Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 10-07-2020, 02:13 PM   #51 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,680
Thanks: 18,777
Thanked 6,076 Times in 3,721 Posts
normal mix

Quote:
Originally Posted by JulianEdgar View Post
The normal mix of correct theory, incorrect theory, irrelevancies, very clearly no experience of on-road testing of a shape anything like this, extrapolated even weirder theory - and so on.

For people who actually want to learn, just look at the pressure chart and the flow pattern, and draw some obvious conclusions about the relationships.






And as for the rear spoiler, just mentally place one at the back of the car (say, the same angle as the windscreen but only 1/5th as high) and then look at what the windscreen did to the pressure of the attached flow in front of it.
I've provided a checklisted, item by item evolution of the phenomena, according to the science. Where one takes it is up to the individual.
Road testing isn't necessary. The photograph provides all the necessary information to make the verdict.
A look at the VW XL1 undergoing smoke flow testing will provide a look at what attached flow actually appears like.

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 10-10-2020, 01:03 AM   #52 (permalink)
Tyrant-at-large
 
Vman455's Avatar
 
Join Date: Feb 2012
Location: Champaign, IL
Posts: 1,700

Little Red - retired - '05 Honda Civic EX
90 day: 49.03 mpg (US)

Pope Pious the Prius - '13 Toyota Prius Two
Team Toyota
SUV
90 day: 59.04 mpg (US)
Thanks: 178
Thanked 1,487 Times in 788 Posts
Quote:
Originally Posted by aerohead View Post
I've provided a checklisted, item by item evolution of the phenomena, according to the science. Where one takes it is up to the individual.
Road testing isn't necessary. The photograph provides all the necessary information to make the verdict.
Road testing; who needs it? And fuel economy testing; better to just believe that something works. Why test mods at all? Faith is all you need apparently.

The big thing on Priuschat these days is a VVT solenoid called the "Red Bullet." Many users have installed one on their cars and made ridiculous claims, such as one person who insists that it improved his fuel economy by 15 mpg. Yet no one who has installed one can explain what it does, not even the person selling them; they can't even be bothered to look up the (Toyota-available and published online) solenoid schematic and apply a little thought, let alone do a controlled test.

Quote:
Originally Posted by aerohead View Post
A look at the VW XL1 undergoing smoke flow testing will provide a look at what attached flow actually appears like.
Oh, you mean like this?



Hey, wait a minute! That shows flow detachment just like the Porsche! It's almost as if the flow over most of the car is turbulent and the streamlines are subject to random high-frequency fluctuation that isn't captured by a single still photograph. No, that couldn't be....
__________________

  Reply With Quote
The Following 2 Users Say Thank You to Vman455 For This Useful Post:
aerohead (10-12-2020), JulianEdgar (10-11-2020)
Old 10-10-2020, 10:09 AM   #53 (permalink)
Somewhat crazed
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 1,327
Thanks: 126
Thanked 367 Times in 308 Posts
My lessons in wing design (OMG not relevant here) says we don't really care if flow is laminar, attached, turbulent, whatever, as long as further following flows are low drag. Built many aircraft using wings that were thought to be using one of the above categories and !suprise! They all flew decent.
  Reply With Quote
Old 10-10-2020, 12:30 PM   #54 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 17,185
Thanks: 4,602
Thanked 5,751 Times in 4,586 Posts
Quote:
flow is laminar, attached, turbulent, whatever.... !suprise! They all flew decent.
Even the whatevers?
__________________
.

We are operating at an overall mechanical efficiency of only four percent… Therefore, we find that if we increase the overall mechanical efficiency to only twelve percent we can take care of everybody. That three-fold increase in the overall efficiency can only be accomplished by redesign. – R. Buckminster Fuller

_________________
  Reply With Quote
Old 10-11-2020, 12:20 PM   #55 (permalink)
Somewhat crazed
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 1,327
Thanks: 126
Thanked 367 Times in 308 Posts
Particularly the whatever's.

Naca 0012 series operations in the reynolds transition portion flew generally the best. Since this is model scale applications, we don't know exactly what the boundary layer state is as it is immeasurable, therefore whatever
  Reply With Quote
The Following 2 Users Say Thank You to Piotrsko For This Useful Post:
aerohead (10-12-2020), freebeard (10-11-2020)
Old 10-11-2020, 02:22 PM   #56 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 17,185
Thanks: 4,602
Thanked 5,751 Times in 4,586 Posts
https://en.wikipedia.org/wiki/God_of_the_gaps
__________________
.

We are operating at an overall mechanical efficiency of only four percent… Therefore, we find that if we increase the overall mechanical efficiency to only twelve percent we can take care of everybody. That three-fold increase in the overall efficiency can only be accomplished by redesign. – R. Buckminster Fuller

_________________
  Reply With Quote
Old 10-12-2020, 06:02 PM   #57 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,680
Thanks: 18,777
Thanked 6,076 Times in 3,721 Posts
sub-critcal Reynolds number

Quote:
Originally Posted by Vman455 View Post
Road testing; who needs it? And fuel economy testing; better to just believe that something works. Why test mods at all? Faith is all you need apparently.

The big thing on Priuschat these days is a VVT solenoid called the "Red Bullet." Many users have installed one on their cars and made ridiculous claims, such as one person who insists that it improved his fuel economy by 15 mpg. Yet no one who has installed one can explain what it does, not even the person selling them; they can't even be bothered to look up the (Toyota-available and published online) solenoid schematic and apply a little thought, let alone do a controlled test.



Oh, you mean like this?



Hey, wait a minute! That shows flow detachment just like the Porsche! It's almost as if the flow over most of the car is turbulent and the streamlines are subject to random high-frequency fluctuation that isn't captured by a single still photograph. No, that couldn't be....
That photo was likely taken at an airspeed below 20-mph. It would be at sub-critical Reynolds number. You should have recognized it immediately. Not germane.
There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.
Is this just an innocent undersight or deliberate obfuscation? Conformation bias?
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 10-12-2020, 06:11 PM   #58 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,680
Thanks: 18,777
Thanked 6,076 Times in 3,721 Posts
immeasureable

Quote:
Originally Posted by Piotrsko View Post
Particularly the whatever's.

Naca 0012 series operations in the reynolds transition portion flew generally the best. Since this is model scale applications, we don't know exactly what the boundary layer state is as it is immeasurable, therefore whatever
Yeah, they test at three different Reynolds number, and without knowing that specifically, even though we know the wing dimensions, and turbulence factor, we can't peg the velocity necessary for that Rn to consider LBL or TBL or transition points.
__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Old 10-12-2020, 06:31 PM   #59 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 17,185
Thanks: 4,602
Thanked 5,751 Times in 4,586 Posts
Quote:
There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.
So where might we find it?
__________________
.

We are operating at an overall mechanical efficiency of only four percent… Therefore, we find that if we increase the overall mechanical efficiency to only twelve percent we can take care of everybody. That three-fold increase in the overall efficiency can only be accomplished by redesign. – R. Buckminster Fuller

_________________
  Reply With Quote
Old 10-12-2020, 09:57 PM   #60 (permalink)
Tyrant-at-large
 
Vman455's Avatar
 
Join Date: Feb 2012
Location: Champaign, IL
Posts: 1,700

Little Red - retired - '05 Honda Civic EX
90 day: 49.03 mpg (US)

Pope Pious the Prius - '13 Toyota Prius Two
Team Toyota
SUV
90 day: 59.04 mpg (US)
Thanks: 178
Thanked 1,487 Times in 788 Posts
Quote:
Originally Posted by aerohead View Post
That photo was likely taken at an airspeed below 20-mph. It would be at sub-critical Reynolds number. You should have recognized it immediately. Not germane.
There's another image produced at supercritical Rn, necessary for the development of a proper turbulent boundary layer.
Is this just an innocent undersight or deliberate obfuscation? Conformation bias?
Confirmation bias? I took a screenshot from the same video that produced the image you're talking about, just a few seconds after. Yeah, I'm trying to lead people astray....

__________________

  Reply With Quote
The Following User Says Thank You to Vman455 For This Useful Post:
aerohead (10-21-2020)
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com