Week 4 Challenge : CFD Meshing for BMW car

Surface Meshing of BMW Car and Wind Tunnel Surfaces

Aim/Objective

For the given model:

• Check and solve all geometrical errors and assign appropriate PIDs.
• To perform surface meshing with the given Target length and element Quality criteria.

Procedure

> Geometrical errors are solved in Topo mode.

> As it is a symetrical geometry only the first half of the geometrical errors are solved and rest is mirrored.

> Major tools used for solving geometrical errors are listed below:

• Faces --> New/Cut/Intersect/Extend/Proj.Cut/Delete
• Curves --> Create/Cons2Curve 
• Cones --> Fill Hole/ Paste

> Faces --> New - To create new surface , Cut - To cut existing surface and create reequired one , Intersect - To itersect one

   or two surfaces , Extend - To extend selected face , Proj.Cut - To cut faces 90 degree , Delete - To delete unnecessary faces.

> Curves --> Create - used to create new curves.

> Cones --> Fill Hole - used to fill a hole or to create new face on hole , Paste - Double cones having minute gap is pasted

    using paste command.

Grill before

Grill is having extra thicknes which creates unnecessary volumes and are non-uniform.

Grill After

Grill having common volume and are uniform.

Rims and Tyre with other surface intersecting

Unnecessary surface is intersecting inside rims and tyres.

Rims and tyre after geometrical cleaning

Rim and tyre - after removing unnecessary surface which is intersecting inbetween.

Grill before

Here grill is having unnecessary volumes.

Grill After Solving Errors

Grill having common volumes and other extra thickness or volumes are removed.

Rear view mirror before

In this case rear view mirror is having unnecessary volumes.

Rear view mirror after solving error

Unnecessary volumes are removed to make as common volume.

> PIDs are created and assigned for the required volumes after solving geometrical errors.

> Initially CFD Mesh is generated for BMW car with the given target length:

• 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

> Element quality criteria for BMW car:

• Skewness - 0.5 mm
• Minimum length - 0.5 mm
• Maximum length - 6 mm

> For surface meshing of wind tunnel target length is as follows:

• Bottom Face - 20 mm
• Top Face - 100 mm
• Side Face - 20 - 100 mm ( Growth Mesh)

> In mesh parameters CFD with tria elements is used. Whereas minimum and maximum target length is also specified. 

> While meshing wind tunnel growth mesh is used. In this Dstart and Dlimit have to set which is 20 and 100. Mesh

   generation grows from 20 to 100.

Results

CFD Meshing of a BMW Car

Surface Meshing of a Wind Tunnel

Learning Outcome

> CFD and Surface meshing with the given quality criteria for different target length.

> Creation of fluid domain (External flow analysis) which is wind tunnel for the BMW car.

ANSA Modle

https://drive.google.com/file/d/1jTmACOr6b3h8i3KHkcOMx3LpMV7TTh3j/view?usp=sharing