Quote:
Originally Posted by ecomodded
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In the top left the steeper slope leaves the smallest wake , with the below depiction showing a diagram with a fairly steeply sloped back on it.
Which makes me think the Boxfish *may* be made less steep to accommodate the passenger seating more then being a perfect angle, it may be a compromise, as with the audi A2 slope, I am thinking.
Could be the steeper angle is actually better ? here is a good example of what I am referring to as "perhaps" the better slope.
The SolarWind looks very close to my Beetles shape, I wonder if it's profile is the more efficient one ..?
on a side note:
I just ordered a anemometer gauge better know as a wind meter , for small scale wind tunnel test so I can test with accurate wind speeds. |
*Each aft-body,of a particular percentage of total body length will have an optimum slope.This slope will change if plan taper or diffusers are added.
*If the aft-body has 'curvature,' rather than a simple hard angle,the whole process begins again,for each aft-body length.
*No aft-body slope can exceed 22-23-degrees or risk losing flow attachment.You may have the appearance of attached flow on the centerline,but you'll have attached longitudinal vortices produced which have high drag.
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*The boxfish roof contour is ideal.
*Here's your Beetle
Here's the SolarWorld GT,it's roof is not ideal (It's a solar array)
Here's Cambridge University's CUER,with Cd 0.10 vs 0.137 for Solar GT
Here is PAC CAR II,Cd 0.075.
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It is scientifically impossible to get low drag with steeper angles without artificial boundary layer control devices.
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The 'Aerodynamic Streamlining Template' is a scientific contour which was proved in the wind tunnel.There is nothing arbitrary about it.And there is no scientific evidence in the public domain in the last 92-years which suggests that we can beat it in any appreciable way.And that includes 'laminar' forms.