Week 4 Challenge : CFD Meshing for BMW car

OBJECTIVE

To check and solve all geometrical errors on half portion and Assign appropriate PIDs for the given model. Perform meshing with the given Target length and element Quality criteria. After meshing the half model, Do symmetry to the other side.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

To create a wind tunnel with appropriate geometry and do surface meshing of the same.

PROCEDURE

• Import the geometry to the ANSA pre-processor.

• Check the model for Single CONS. If the model contains only Single CONS, then do the Topo function (Topo>Faces>Topo).
• Check wether the model given is fine or not i.e., check for CONS resolution. If the CONS resolution is not accurate as shown in figure below, it can be solved in two methods.

• First method, (Topo>Auxiliaries>Fine) as shown in figure below.

• Second method is done by selecting the entire model for increasing the CONS resolution (Mesh>Perimeters>Length). Give the perimeters and macros length as 1mm as shown in figures below.

• Increased CONS resolution is seen in the figuirews below.

• Since the model is symetrical, the topo cleanup can be done one side only. This one sided topo cleanup will be reflected on the symetrical side. So on side of the model can be deleted as shown in the figure below.

• Since only outside features are required, the inside features can be avoided. To make this happen avoid the presence of triple CONS. So topo cleanup is done parts by parts as shown in the figures below.
• Before and after the Topo cleanup for headlights is shown in figures below.

• Before and after the topo cleanup for grills is shown in figures below.

• After the topo cleanup of logo is shown in the figure below.

• Befor and after the topo cleanup of mirror is shown in the figures below.

• Before and after the topo cleanup of Tires is shown in figures below.

• Topological cleanup is done for half of the model as shown in figure below.

• Asign PIDs for the model as shown in figures below.

• After asigning PIDs for the each parts as mentioned, surface mesh the mentioned parts by setting minimum and maximum target length in the quality criteria and target lengths with the element type as tria in mesh parameters.
• After completing the surface meshing of one half click Tranform > Copy > Select the entities > Symmetry > Mirror 3 Point Plane > Select 3 points check the preview and click Finish. Symmetric model obtained is shown in the figure below.

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

• Mesh all the faces of tunnel and create fine mesh at bottom and course mesh at top using Spacing option which helps to enable to save time as over focus is more to car geometry as shown in the figure below.

• Next mesh the required volume of wind tunnel and the car model volume.

RESULTS

• Surface meshed parts is shown in the figures below with respective target lengths and quality criteria.

BMW Logo

• Target length = 1mm
• Minimum length = 0.4mm
• Maximum length = 2mm
• Element type = tria

Grills

• Target length = 1mm
• Minimum length = 0.3mm
• Maximum length = 2mm
• Element type = tria

Windows

• Target length = 2mm
• Minimum length =1mm
• Maximum length = 3mm
• Element type = tria

Lights

• Target length = 4mm
• Minimum length =3mm
• Maximum length = 5mm
• Element type = tria

Rims and Tyres

• Target length = 2mm
• Minimum length =1mm
• Maximum length = 3mm
• Element type = tria

Silencer

• Target length = 3mm
• Minimum length =1mm
• Maximum length = 5mm
• Element type = tria

Rearview mirror

• Target length = 2mm
• Minimum length =1mm
• Maximum length = 3mm
• Element type = tria

Body

• Target length = 3mm
• Minimum length =1mm
• Maximum length = 5mm
• Element type = tria

Wind Tunnel

• Bottom Surface = 20mm
• Top surface = 100mm
• Side surface = Spacing from start = 20mm to limit = 100mm

• Required volume for volume meshing is shown in the figure below.

CONCLUSION

• The specified geometry is examined, and its surface meshing and topological cleanup are completed. Construction of a wind tunnel and surface meshing are both done there. Volumetric meshing will be used in the future because it requires time.

NOTE: Tried uploading the meshed model file but keeps canceling out. May be i have a bad network conection don't know the actual reason. Since time is less for re-uploading and sending the model file again so submitting my report without the model file. Please do consider it.