Quote:
Originally Posted by Tesla
Interesting,
I am finally starting to get a handle on what the numbers you quote mean, can be a bit slow at times.
With the Tuna, it was near enough to template, 2.5:1, on side profile, but on plan view is at ideal wing cross section, 4:1.
I was thinking how can we take something from this, which one of these is the governing measure, or are they the outer limits that natural selection has shown to achieve the most efficient movement through water (or any fluid).
With the wing section I assume this means in wing form, that it theoretically can continue this to infinity at 4:1 as the minimum drag form, where as with the body of rotation is at 2.5:1.
So with motor vehicles in ground effect (mirror) we have some elements of both of these characteristics, it is like a body of rotation, but has flatened sides, top, bottom etc, which give it some wing character.
Do we need to consider our vehicles in this manner and take some elements from each profile to best address the aerodynamic drag?
Don't know what or how, just playing with ideas.
|
here are some elements which led me to the 'Template.'
*Paul Jaray,who was employed at the Zeppelin works is given credit for the longitudinally asymmetric airship body (blunt nose with tapering tail),although Pierre Juliene (sp?)had flown a model airship of this form inn 1850.
*This airship form is the streamline body of revolution.
*Paul Jaray was the first to use the term 'streamline.'
*Jaray took an airship body and sliced it in half,longways,to create a 'half-body',or 'pumpkin seed',which today,remains one of the lowest drag forms ever measured as a road vehicle.
*The pumpkin seed has twice the drag as the streamline body it is derived from.
-------------------------------------------------------------------------
*The streamline body of lowest drag has a fineness ratio of L/D= 2.1
*This form is unsuitable as an airship,as it flies like a fumbled football,makes the whole crew airsick,is unsuitable as a photographic or weapons platform.So while it does have the lowest drag,you'll never see it in service.
*As a 'bluff body' road vehicle in ground effect,this forms aft-body is a bit too steep to protect the boundary layer and is prone to premature separation.
*Mair and Buchheim researched separation-free aft-body contours and reported that we should never exceed 22-23 degrees,respectively.
*The L/D= 2.5 streamline body is the shortest body which respects the 22-degree rule (it's conservative).
*It has a free-air Cd 0.04.
*As a half-body in ground proximity it has Cd 0.08.
*When narrow wheels and tires are added the drag goes to Cd 0.12.
-------------------------------------------------------------------------
As a 'pure' half-body it would make for a 'wide' vehicle.The convention (if there actually is such a thing) is to narrow the body in plan,morph it into more of a rectangle in section for the passenger compartment,then re-morph it back into a more streamline body section for the tail.
-------------------------------------------------------------------------
Some of the researchers or teams who have worked with the pumpkin seed are:
*Paul Jaray
*Walter E.Lay
*Elliott G.Reid
*Heald
*Fachsenfeld
*Kamm
*Reid Railton's 'Railton 'Mobil' Special'
*Jean Andreau's 'Thunderbolt'
*MG EX 181
*Mickey Thompson's 'Pumpkinseed'
*Walter Korff's dry lakes streamliner
*Doug Malewicki's' California Commuter'
*AeroVironment/GM Sunraycer
*Honda Dream I,II,III
*Cal Poly
*MIT
*University of N.Texas
*B'o'chum University,Germany
*other university solar race teams
--------------------------------------------------------------------------
*It looks like the side elevation of the vehicle should stay close to the 'Template' and then for plan-view,since the vehicle is 'narrow',lean towards the 4:1 'Section' and do our best to blend it all together.
--------------------------------------------------------------------------
I'm looking at some other teardrops and one has a little more aggressive early curvature like your NACA 0039
section and I think what you have would make a fine tool to work with,especially since you can get such specific vectors at any position.
--------------------------------------------------------------------------
I'll never 'finish' looking at this stuff,but I think we're closing in on a useable 'Rosetta Stone' for decyphering the air.