Week 2 Challenge : Surface meshing on a Pressure valve

Aim: Surface meshing of a Pressure Valve (3 files for 3 mesh length)

Procedure:

A. Correcting the geometry

1. Open the model in ANSA.
2. Check for errors using Checks>Geometry. Select ANSA Check from the dialog box and select the following checkboxes: Unchecked Faces, Collapsed Cons, Triple Cons, Needle Faces, Overlap Faces, Cracks, and Single Cons.
3. Click on execute and check for the geometric errors listed by the software.
4. Fix the geometric errors using NEW function in Faces Section of TOPO Module.
5. After fixing the geometric errors notice that a surface at the bottom of the valve remains open. Create a new surface here resulting in the formation of a Triple Cons. Ignore this error as this Triple Cons is required for the model to function properly.

B. Labelling the PIDs

1. Open the properties module from the top toolbar.
2. Create 7 new elements, namely, inlet, outlet, body, spring, base, valve head and column, using Right click>New>PSHELL>PSHELL. Specify the color of each element as per requirement.
3. Assign the PID to respective parts of the pressure valve as named. This will enable in easier selection of parts for meshing.
4. Remove any double CONS whose length is smaller than that of the desired mesh length by choosing Cut option from Faces Section of TOPO module. Subsequently, right click on the double CONS that should be removed.
5. After allocating the PIDs to relevant surfaces, delete the PID which was initially allocated to the pressure valve. To achieve this first select the Undelete function from Faces menu, then select the entire model and click the middle mouse button. Now the default PID is active in the properties dialog box and can be deleted.

C. Meshing the valve surface

1. Select the mesh module.
2. Click on length function in perimeters.
3. Select perimeters>Select model>Set the mesh length.
4. Select Macros>Select model>Set the mesh length.
5. Select Mesh Parameters from tool bar above set mesh length and select element type as tria.
6. Select mesh quality>Activate minimum length and maximum length options> Set them according to your mesh length.
7. Select spot mesh function from Mesh generation section. Select the PIDs one-by-one and apply the spot mesh on each surface. Check for the mesh quality on each surface. Observe the changes occurring in smaller surfaces as a result of mesh length being larger than the characteristic length of element.

Learning Outcomes: Learned the meshing of an entire pressure valve after performing TOPO cleanup on the surface. Learned how to remove geometrical errors on the surface, create new PIDs and remove deleted surfaces from the model. Learned the influence of mesh length on the meshing of surfaces and increase in the number of tria elements.

Result:

Parameters	Mesh Length 5 mm	Mesh Length 3 mm	Mesh Length 1 mm
Tria element	9010	23852	209906
Closeness of Surface Geometry to original model	All the external surfaces retain their original geometry but the spring, edges of valve head and curves in the body lose their geometric integrity.	All the external surfaces including the curves on body retain their original geometry. The spring retains its original shape but the cross-section size changes.	All the surfaces retain their original geometry.
File Size	3172 kB	4833 kB	21731 kB

As can be seen from the table above, a smaller mesh length creates smaller elements on the surfaces of the model leading to a detailed analysis of each curve. As smaller elements increase the computing demand for the model, so the size of the file also increases significantly.

Conclusion: The surfaces of the pressure valve were meshed with mesh lengths set as 1 mm, 3 mm and 5 mm while the mesh element was tria. The influence of mesh length on the geometry of various surfaces and PIDs was observed.