A QUICK OVERVIEW OF STAR CD

by Benoit Seille and Ugo Schuck

When you start StarCD for a new project, you need to type  the nam e of your project in the Enter Case Name text box, after that deselect Resume from Existing .mdl File? and Append to Previous .echo File? and click the Continue button.
After that, 3 windows appear, the first one is the main window called Prostar, the second one is the Star GUIde window and the last one is the Prostar Output window.
In fact, to run an analysis, you just need to follow the different steps of the NAV CENTER in the Star GUIde window. Our manual is in in fact jsut a little tutorial to generate a 2D mesh with really simply boundary conditions.

•  Creating a Mesh
To create a 2D mesh you need to click on the Create and import grids folder, Create grids folderand run Create 3-D grids using simple shapes in the NAV CENTER.  We are going to craete a 3D mesh, but we take a very small width, to be like in a 2D mesh.

You just have to enter the paramaters shown below and click Generate Mesh in the Star GUIde window.

By clicking on Re-Plot or Cell Plot in the main window, the mesh will appear in this window. After that, to save it, you need to to click on Save Model in the File menu in the main window.

Here is our mesh, it's just a rectangular parallelepiped, which is in fact a rectangle because the width is very small:

•  Define Boundary Regions
The next step for us in the NAV CENTER is to click on the folder Locate Boundaries, and to run Create Boundaries. This is maybe the most difficult thing to do with Star CD. Here is what you have to do:

-The first step is to create two symmetry conditions. For this, click on 1 in Boundary Region and choose Symmetry in Define Region Type. Give a name like "Symmetry1", in Boundary Region Name and click Apply. Click on the Surface Based on Edges Button and click on any edge on your surface in the main window. Do it again for the opposite face (called "Symmetry2").
-We use two outlet conditions, on two adjacents edges of the rectangle. To do that, it's the same than with the symmetry condition except you click on the Select a Zone button  and not on the Surface Based on Edges button. In this way you choose a zone in the main window for your Boundary condition and every whole surfaces in this zone will be selectioned.
-We use four inlet conditions two on each edge of the other edges of the rectangle. For that we do the same as for outlet conditions.

Finally, we have the following grid with its  boundary conditions:

You can check the boundary regions by clicking on Boundary List in the Lists menu in the main window.

•  Models
For this, click on the folder called Thermophysical Models and Properties and go in the sub-folder called Liquid and Gases.
Just follow all the steps concerning molecular properties, turbulence models, initialization etc...
•  Boundary Conditions
Open the folder Define Boundary Conditions and run Define Boundary Regions. Now enter all the boundary conditions in your different boundary regions created previously.

•  Solution Method and Analysis Running
The next step is to choose the solver and the different schemes of the study by clicking on Analysis Controls and then Solution Method.  You just have to follow the guide and change the different parameters.

Now, you have to check your model by clicking on the folder Check Model Setup and running Check Everything. Finally click on the All button. If there are troubles in your model, one new window will appear and will explain you what is your mistake.

Finally, to run your analysis click on the folder Analysis Preparation/Running. The most important things you have to check are Set Run Time Controls to enter number of iterations and Run Analysis Interactively where you will start your running by clicking on Start New Analysis.

•  Loading datas and creating plots
To finish and to see results, it's quite easy, click on the Post-Processing folder in the NAV CENTER and run Load Data. Click on Open Post File button, and go to data.
In this window, choose your scalar or your vector datas. Click on Get Data button  and on the Go To Create Plots button.

Now you are in the Create Plots menu, choose your plot (contour or vector) and click on the Plot to File and Plot to Screen buttons.
Go in your main window and click on Re-Plot or on Cell Plot.

• Some tips about Star CD
-Maybe the most difficult with Star CD is to define boundary region. You can click the cell by choosing them one after one, but it's the more tedious. If it doesn't work with the Surface Based on Edges and Select a Zone buttons, you need to see vertices. To do that, in the main window, click on V->, all, Vertex, Cell Plot or Re-Plot.
-After each modification, to see it click on Re-Plot or Cell Plot buttons in the main window.