Challenge

Week 4 Challenge : CFD Meshing for BMW car

AIM:

OBJECTIVE:

To open the given car geometry in ANSA and to clean up the geometry appropriately.
To carry out triangular meshing on the surface of geometry with different target lengths as mentioned in the question,
To create a wind tunnel with the appropriate geometry and do surface meshing.
To perform the volumetric meshing (CFD Meshing) of wind tunnel and car geometry.

PROCEDURE:

Open the geometry in the ANSA software and increase the resolution of the geometry by providing Length and Macros from the Meshing session.

Errors are spotted in the below view, here errors are cleaned up by clearing it on topo mode by doing symmetry.

As the geometry is symmetric with the centre it is advised to delete half the geometry and work on the remaining part as shown below and finally do a symmetric approach.

Isolate every part of the car such as the front Grills, Logo, Wheel and Rim, Lights, Window, Mirror, Silencer and body. Then perform surface cleanup of each part by deleting overlapped, unwanted surfaces and penetrated surfaces by using the universal delete option, fill the gaps present by creating a new surface from the New option on the left tabular column followed by selecting either Existing Surf or COONS or FITTED option.

Use Cons2Curve or Create curve option to get the traces of deleted faces which helps to recreate those faces in future.

Remove small faces, and unwanted hot points and delete unwanted cuts on the surface of each part.

After completing the cleanups provide each part with a suitable PID name by selecting the Property from the top tabular column and creating new PIDs and by renaming existing PIDs. Then assign each PID appropriately. The figure shown below represents the completed geometry.

Now move to the meshing tab. On the meshing, tab set the perimeter and macro length as mentioned for each PID.
From the Mesh parameter drop-down set meshing type as triangular and target length, Minimum and Maximum Target length. Set minimum and maximum target length in quality criteria also.
Target lengths for the different parts of a model are as follow:
Body - 3 mm
Lights - 4 mm
Grills - 1 mm
Rims and Tyres - 2 mm
Optical Rear view mirror - 2 mm
Window - 2 mm
Silencer - 3 mm
Logo - 1 mm
Providing quality criteria and mesh parameters for the logo.

On the left tabular column click on spot mesh under the Mesh generation section and select each PID and do meshing enable hidden mode and verify any OFF elements are present if so reconstruct mesh by using Reconstruct option under Shell Mesh. Again if any off elements are present check the geometry and do the necessary cleanup.
Repeat the above steps with the appropriate target size, minimum and maximum target size for every PID. The surface meshing of each PID is shown in the Result session.
Perform meshing of body PID at last. While meshing the body deselect the common cons of the body with other PIDs.

After completing the surface meshing of one half click Transform > Copy > Select the entities > Symmetry > Mirror 3 Point Plane > Select 3 points check the preview and click Finish. Remove if any single cons present and do a geometry check. The figure shown below is the final meshed car geometry.

After the symmetry checks the geometry for any crack, single cone, overlap faces, penetration etc.. by using check manager. If any errors are encountered resolve those.

Now create the wind tunnel by using creating points, and curves and by creating different faces of the wind tunnel using those curves in such a way that the front face of the tunnel should be at a distance of 4X, and the rear face of the tunnel should be at a distance of 6X, the top face of the tunnel should be at a distance of 3X, the bottom face of the tunnel should be very close to the wheel, the Side face of the tunnel should be at X distance from the car geometry. Where X represents the total length of the car.

Mesh all the faces of the tunnel to create fine mesh at the bottom and course mesh at the top using the Spacing option. which helps to enable saving time as over-focus is more to car geometry.

After completing the surface meshing move to the volume meshing tab, select Define and select auto-detection. Here delete the unwanted volumes like a car inside the volume, wheel volume, and silencer volume. Maintain the volume between the car geometry and wind tunnel. Then Ramesh the selected volume with the Tetra CFD option.

CONCLUSION:

The given geometry is studied and a topological cleanup and surface meshing of the given geometry is carried out. A wind tunnel is constructed and the surface of meshing is also done on it.
Doing this project it helps to gain more about topological cleanup, constructing new surfaces, surface meshing and volumetric meshing by using different sets of tools in ANSA software.

UPLOADED MODEL:

As the size of the model is too large to upload directly, the 'google drive' link is been shared to access the corrected model.

Ship work like this
in your own course.