates the following features ofCFX-5:

• Modifying an existing database.

• Setting up a transient calculation.

• Transient Rotor-Stator interface condition.

• Creating a transient animation.

Session FileThe following section describes how to modify the existing database todefine the transient rotor-stator simulation. However, as an alternativeto this, you can play a CFX-Build session file to complete thepreprocessing. To do this, select Tools > Examples... from the MainMenu and then use the Playback action, selecting the file Axial.ses .Note that this session file will create a new database called Axial.dband will not modify the existing database. It will also copy the requiredmesh files from the examples directory to the current working directory.

If you use the session file to create the model, you can continue withthis tutorial from Obtaining a Solution to the Transient Rotor-StatorModel (p. 387) .

Opening the Existing DatabaseIf you wish to keep a copy of the frozen-rotor database you shouldmake a copy and re-name it before proceeding.

• Start CFX-Build from the CFX-5 Launcher.

When CFX-Build is loaded, select File > Open... from the Main Menu.

• Select the database AxialIni.db then click OK.

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You will be asked if you would like to re-import your meshes. Since wewill not be modifying the position of the meshes, or adding any newmeshes, there is no need to re-import them.

• Click No in the message window.

Modifying the Fluid DomainYou need to modify the domain to define a transient simulation. Youare going to run for a time interval such that the rotor blades passthrough 1 pitch (6.372o) using 10 timesteps. This is generally too fewtimesteps to obtain high quality results, but is sufficient for tutorialpurposes. The timestep size is calculated as follows:

Rotational Speed = 523.6 rad/s

Rotor Pitch Modelled = 2*(2 π/113) = 0.1112 rad

Time to pass through 1 pitch = 0.1112/523.6 = 2.124e-4 s

Since 10 timesteps are going to be used over this interval then eachtimestep should be 2.124e-5 s.

• Click on the Domains button on the Main Window to open theDomains panel. Select:

Modify

Fluid Domain

• With the rotor domain highlighted in the Existing Fluid Domainlistbox, click on the Domain Options... button.

• Change the Simulation Type to Transient .• Switch the Val. option to List next to the Timestep field, then

enter 10*2.124e-5 s as the list.• For the Time duration enter a Total Time of 2.124e-4 s.• Click Close on the Domain Options panel.

• Click -Apply- on the Domains panel.

You will receive a message telling you to update the Initial Values andSolver Control forms.

• Click OK in the message window.




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There is no need to modify the stator domain since it is a copy of therotor domain.

Note: A transient rotor-stator calculation will often run through more than one pitch.In these cases it may be useful to look at variable data averaged over the timeinterval required to complete 1 pitch. You can then compare data for each pitchrotation to see if a “steady-state” has been reached or if the flow is still developing.See Time Averaged Variable Data for Transient Runs (p. 93 in CFX-5 Solverand Solver Manager) for detail on how to obtain time-averaged variable data.

Modifying the Domain Interface• Click on the Domain Interfaces button on the Main Window. Select:

Modify

Domain Interface

• Check that Interface is highlighted in the Existing DomainInterfaces listbox.

• Change the Frame Change model to Transient Rotor Stator thenclick -Apply- .

Modifying the Initial Values• Click on the Initial Values button on the Main Window. Select:

Set

Domain Initial Cond.

• Highlight both rotor and stator in the listbox.

In the first part of this tutorial you set the initial conditions for allvariables as either Automatic or Automatic with Value . This meansthat when an initial guess file is specified, the solution fields from thisfile will be automatically used instead of the specified or default values.

• Click the Initial Time... button.

• Select the Automatic with Value option and enter a Time of 0 s.• Close the Initial Time form.

• Press -Apply- to set the initial conditions




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Modifying the Solver Parameters• Click on the Solver Control button on the Main Window. Select:

Set

Solver Parameters

• Open the Convergence Control form and check that the Max.Iterations per timestep is set to 3. We do not generally recommendusing a large number of iterations per timestep, see Timestep Sizefor Transient Problems (p. 494 in CFX-5 Solver and SolverManager) for details.

• Press -Apply- to set the solver parameters.

Select:

Create

Transient Res. File

• Set the Time of Results File: option to Every and then enter2.124e-5 s.

• Click the Variables... button to specify the variable to include in thetransient results files.

• Select the variables Pressure , Velocity , and Velocity in StnFrame (use the <Ctrl> key to pick more than one variable), thenclick OK. Note that Velocity is always defined in the localreference frame, so it will give the rotating frame velocity in therotor component.

• Press -Apply- .

Writing the New Definition File• Select the Definition File button from the Main Window. Select:

Write

• Change the File Name to Axial.def .

• Choose to Shutdown CFX-Build and Start Solver Manager .

• Press Apply to write the definition file.




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Obtaining a Solution to the Transient Rotor-Stator Model

When the CFX-5 Solver Manager has opened you will need to specifyan Initial Values File before starting the CFX-5 Solver.

• Click on the Browse icon next to the Initial Values File box.

• Select the results file from the Frozen Rotor solution,AxialIni_001.res , then click Open .

Serial Solution

• If you do not have a license or do not want to run CFX-5 in parallel,you can run in serial by clicking the Start Run button. Solution timein serial is similar to the first part of the tutorial.

Parallel Solution

You can solve this example using either Local Parallel or DistributedParallel in exactly the same way as in the first part of the tutorial. SeeObtaining a Solution to the Frozen Rotor Model (p. 376) if you needfurther guidance.

Monitoring the Run

During the solution you look for the additional information that isprovided for transient rotor-stator runs. Each time the rotor is rotated toits next position, the number of degrees of rotation and the fraction ofa pitch moved is given. You should see that after 10 timesteps the rotorhas been moved through 1 pitch.

You will also notice a jump in residuals (to the order of 1E-02). This isto be expected for a transient simulation under these conditions, and isnot indicative of a problem




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Viewing the Results

To examine the transient interaction between the rotor and stator, youare going to create a blade-to-blade animation of pressure. Since thisrequires a location that is not a flat plane, you must first define alocation that can be used.

• Click the View Toward -X icon from the Viewer toolbar then zoomin so that the geometry fills the Viewer.

• Select Tools > Expressions from the main menu.

• Click the New icon in the Expression Editor to define a newexpression.

• Enter the name as Radius then click OK.• Type in the Definition as sqrt(x^2+y^2) .• Click Apply to create the expression, then close the Expression

Editor window.

• Select Tools > Variables from the main menu.

• Click the New icon in the Variable Editor to define a new variable.• Enter the name as Radial Distance then click OK.• Select Radius from the drop-down Expression list.• Click Apply to create the variable, then close the Variable Editor

window.

You will now create two isosurfaces of the variable RadialDistance , one for each domain, coloured by Pressure. Separateisosurfaces are defined for each domain, so that different instancingtransformations can be applied to them later in the tutorial.

• Click the Create isosurface icon from the main toolbar and enterthe name as stator plot .

• On the Geometry tab panel set:• Domains to stator .• Variable to Radial Distance and enter a Value of 0.41 m.

• On the Colour tab panel set:• Mode to Variable .• Variable to Pressure .• Range to User Specified .




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• Min to -12000 Pa and the Max to -8000 Pa.• Click Apply to create the isosurface.

• Create a second isosurface called rotor plot using the samemethod, except this time set the Domains to rotor on the Geometrytab panel.

If you rotate the model, you should see that the isosurfaces follow thecurvature of the hub and shroud.

Next, you will use instancing transformations to view a larger section ofthe model.

• Click on the Create instancing transformation icon from the maintoolbar, enter the name as stator transform ,then click OK.

• Enter 6 as the # of Copies .• Make sure that Apply Rotation is checked, Principal Axis is

selected as the Method , and that Z is chosen as the Axis .• Toggle Full Circle OFF , enter a value of 6 degrees into the

Angle box, then click Apply .

• Create another transform, called rotor transform , using thesame settings, except this time enter an Angle of 6.372 degrees.

Next, you need to modify the isosurfaces to use these transformations.

• Edit the stator plot and rotor plot objects to use the Transformstator transform and rotor transform respectively (located at thebottom of the Render tab panel).

You can now create a transient animation. Start by loading the firsttimestep:

• Select the Toggle timestep selector icon from the main toolbar.

• Highlight Time Value 0 , then click Apply to load the timestep.You should see the rotor blades move to a new position.

• Turn off visibility for the Wireframe object.




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• Position the geometry to a similar position as shown below, readyfor the animation. During the animation the rotor blades will move tothe right. You might want to make sure you have at least two rotorblades out of view to the left side of the Viewer, these will come intoview during the animation.

• Select the Toggle animation panel icon from the main toolbar.

• Press the New Keyframe icon in the Animation Editor.

• Load the Time Value 0.0002124 using the Timestep Selector panel.

• Click the New Keyframe icon in the Animation Editor to createKeyframeNo2 .

• Highlight KeyframeNo1 , then set the # of Frames to 9.

• Click on the Options button and set Timestep to TimeValueInterpolation .

The animation now contains a total of 11 frames (9 intermediate framesplus the two Keyframes), one for each of available Time Values.




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• On the Animation Editor panel, enable the Save Animation Movietoggle.

• Click the Browse icon next to the MPEG File box to set a file name(ending in .mpg ).

• If Frame 1 is not currently loaded (shown in the top right corner ofthe Animation Editor), press the To Beginning button to load it.Wait for CFX-Post to finish loading the objects for this frame beforeproceeding.

• Click the Play Forward icon.

It will take some time for the animation to complete. To view the MPEGfile, you will need to use a viewer which supports the MPEG format.

Note: MPEG files larger than 496 by 496 pixels that are created by CFX-Post willnot play in Windows Media Player. Other players (such as Apple Quick time) canbe used to play these files. If you want to play MPEG files larger than this inWindows Media Player, you can save the intermediate JPEG files and use yourown MPEG encoder to generate the MPEG.

You will be able to see from the animation, and from the plots createdpreviously, that the flow is not continuous across the interface. Asdiscussed in the introduction to this tutorial, this is because a pitchchange occurs. The relatively coarse mesh and the small number oftimesteps used in the transient simulation also contribute to this. Themovie was created with a narrow pressure range compared to theglobal range which exaggerates the differences across the interface.

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