[kach22i]

Brilliant perspective of the photo may provide a clue to the answer. The car body is beyond, and I suspect the ridges break up a standing wave caused by the down-force vortex which forms following a Gurney Flap.

F1JOURNAL.COM


My experience on this topic is in acoustics (4-years ago):
Do you have a variable splitter plate? - The Virtual Hoverrally - Page 2

[quote name='kach22i' timestamp='1280573265' post='21585']
Don, you are correct, everything each side of the fan is a noise source. The closer in proximity the object (splitter, support mount...etc), the more noise potential. I have successfully lowered the perceived noise of my Scat II by distributing the sound nodes (energy pattern) of the splitter plate.

My splitter plate's leading edge is now wavy (serrated) with an undulating edge, not unlike that of a bread knife. The concept here is that perceived loudness is based on the highest sound node (peak) and typically higher frequencies are also thought of as louder over similar lower tones. I also moved the splitter closer to the fan so it should be a wash between pressure escaping though the uneven edge verses a straight edge further back.

5 Ways to Use a Serrated Knife... Other Than Cutting Bread! | The Kitchn


Pictures by kach22i - Photobucket




Making a tail cone - foam - The Virtual Hoverrally - Page 2

Even at idle it's effects are very noticeable. Notice too that the lip points into the flow at right angles depending which side of the thrust swirl you are on

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