Dimples on airfoil

[bonguboy]

science fair is due on 1/16/15. My teacher said we need to conduct an interview. Please answer questions below. Please also state your name and what education(for example: Johnny Donny UCLA)(required for science fair)
Q. Do you believe that Bernoulli’s Principle is correct or do you believe that Newton’s Laws are true?

Q. Do you think that golf dimples positively affect the drag and lift on an airfoil?

Q. Do you have any reasons why you think that the dimples positively or negatively affect drag and lift?

Q.Would you say dimples on wings would be worth the hassle?

Q. What part of the wing do you think is the most affecting to the drag of a wing?

Thanks!

[bradleyshanrock-solberg]

I'm not sure this is an appropriate use of this forum but I'll let the moderators decide that. I'm answering without looking up anything online. You can use my login name. I have a BS in Engineering and Applied Science from the California Institute of Technology, and a couple years graduate work in Materials Science. I've had training in aerodynamics and fluid flow but never applied it beyond the classroom, and those classes were in the late 1980s.

1 First question is a trick question. Both are "true" where they apply. Newtons laws describe motion very well in most environments humans can live, but break down in high gravity environments or at very high speeds, Bernoulli’s Principle works for most incompressible liquids (such as water) and in most conditions humans can generate but break down if you're traveling through atmosphere at multiple times the speed of sound. The two things are related, Newton's 2nd law is an assumption before you get to Bernoulli's principle.

2. on Earth's atmosphere, I think so. I've not studied golf balls, but the stitches on a baseball matter because of its size and weight in Earth's air - a Softball lacks the same characteristics which is why a pitcher can't put "motion" on a ball the same way with a softball as they can with a baseball. I'd assume golfballs are designed in a similar way in absence of other evidence.

3. It goes into turbulent flow, which is a pretty advanced topic for most people (I studied aerodynamics my third year in college, as part of an engineering program). They matter if the golf ball is spinning (same as with a baseball, I'm assuming they are similar., and after 30 years, I don't remember the math on why, although I can remember a diagram on a chalkboard illustrating the principle

4. I don't think dimples on wings would have the same effect as those on golfballs or baseballs (wings don't spin and aren't spheres), but small changes in a wing structure do affect how it behaves. At some speeds, with some wing geometries, they might perhaps help with either vibration or lift or drag.

5. It's a complex mix of angle of attack of the wing vs motion of the aircraft, the cross-section of the wing itself and the speed the airplane is moving (what works well at sub-mach works poorly when you break the sound barrier, and a pilot can do quite a bit to affect the drag on his wing by varying the position of the aircraft relative to its motion or by shifting controls ("air brakes", similar) to change the geometry of the wing itself in flight.

[bonguboy]

Thank you!