StarCd modelling


  1.1-Mesh generation based on a multi-block technique

            Given that there are no geometric complexities, we use one of Prostar's automatic meshing facilities to create the basic grid. The stategy choosen here is to divide the geometry into two sections. The appropriate STAR GUIde panel is then applied to each section in turn to create two subsets of the final mesh. These are finally coupled together to create a mesh covering the entire model. We use the option "Assemble grid " to remove the discontinuities and to merge all the vertices. The following graph shows the geometry and the first mesh :
 

 

 

            The mesh is now complete. however, the walls still need to be created. this is done simply by deleting the cells occupying the volume corresponding to each wall. The procedure used is :
-View>axis>+Z
- Tools>Cell Tool>New>Zone
- we draw a polygonal plot around the cells limitating the wall (a wall is corresponding to a unique cell in x direction but to a length of 10 cm in the y direction )
- We click Delete Cells>Cell Set
-Replot
We see that the cells in the zone chosen have disapeared. We repeat this procedure for the 9 walls and we obtain the next picture


 

 


            I choose to take 5 cells between 2 walls.

       Before going the next step, we have to remove all deleted (merged) vertices and cells from the model to create a new renumbered mesh :
-Tools>Vertex Tools>Merge/Cmpress>Compress
-In the Vcompress dialog, accept all defaults and click Apply
-Close the Vcompress dialog
-Close the Vertex Tool
-In the Cell Tool, click Compress
-Close the Cell Tool

At this point, it is prudent to check the quality of the mesh. PROSTAR provides a number of automated tools that streamline this process. the check tool is accessed by clicking on folder " Check and fix grid "  in the Navigation Centre.
 
 

        1.3-Boundary conditions

            Specification of boundary conditions involves the use of two panels. The first one, "Create Boundaries", enables the boundary regions to be positioned within the model. The second, "Define Boundary Regions", is used to specified the properties of the regions. In this case, there are four boundary regions : an inlet, an outlet ,a symmetry and a wall. PROSTAR  automatically assumes that any external surfaces that have not been specified by the user belong to Region 0 and, by default, Region 0 is a no-slip, adiabatic wall. Therefore, wall boundaries do not have to be specifically identified in this particular problem. For the other three boundary types, we assign a region number to the inlet, outlet and 2 symmetry regions.
            Now that the boundary regions have been physically located, we have to define the particular properties of each region by using in the main PROSTAR window, the folder "Define boundary conditions". the values we have entered are display on the three following figures :
 


 
 
 

               Inlet boundary region settings                                                                            Wall boundary region settings

     
 

    Symmetry boundary region settings                                                                                   Outlet boundary region settings
 
 
 
 

        If we plot all the Boundaries, we obtain this figure showing all the what we set


 
 

    The model building process is now complete. The next step is to do a final comprehensive check for any errors or inconsistencies before setting up the CFD analysis run by clicking on the folder "Check Model Setup , Check Everything".