Quote:
Originally Posted by bs25942
For the side taper:
I have overlaid both my original template and the suggested template on the car. Will the original not work because it is too aggressive of an angle for the air to stay attached? The suggested template seems pretty flat or maybe I did not line it up correctly. Obviously I would rather have a flatter angle with no air separation versus a steeper one but I also want the cross section to be as small as possible at the end.
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If your car was actually a half-body,the sides would be identical to the top.With this,the flow velocity and pressure along the sides would be closer to the top flow.
With the CIVIC,the airflow over the greenhouse is faster,and at a lower pressure than at the sides do to the way the streamlines are divided at the nose and windshield.
With less body camber,and higher pressure,the side flow cannot support attached flow over as radical a curvature as on top without triggering separation.
The more gentle curvature of the 2-D strut of minimum drag (second image,center table) has the sectional density necessary for a more gradual pressure rise which will not jeopardize the boundary layer.
A number of the lowest drag cars ever constructed happen to use this more gentle 2-D section profile for their plan view boat-tailing.
Until more data comes along I believe it to be the safest bet.
Here is Kamm's research model for Jaray-type rear ends.The longest, most gentle plan-view contour netted him the lowest drag.
