Thread: dragging dust
View Single Post
Old 08-06-2019, 07:54 PM   #8 (permalink)
Ecky
Master EcoModder
 
Ecky's Avatar
 
Join Date: Dec 2011
Location: Vermont
Posts: 3,597

Gaptooth (retired) - '00 Honda Insight
Team Honda
Gen-1 Insights
90 day: 54.26 mpg (US)

Such Fit - '07 Honda Fit Sport
90 day: 41.27 mpg (US)

Connect - '15 Ford Transit Connect XL
90 day: 24.41 mpg (US)

K-sight - '00 Honda K-sight
90 day: 41.17 mpg (US)
Thanks: 1,357
Thanked 1,492 Times in 945 Posts
Quote:
Originally Posted by Vman455 View Post
Just a terminology note: "laminar" =/= "attached." That far back on any car at any appreciable speed*, the flow is turbulent--but attached over the rear window as you observed.

*Flow characteristics are related to the Reynolds number, which is the ratio of the inertial forces acting on the fluid particles to the viscous forces. When the inertial forces outweigh the viscous forces, i.e. Reynolds number is large, the flow will be turbulent. And since the inertial forces are the product of fluid velocity and test length, as speed increases or the point of investigation moves further along the body, Reynolds number increases. Since the kinematic viscosity of air is very small, 1.46x10^-5 m^2/s, it doesn't take much speed or much length for the flow over a car to transition from laminar to turbulent.
I stand corrected.

Regardless it's pretty cool to be able to drive through a rainstorm and have a nearly horizontal window at the back of the car remain completely dry.
  Reply With Quote
The Following User Says Thank You to Ecky For This Useful Post:
aerohead (08-07-2019)