CADFamily.com: CFX Mixing T-Junction Part A

This introductory tutorial models mixing of hot and cold water streams

The workshop starts from an existing mesh and applies boundary conditions to model a cold main inlet and a hot side inlet

Analysis goals for this type of problem could be to determine:

-how well do the fluids mix?

-what are the pressure drops?

Note: It’s a good idea to identify the quantities of interest from the start. You can use these to monitor the progress of the solution

Pre-processing Goals

Start in Workbench

The first step is to start Workbench:

1.From the windows Start menu, select Programs > Ansys 12.0 > Workbench

2.When Workbench opens, select File > Save and save the project as MixingTee.wbprj

Start a CFX case

3.Next, expand the Component Systems toolbox and drag a CFX analysis into the top left area of the Project Schematic

4.Double-click on Setup to launch CFX

5.When CFX-Pre opens, right-click on Mesh in the Outline tree and select Import Mesh > ANSYS Meshing

6.Select the file fluidtee.cmdb and click Open

CFX-Pre GUI Overview

CFX-Pre Mesh and Regions

CFX-Pre–Domain settings

1.The first step is to change the domain name to something more meaningful.

2.Right-click on Default Domain in the Outline tree Select Rename

-The domain name can now be edited

3.Change the domain name to junction

CFX-Pre–Domain settings (continued)

4.Double-click on the renamed domain junction

5.Set the Material to Water.

-The available materials can be found in the drop-down menu

Note that CFX has a comprehensive library of materials. These can be accessed by using the
icon and then selecting the Import Library Data icon.

6.Click the Fluid Models tab

7.In the Heat Transfer section, change Option to Thermal Energy

-Heat Transfer will be modelled. This model is suitable for incompressible flows

8.Leave all other settings as they are

-The k-Epsilon turbulence model will be used, which is the default

9.Click OK to apply the new settings and close the domain form

Boundary Conditions

The next step is to create the boundary conditions. You will create a cold inlet, a hot inlet and an outlet. The remaining faces will be set to adiabatic walls. Currently all external 2D regions are assigned to the junction Default boundary condition.