Turbo Pre and Post

Introduction

A simple workshop follows to demonstrate how to use the Turbomachinery mode in CFX-Pre and CFD-Post.

This workshop models an Axial fan. The model consists of a single rotating domain for the fan blade with stationary domains upstream and downstream of the blade.

The full axial fan contains ten blades. Due to rotational periodicity a single blade passage will be modeled. Frozen Rotor interfaces are used to connect the rotating and stationary domains.

Turbo-Pre

1.Open Workbench (Start > Programs > ANSYS 12.0 > ANSYS Workbench)

2.Drag CFX into the project schematic

3.Start CFX-Pre by double clicking Setup

4.Select Tools > Turbo Mode

Basic Settings

The Turbo mode uses a setup wizard to walk you through CFX-Pre. The first step is the Basic Settings panel:

1.Set the Machine Type to Fan

2.Select Z as the Rotation Axis

Notice that the rotational axis is displayed in the Viewer

3.Click Next >

Component Definition

The Component Definition panel is used to import meshes, select the rotation speed for each component and set the tip clearance (if any). Start by defining the first stationary component:

1.Right-click in the Component Definition white space, and select Add Component…

2.Select the Type as Stationary and set the Name to S1

3.Select the Mesh File as fan.gtm

4.Expand the Available Volumes frame and select the Volumes as INBlock Main

5.Expand the Region Information frame and compare with the picture on the next page and make the necessary changes

The Region Information is used by CFX-Pre to identify mesh regions of interest. CFX-Pre will try to automatically identify these regions, but manual input may be required depending on how the regions are named in the mesh file.

CFX-Pre will automatically create boundary conditions and domain interfaces using these regions, so checking the Region Information at this stage will save time later.

-The mesh file contains all three components, but only one of those components is to be included in S1

-Default values can be used for all other options

Now define the rotating component:

1.Right-click in the Component Definition white space, and select New Component…

2.Select Rotating and set the Name as R1

3.Set the Rotating Value to –3000 [rev min^-1]

-The rotation direction is shown in the Viewer

4.Do not select a mesh file. The mesh has already been imported in the previous step. Under Available Volumes select Passage

5.Expand the Wall Configuration frame. Set Tip Clearance at Shroud to YES and Tip Clearance at Hub to NO

-This sets boundary conditions for a fan with a rotating hub and a counter-rotating shroud surface

6.Expand the Region Information frame and compare with the picture below and make the necessary changes

-This sets boundary conditions for a fan with a rotating hub and a counter-rotating shroud surface

Now define the second stationary component:

1.Create a new stationary component named S2

2.Under Available Volumes select OUTBlock Main

3.Expand the Passages and Alignment frame

-The number of Passages in 360 and the number of Passages To Model is determined automatically

-You can change the automatic values or apply a Theta Offset by clicking the Edit button, but this is not necessary for this case

4.Expand the Region Information frame and compare with the picture next page and make the necessary changes

5.Click Next > to proceed

Physics Definition

All Physics settings, including Fluid Type, Simulation Type, Inlet and Outlet boundary conditions, Interface types, and Solver Parameters are set in one panel.

1.The default Fluid, Simulation Type and Model Data are appropriate for this simulation

2.Select Boundary Template as P-Total Inlet Mass Flow Outlet

-The Boundary Template provides quick setup of the most common turbomachinery boundary combinations

3.Set P-Total to 0 [atm]

4.Set Mass Flow to Per Component and then enter a Mass Flow Rate of 0.04 [kg s^-1]

5.Set Flow Direction to Cylindrical Components with direction set to 1,0,0

6.Change the Interface Default Type to Frozen Rotor

7.Expand the Solver Parameters frame

8.Set the Convergence Control to Physical Timescale with a value of 0.02 [s] (select the expression icon to allow this to be entered)

-This sets the timescale to roughly 6/ω, where ω is the machine rotational speed in [rad/s]. Typically, the timescale for rotating machinery is specified somewhere between 0.1/ω and 10/ω.

9.Click Next > to proceed

Interface Definition

Interfaces are automatically created using the Region Information from the Component Definition panel.

1.Select each interface to verify it has been created correctly

-There are two Frozen Rotor interfaces, three Periodic interfaces and an interface near the blade tip to connect dissimilar meshes together

-The interfaces have been correctly created

2.Click Next > to continue

Boundary Definition

Boundary conditions are also automatically created using the Region Information from the Component Definition panel and information from the Physics Definition panel.

1.Select each boundary condition to verify the settings are appropriate

2.Select Next > to continue

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