Quote:
Originally Posted by ERTW
Phil, do you have a front view and a plan view of the template? I don't think I'm getting the shape right. I set ground clearance at 10% of the body thickness with sharp edges and the Cd is coming in at 0.275 :/ Do you have a solid model?
I've also taken a 4:1 rear body with a 1:1 front end (same length as a 2.5:1 ellipse) which comes out to Cd 0.247. Using a 6:1 rear body (used to model dolphins) only dropped it to 0.243. Both had a 10% fillet and 10% ground clearance. What do you think?
edit: I rounded the bottom edge (R5" or 10%)...Cd 0.191, CL ~ 0.055. Sharp leading edges are a no no! I want to protrude the nose a little into the wake, and sharpen up the trailing edge. I believe it "wants" a 20% radius on the leading edge, and ~12.5° max angle. I think 25% ground clearance is closer to your template (and helps get it above the earth's boundary layer). I'll report it asap.
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I don't have the other views yet.I can't seem to keep with all the traffic here at EcoModder.
I don't have a solid model either.
Looking at your image,it looks like the front profile rises to the max camber point,but does not reside there before the downward slope begins to the rear.
This is the most important thing about the template.It must be exactly like it it shown.
Shorter and we have separation.
Longer,and surface friction goes up.
Essentially,we take a 2.5:1 streamline body of revolution,bring it right down into the ground,where only half is above ground,the other half submerged( ground reflection),then cut away for ground clearance with no alteration of the height.
The ground clearance I show in the template is the minimums for the 16-degree/10-degree/10-degree SAE approach,breakover,and departure angles.This clearance needs to be maintained as well.
The body must be narrowed,as it would be too wide,so some morphing is required.
I was to have minimum radii at the lower edge,blended into the wheel fairings.
Above the max vertical camber point ( in line with max protrusion of nose ) the whole body is rolling into curvelinear tumblehome as Jaray's pumpkin seed.As the University of Bochum Solar West GT.Ditto Schlor Car.
The front elevation is going to be very much like the Bochum car.
The plan view will be much like the 1957 MG EX 181.The is a auto blueprint of this car online.
Walter Lay's pumpkin seed car of 1933 has a perfect match with the template aft-body.It showed at Cd 0.12.Jaray's was hypo-template and came in at Cd 0.13.I truly believe that these are the numbers we should be seeing.And that's with ideal cooling systems,features drag,wheels,etc..
The 1987 GM Sunraycer is a dead match to the template,from nose,out to 25% aft-body,afterwhich it refllexes and goes hyper-template a bit out to 89% of the template aft-body length.At Cal Tech,with wheel fairings,the Sunraycer model registered Cd 0.089.
I love your images! I was looking at the Honda Dream paper about their CFD.They broke the car body into 850,000 panels and solved simultaneously with the Navier-Stokes Equation.Blows my mind!