Preprocessing of BMW M6 model using ANSA

To clean the given cad model of BMW M6 for generating surface mesh and also creating wind tunnel for drag analysis on the given model

Procedure

• Geometry clean up
• Assigning PID with given length
• Surface Mesh generation
• Create wind tunnel

Geometry clean up

• When the cad model is imported it has lots of topological errors as shown below:

• Following errors occured

• We see a that the model is having symmetry so we will work on the half portion only.

• Removing all the styling lines left by the CAD Engineer

• Detailed features such as logo of car is removed to reduce the run time.

• After correction

• Eliminating single cons

• Cleaned surface is shown below

• Cleaning Grills

• After clearing all the errors we will run geometry check under checks manager>geometry

• Some of tools used for removing geometrical errors are mentioned below:
• Faces>New>Coons,Fitted,Planar
• Faces>Intersect
• Cons>Paste,Release
• Cons>Fill hole
• Hot Points>Parametric cut

PID

• After cleaning all the geometrical errors we will assign the PIDs.
• The entities in model are segregated into different hierarchies under Model>Parts
• Using model browser different parts can be created as follows:

• Now properties are added to further categorise the parts

Meshing

• Assigning length for each PID as per given
• Body 3mm
• Lights 4mm
• Grills 1mm
• Tires and Rims 2mm
• ORVM 2mm
• Windows 2mm
• Silencer 3mm
• Logos 1mm
• Now generate the surface mesh using mesh generation<free option.

• Surface mesh is generated now obtain the symmetry for the model.

• We will also provide the quality criteria as follows:

• Using reconstruct,paste,Mv surf option correct the areas which failed for quality criteria

Wind Tunnel

• Now wind tunnel is created by tool resize planes where all the planes are intersecting each other and eliminate the unwanted surfaces.

• Wind tunnel size must be as follows:
• 4*front of the car
• 6*rear of the car
• 3*top of the car
• Bottom proximity with tires
• 1*from center plane for left and right sides

• Apply spacing edge sizes from 20 to 100 for a finer mesh.

Learning Outcome

• Learned geometry clean up.
• Learned to arrange parts in model browser.
• Learned to assign PIDs with different lengths.
• Learned several tools for correcting quality criteria under mesh mode.
• Created wind tunnel.

Conclusion

• In this project surface mesh was generated after cleaning up the geometry.
• A wind tunnel was created and a spacing length mesh was applied.
• A tetrahedral volume mesh was performed but due to very small element size process would take a lot of time so volume was defined for future analysis.