Week 2 Challenge : Surface meshing on a Pressure valve
Surface meshing on a Pressure valve
The whole process for Meshing is divided into
a) Geometrical surface cleanup
b) Assigning properties for components of assembly
c) Meshing for each component
For CFD analysis of any body, the body must not have any porous openings, inorder to implement Volumetric Meshing and Analysis, hence visible presence of holes have to be closed and whole surface area has to generated without viloating the uniformity and symmetricity of the geometry in question.
Geometrical Cleanup :
Geometrical cleanup involves avoiding Single CONS and holes in a body
STEP I : Observing and checking Single CONS
One can observe single cons of a model by 2 ways :
Go to Tools > Checks > Geometry
Now drag the option list and check Single Cons option
Now hit Execute
Another way of checking cons is through wire frame mode
Uncheck Crosshair > Uncheck Double Cons > Uncheck Triple Cons > Uncheck Shadow mode (or hit Ctrl + Shit) for Wireframe mode
STEP II : Single cons treatment
After checking for Single CONs, one needs to resolve these by creating surfaces and filling holes wherever it is necessary.
Go to Topo > Faces > New
We are given with 4 types of creating new faces. Currently, i've choosen COONS option & checked loop for symmetrical single CON entity
Hit COONS (Left Click) > Hit Loops (Left Click) > Select Entity > Right Click
Now we are given with a preview of the surface created using COONS and if the surface is acceptable for us & does not create any interference with neighbouring surfaces and shows uniformity, then it can be accepted.
NOTE :
For interfering surfaces while filling the holes with new faces, a seperate treatment has to be done.
Ex : Below shape of the single CON will lead us to interfering surface, if one uses LOOP as an option to select Single CONS
Therefore, one can select the single CON entity by diving the whole Single CON hole into 2 ways.
One needs to select Entity option before selecting the single CON surfaces.
> Select the two opposite sides of the traingular surface and from the surface from above method.
> Then select the whole left out reactangular surface and generate surface.
Now one can clearly see that, there are no interferring non uniform surfaces in the preview.
NOTE :
For single CONS for non-uniform length in a radial or circular environment, again choose entity option for selecting CONS. Avoid using LOOP in such cases.
Blue colour on the surface indicates, that its a Triple CON, which in this case is not an error and doesnt involve any non-uniform geometry surface.
This is due to coincedence of three surfaces on a single point
STEP III : Smaller and interferring surface treatment
One needs to also check for surfaces which are having very small surface areas. Unwanted Double CONS where its necessity is not validated must be removed, since this will be a problem for giving target length for meshing.
Go to Topo > Faces > Cut .
> Now right click on the unwanted double cons to increase the surface area and to join the double con with the larger area itself
> You will be able to an orange line instead of yellow line which indicates the previous history of the line
Similarly these steps have to be incorporated throughout the geometry of the surface.
Assigning properties for components of assembly
The valve assembly comprises of
- Body
- Inlet
- Outlet
- Valve Head
- Valve Spring
- Column Support
- Base Surface
Each of these components have to be isolated and meshed seperately for convenience of further usage of these components.
Assigning names for all these components helps us bifuracte components easily and also to to hide and show compnents easily.
This is done using Property Manager.
Go to Properties > Right click > New > PShell > PShell
A new box appears, where one can input the name of the properties to be listed. One has to input the name of the components for easy bifurcation and usage.
After creating properties for all components by naming & colour defining the geometry, one can proceed to the next step of Meshing
Meshing for each component
Select and check the component to be meshed one by one using Propert Manager. Meshing procedure is followed by
Go to Mesh > Perimeters > Length > Check Permeters (Inorder to select the component fully, press shift & drag the mouse)
> Input the Target Length as 5mm
Next similar process has to be done Macros
Go to Mesh > Perimeters > Length > Check Macros (Inorder to select the component fully, press shift & drag the mouse)
> Input the Target Length as 5mm
> Now Go to Utilities > Mesh Parameters
Input the following as below :
1. Target Length = 5mm
2. Minimum Target Length = 3mm
3. Maximum Target Length = 7mm
Hit ok
> Now Go to Utilities > Quality Criteria > Check Min. Length (Also enter value as 3 mm) > Max. Length > (Also enter value as 5 mm)
> Now Go to Mesh Generation > Spot Mesh > Visible
Google drive link for meshing files :
1. Target length of 5 mm
https://drive.google.com/file/d/1Lw3GRCpf_GLb7u-hUNnjgTGJyiaJ6Bmk/view?usp=sharing
2. Target length of 3 mm
https://drive.google.com/file/d/1R97HugV92bNBZ5HH1-aPw8kZ1KoIwLpH/view?usp=sharing
3. Target length of 1 mm
https://drive.google.com/file/d/19w8EJoXyb7ntKyBYDz6O2w4q2HcZ6NvU/view?usp=sharing
Interpretation :
Conclusion :
> For the geometrical components bearing lesser surface areas and intricate curve profiles, meshing target length demands lesser magnitude in order to capture the profile of the geometry nearly equivalent to real life geometry equivalent.
> The reason behind this is, geometry of the mesh element cannot bear curve or circular nature if the
Size of the element > Surface area
> Ultimately question arises on compromisation of Compuatational time by increasing the number of mesh elements.
Stats for the exponential raise on number of mesh elements are as below
| Sl.No | Element Shape | Element Length | No of Elements |
| 1 | Tria | 5 mm | 8842 |
| 2 | Tria | 3 mm | 23939 |
| 3 | Tria | 1 mm | 210423 |
> Optimum way of reducing the number of mesh elements is to increase the meshing accuracy only for the geometrical surfaces of intricate and lesser surface area profiles which are continuosly changing their profile.
> Target length as a parameter has to be treated as a Conditional Format Operator to have efficient usage while analysis in CFD for saving computational Time.