vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

that is required for an inviscid flow, as the tangential velocity is computed as part of the solution.

11.4.8. Operating Conditions

1. Set the operating pressure.

Setup → Boundary Conditions → Operating Conditions...

a.Enter 0 atm for Operating Pressure.

b.Click OK to close the Operating Conditions dialog box.

Since you have specified the boundary condition inputs for pressure in terms of absolute pressures, you have to set the operating pressure to zero. Boundary condition inputs for pressure should always be relative to the value used for operating pressure.

11.4.9. Mesh Interfaces

1. Create a periodic mesh interface between the rotor and stator mesh regions.

Setup → Mesh Interfaces New...

Select Manual Create...

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
382	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

a.Enter int for Mesh Interface.

b.Enable Periodic Repeats in the Interface Options group box.

Enabling this option, allows ANSYS Fluent to treat the interface between the sliding and non-sliding zones as periodic where the two zones do not overlap.

c.Select rotor-interface from the Interface Zones Side 1 selection list.

Note

In general, when one interface zone is smaller than the other, it is recommended that you choose the smaller zone as Interface Zone 1. In this case, since both zones are approximately the same size, the order is not significant.

d.Select stator-interface from the Interface Zones Side 2 selection list.

e.Click Create/Edit... and close the Create/Edit Mesh Interfaces dialog box.

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	383

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

f.Close the Mesh Interfaces dialog box.

2.Check the mesh again to verify that the warnings displayed earlier have been resolved.

Domain → Mesh → Perform Mesh Check

11.4.10. Solution

1.Set the solution parameters.

Solution → Solution → Methods...

Select Coupled from the Pressure-Velocity Coupling group box. 2. Change the Solution Controls

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
384	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

Solving → Controls → Controls...

a.Enter 0.5 for Momentum and Pressure in the Explicit Relaxation Factors group box.

b.Enter 0.9 for Temperature in the Under-Relaxation Factors group box.

3.Enable the plotting of residuals during the calculation.

Solution → Reports → Residuals...

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	385

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

a.Ensure that the Plot is selected in the Options group box.

b.Select relative from the Convergence Criterion drop-down list.

c.Enter 0.01 for Relative Criteria for each Residual (continuity, x-velocity, y-velocity, z-velocity, and energy).

d.Click OK to close the Residual Monitors dialog box.

4.Enable the plotting of mass flow rate at the inlet (rotor-inlet).

Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate...

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
386	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

a.Enter surf-mon-1 for the Name of the surface report definition.

b.In the Create group box, enable Report File, Report Plot and Print to Console.

c.Enter rotor-inlet in the Surfaces field to filter the list.

d.Select rotor-inlet from the Surfaces selection list.

e.Click OK to save the surface report definition settings and close the Surface Report Definition dialog box.

surf-mon-1-rplot and surf-mon-1-rfile that are automatically generated by Fluent appear in the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).

5.Enable the plotting of mass flow rate at the outlet (stator-outlet).

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	387

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

Solution → Reports → Definitions → New → Surface Report → Mass Flow Rate...

a.Enter surf-mon-2 for the Name of the surface report definition.

b.In the Create group box, enable Report File, Report Plot and Print to Console.

c.Enter stator-outlet in the Surfaces field to filter the list.

d.Select stator-outlet from the Surfaces selection list.

e.Click OK to save the surface report definition settings and close the Surface Report Definition dialog box.

surf-mon-2-rplot and surf-mon-2-rfile that are automatically generated by Fluent appear in the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
388	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

6.Enable the plotting of the area-weighted average of the static pressure at the interface (stator-interface).

Solution → Reports → Definitions → New → Surface Report → Area-Weighted Average...

a.Enter surf-mon-3 for the Name of the surface report definition.

b.In the Create group box, enable Report File, Report Plot and Print to Console.

c.Retain the default selection of Pressure... and Static Pressure from the Field Variable drop-down lists.

d.Enter stator-interface in the Surfaces field to filter the list.

e.Select stator-interface from the Surfaces selection list.

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	389

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

f.Click OK to save the surface report definition settings and close the Surface Report Definition dialog box.

surf-mon-3-rplot and surf-mon-3-rfile that are automatically generated by Fluent appear in the tree (under Solution/Monitors/Report Plots and Solution/Monitors/Report Files, respectively).

7.Initialize the solution using the values at the inlet (rotor-inlet).

Solution → Initialization → Options...

a.Select rotor-inlet from the Compute from drop-down list.

b.Select Absolute in the Reference Frame list.

c.Click Initialize.

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
390	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

8.Save the initial case file (axial_comp.cas.gz).

File → Write → Case...

9.Run the calculation for one revolution of the rotor.

Solution → Run Calculation → Advanced...

a.Enter 6.6667e-6 s for Time Step Size.

The time step is set such that the passing of a single rotor blade is divided into 15 time steps. There are 16 blades on the rotor. Therefore, in each time step the rotor rotates 360/16/15=1.5 degrees. With a rotational speed of 37,500 rpm (225,000 deg/sec), 1.5 degrees of rotation takes 1.5 / 2.25e5 = 6.6667e-6 sec.

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	391

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

b.Enter 240 for Number of Time Steps.

There are 16 blades on the rotor, and each rotor blade period corresponds to 15 time steps (see above). Therefore, a complete revolution of the rotor will take 16*15=240 time steps.

c.Retain the default setting of 20 for Max Iterations/Time Step.

d.Click Calculate.

The residuals jump at the beginning of each time step and then fall at least two to three orders of magnitude. Also, the relative convergence criteria is achieved before reaching the maximum iteration limit (20) for each time step, indicating the limit does not need to be increased.

Figure 11.3: Residual History for the First Revolution of the Rotor

10.Examine the flow variable histories for the first revolution of the rotor (Figure 11.4: Mass Flow Rate at the Inlet During the First Revolution (p. 393), Figure 11.5: Mass Flow Rate at the Outlet During the First Revolution (p. 393), and Figure 11.6: Static Pressure at the Interface During the First Revolution (p. 394)).

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
392	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

Figure 11.4: Mass Flow Rate at the Inlet During the First Revolution

Figure 11.5: Mass Flow Rate at the Outlet During the First Revolution

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	393

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

Figure 11.6: Static Pressure at the Interface During the First Revolution

The flow variable histories show that the large variations in flow rate and interface pressure that occur early in the calculation are greatly reduced as time-periodicity is approached.

11.Save the case and data files (axial_comp-0240.cas.gz and axial_comp-0240.dat.gz).

File → Write → Case & Data...

Note

It is a good practice to save the case file whenever you are saving the data file especially for sliding mesh model. This is because the case file contains the mesh information, which is changing with time.

Note

For transient-state calculations, you can add the character string %t to the file name so that the iteration number is automatically appended to the name (for example, by entering axial_comp-%t for the File Name in the Select File dialog box, ANSYS Fluent will save files with the names axial_comp-0240.cas and axial_comp-0240.dat).

12. Rename the report output file in preparation for further iterations.

Solution → Monitors → Report Files → surf-mon-1-rfile Edit...

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
394	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

a.Enter surf-mon-1b.out for Output File Base Name.

b.Click OK to close the Edit Report File dialog box.

13.Similarly, change the output file names for the surf-mon-2-rfile and surf-mon-3-rfile report file definitions to surf-mon-2b.out and surf-mon-3b.out, respectively.

14.Continue the calculation for 720 more time steps to simulate three more revolutions of the rotor.

Solution → Run Calculation → Advanced...

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	395

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

15.Examine the flow variable histories for the next three revolutions of the rotor to verify that the solution is time-periodic (Figure 11.7: Mass Flow Rate at the Inlet During the Next 3 Revolutions (p. 397) Figure 11.8: Mass Flow Rate at the Outlet During the Next 3 Revolutions (p. 397), and Figure 11.9: Static Pressure at the Interface During the Next 3 Revolutions (p. 398)).

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
396	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

Figure 11.7: Mass Flow Rate at the Inlet During the Next 3 Revolutions

Figure 11.8: Mass Flow Rate at the Outlet During the Next 3 Revolutions

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	397

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

Figure 11.9: Static Pressure at the Interface During the Next 3 Revolutions

16.Save the case and data files (axial_comp-960.cas.gz and axial_comp-960.dat.gz).

File → Write → Case & Data...

17.Change the file names for surf-mon-1b.out, surf-mon-2b.out, and surf-mon-3b.out to surf-mon- 1c.out, surf-mon-2c.out, and surf-mon-3c.out, respectively (as described in a previous step), in preparation for further iterations.

18.Add a point at the interface of the stator.

Results → Surface → Create → Point...

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
398	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

a.Enter -0.02 for x0, -0.08 for y0, and -0.036 for z0 in the Point Surface dialog box.

b.Retain the default, point-1 for New Surface Name.

c.Click Create and close the Point Surface dialog box.

19.Enable plotting of the static pressure at a point on the stator interface (point-1).

Solution → Reports → Definitions → New → Surface Report → Vertex Average...

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	399

vk.com/club152685050Using Sliding Meshes | vk.com/id446425943

a.Enter surf-mon-4 for the Name of the surface report definition.

b.In the Create group box, enable Report File, Report Plot and Print to Console.

c.Retain the defaults of Pressure and Static Pressure for Field Variable.

d.Enter point-1 in the Surfaces field to filter the list.

e.Select point-1 from the Surfaces selection list.

f.Click OK to save the surface report definition settings and close the Surface Report Definition dialog box.

20.Continue the calculation for one final revolution of the rotor, while saving data samples for the postprocessing of the time statistics.

	Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
400	of ANSYS, Inc. and its subsidiaries and affiliates.

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

Solution → Run Calculation → Advanced...

a.Enter 240 for Number of Time Steps.

b.Enable Data Sampling for Time Statistics in the Options group box.

Enabling Data Sampling for Time Statistics causes ANSYS Fluent to calculate and store mean and root-mean-square (RMS) values of various quantities and field functions over the calculation interval.

c.Click Calculate.

21.Save the case and data files (axial_comp-1200.cas.gz and axial_comp-1200.dat.gz).

File → Write → Case & Data...

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	401