Quote:
Originally Posted by Tesla
That's kind of the direction I am heading in.
In my case 6' high from ground level, 6' wide, a clear 1+' of ground clearance and 8' of flat roof.
I believe this requires a different approach for a vehicle that is 4' high 6' wide, only 6" ground clearance and 4' of flat roof.
The dimensional differences result in it not fitting within the template profile at all, where as the std road vehicles are generally a rough fit.
I think the underside needs to be treated more like the solar racers, leaving the elevation, getting good smoothing and allowing more free flow, the question then begs, where to position the stagnation point at the front, as we basically want to achieve a natural distribution between top, sides & under.
My feeling is a split somewhere around 35% each side and 15% over and 15% under, with a stagnation point & radiator inlet in the lower half of the front under bonnet face, which is where it basicall is after the upper grille block, which I did with an upward tapered panel to get smooth transition to the bonnet.
When you say L/W of 4 in 2d profile does that basically translate to 2:1 in the symetrical form, so shorter than the template proportionally?
|
Looking down from above (plan view) the section would be 4X as long as it is wide.If you look at the aft portion of this section,you will see that this tail is actually longer than that of the 'Template.'
Fachsenfeld used this in his patent application illustrations,whereas most of the streamlining was done along the sides.The body began to narrow at the A-pillar,a bit more radical than EV1,which began its taper midway down the door.
A number of VERY low drag cars have used this approach.
No matter what you do,the roofline or body sides should never exceed 22-23 degrees.A turbulent boundary layer cannot support attached flow with a steeper curvature unless you provide blown or suctioned slots.
If you have a notchback car go ahead and use VGs as on the Lancer.
For large trucks and vans there is little evidence (none that I personally know of)that anything which might help an airplane would help a road vehicle,except slots.Hucho had no evidence that VGs or turning vanes could help lower drag of a truck.
In free flight,the aft-body of an aircraft fuselage,or bullet enjoys a jet-pumping action which doesn't occur in ground proximity.On the ground,the flow is asymmetric and causes a doubling of drag.
The reason for the 'Template' was that it was developed from a separation-free form.Since aerodynamic streamlining is predicated on reduction or elimination of flow separation,it is a 'natural.'
And the curvature is already as steep as it can be without triggering separation.If you make the tail steeper you will increase pressure drag (the big no-no!) If you make the tail longer you're adding additional skin friction ( the lesser of two evils).
And don't be looking at 'laminar' sections either.They would only help you alone on a closed course,with zero wind,at around 20 mph.If the wind came up,or you got into traffic,or went any faster,the section would transition right into a turbulent boundary layer and skin friction increase.
