View Single Post
Old Feb 24, 2011, 12:18 PM
JetPlaneFlyer is offline
Find More Posts by JetPlaneFlyer
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Joined Mar 2006
13,429 Posts
Originally Posted by Dickeroo View Post
My friend, Bob Tilden, sent me this video which shows an inflatable wing which has a series of indented ribs running the length of the wing. The wing is then placed in a smoke tunnel and compared against a conventional airfoil. You can clearly see how the ribbed configuration prevents separation of airflow whereas the conventional wing is unable to hold the airflow closer to the surface of the airfoil. Quite possibly, a similar thing is happening with the KF steps.
As the others have said.. 'trips' or 'turbulators' are nothing new and have been used on freeflight models for decades in low Re applications. The 'humps' in the inflatable wing are not your typical turbulator design but they work on the same principal. The Re numbers that benefit most from turbulators are generally lower than most RC models would fly at.

It is possible that KF steps could work like turbulators, but only if they are very small. The typical KF step is almost certainly far too deep for flow to re-attach itself after passing over the step. Also the turbulator location is very critical. You can clearly see in the video that at Re = 50k flow separation occurs on the normal wing within about 15-20% chord width of the leading edge. To have any positive effect the step would have to be located before the separation point, and I've never seen a KF wing that was designed that way, steps are always at least 50% chord by which time the flow would be well and truly detached.

A simple way to add a turbulator is glue a length of thread along the wing surface, or perhaps a strip of tape.
JetPlaneFlyer is offline Find More Posts by JetPlaneFlyer
Last edited by JetPlaneFlyer; Feb 24, 2011 at 12:24 PM.
Reply With Quote