Project 1 : CFD Meshing for Tesla Cyber Truck

• Aim:

For the provided Tesla Cybertruck model, conduct a thorough examination to identify and address any geometric errors. Assign appropriate Property IDs (PIDs) as needed. Execute meshing with a target length that suits the model and adhere to element quality criteria. Additionally, create a wind tunnel and proceed with volumetric meshing for comprehensive analysis.

• Objective:

The determination of target lengths for different model components is at the discretion of the user, with the understanding that a finer mesh offers improved results, albeit at the expense of longer processing times.

Meshing the wind tunnel volume using tetra elements may extend to a two-day timeframe. While not obligatory, it is advisable to allocate dedicated time for comprehensive meshing due to the significance of this major project. A detailed report on the meshing process is expected.It is imperative to ensure that all 2D elements (Trias) within the model meet the specified quality criteria, specifically maintaining zero off elements. Performance in this regard will directly impact the evaluation and allocation of marks.

• Model:

Fig 1: Tesla Cybertruck Initial car model

• Procedure:

1. Topo/geometry clean-up:

a. Upload the ANSA file onto screen to perform topo/clean and meshing on the later stages.

b. Navigate to the mesh section, select the desired length, and input 1 mm in the parameters to refine the sharp curves of the car, enhancing its aesthetic appearance.

c. Given the car's symmetry from the center to either end, it is possible to eliminate one side and execute essential operations. Utilize the symmetry option to generate the entire car.

Fig 2: Model split to half for easier clean up

d. We are ready to initiate the topological clean-up process by eliminating singular and redundant triple constraints. Begin by selecting the entire model in the 'topo' section, enabling the identification and joining of any unconnected single or triple constraints. This initial step aids in identifying and addressing the necessary clean-up tasks.

Fig 3: Performing topo clean-up

- After reviewing and completing the topological clean-up for the entire half-car model, the next step involves conducting geometry checks. This is essential to identify small cracks, unchecked faces, and any extraneous elements that may adversely affect the geometry. Subsequently, we must perform necessary checks and proceed with geometry cleaning to ensure the model's integrity.

- After verifying the geometry and confirming its error-free status, the subsequent step involves assigning names to various components using PID (Part IDentification).

Fig 4: Model in PID mode

- After the assignment of names, the next step involves selecting the quality criteria method. Navigate to the openFOAM solver adjacent to the volumetric mesh and opt for the specified quality criteria provided below.

- Utilizing the measure tool enables us to calculate the smallest distance between two constraints or hot points. Based on this measurement, we can then set our minimum and maximum length in the mesh parameters accordingly. Neglecting this crucial step may result in a failed mesh.

2. Surface meshing:

To meet the specified mesh targets for each PID region, it is necessary to mesh the components individually.

To mitigate the risk of mesh failure and off elements, allocate the mesh parameters and quality criteria for each PID accordingly. Ensuring the correct assignment of minimum and maximum length is crucial in achieving a successful meshing process.

Fig 5: Car body surface meshed with 0 off elements

Fig 6: Tyres surface meshed with 0 off elements

After meshing, we can choose re-construct under shell mesh to reduce the off elements. And later the remaining off elements can be edited manually.

Fig 7: Entire car model with 0 off elements

- Performing symmetry on the car model:

a. Perform symmetry under transform option to create a exact same opposite body of the car to create a full body car.

c. After choosing the model, middle click mouse, we get a window, choose symmetry and choose mirror 3 points plane and choose 3 points on the edge to be performed symmetry.

Fig 8: Performing symmetry transform option

d. After choosing 3 points, middle click twice and the symmetry is performed, click middle click again to confirm the geometry and complete the process.

e. There will be few single cons present near the middle section, use paste or other tools to solve the probem.

Fig 9: Full car body after performing symmetry operation

- Creating wind tunnel:

a. First, we need to create reference points to create wind tunnel surfaces.

b. Select relative under points in topo mode, create a point below the car taking one reference point and entering the correct values.

Fig 10: Creating realtive points to create tunnel surface

c. And calculating the wind tunnel dimensions appropriately, we can create the wind tunnel accurately.

d. The wind tunnel dimmensions are: ( standard distance of the tunnel wrt to car model)

car model: 5906mm .................. (x)

Front surface distance(from reference point): 23624mm .................. (4x)

Back surface distance(from reference point): 35436mm .................. (6x)

Top surface distance(from reference point): 19749mm .................. (3x)

e. After creating the bottom surface use the curves for having the reference of cons, we can delete all the hot points and curves.

Fig 11: Tunnel buttom surface.

f. Generate all additional wind tunnel surfaces by utilizing the "New Surface" option.

Fig 12 a,b: Wind tunnel

- Surafce meshing of wind tunnel:

a. It is crucial to implement surface meshing with varying mesh lengths, considering the proximity to the car and regions farther away.

b. Consequently, different mesh lengths must be applied to the bottom and top surfaces of the wind tunnel.

c. The spacing option should be utilized to create a mesh with lengths ranging from small to large, ensuring a gradual variation in mesh size.

d. By following this approach, surface meshing can be successfully accomplished.

Fig 13: Wind tunnel surface mesh with varying mesh length

- Volumetric mesh of wind tunnel-car volume:

a. Since we are interested only the volume between the car model and wind tunnel, we can delete other volumes of the car model which is not necessary.

b. Since performing the volumetric mesh takes 2-3 days, volumetric mesh is not performed as given by the challenge question.

Fig 14: Car body volume

Fig 15: Tyres volume

• Learning outcomes:

a. Acquired a comprehensive understanding of CFD meshing skills from the ground up.

b. Executed diverse topological clean-ups employing various tools.

c. Recognized the significance of double connectors while eliminating unnecessary triple and single connectors.

d. Leveraged the benefits of symmetry to streamline workflow, reduce workload, and enhance result accuracy.

e. Generated surfaces by referencing hot points and employing relative points.

f. Conducted surface meshing for diverse components, adapting to varying mesh lengths. g. Utilized the spacing option in surface meshing to achieve diverse mesh lengths along surfaces.

h. Employed the re-construct option to reduce off elements to a level where manual editing becomes feasible.

i. Applied mesh modifying tools such as move, split, and smooth options to enhance mesh quality.

• Results:

- Completed cybertruck model with wind tunnel: Click Here

• Conclusions:

1. The Cybertruck car model has undergone topological cleaning and surface meshing in a suitable manner.
2. A wind tunnel has been established and surface meshed in proportion to the size of the car model.
3. Distinct volumes for the car model have been generated, considering the separation of the tires from the car body.
4. A unified volume is fashioned solely for the car body, facilitating a streamlined process when generating a volumetric mesh.
5. Upon successful volumetric meshing, essential physics tests can be conducted on the wind tunnel volume model.