Examples


Meshing a simple Geometry
Meshing a Complex Geometry
Meshing a Complex Grid


Meshing a Simple geometry

I - General method

In the STAR GUIde window, use the tool:

Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

Click on the button Select Coordinate System:
  Choose cartesian for rectangular shapes, cylindrical for circular shapes and click on Set Active. To change the origin, create a new local coordinate system and set it active. Click on Close


Click on Select Cell Type:
  Click on the first type: 1 Fluid and on the right, choose Shell for the Cell Type. Click on Apply.


Fill in the Extent of Domain with the minimum and maximum values of the variables defining the geomerty and set the Number of Cells for each variable. Click on Generate 2-D Mesh.

It is necessary to generate 3D mesh from 2D mesh even for a 2D mesh. Indeed calcualtions are computed with volumes and a 2D mesh becomes a 3D mesh with only one cell depth. Click on Generate 3-D Mesh from 2-D Mesh. This command will automatically replace the Shells by Fluid Cells. It also creates symmetry boundaries to both sides of the new fluid cells.

II - Examples

Case 1 : Simple Geometry

Here is a scheme of the geometry that we would like to mesh :

In the STAR GUIde window, use the tool:

Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

Click on the button Select Coordinate System. Click on 2.Cylindrical, Set Active, Close
Click on Select Cell Type. Click on Type: 1 Fluid, select Cell Type: Shell, click on Apply, Close.

 

Set the values and click on Generate 2-D Mesh, Generate 3-D Mesh from 2-D Mesh.

 

Case 2 : more complex geometry including circular and rectangular shapes

Here is a scheme of the geometry that we would like to mesh :

In the STAR GUIde window, use the tool:

Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

Click on the button Select Coordinate System. Click on 1.Cartesian, Set Active, Close
Click on Select Cell Type. Click on Type: 1 Fluid, select Cell Type: Shell, click on Apply, Close.

Fill in the Extent of Domain with the values:
    5 5 10
    5 5 10
and click on Generate 2-D Mesh

Now let's create the two Vertices of the part of the right.

In the STAR GUIde window, use the tool:

Create and Import Geometry
    Create Geometric Entities

In the Vertices tab, click on the button Vertices, enter the vertex location by filling in the 3 cells and click on Done
    1st point: x=-5 y=10 z=0
    2nd point: x=-5 y=-5 z=0



Now let's mesh the trapezoidal part.

That for, we can use the patch command: in the Prostar Output window, type:
patch vx vx vx vx 10 10
(vx correspond to the 4 vertices that will be pointed at the screen; 10 10 the number of the cells in the x and y direction)
Press the return button and then in the main Prostar window, click on the 4 vertices that define the trapezoidal shape.

CAUTION! To use the patch command, it is important to move the Prostar Output window the left of the screen so that it does not hamper the plotting of the vertices.
Therefore move the Prostar Output window on the left, click on Replot in the main window.

Then in the main Prostar window, go to C->, choose All and click on Cell PLot.



Then generate 3D mesh from 2D mesh.

In STAR GUIde: Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

 

Click on Generate 3-D Mesh from 2-D Mesh

Merge the two 3D meshes.

In STAR GUIde:
Create and Import Grid
    Assemble Grids

Click on the button Merge.

TOP

 

 


 

Meshing a Complex geometry

Here is a scheme of the geometry to mesh :

NB : the hole in the middle of the rectangle is empty.

The mesh is devided into 8 regions as it is shown below :

 

To create the outer rectangle, create first the vertices that correspond to the 4 corners.

In the STAR GUIde window, use the tool:

Create and Import Geometry
    Create Geometric Entities

In the Vertices tab, click on the button Vertices, enter the vertex location by filling in the 3 cells and click on Done
    1st point: x = -1500 ; y = 500 ; z = 0
    2nd point: x = 1500 ; y = 500 ; z = 0
    3rd point: x = -1500 ; y = -500 ; z = 0
    4th point: x = 1500 ; y = 500 ; z = 0

Now let's create the inner circle.

 

To draw a circle with Prostar, first create several Vertices and link them with a Spline.

First, create 2 vertices at the tips of a diameter...
In the STAR GUIde

In left part:
  -> Create and Import Geometry
  -> Create Geometric Entities
In right part:
  -> Select Items: Vertex
 Select the Vertices tab
  -> Select the Cartesian Coordinate System
  -> Select Create vertex
  -> Click on Vertices
  -> Type the 3 Coordinates 0,300,0
  -> Click on Done
  -> Type the 3 Coordinates 0,0,0
  -> Click on Done

...then create a local cylindrical coordinate system at the center of the circle,...

In the main Prostar window

Click on the orange button CSYS
Select an empty line (n4)
Select Cylindrical for the type of Coordinate System
Type the coordinates of the origin in the active system0 150 0
Click on New Local
To display this Coordinate System, click on Show Triad
Click on Set Active to use it

...and generate vertices on the circle...

In the Prostar Output window

To create the first half-circle, type
  vfill,1,2,20,3,1 Return
The parameters are:
 the number of the first Vertex: 1
 the number of the second Vertex: 2
 the total number of new Vertices: 20
 the number of the first new Vertex: 3
 the step for the new Vertices numbering: 1

This command creates points between two points with a regular linear variation of the coordinates. So in a Cartesian Coordinate System, all the points are aligned. Here, with the Local Cylindical Coordinate System defined above, the two points have the same distance to the axis and the same height. The sole variable coordinate is the angle and so the new points are on a half-circle.

Then change the direction of rotation
  csdir 180 Return
and create the clockwise half-circle
  vfill,1,2,20,23,1 Return

...Finally, link the vertices with Splines.

In the main prostar window, click on Tools > Spline Tools
In the Spline Tool Window, click on New Spline and then click on every vertex of the circle.
Finally, click on Done.

 

Now that the required vertices are created, you will use the patch command to mesh the 8 regions.

First, create 8 vertices as it is shown on the frame below :

Then type the following command in the Prostar Output Window :
patch vx vx vx vx 20 20
where vx correspond to a vertex clicked on in the prostar window and 20 and 20 to the number of cells in the x and y directions.

and click on the 4 corners of the region.

Use the same patch command for the other regions.

CAUTION : it is preferable to click on the 4 corners of each region in the same order.

Then generate 3D mesh from 2D mesh.

In STAR GUIde: Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

 

Click on Generate 3-D Mesh from 2-D Mesh

Merge the two 3D meshes.

In STAR GUIde:
Create and Import Grid
    Assemble Grids

Click on the button Merge

 

TOP

 


Meshing a Complex grid

Here is a scheme of the geometry to mesh :

NB : the hole in the middle of the rectangle is empty.

The mesh is devided into 5 regions as it is shown below :

 

To create this mesh, the work can be devided into 2 steps :
1 - Create the circular part (region 5)
2 - Create the cells in the outer rectangular part (Regions 1, 2, 3 and 4)

To create the circular part, see the 1st example of the simple geometry creation (where Rmin = 300 and Rmax = 350).

To create the rectangular part, create the 4 vertices that correspond to the 4 corners :

In the STAR GUIde window, use the tool:

Create and Import Geometry
    Create Geometric Entities

In the Vertices tab, click on the button Vertices, enter the vertex location by filling in the 3 cells and click on Done
    1st point: x = -1500 ; y = 500 ; z = 0
    2nd point: x = 1500 ; y = 500 ; z = 0
    3rd point: x = -1500 ; y = -500 ; z = 0
    4th point: x = 1500 ; y = 500 ; z = 0

To create the grid, use the PATCH command.

CAUTION : Here, the region to mesh includes a circular part.

In order to define the patch command correctly, like this :

and not like that :

You have to create a spline that will link the vertices of the circular area.

To create this spline, in the main Prostar Window, click on :
    Tools
        Spline Tools

To use the New Spline command, you first have to plot the vertices of the spline you want to create.
Therefore, select the vertices that are include between Rmin = 349 and Rmax = 351, and between theta = 44.9 and theta = 135,1.
To do that, type in the Prostar Output the following command :

    vset newset gran 349 351 44.9 135.1 -0.1 0.1 2 (here 2 corresponds to the cylindrical coordinate system)

Click on Replot.

 

Now that the required vertices are plotted on the screen, zoom on the region where they appear and click New Spline in the Spline Tools window.
In the Prostar window, click on every vertex and when it is over, click on Done : the spline is created.

Now, you can patch the zone, which means that you can create a mesh by click on the 4 corners of the regions. Where there is now spline, the patch command makes straight lines between 2 vertices, that is why you've just create a spline.

To use the patch command, you can type in the Prostar Output window :
patch vx vx vx vx 20 20 (here 20 and 2 correspond to the cell number in the x and y directions)
and then click on the 4 vertices that correspond to the 4 corners of the region.

You also can click on Plot in the main Prostar Window Menu and the go to Number -> Vertex
Click on Replot in main window, zoom in the regions of the 4 corners to see and note the numbers of the 4 vertices.
The in the Prostar Output Window type :
patch n1 n2 n3 n4 20 20 (where n1, n2, n3 and n4 correspond to the numbers of the 4 corners)

By using this method for the 3 other regions of the geometry, you can obtain :

 

Then generate 3D mesh from 2D mesh.

In STAR GUIde: Create and Import Grid
    Create Grid
        Create 2D Grids using Simple Shapes

 

Click on Generate 3-D Mesh from 2-D Mesh

Merge the two 3D meshes.

In STAR GUIde:
Create and Import Grid
    Assemble Grids

Click on the button Merge

TOP