MESH PROCEDURE DESCRIPTION FOR A CYLINDRICAL VAT

To mesh the reactor, we decided to define a bidimensional geometry which could be extruded to a tridimensional geometry : the 2-D mesh is designed to fit each part of the reactor ( central axis, blades), and then we can remove on the 3-D reactor the mesh parts we don't need because they correspond to solid parts of the reactor : just the fluid area need to be meshed. This page explains in details the process.

We first designed a 2D mesh. This mesh will allow to represent all parts of the reactor. The geometry we chose for the 2D basis is decomposed in quarters. We extruded this 2D quarter mesh in a 3D mesh. Then by symmetry we obtained the complete reactor. When the boundary conditions are defined, the mesh can be directly read by Fluent 5.

We built a mesh for two models of cuves : a cylindrical cuve with flat bottom, and a another with a round bottom.

CASE OF A CYLINDRICAL VAT WITH FLAT BOTTOM

Meshing the 2D quarter geometry

The following image shows the quarter geometry :

Quarter geometry.

Then the edged points are added on all the edges :

Quarter geometry with edge points.

Each face is meshed separetely. For each part of the mesh, the corresponding Gambit dialog box is added, in order to show the type of mesh is used.

 Note : it is important not to choose "Apply" in the spacing   box, otherwise the spacing is applied, without respecting the points previoulsy chosen for the edges.

The following image shows a global view of the mesh. For a better understanding, this mesh has been made with less points than the real mesh :

Extruding the quarter basis in a 3-D mesh :

To extrude the mesh vertically we first need to define the vertical edges along which you want to extrude the 2D mesh. Then faces are defined.

3-D geometry.

Then the meshed face is copied on the opposite face as shown on the following window :

Copying the meshed basis face.

After that operation, the volume is meshed : you have to choose the element, their type, and the vertical spacing.

Meshing the resulting volume.

CASE OF A CYLINDRICAL VAT WITH ROUND BOTTOM

As real experimental vats have usually a round bottom, we built such a geometry. As for the body of the vat, we built only a quarter of the geometry and we obtained the complete bottom by symmetry. We built an ellipsoidal shape for the bottom, to do so we draw an ellipse, we defined a face and then we got the volume by rotating it : the cross-section is shown on the top left picture. We considered that the shape of the agitator has also an ellipsoidal shape, it follows the shape of the bottom of the vat : we can see it on the top right picture. To draw this part of the agitator we made an intersection between the vertical faces of this agitator and an ellipsoidal-shaped volume as shown on the top right picture.

Building of a round bottom for the vat.

Then we remove the volume corresponding to the agitator part, we mesh each face separately with an appropriate mesh type, and finally we ask Gambit to mesh the volume : doing this way, we can control the type of mesh imposed on the faces, and refine it when necessary.