Week 2 Challenge : Surface meshing on a Pressure valve

AIM: Surface meshing on a Pressure valve

Objectives:

1. To check for the geometrical errors.
2. To perform Topology cleanup accordingly.
3. To set three different target lengths as three different cases and mesh the model.
4. To apply any one target length from the above at a time for the entire model as One case.
5. To write a report in detail about the meshing process
6. To do 3 cases of 3 different models with target length 1mm, 3 mm and 5 mm.
7. To mention case that is giving good results with the reason.

Procedure:

1. Topo-Cleanup:

The first thing to do is to check the single cons and triple cons in the model. Single cons are cons that are shared with only one surface, meaning an open surface. For closed geometry, such open surfaces are not expected, so they must be resolved. Triple cons are created due to the con shared with the three surfaces and also need to be resolved based on the weather that is desired or not at that location. Triple cons are not always faults, but it does show that local volume can form because of these faces. These single and triple cons are identified using geometric checks.

It can also be seen by disabling the double cons from bottom bar with wire frmae mode (cntrl+shift). We observed various single cons and few triple cons. There are few open surfaces that are forming single cons and it is filled by creating surfaces in FACES option.

Faces - New - COONS / Fitted / Existing Surface/ Planar - suitable option is selected accordingly and surfaces are filled.

In many places, one or more of these options may give satisfactory results, so the appropriate method is chosen based on the most satisfactory surface formation. For closed areas, we can also use the Fill Hole option in the CONS section inside the "Topo" Deck.
In complicated geometry, shaping the entire surface may not work properly, so the surface must be created in small parts. The geometry should be closed for CFD analysis, so the bottom, top and side surfaces are closed using the hole fill hole option or the Coons option.
At the bottom hole, a triple taper is formed after the face is closed, and the triple taper is visible there due to the fact that the three faces are touching, so it is not treated as an error there.

The final model after topo-cleanup will be free from single con, undesired triple con and unnecessary surfaces as shown in figure.

2. PID Allocation:

PID is property ID , used to store the specific information about geometrical entities , apply boundary conditions for CFD application.  Whole geometry is divided into  number of PID’s. PID’s are created by using :

Open PID Window – Right click – New - name the PID – as Body , Inlet, Outlet, Head, Spring, Rod, Base.

All generated PIDs are allocated using PID allocation: Right click on the PID name – Apply – Select the component we need to assign this name to – Component selection can be done using ENT mode (selects by entity), PID mode (selects PID wise) or PID region (selects the region considering any discontinuity in the connection as a single entity) - ok

3. Meshing:

Any small surfaces or cons or region between two nodes having length less than desired mesh length need to be removed having no significance which may result in mesh failure at that location by using cut.

Faces –cut –Right click on the con –It will show history of the removed con in orange colour

Meshing can be done directly for whole geometry here if all the components have same mesh length or The components having different mesh length can be meshed PID wise using Spot Mesh option. Before Mesh Generation we need to provide Length as Perimeter and Macros with Mesh Parameter and Mesh Quality Criteria.

But our objective is to use same length for whole geometry so we can use spotmesh –visble for selecting whole geometry at once.

Mesh is generated for three lengths 5mm, 3mm,1 mm respectively.

Results:

Case 1 = 5mm

Case 2 = 3mm

Case 3 = 1mm

Conclusions:

1. A mesh size of 1mm will be more suitable compared to 5mm and 3mm due to the accuracy of capturing the exact profiles of the spring and head which are without any distortion of the surfaces. This also verifies that when the length of the mesh exceeds the size of any geometric entity, it tends to distort the geometry, which can lead to a misinterpretation of the physics going on at that location, and can also cause an error when transforming information from neighboring cells.
2. As the mesh size becomes finer, the number of cells increases rapidly. So different mesh size for different components will be suitable to avoid using more computing resources and computing cost.