Physics Setup — Lesson 5

Update Project

In the Project Schematic window, notice that there is a lightning symbol in the mesh box. This means that we need to update the project in order to continue. Press  to apply the mesh. The lightning symbol should now be replaced by a green check mark , meaning we are ready to move on.

Launch Fluent

To begin setup, double click  . This will first launch a dialogue box with some options. Under Options, check the box marked Double Precision, and under Processing Options, select Parallel and change the Number of Processes to 2.

Once the options are set, press OK to launch Fluent.

Turn on Energy

The first thing that needs to be done is to tell Fluent to solve for temperature. To do this, we need to turn on the Energy Equation. Under Problem Setup, select Models. In the Models window, double click Energy. The Energy window should pop up. Check the box next to Energy Equation and press OK.

Materials

Next, we will create the materials we are using in the simulation and define their material properties. For reference, the material properties needed for this simulation are included in the table below.

Air

Under Problem Setup, select Materials. In the Materials window under Fluid select Air, and press Create/Edit.... Define the material properties for air as shown in the table above.

When you are finished entering the material properties of air, press Change/Create and close the window.

Copper

Now, highlight aluminum in the material properties window and select Create/Edit. We are not using aluminum in this simulation, so we need to change the name and the properties to reflect copper. In the popup window, change the Name to Copper, and the Chemical Formula to Cu. Also, change the material properties to the values shown in the chart above.

Now, press Change/Create. You will be asked if you want to overwrite aluminum; press Yes. You may now close the popup window.

ABS Plastic

Now, we need to create a new material. In the Materials window, highlight Solid and press Create/Edit. Notice that the material properties for copper appear in the popup window. This is OK, but we need to remember that we do not want to overwrite the copper data. Rename the new material ABS and for simplicity, also enter the Chemical Formula as ABS. Enter the material properties for ABS as shown in the table above.

When the material properties are entered correctly, press Change/Create. The popup will appear asking us if we want to overwrite the material properties for copper. We do not want to overwrite copper, so press No. This should create ABS as a new material in the material list.

Boundary Conditions

Now, we need to enter the boundary conditions for this problem. In the Outline, select Boundary Conditions to bring up the boundary conditions window.

Inlet

In the Boundary Conditions window, select Inlet. Check to make sure that the Type has correctly defaulted to Velocity-Inlet and press Edit. In the Momentum Tab, we will specify the velocity of the incoming air. Knowing that the inlet feed rate is 35 ft³/min and that the diameter of the holes is 4.72 inches, we can solve for the inlet speed.

Input the speed into the Velocity Magnitude. Please note that the units for the Velocity Magnitude should be in/s and not m/s as in the picture.

Next, click on the Thermal Tab. We need to input the temperature of the incoming air. The ambient air is 114 degrees Fahrenheit. Fluent only accepts temperatures in Kelvins. 114 degrees Fahrenheit = 318.706 Kelvins. Input the ambient temperature, and press OK

Outlet

In the Boundary Conditions window, select Outlet. Check to make sure that the Type is set to Pressure-Outlet and press Edit. In the Momentum tab, the Gauge Pressure (pascal) should be set to 0. Next, click on the Thermal tab. Change the Backflow Total Temperature to 318.706 Kelvin and press OK.

Wall

Next, we need to specify the wall material as ABS plastic. In the Boundary Conditions menu, select wall-solid and press Edit. Select the Thermal tab, and change the Material to ABS.

When finished, press OK.

Heat Generation

In the Outline window, select Cell Zone Conditions. Under Zones, select HeatGeneration and press Edit. Change the material name to Copper. Check the box next to Source Terms, then select the Source Terms Tab.

In the Source Terms tab, select Edit. Change the number of Energy Sources to 1, then use the pull down menu and select constant. Enter the heat generation as 40682 w/m³.

When finished, press OK.

Reference Values

Now that we are done defining the boundary conditions, we need to specify reference values. In the Outline, select Reference Values. Underneath Compute From, select Inlet.