Measuring Drag

[eeouyang]

Hello!
So my science fair project involves a wind tunnel and an aerofoil and I wanted to see how much drag each of the wings produced. I know lift is a viable option but I feel like drag would serve my purpose better. I need help finding a way to measure drag with its steps laid out. I have already heard about the strain gage but if there is a way, is it possible to put it in layman terms and explain the process step by step?
Thank you!!

[rmarz]

eeouyang - It sounds like you want to evaluate airfoil designs that measure lift versus drag. Clearly an efficient airfoil produces a maximum lift component (force that is perpendicular to air stream) with a minimum of drag (force or resistance opposite to the air stream). But there are other things to consider. A perfectly symmetric airfoil at a zero degree angle-of-attack will produce no lift and only drag, as the potential lift forces will cancel each other out. I just introduced you to the concept of angle-of-attack, AOA, which you should research to better understand before you just try to measure forces generated in an air stream or wind tunnel. There is a lot of benefit in understanding basic aerodynamic forces (lift, weight, thrust, drag) that will help you in your experiment design.

Rick Marz

[eeouyang]

eeouyang - It sounds like you want to evaluate airfoil designs that measure lift versus drag. Clearly an efficient airfoil produces a maximum lift component (force that is perpendicular to air stream) with a minimum of drag (force or resistance opposite to the air stream). But there are other things to consider. A perfectly symmetric airfoil at a zero degree angle-of-attack will produce no lift and only drag, as the potential lift forces will cancel each other out. I just introduced you to the concept of angle-of-attack, AOA, which you should research to better understand before you just try to measure forces generated in an air stream or wind tunnel. There is a lot of benefit in understanding basic aerodynamic forces (lift, weight, thrust, drag) that will help you in your experiment design.

Rick Marz

Thank you for replying!
My project involves a winglet and I wanted to see whether it would reduce wingtip vortices and drag. I understand lift and AOA but my project's idea necessitates a way to measure drag as the only thing i change in each wing is the angle and which the winglet is bent. That is to say, lift isn't too much of an issue rather the drag is what i am most intrigued about. Maybe there is an equation to get from lift to drag?

[rmarz]

eeouyang - Thanks for the additional information. You have a much better understanding of what you are attempting than I originally thought. There are many interactive variables at work and my concern is that a low velocity wind tunnel and the ability to measure very slight changes in drag (forces to be measured) may be a significant challenge except in a highly instrumented wind tunnel environment. Here is an interesting study on the subject and it might help you to better understand the problem and some results that have been observed in a much more controlled environment. Good luck on your project.

Rick Marz

http://www.altairatc.com/india/bangalor ... raguru.pdf