We explain how the rotation of a boomerang generates non-uniform lift causing precession making it return after traveling a long distance.
A Boomerang Acts Like a Wing
Shortcut to Action of a Wing
Sideview of velocity and pressure, and topview of streamwise vorticity of Naca0012 wing at aoa = 14. Observe the turbulent streamwise vorticity emanating from separation instability. Computed solution of the Navier-Stokes equations with slip boundary condition . It is possible that the rims (and holes of some frisbees) of a frisbee trigger transition to turbulence in the boundary layer and thus improves
the flight.Principle of action of a wing: Potential flow (upper left) with zero lift/drag modified by low-pressure counter-rotating rolls of streamwise vorticity from instability mechanism at separation (upper right), switching the pressure on rear wing (bottom left ) to give both lift and drag (H high, L low pressure). Viscous flow separating at the crest with low lift and large drag (bottom right).
Action of a Boomerang
The following figure is taken from the educational site Hyperphysics and describes how for a
- the wing shape generates lift from rotation and forward motion
- the spin combined with torque from non-uniform lift causes a drift to the left (if thrown with the curved side to the left).
Misconceptions and Confusion
- Popular Mechanics on LIFT: Air passing over the curved top of a boomerang’s airfoil — at the leading edge of the wing — is forced to go faster than air passing over the relatively flat underside. As described by Bernoulli’s principle, this generates less pressure above the wing, creating upward lift.
- Popular Mechanics: Eric Darnell, a soft-spoken 62-year-old Quaker and backyard inventor from South Stafford, has coached three U.S. boomerang teams and explains with a blizzard of information about airfoil shapes, Reynolds numbers, local atmospheric conditions, wind shear and the effects of drag: “One of the things that is near and dear to my heart about boomerangs is that there’s still some magic involved. You can’t completely computerize them. I’ve seen computer-designed boomerangs, and they’re junk… it’s not in textbooks about airfoils.”
- Boomerangs.com:The question, what kind of mechanisms convert the drag force into the lift one, still remains under discussion.
- Sports Science:The air moves faster over the upper surface than the air moving over the lower surface. This means that a pressure differential exists between the lower and upper surface which translates into lift.
- Research Support Technologies: Air stream “sticks” to surface and bends down the near upper surface of the wing not due to Pillow phenomenon but due to Coanda effect.