Project 1 : CFD Meshing for Tesla Cyber Truck

In this project, a Tesla car cybertruck in a wind tunnel will be meshed in ANSA .The geometry has multiple errors,these errors will be fixed .The mesh's element's lengths are some for each component of the geometry,but the mesh will be generated separately .The mesh length specification are:

• Body=5mm
• Lights=5mm
• Rims and Tyres =5mm
• Window=5mm

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

Since the car is symmetric, a cut was performed on the truck along the YZ plane .To ensure the cut was perfect, views of the car from all 4 sides is verified.

Change ENT to PID

TOP VIEW:

FRONT VIEW:

LEFT VIEW:

BOTTOM VIEW:

BACK VIEW:

WIREFRAME MODE: ctrl+shift shortcut method.

BEFORE:

AFTER:

BEFORE:

AFTER:

Since the car is symmetric, a cut was performed on the truck along the YZ plane .To ensure the cut was perfect,views of the car from all 4 sides as verified.

As we can see the cut is perfectly in the center.

This is the truck after deleting one half.

Turn off the all boolean operation and perfectly show the half portion of the car.

After the plane cut see the symmetry of the car in only shown single conc.

Double conc view and triple con is none.

Upon the further inspection ,the errors are primarilynof three types,

SINGLE CONC,

OVERLAPED SURFACE,

EXTRA SURFACE.

These errors were rectified using t5he TOPO sidebar and all errors were rectifie.

After the all issuses were fixed, the geometry checking tool was run(CHECKS--GEOMETRY).

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

The RESULT of the geometry checking tool are below.

Since only one half the model is being worked on.There are single cons are along the symmetry plane.

Running the geometry checking tool again without checking for single conc shows the following results.

The model came with existing PID's, these were created or modified/renamed to the following.

PIcture of the car viewed by PID's.

SURFACE MESHING:

The processsing to the actual meshing process is complete.The surface mesh will be generated first under CLASSIC MESH model.

The PID's were grouped by mesh size for convinence.For each size;macros,mesh parameters and quality criterion were defined as follows.

MESH SIZE IN 5mm:

The quality of the mesh is defined in this step, this is done by to quality criteria.

The minimum length of 0.2mm is choosen to capture the gaps between the groves on the outer surface of the tyre, as seen below.

This is where the quality of mesh will be defined,this is done by going to;MESH PARAMETER.

The target lenth is entyered as 5mm and the element type is set to Tria.

MESH PARAMETER:

Go to perimeter -->Length-->Perimeter,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.

The same process is repeaed for MACROS AS WELL .

The mesh is generated for the following parameters using the spot mesh,this is done by going to

MESH GENERATION --->SPOT MESH--->VISIBLE.

The quaality criteria of the meshed element are checked by switching over to the hidden.

After number off elements are found in the meshed PID's,the next set PID's are meshed.

MESH SIZE;5mm:

The quality of the mesh is defined in this step,this is done by going to quality critria.

The minimum length is choosen from analysising the geometry in details.

There is where the quality of mesh will be defined.

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.

The same process is repeated for Macros as well.

The mesh is generated for the following parameters using the spot mesh, this is done by going to

Mesh Generation --> Spot Mesh --> Visible.

The quality criteria of the meshed elements are checked by switching over to the hidden view:

Join, Split, Move, Reconstruct and Paste.

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

The minimum length is chosen from analysising the geometry in detail.

This is where the quality of mesh will be defined, this is done by going to: Mesh Parameters. The target length is entered as 5mm and the element type is set to Tria.

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.

The same process is repeated for Macros as well.

The mesh is generated for the following parameters using the spot mesh, this is done by going to

Mesh Generation -> Spot Mesh -> Visible

The quality criteria of the meshed elements are checked by switching over to the hidden view:

No eff elements are present in the body.

Now, the surface has been meshed for the half body. The body has to be mirroed now.

This is done by going to:

Transform -> Copy -> Entities

Shift + left click drag to select all entities:

Click the middle mouse button to open the copy menu.

Select three points on the symmetry plane of the car OR ( on the single cons)

Click on OK, and after verifying the mirror is correct. Click on Finish to generate the copy.

After pasting, A final geometry check is performed and no errors were found:

• Surface meshing for the car is complete. A wind tunnel is used for CFD simulations, and has to be created in ANSA.
• The wind tunnel is a cuboid, and the car is placed inside it.
• The inlet of the wind tunnel is 4 times the charecteristic length of the car from the front of the car, the outlet of the wind tunnel is 6 times the charecteristic length of the car from the back of the car.
• The height of the wind tunnel is 3 times the charecteristic length of the car from the top of the car.
• While, the width of the wind tunnel is 1 time the charecteristic length of the car from the sides of the car.

Using the above information, multiple vertices of the wind tunnel were created using:

TOPO -> Points -> Relative

These points were joined to form a linear curve using:

TOPO -> Curves -> Create

The curves were used to create surfaces using:

TOPO -> Faces -> New

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

Go to Perimeters -> Length -> Perimeters, the top plane's edges are selected. After selection, the middle mouse button is pressed and mesh length (100mm) is entered.

The same process is repeated for Macros as well.

The mesh is generated for the following parameters using the spot mesh, this is done by going to

Mesh Generation -> Spot Mesh -> Visible

The Mesh quality was not checked as quality of elements at the boundaries do not matter as no data is obtained near the planes.

Mesh Size: 20mm;

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

This is where the quality of mesh will be defined, this is done by going to: Mesh Parameters. The target length is entered as 20mm and the element type is set to Tria.

Go to Perimeters -> Length -> Perimeters, the bottom plane's edges are selected. After selection, the middle mouse button is pressed and mesh length (20mm) is entered.

The same process is repeated for Macros as well.

The mesh is generated for the following parameters using the spot mesh, this is done by going to

Mesh Generation -> Spot Mesh -> Visible

The Mesh quality was not checked as quality of elements at the boundaries do not matter as no data is obtained near the planes.

Click on OK and verify the steps and labels.

Note: the lower part of the vertical edges have to be selected.

The mesh is generated for the following parameters using the spot mesh, this is done by going to

Mesh Generation -> Spot Mesh -> Visible

The Mesh quality was not checked as quality of elements at the boundaries do not matter as no data is obtained near the planes.

The surface mesh is now complete for both car and the wind tunnel, there are about 24.78 million elements, all of them are trias.

Front view with lights and front wheel,

This is the inlet/front of the wind tunnel, notice how the element size increases as we move upwards.

VOLUMETRIC MESH:

Click on OK, and ANSA will generate volumes automatically.

Click on each volume and view its preview, the required volumes (volumes where fluid flow will occur) are renamed and the other volumes are deleted.

After deletion, these volumes remain:

Double click on the volume and change "Mesh with" to Tetra CFD. Tetra is the shape of the mesh's elements and CFD is the application.

Right click on the volume and click Remesh, this will mesh the volume with the selected element type (Tetra CFD)

Conclusions and Observations

1. ANSA is a powerful meshing tool and a proper workstation is required to mesh complex geometry such as this truck.

2. There were multiple instances during this project, that ANSA would freeze for 10-20 minutes while it was meshing any surface.

3. SpotMesh produces a lot of off elements, and they were fixed using the Reconstruct tool which took a lot of time and memory.

4. Volume meshing could be performed due to high performance requirements, and lack of computer memory. ANSA crashed a few times while trying to generate volumetric mesh