Additional Info

• ID Code: F5-11
• Purpose: Illustrate the pressure difference across an airplane wing.
• Description: A blower creates air flow past the airfoil, which can be rotated. The difference in pressure between the top and the bottom surfaces of the wing is indicated by the manometer, a water-filled tube in which the displacement of the water indicates the pressure differential.
  This is an excellent way to challenge students to think about the forces involved in lift and drag on an aircraft, and how an airfoil keeps a plane in the air.

  The nature of the actual lifting force on a real airplane wing is complex. See the Demonstration Reference File for several papers which discuss this problem. One can argue that the Bernoulli effect creates a pressure difference between the top and the bottom of the airplane wing. However, this pressure difference, in the absence of air deflection downward cannot explain the lift required to keep the airplane up in the air. According to Newton's third law, there must be deflection of the air downward due to either or both: deflection of the air due to the angle of attack of the wing, and shedding of vortices at the trailing edge of the wing.

  An alternative explanation of airplane wing lift involves the Coanda effect and downward deflection of the air passing over the wing. According to the Coanda effect, the air flow follows the contour of the wing, ultimately moving at an angle downward from the rear of the wing. The reaction force acting on the wing provides the wing lift.

• Availability: Available
• References: REFERENCES: (PIRA 2C20.50)