vk.com/club152685050Using a Single Rotating Reference| vk.com/id446425943Frame

Figure 9.1: Problem Specification

As noted by Pincombe [1], there are two nondimensional parameters that characterize this type of disk cavity flow: the volume flow rate coefficient, , and the rotational Reynolds number, . These parameters are defined as follows:

(9.1)

(9.2)

where is the volumetric flow rate, is the rotational speed, is the kinematic viscosity, and is the outer radius of the disks. Here, you will consider a case for which = 1092 and = .

9.4. Setup and Solution

The following sections describe the setup and solution steps for this tutorial:

9.4.1.Preparation

9.4.2.Mesh

9.4.3.General Settings

9.4.4.Models

9.4.5.Materials

9.4.6.Cell Zone Conditions

9.4.7.Boundary Conditions

9.4.8.Solution Using the Standard k- ε Model

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

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

9.4.9.Postprocessing for the Standard k- ε Solution

9.4.10.Solution Using the RNG k- ε Model

9.4.11.Postprocessing for the RNG k- ε Solution

9.4.1. Preparation

To prepare for running this tutorial:

1.Download the single_rotating.zip file here.

2.Unzip single_rotating.zip to your working directory.

3.The file disk.msh can be found in the folder.

4.Use Fluent Launcher to start the 2D single precision (disable Double Precision) version of ANSYS Fluent. Fluent Launcher displays your Display Options preferences from the previous session.

5.Run in Serial under Processing Options.

9.4.2. Mesh

1.Read the mesh file (disk.msh).

File → Read → Mesh...

As ANSYS Fluent reads the mesh file, it will report its progress in the console.

Note

The Fluent console will display a warning that the current setup for the boundary conditions is not appropriate for a 2D/3D flow problem.

You will resolve this issue when you modify the solver settings in a subsequent step.

9.4.3. General Settings

1.Check the mesh.

Domain → Mesh → Check → Perform Mesh Check

ANSYS Fluent will perform various checks on the mesh and report the progress in the console. Make sure that the reported minimum volume is a positive number.

2.Examine the mesh (Figure 9.2: Mesh Display for the Disk Cavity (p. 322)).

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	321

vk.com/club152685050Using a Single Rotating Reference| vk.com/id446425943Frame

Figure 9.2: Mesh Display for the Disk Cavity

Extra

You can use the right mouse button to check which zone number corresponds to each boundary. If you click the right mouse button on one of the boundaries in the graphics window, information will be displayed in the ANSYS Fluent console about the associated zone, including the name of the zone. This feature is especially useful when you have several zones of the same type and you want to distinguish between them quickly.

3.Define new units for angular velocity and length.

Domain → Mesh → Units...

In the problem description, angular velocity and length are specified in rpm and cm, respectively, which is more convenient in this case. These are not the default units for these quantities.

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

vk.com/club152685050 | vk.com/id446425943

Setup and Solution

a.Select angular-velocity from the Quantities list, and rpm in the Units list.

b.Select length from the Quantities list, and cm in the Units list.

c.Close the Set Units dialog box.

4.Specify the solver formulation to be used for the model calculation and enable the modeling of axisymmetric swirl.

Physics → Solver

a.Retain the default selection of Pressure-Based in the Type list.

b.Retain the default selection of Absolute in the Velocity Formulation list.

For a rotating reference frame, the absolute velocity formulation has some numerical advantages.

c.Select Axisymmetric Swirl from the drop-down list in the Solver group box.

9.4.4. Models

1.Enable the standard - turbulence model with the enhanced near-wall treatment.

Physics → Models → Viscous...

Release 2019 R1 - © ANSYS,Inc.All rights reserved.- Contains proprietary and confidential information
of ANSYS, Inc. and its subsidiaries and affiliates.	323

vk.com/club152685050Using a Single Rotating Reference| vk.com/id446425943Frame

a.Select k-epsilon (2 eqn) in the Model list.

The Viscous Model dialog box will expand.

b.Retain the default selection of Standard in the k-epsilon Model list.

c.Select Enhanced Wall Treatment in the Near-Wall Treatment list.

d.Click OK to close the Viscous Model dialog box.

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