Week 2 Challenge : Surface meshing on a Pressure valve

OBJECTIVE

Perform geometrical cleanup after performing geometry check for multiple checks & rectify them to ensure a close surface for performing a CFD meshing using element size of 1mm, 3mm, 5mm. The nature of element shape should be TRIA element.

GEOMETRY

Figure 1 represents the CAD model required for preprocessing. The model shown in Figure 1 is in raw state where a lot of faces are missing. There also exist multiple single cons which ensures that the geometry is not close. Figure 1 is in ENT-TOPO mode which shows the need of geometry cleanup for the given model.

Figure 1- Given CAD model for the preprocessing work

Figure 2 shows PID mode of CAD geometry. Here every part has been shown in a single colour. We have to assigned PID to every single component so that we can easily handle & speed up our task performance capacity.

Figure 2- PID mode of given CAD model for the preprocessing work

Figure 2 also shows the valve, column & spring before geometry cleanup. We can observe a missing bottom plate & we have to ensure that it must be present before start of meshing because CFD meshing requires a close surface.

GEOMETRY CLEANUP

Figure 3 shows that geometry has been repaired by inserting missing faces. This also results in removal of all single cons because there are no red colour lines which represents single cons. This is a closed surface and after assigning PID it is in a condition to be mesh.

Figure 3- Repaired model after geometry cleanup

There is a triple con present as shown in cyan colour. This has been verified that there must be 3 surfaces instead of error. Details regarding PIDS has been discussed in next subtopic.

Figure 4- Repaired model after geometry cleanup in shadow mode

PID ASSINGMENT

After performing geometry cleanup, we must assign different PIDS to different component. It makes easier to select every individual component & also switching among them is too easy.

Figure 5- PID assignment for every component

Image in Figure 5 shows the details of assigned PID. Every component can be identified by different colour as shown.

MESHING OF PID’S

This is the method pf dividing the CAD model in finite number of small elements. This is known as discretization of our CAD model into FVM or FEM. It ensures that our cad model is divided into finite number of volume or elements of small size. We can also have control of element shape & size.

For this particular project we will use only Tri shaped element. This shape is of 2D in nature. We do have quad shape element for 2D surface meshing. The Tri mesh (Unstructured) are comparatively easier to generate because of the availability of the automated mesh generator.

MESH SIZE – 5mm

1. INLET & OUTLET

Figure 6- Inlet & Outlet part of model after meshing

Figure 6 shows Images in blue colour and grey colour. Image in blue colour shows outlet & grey colour image shows inlet. Meshing size is of 5mm target length & minimum element size is of 3mm & maximum element size is of 5mm. Also, the shape of element is tria in nature because it’s easy to construct

2. VALVE, COLUMN & SPRING

Figure 7- Meshing of surface of Valve, Column & Spring

In figure 7, the images show the meshing on the surface of valve along with column & spring. Here the column & spring has distorted due to bigger element size. This shows that there is a huge scope of improvement in meshing size to capture the spring accurately.

3. OUTER BODY

Image in Figure 8 shows that mesh has been captured accurately on outer body using 5mm target element size using TRIA shape element.

Figure 8- Meshing of Outer Body of CAD model

MESH SIZE – 3mm

1. INLET & OUTLET

Here element size has been reduced to 3mm target size along with maximum element size as 5mm & minimum size as 1mm. It resulted into increase in number of elements.

Figure 9- Inlet & Outlet part of model after meshing

2. VALVE, COLUMN & SPRING

Figure 10- Meshing of surface of Valve, Column & Spring

In figure 10 we can observe that there is an increment in surface mesh quality of spring. It seems to be less distorted with respect to 5mm element size. This will also yield better result with respect to 5mm element size.

3. BODY

Image in Figure 11 shows that mesh has been captured accurately on outer body using 3mm target element size using TRIA shape element. Better result can be seen at 3mm size with respect to 5mm.

Figure 11- Meshing of Outer Body of CAD model

MESH SIZE – 2mm

1. INLET & OUTLET

Figure 12- Inlet & Outlet part of model after meshing

Here element size has been reduced to 2mm target size along with maximum element size as 3mm & minimum size as 1mm. It resulted into increase in number of elements with best surface meshing among all 3 sizes.

2. VALVE, COLUMN & SPRING

Figure 13- Meshing of surface of Valve, Column & Spring

In figure 13 we can observe that there is an increase in surface mesh quality of spring. It seems to be least distorted. This will also yield best.

3. BODY

Image in Figure 14 shows that mesh has been captured accurately on outer body using 1mm target element size using TRIA shape element. Best result can be seen among all three sizes.

Figure 14- Meshing of Outer Body of CAD model

CONCLUSION

1. SPRING has distorted most in 5mm meshing due to large element size
2. Meshing with 2mm element size gives the best possible surface meshing for all other component along with spring
3. The best possible meshing has been observed with least element size