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Old 07-25-2019, 05:33 PM   #11 (permalink)
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I feel like the underachieving student with the brain trust here at EM, but asking silly questions is just a part of my learning process.
You asked for other threads: ecomodder.com/forum/google_search_results for q=skin+friction

I like the way you think. Instead of Aerodynamics of Road Vehicles, try Viktor Schauberger:


https://duckduckgo.com/?q=viktor+sch...sine&ia=videos

The air curtains and your decklid mod are external ducts. The trick is short and fat to move a lot of air with least skin friction. The first example that caught my eye was this Ferrari:

All it does is bleed air away from the A-pillar. A favorite would be the GTI W12-650


Quote:
the math says you can not see Sardinia from Genoa but in reality you can .
the math says gravity bends light , reality and observation says it does not .
[citation needed]

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Old 07-25-2019, 08:41 PM   #12 (permalink)
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Quote:
Originally Posted by mwebb View Post
the math says gravity bends light , reality and observation says it does not .
Gravitational lensing is a well-known phenomenon predicted by Einstein and verified since. You may want to rethink impugning math so much, since nearly everything that underpins our modern lifestyle has been made possible because of it.
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Old 07-25-2019, 10:45 PM   #13 (permalink)
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Quote:
Originally Posted by Vman455 View Post
Gravitational lensing is a well-known phenomenon predicted by Einstein and verified since. You may want to rethink impugning math so much, since nearly everything that underpins our modern lifestyle has been made possible because of it.
I was pretty certain gravity can bend light otherwise how can you explain a black hole being.... black, i.e. no light being able to escape the gravity.
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Old 07-26-2019, 11:40 PM   #14 (permalink)
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Einstein’s General Theory of Relativity is Questioned But Still Stands ‘For Now’ – W. M. Keck Observatory

Einstein’s General Theory of Relativity is Questioned But Still Stands ‘For Now’
Posted July 25, 2019
Detailed UCLA-led analysis of the star’s orbit near supermassive black hole gives a look into how gravity behaves

The analysis suggests the stars light is red-shifted by climbing out of the [invisible] black hole's gravity well. At the perigee of it's highly eccentric orbit, it's traveling at 2.5% the speed of light.
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Old 07-27-2019, 12:29 PM   #15 (permalink)
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Yeah but wouldn't installing a black hole in the bed of my truck cause a significant loss in gas mileage?

Not sure if it's tailgate up or down works with the black hole mod.
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Old 07-27-2019, 01:47 PM   #16 (permalink)
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squeeze it forward

Quote:
Originally Posted by hat_man View Post
I think I'm understanding it better now.

So the most efficient "model" would be the AST viewed in 3-D. Like a teardrop. Not practical for a vehicle so a near half teardrop with the road being the mid-plane (?) of the teardrop.

So another question.....in my mind I'm seeing a half teardrop with lines representing the (laminar?) flow along it's surface. As the pressure travels rearwards along the teardrop (and comes back together) does it's cumulative effect "squeeze" the tail of the teardrop causing theoretical forward movement? Like pinching a watermelon seed between your thumb and forefinger and shooting it at your wife? So if you rob some of the pressure through the middle (6" tube) you decrease the amount of pressure along the sides of the teardrop and lessen the "squeeze"? Not only would it decrease the pressure moving down the sides but could create drag along the insides of the tube because of the friction?

That would be why a boat tail works so well? It helps direct the flow along the sides into the low pressure void at the rear of the vehicle? I can see now how an aero cap and a boat tail would be beneficial for a pickup truck.
The energy lost to surface friction removes energy at the rear of the car,which is present at the front.So it's impossible to generate thrust.All you can do is eliminate any separation,and as the velocity decreases along the streamline body,the local static pressure increases (static-regain) according to the Bernoulli Principle.Fully-boat-tailed,all the body has is surface friction,there's zero pressure drag.Reducing,or eliminating pressure drag,is,by definition,the object of streamlining.
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Old 07-27-2019, 01:53 PM   #17 (permalink)
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heat the air

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Originally Posted by ASV View Post
its an idea that is almost good
the thing is its incomplete
you have to overcome the penalties you incur by taking some of the air away from the carefully curved and angled areas in the back that helps squeeze the car forward like a watermelon pip and by adding surface area

there are however ways that you can do that
primarily I think would be to heat the air so that it supplies -more- volume to the low pressure zone than it robs from the air foils of the body work
if you took that heat from the engine cooling system you could shrink or even eliminate
the radiator doubling up as it were on your benefit

If your tube was tapered like a long rocket cone ????
maybe even a little thrust
Incompressible,sub-sonic flow would make it impossible to generate expanded-air thrust.You'd have to be above 250-mph in a car before any effect could be achieved.Even the P-51 Mustang had to be going over 300-mph to get a little boost off its heat exchangers.
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Old 07-27-2019, 01:59 PM   #18 (permalink)
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math

Quote:
Originally Posted by mwebb View Post
why not
just try it ?

many times in the world experts will tell you the math says it can not work

but
in reality the math can lie , the math is wrong on many things .
because much of the math is broken deliberately ....

the math says you can not see Sardinia from Genoa but in reality
you can .
the math says gravity bends light , reality and observation says it does not .

just give it a try , what do you have to loose ?

even if you do not see the results you wanted to see , you will learn ,
I'm uncertain what your background is,but fluid mechanics is an extremely mature science and we've had the lowest drag form automobile body available to us since 1922.Results from the mathematics is unimpeachable.
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Old 07-27-2019, 02:06 PM   #19 (permalink)
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Shauberger

Quote:
Originally Posted by freebeard View Post
You asked for other threads: ecomodder.com/forum/google_search_results for q=skin+friction

I like the way you think. Instead of Aerodynamics of Road Vehicles, try Viktor Schauberger:


https://duckduckgo.com/?q=viktor+sch...sine&ia=videos

The air curtains and your decklid mod are external ducts. The trick is short and fat to move a lot of air with least skin friction. The first example that caught my eye was this Ferrari:

All it does is bleed air away from the A-pillar. A favorite would be the GTI W12-650



[citation needed]
Viktor's craft is in pure,incompressible flow,which an automobile would not achieve until 735-mph.We'd be into ballistics,which is entirely different physics.
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Old 07-27-2019, 02:41 PM   #20 (permalink)
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I wasn't so much thinking it would generate "thrust". I guess I was seeing X amount of pressure applied to each side of a watermelon seed at the widest part somewhat cancelling each other out (180 degrees apart resulting in a 0). But the same X amount of pressure applied to each side of the tapered part being more than 0 because the side pressures being less than 180 degrees apart. Not that it would result in more than X, but rather a greater percentage of X being "usable". Does that make sense?

I can see the concept in my mind but just can't put it into words. Especially in tech speak.

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