Quote:
Originally Posted by freebeard
I showed my work in post #10
The original file name was 'template MRT1022.jpg'. I find a proportion of 7 to 4 or 1.75. Width at the base of the B-pillar is 56".
So if I 'eat' the vortexes at the drip-rail, I could lose attached flow down the back. But if the vortexes impact on the flat top of the boat-tail instead of the road, wouldn't that break them up? Or would the degenerate into new vortexes on the edge of the tail?
The Coanda thing is a little in-joke among myself. You can ignore it. The fenders would probably go to an aero-form, but they would be a lot more work, with the compound curves. I know the bottom half of the boat-tail is compromised. |
Looking at an image of a 1966 VW 1300 Beetle from car-blueprints it looks like a workable plan-view tail would come to a point at about 33.5" behind the body ducktail.And if the rear wheels were 'inside' the body,as with EV-1 and the 1st-gen Insight she might do okay as a minimum.
The problem I see is in elevation,where the body is twice as blunt as what we see,completing a mirror image of itself below the ground.
From wind tunnel studies,any roofline faster than the "Template" is going to invite separation and vorticity formation,produced by disparate flow velocities and pressures along sides and top,as well as the slope of the back itself.
With the boat tail below the greenhouse,it does nothing to mitigate the velocities of the air along the sides and top,so it can't really prevent the separation and vortex formation.
And it may be that the vortices will simply propagate outwards above the tail.
If they strike the tail's top surface it will cause an asymmetric discontinuity in the vortices themselves as they crash into the tails top.
The only fix I can think of is to raise the 'roof' of the tail to mimic something like the 'Template.' It should kill the vortices.
You'd need a 'tunnel' to preserve rearward vision and you might want to move the mirrors outward to help with the blind spot created by the tunnel.
If you truncated the tail even with the back of the original bumper you'd have the potential for around Cd 0.25.It would look like the images on page-3 of your thread.