Quote:
Originally Posted by lunarhighway
ok i did a little more reading on wikipedia, as their info is usually fairly easy to digest and not overly complicated.
one interesting thing is this:
this propperty makes them usefull in aviation appli
" "cations, where one wants to delay wing stall by keeping the airflow attachted with vortices where it would otherwise separate.
however www.airtab.com - The smart way to cut the cost of your highway fuel costs manifacturer of the airtabs state in their instalation guidelines:
this indicates that their purpous is not to reattach air to the surface but that a different purous is intended.
if we look back at the naca intake :
than perhaps the VG's like airtabs seen on cars work the same as a naca duct by drawing air into the wake of the car, and thereby increasing the pressure slightly. since this negative pressure behind the car actually pulls it back an increase in pressure would be a very good thing.
further the presence of of the vortices might cause the wake to form in a different way wich is more beneficial.
tuft testing is obviously fairly useless in this case as all the action goes on behind the car... (unless one uses very long strings, but that could lead to hairy situations). pressure measurements behind the vehicle might reveal a difference in pressure tough.
sometimes i really wich i had a windtunnel |
PBS Television re-broadcast "Raptor Force",a program which undertook to decribe how aeronautical engineers are borrowing technology from raptor birds.------------------------------ Part of the program dealt with the Grey Owl,which uses stealth and extremely sensitive hearing to locate Voles beneath snow.---------------------- The back of the owl wing is sawtoothed,and they made particular mention to it as a noise abatement aerodynamic adaptation.As air sheds off the top and bottom of the back of the wing,the sawtooth feathers break up shedding vortices with an accoustic signiture which would otherwise interfere with the owl's ability to "hear" the voles beneath the snow.Feather- down also absorbed "noise" in the boundary layer and further aided the birds ability to fly undetected.------------------- No mention is made to drag reduction,however in a different segment,regarding the F-117 Stealth Fighter,they did mention that aerodynamacists had definitely made the connection between "noise" and power loss,and while stealth was the overriding consideration for the aircraft,the notion of stretching the JP-4 a little,was,no doubt,a fringe benefit they wouldn't argue about.--------------------------------- So the sawtooth appears to definitely affect the separating flow,perhaps establishing a micro,rather than macro turbulence environment.---------------- Perhaps Santa will bring ecomodder that big windtunnel for Christmas and we can find out.