Tuft testing A-pillar vortex generators

Text and pics: Julian Edgar

Here’s an example of using tufts to test an aerodynamic modification.  

The car was a W212 Mercedes E class and the intent of the modification was to reduce flow separation around the A-pillars on the side glass. The testing was of small vortex generators made from rubber wedges. 

 A W212 E-class Mercedes. (Pic courtesy Mercedes)

Small rubber doorstops were cut down to form tiny, slightly flexible vortex generators. 

 The vortex generators. Double-sided tape was used to hold them in place. This was sufficiently sticky that the vortex generators didn't fall off but also allowed their angle to be altered during testing.

 The window tufted.

The results, as shown by whiteboard marker drawn on the inside of the glass. The solid lines show the variation in tuft position without the vortex generators – the ‘V’ indicates the angles over which the tufts were fluttering. The dotted line shows the tufts with the vortex generators in place – they are much more stable in behaviour and better aligned longitudinally.

The external view. Even a still photograph shows the change in airflow pattern.

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