Quote:
Originally Posted by AeroMcAeroFace
Which template? Is it 21, 22, 22.5 or 23 degrees maximum curvature, all of which are claimed to be the "maximum" before flow separates.
The cars with roofline separation, the evidence is that they don't fit the template. The evidence for the template is that these cars have roofline separation. Circular logic?
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Great question!
1) The question would depend upon the profile.
2) I've been working with eight of them.
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3) What is 'mission critical' is that, whatever streamlined profile was chosen by the manufacturer, that that profile be maintained all the way to bodies end.
4) No 'kinks'.
5) No pressure spikes.
6) Only the moderate pressure increase that a streamlined profile will produce.
7) Otherwise, you cross the critical threshold of an already adverse pressure gradient, triggering separation.
8) The ultimate profile tangent slope angle, at any point along the aft-body, is determined by the chosen profile, and how much of it is used.
9) Really low drag bodies use ALL of it. Like the VW Flow-Body long-tail, which never exceeds 23-degrees. Cd 0.14.
10) You can't get below Cd 0.15 without the extra length.
11) And with cars designed for low drag, the length vs Cd relationship was discerned and expected trend is in fact confirmed.
12) A closer approach to the Cd 0.09-tp-Cd 0.07 of the basic bodies is only achievable through further integration of the wheels into the body.
13) The dimensional analytics can identify the original profile, and allow elongation with an extremely high confidence level that flow attachment will be maintained.
Like an electrocardiogram. A mere glance from a cardiologist will tell them if you have an irregular heartbeat. The Cartesian grid, the actual signal from your heart, plus their medical training, has ingrained the 'normal' heartbeat 'template' into their memory. It saves a lot of diagnostic time.
