FLUENT - Steady Flow Past a Cylinder Step 1

Step 1: Create Geometry in GAMBIT

In an external flow such as the flow past a cylinder, we have to define farfield boundaries and mesh the region between the cylinder geometry and the boundaries. Farfield boundaries should be placed well away from the cylinder so that they are not under the influence of the flow around cylinder.

(Add Figure)
Figure above shows the geometry of such mesh.

Strategy for Creating Geometry

There are different methods in creating geometry. The most fundamental approach in creating geometry is the bottom-up vertical hierarchy approach. We will start with first creating vertices, then connecting the vertices to form edges, and finally connect the edges to form faces. Note that in 3D problems, you'll have to form a "volume" from faces. So the hierarchy of geometric objects in GAMBIT is vertices -> edges -> faces -> volumes.

For this tutorial also, be will be using mostly the graphics user interface in creating the geometry.

Create a Working Directory

Create a folder called cylinder in a convenient location. We'll use this as the working folder in which files created during the session will be stored.

Start GAMBIT

Create a new directory called cylinder and start GAMBIT from that directory by typing gambit -id cylinder at the command prompt.

Under Main Menu, select Solver > FLUENT 5/6 since the mesh to be created is to be used in FLUENT 6.0.

Create Vertices

The coordinates needed for the mesh are shown below

Since we are using the GUI in creating the geometry, we do not have to worry about the specific order of the coordinates.

To create a vertex, do the following:

Operation Toolpad > Geometry Command Button > Vertex Command Button > Create Vertex

Create the vertices by entering the coordinates under Global

Click the FIT TO WINDOW button to scale the display so that you can see all the vertices. The resulting image should look like this:

(Click picture for larger image)

Create Edges

Now we can create the edges using the vertices created.

Operation Toolpad > Geometry Command Button > Edge Command Button > Create Edge

Create the edge AB by selecting the vertex A followed by vertex B. Enter AB for Label. Click Apply. GAMBIT will create the edge. You will see a message saying something like "Created edge: AB'' in the Transcript window.

Connecting arc edge.

Connecting straight edge.