This tutorial will demonstrate how to read a surface mesh and create a volume mesh for a CFD simulation. Figure 1 shows the geometry which will be used for this tutorial; it represents an adjustable throttle. The file containing the surface mesh for this tutorial is called Throttle.msh and it can be downloaded from the enGrid download page from here.
|Figure 1: Throttle geometry|
To start, please import the file choosing:
|Figure 2: After importing the surface mesh|
enGrid colours the faces of the surface grid in order to determine which side of the surface is inside a flow domain and which is outside. The outside is coloured in a pale green, but Figure 2 shows pale yellow; this means the surface is wrongly oriented and it needs to be corrected. To do this, please choose
Unfortunately all faces belong to the same boundary condition and thus it is not possible to see inside the domain. To change this you can pick a surface on the side of the cylindrical geometry and then change its boundary condition to a different value. To pick a face, please point the mouse over a triangle and press the P key on your keyboard. Afterwards you should see something similar to Figure 3.
|Figure 3: Picking a boundary face|
To change the boundary code, please select:
Due to the upcoming support for multiple volumes, you also need to define a volume. This is done by adding a new volume and indicating which boundary codes are part of it and which color the outer side of the boundary relative to the volume currently has. To do this, select:
Creating a first volume mesh, including the boundary layer, is fairly easy now. First choose:
|Figure 4: Wall boundaries on which a boundary layer mesh will be created|
To create the grid, simply select:
After enGrid has finished you can select tetras and wedges from the available options on the right side of enGrid ’s main window. Don't forget to also check Enable volume elements.
In order to see inside you should also enable the clipping options. The origin of the clipping plane can be set to (0,0,0) and the normal vector to (0,0,-1). If you now select to view only boundary condition 1 and choose:
|Figure 5: Section cut showing the internal mesh and the internal geometry|
To get a nice tetrahedral part of the grid it is advisable to execute: