Physics Setup — Lesson 5

Note that the look and arrangement of the menu setup in Fluent has changed a bit since this tutorial was created. If something has changed in the menu setup from the description below, you can often find the equivalent options by poking around in the menus. 

Update the Project and Open Fluent

Before we open Fluent, we need to right-click on the Mesh cell and choose Update. You should see a checkmark next to Mesh. Double-click Setup

to open Fluent.

Initial Settings

Double-Click Setup in the Workbench Project Page.

When the Fluent Launcher appears, choose "Double Precision" under "Options" and then click OK as shown below. The Double Precision option is used to select the double-precision solver. In the double-precision solver, each floating point number is represented using 64 bits in contrast to the single-precision solver which uses 32 bits. The extra bits increase not only the precision, but also the range of magnitudes that can be represented. The downside of using double precision is that it requires more memory.

Problem Setup — General

Now, Fluent should open. If you are running Fluent on Apps on Demand, you may need to hit the Maximize button (highlighted with the arrow in the snapshot below) to scroll down the tree in the Outline View.

We will begin setting up some options for the solver. In the left-hand window (the Outline window), under Problem Setup, select General by double clicking. The only option we need to change here is the type of solver. In the Solver window, select Density-Based. It is also a good idea to click the "Check" button under the Mesh options, as this will check if the mesh was created and transferred correctly.

Models

In the outline window, double-click Models. We will need to utilize the energy equation in order to solve this simulation. Under Models, highlight Energy - Off and click Edit.... Now, the Energy window will launch. Check the box next to Energy Equation and hit OK. Doing this turns on the energy equation.

We also need to change the type of viscosity model. Select Viscous - Laminar and click Edit.... Choose the Inviscid option and press OK.

Materials

In the Outline window, double-click Materials. In the Materials window, highlight Fluid > Air, and click Create/Edit.... this will launch the Create/Edit Materials window; here we can specify the properties of the fluid. Set the Density to Ideal Gas, the Specific Heat to 1006.43, and the Molecular Weight to 28.966. When you have updated these fields, press Change/Create. Then click Close.

Boundary Conditions

In the Outline window, double-click Boundary Conditions. We will now specify each boundary condition for the simulation.

Farfield

In the Boundary Conditions window, select farfield. Use the drop-down menu to change the Type to pressure-far-field. You will be asked to confirm the change by pressing OK. (Note: In newer versions, this step is not needed.) Next, a dialogue box will open with some parameters we need to specify. Change the Gauge Pressure (Pascal) to 101325, and Mach Number to 3.

Also, select the Thermal tab, and ensure that the temperature correctly defaulted to 300 K. When you are finished, press OK.

Wedge

In the Boundary Conditions window, select wedge. Use the drop-down menu to change the Type to wall.

Symmetry

In the Boundary Conditions window, select symmetry. Use the drop-down menu to change the Type to symmetry.

Operating Conditions

In the Boundary Conditions window, select the Operating Conditions button. Change the Gauge Pressure to 0. Then press OK.

It is important to check the operating conditions. When setting the density in materials to Ideal Gas, Fluent calculates the density using the absolute pressure. However, the pressure we specify is the gauge pressure, not the absolute pressure. Fluent will use the absolute pressure to compute the density, therefore if we do not set the operating pressure to 0 our density will be incorrect for the flow field.