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Author Topic: Vortex Generators  (Read 137 times)

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Offline Deerslayer

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Vortex Generators
« on: January 08, 2018, 10:56:41 AM »
Vortex Generators (VGs) have been around for many decades. I first noticed them on airliners I flew on back around 1970. You may notice them on smaller airplanes, especially of the STOL variety such as some bush planes.

About four years ago, my son started flying a Cessna 206 floatplane for his client. He installed a VG kit on it. The kit was a properly engineered and certified modification, cost $2500, which he installed over the course of a day or so. There was some huge number of these things, epoxied onto the top of the wings and onto the underside of the horizontal stabilizer. Their effect was to improve airflow separation over these surfaces. This resulted in approximately 5 knots lower stall speed or could allow a higher payload capacity. Floatplanes often have to squeak into, or hop out of, very confined areas with nasty trees, etc., in close proximity. The VGs were the one thing that could be done to improve things.

At that time, I became interested in finding out the science of VGs and how their effects are investigated and quantified. The information is out there, and there is fluid dynamics math, but some of it left me a bit bewildered.  I like pictures and videos! (Be patient, there is one coming up shortly...)

More recently, VGs started showing up on RC models. The Visionaire, Carbon Z Cub, Scimitar, all of which I have owned, are just a few that come to mind. Do they work at this small scale and low Reynolds Numbers? Hard to quantify, but experienced pilots report that they do make a difference, at least on some airfoil and airframe configurations.

I found this video to be enlightening. The fellow is admittedly not an aeronautical engineer or fluid dynamicist but he has done a terrific job of explaining things and documenting his experiments. The RC plane test near the end is a particularly compelling argument to accept the value of VGs and not just grab the Exacto knife and slice them off (as some amongst us may have done in the past!).

So, please sit back and check out this:

https://www.youtube.com/watch?v=eP-YUDe9HF0&feature=youtu.be
My purpose in Life is to serve as a Warning to others