Re: Re: Re: Re: Re: Re: Re: Air


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Posted by Tabor Fisher on January 13, 2003 at 19:01:54:

In Reply to: Re: Re: Re: Re: Re: Re: Air posted by Brian Frederiksen on January 13, 2003 at 08:24:46:

Brian,

This venturi effect sounds like it creates a vaccum...much like the Bernoulli effect I studied in vocal pedagogy class. They seem to be related principles.


THE BERNOULLI EFFECT (for singing)

Bernoulli's aerodynamic law: TE = d x *(v2p) = C where TE = total energy in a system, d = density, v = velocity, p = pressure of the fluid and C is a
constant. The law states that if the vlocity of fluid flow increases, the pressure drops and vice versa. The Bernoulli effect explains the fact that when fluid
(including gases such as air) flows through a narrow constriction, the velocity of the the flow increases and the pressure of the fluid drops.

This assumes (correctly!) that the total amount of energy (TE) in a system is constant and is equal to kinetic energy (KE) and potential energy (PE);
(TE = PE +KE = C). Therefore, when KE (velocity) increases as when fluid passes through a constriction, PE (pressure) must drop.

Example: Assume, in one end of a cylinder, A1 (area of opening) is 2 m2 and V1 (velocity of air) is 5m/sec and therefore, U1 (volume velocity) is 10
m3/sec. If in the other end of the cylinder, A2 is 1 m2 and U2 is 10 m3/sec, then V2 must be 10 m/sec. The pressure, therefore, must reduce to
compensate for increased velocity. The pressure drop creates a partial vaccum which, in turn, causes vocal folds to be sucked in at the midline.

this is the same principle which creates lift for airplanes.





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