Project 1 : CFD Meshing for Tesla Cyber Truck

Aim/Objective

For the given model, check and solve all geometrical errors and Assign appropriate PIDs. Perform meshing with the suitable Target length and element Quality criteria.

Procedure

Step 1: Geometry Preparation

Import the Geometry Model

File -> open -> (select the file)

Step 2: Topology clean-up

• The Model has a lot of single Cons. “Topo” operation can be performed on the model to join the single cons.
• Wire frame mode -> selecting only single cons.to be visible -> red lines show the number of missing surfaces.
• Unnecessary inside surfaces also need to be deleted from the model since we will need only the outer surface to generate the volume mesh.
• Next step involves solving the topology issues of all parts individually using the available tools in the TOPO deck of ANSA.

Step 3: Wind Tunnel Creation

Since the application of this model involves external flow analysis, we need to create a wind tunnel around the car

• The dimensions of the wind tunnel need to be according to certain thumb rules as mentioned below-
  • Considering the length of vehicle as “X” = 5715 m (through measure tool)
  • Base surface can be at approximately at 475mm distance from bottom of vehicle.
  • Front surface of the wind tunnel should be “4X” distance from the front of the vehicle.
  • Back surface of the wind tunnel should be “6X” distance from the back of the vehicle.
  • Height of wind tunnel should be “3X” distance from the top of the vehicle
  • Side surfaces of the wind tunnel should be “X” distance from each side of the vehicle.
• Based on above criteria, points need to be created below the vehicle to define the perimeter of the Base Surface.
• To create a point from an existing point: Points -> Relative -> {Specify the X/Y/Z distance and middle click}
• Select a point in middle of car from bottom surface and create a point below it.

• With reference to that point create a point in front of car and a point at the back of the car based on above mentioned criteria.
• With reference to the front, middle and back points create points on either sides based on the above mentioned Criteria.

• From the created points, make a perimeter using “Curves” tool.

• Make a surface from the created Perimeter.

• The Bottom surface can be offset by some distance (according to above mentioned criteria for wind tunnel) to obtain the Top Surface of the Wind Tunnel.

• Using the Base and Top Surfaces, all surface of Wind tunnel can be generated.

• After creating the wind tunnel, points and curves which were created earlier can be deleted.

Step 4: Creating and Assigning PID’s

• For convenient handling and meshing of the model PIDs need to be created and assigned to the respective components.
• PID Creation: Properties -> Right click -> PSHELL -> PSHELL -> (specify PID details like Name, etc.)

• Assigning PIDs: Properties -> select the PID to be assigned -> Right click -> Apply -> select the corresponding Macros -> Middle click (to assign the PID)
• After completing the above-Mentioned Procedure, the components assigned to various PIDs need to be checked again.

PID: Lights

PID: Windows

PID: Tyres and Rims

PID: Body

PID: Wind Tunnel Bottom Surface

PID: Wind Tunnel Top Surface

PID: Wind Tunnel Front Surface

PID: Wind Tunnel Back Surface

PID: Wind Tunnel Side Surface

Step 5: Meshing

5.1: Surface Meshing

5.1.1: Mesh Quality Criteria

• Every component needs different quality criteria based on the required target length
• To set Quality Criteria: Quality Criteria -> Set Min and Max Length

5.1.2: Mesh Parameters

• Every component needs different mesh parameters based on the required target length
• To set Mesh Parameters: Mesh Parameters -> Specify the Target Length, Specify the min length, Element type = Tria

5.1.3: Mesh Length

• Different target lengths need to be set up for each component as per the problem statement
• To Set Target length on Perimeters: Perimeters -> Length -> perimeters -> select the CONS on which mesh length needs to be specified -> Specify the required Target length -> Middle click (apply mesh length setting)
• To Set Target length on Macros: Perimeters -> Length -> macros -> select the Faces on which mesh length needs to be specified -> Specify the required Target length -> Middle click (apply mesh length setting)
• Target Length for Vehicle Body = 10 mm
• Target Length for Windows = 15 mm
• Target Length for Lights = 5 mm
• Target Length for Tyres and Rims = 15 mm
• Target Length for Wind Tunnel Surfaces: Top Surface - 200 mm target length, Base Surface- 40 mm target length, Side Surfaces – gradually increasing mesh parameters using “spacing” tool

5.1.4: Mesh Generation

• Mesh needs to be generated for each component according to the problem statement.
• Surface mesh needs to be generated for the Wind Tunnel surfaces also.
• To generate surface meshes: Spot Mesh -> Select all parts to be meshed -> Middle Click
• Mesh Generation needs to be performed along with the above specified operations in specific order for each component separately
• Order to be followed for mesh generation: Specify Quality criteria -> Specify Mesh Parameters -> Assign Mesh Length -> Generate Surface Mesh

The generated surface meshes are as follows:

Mesh for Lights:

Mesh for Windows:

Mesh for Tyres and Rims:

Mesh for Body:

Mesh for Wind Tunnel Bottom Surface:

Mesh for Wind Tunnel Top Surface:

Mesh for Wind Tunnel Front, Back and Side Surfaces:

5.2: Volume Meshing

• Define the Volumes: Volume Mesh -> Volumes -> Define -> select “whole db” -> select “ok”

• From the volumes detected by the software, select the volumes that are not needed.
• Delete the selected volumes. Now only the required volumes are left.

• Generate volume mesh (Tria CFD) for the required volumes.
• To generate volume mesh: Right click on the volume to be meshed -> remesh

NOTE: In this project the volume mesh is not generated in the submitted model due to the time constraints and hardware limitations

Learning Outcomes

• Topology Clean-up
• Surface Meshing
• Wind Tunnel Creation

Result

• Geometry checked for abnormalities and all geometrical errors solved
• Surface Mesh Generated for the given Model
• Wind Tunnel created and meshed based on thumb rules for dimensions.
• Volume mesh is not generated in the submitted model due to the time constraints and hardware limitations. Total Elements in Surface Mesh = 147048

Final Surface Mesh:

Conclusion

• In case of Models with symmetry, Half/Quarter Models can be used to save manual work, and computation time for complicated models. This is not used in this project since the topology clean-up was feasible for full model directly.
• Learned advanced application of TOPO deck for geometry clean-up.
• Learned surface meshing in case of different components with varying mesh lengths.
• Learned how to create wind tunnel and what thumb rules are used for the same.