Week 2 Challenge : Surface meshing on a Pressure valve

In this project, a pressure valve will be meshed in ANSA. The geometry has errors, and the project will be for three different mesh lengths. (1mm, 3mm and 5mm)

The geometry was imported into ANSA and this is the initial geometry:

There are multiple holes in the geometry, which have to be fixed before the meshing process can start.

The geometry is checked using ANSA's inbuilt Geometry Checker tool, this is done by going to: Checks -> Geometry

The default type is chosen, and the following errors are checked. The checking process is started by clicking the Excecute button.

Upon execution, these errors were found:

Upon further inspection, the errors mostly consist of holes on the body's surface.

The holes in the surface can be closed by multiple methods, this is done by going to: TOPO -> Faces -> New -> - there are multiple methods here, and each method can be used depending on the type of hole to be patched.

The COONS method was most used method, and an example of where the method is used is shown below:

An example of where the EXISTING SURF method was used is shown below:

The EXISTING SURF can only be used when the hole is part of a larger face

After all holes were patched, the geometry checking tool was run again to only find these errors:

The triple cons may seem like a serious error at first, but as seen from its location in the geometry, the triple cons are necessary to completely close the volume so that CFD simulations can be performed with the extrated volume.

Creation of PIDs: PIDs are user-defined selections of geometry, commonly used to designate sub-parts of the geometry. Such as wheels, body, door, rear wings, etc. in a car. They are used to generate PID specific meshes, with different mesh properties for each PID.

The PIDs are created by going to Properties -> RightClick/New -> PSHELL -> PSHELL

PIDs are created and the geometry is selected using multiple tools available in ANSA, such as ENT selection, PID_Region selection, lock, not, !not and or.

All the following parts of the valve were assigned a PID:

The preproccesing to the actual meshing process is complete. The mesh will be generated for 3 different sizes under the Classic Mesh Model:

Mesh Size: 1mm

Go to Perimeters -> Length -> Perimeters, the whole geometry can be selected with the box select tool. After selection, the middle mouse button is pressed and mesh length (1mm) is entered.

Entering mesh length in mm.

The same process is repeated for Perimeters as well.

This is where the quality of mesh will be defined, this is done by going to: Mesh Parameters. The target length is entered as 3 and the element type is set to Tria.

The quality of the mesh is defined in this step, this is done by going to Quality Criteria F11

The mesh is generated for the following parameters using the spot mesh, this is done by going to Mesh Generation -> Spot Mesh -> Visible

This mesh contains 209946 elements, all of them are triads.

Zooming in,

Viewing the spring and valve head,

The curvature of the valve head and the spring are accurately captured for the 1mm mesh.

Mesh Size: 3mm

Go to Perimeters -> Length -> Perimeters, the whole geometry can be selected with the box select tool. After selection, the middle mouse button is pressed and mesh length (3mm) is entered.

Entering mesh length in mm.

The same process is repeated for Perimeters as well.

This is where the quality of mesh will be defined, this is done by going to: Mesh Parameters. The target length is entered as 3 and the element type is set to Tria.

The quality of the mesh is defined in this step, this is done by going to Quality Criteria F11

The mesh is generated for the following parameters using the spot mesh, this is done by going to Mesh Generation -> Spot Mesh -> Visible

This mesh contains 23880 elements, all of them are triads.

Zooming in,

Viewing the spring and valve head,

The curvature of the valve head and the spring are captured coarsely for the 3mm mesh. This mesh should be used as a baseline inital simulation and not for any quantitative results.

Mesh Size: 5mm

Go to Perimeters -> Length -> Perimeters, the whole geometry can be selected with the box select tool. After selection, the middle mouse button is pressed and mesh length (5mm) is entered.

Entering mesh length in mm.

The same process is repeated for Perimeters as well.

This is where the quality of mesh will be defined, this is done by going to: Mesh Parameters. The target length is entered as 3 and the element type is set to Tria.

The quality of the mesh is defined in this step, this is done by going to Quality Criteria F11

The mesh is generated for the following parameters using the spot mesh, this is done by going to Mesh Generation -> Spot Mesh -> Visible

This mesh contains 8838 elements, all of them are triads.

Zooming in,

Viewing the spring and valve head,

The curvature of the valve head and the spring are poorly captured for the 5mm mesh. The spring, instead of being of a circular cross section, is just a flat plate. This mesh should not be used for any purpose whatsoever.

Conclusion

1. The 1mm mesh gives the best result, and must be preferred for all quantitative purposes.

2. The 3mm mesh may be used as a baseline mesh to check if the simulation runs well and to verify qualitative outputs.

3. The 5mm mesh should not be used for any simulation due to poor capture of valve head and spring.

4. ANSA's geometry checking and fixing tool can be used to fix minor issues in the geometry.