Wednesday, 18 June 2014 10:56

## F5-03: THIN METAL SHEETS - COANDA EFFECT

• ID Code: F5-03
• Purpose: Demonstrate a fluid-flow model of the vocal folds.
• Description: Blow down between the thin sheets. Air follows the curve of the sheets, according to the Coanda effect. The reaction force on the sheets pulls them together. When the sheets close, air pressure builds up, opening them and restarting the periodic cycle. We use an air gun for this demonstration so that we can keep the geometry uniform; it is easier during a lecture for the demonstrator to simply blow his or her breath into the region between the plates. This demonstration is often incorrectly explained using the Bernoulli principle. According to the INCORRECT explanation, the air flow is faster in the region between the sheets, thus creating a lower pressure compared with the quiet air on the outside of the sheets. This lower pressure causes the sheets to come together, whence the pressure builds up, forcing them apart, etc.

This is demonstrably incorrect, as can be seen in the videos below, where one of the sheets is held away from the other and the air stream directed as in the above video. Note that the remaining sheet that is hanging moves toward the center even in the absence of the other sheet, so it does not form a narrow constriction. What is happening here is that the air moves along the surface of the sheet, according to the Coanda effect, leaving in a direction away from the center line of the two sheets. The reaction force on the sheet causes it to move toward the center line of the two hanging sheets. Click your mouse on the photographs below to see these two demonstrations of the Coanda effect.

• Availability: Available
• #### F5-01: TOY CAR AND BALL - COANDA EFFECT

Demonstrate levitation of a ball in a cute way. Read More
• #### F5-02: BALL ABOVE MOVING CART - COANDA EFFECT

Demonstrate levitation of a ball by an air stream. Read More
• #### F5-03: THIN METAL SHEETS - COANDA EFFECT

Demonstrate a fluid-flow model of the vocal folds. Read More
• #### F5-04: LARGE BALL AND FUNNEL - COANDA EFFECT

Illustrate the Coanda effect in a dramatic way. Read More
• #### F5-05: SMALL BALL AND FUNNEL - COANDA EFFECT

Illustrate the Coanda effect in a dramatic way. Read More
• #### F5-06 BEACH BALL - COANDA EFFECT

Illustrates the Coanda effect Read More
• #### F5-07: SPOOL AND CARDBOARD

Illustrate properties of fluid flow in a counterintuitive way. Read More
• #### F5-08: MARBLE IN WATER JET

Demonstrate levitation by a water stream. Read More
• #### F5-09 HAIRDRYER AND PING PONG BALL - COANDA EFFECT

Demonstrate levitation by an air stream. Read More
• #### F5-10: CHIMNEY DRAW WITH WATER

Illustrate the concept of chimney draw. Read More
• #### F5-11: AIRPLANE WING

Illustrate the pressure difference across an airplane wing. Read More
• #### F5-21 VENTURI TUBE WITH MANOMETERS

Illustrates the venturi effect Read More
• #### F5-22 VENTURI TUBE WITH PING PONG BALLS

Illustrates the venturi effect Read More
• #### F5-24: VENTURI TUBE WITH WATER - MANOMETERS

Illustrate the Venturi effect in water. Read More
• #### F5-31: MAGNUS EFFECT - FLETTNER'S SHIP

Demonstrate the Magnus effect. Read More
• #### F5-32: CURVE BALL

Demonstrate a curve ball as an example of the Magnus effect Read More