# When is Lift on an aerofoil proportional to velocity?,

Andrew__
Hello,
I was doing my physics coursework, and blew a hairdryer at my makeshift aerofoil across distances of about 10cm and wind velocities of 8-11 m/s, then measured the lift off of a balance. I found they were proportional, exactly (!?), after doing some research I found drag is proportional to velocity for a laminar flow with no turbulence, could this be a similar case but for just very low wind velocities and lift? The gradient of the trendline on excel was *exactly 1 and no constant on the end (through the origin) for speed vs lift, and so was the gradient of a log graph. The reason is I doubt I will be able to find lift coefficients using the V^2 rule, thank you very much in advance?

## Answers and Replies

Andrew__
I mean the lift vs speed graph was directly proportional (not a gradient of 1)

Science Advisor
Gold Member
If your Reynolds number is small enough that the flow can be considered creeping flow (aka Stokes flow) then yes, both drag and lift will be directly proportional (or very nearly so) to the velocity. I would doubt your Reynolds number is low enough for that, though.