|
|
|
Bernoulli's Principle of Pressure
Daniel Bernoulli* studied the flow of fluids (liquid or gas) as it reaches a region where
the pipe diameter is reduced. Bernoulli stated that the velocity of a fluid, as it flows
through the narrowest diameter is increased and that the pressure in that region is
decreased.
A practical application of Bernoulli's Theorem is the Venturi Tube. A Venturi tube
consists of a tube which narrows to a throat (reduced diameter). The airflow at the throat
is increased while the pressure is decreased.
|
The temperature at the throat is also reduced,
however this phenomenon is not related to the Bernoulli principle. The relationship between
pressure and temperature is defined by Boyle's** law. Boyle's law states that the volume of
a gas is inversely proportional to it pressure at a constant temperature. The expansion of
fluid as it passes the throat causes a temperature decrease.
A simple way to demonstrate the Bernoulli's principle is illustrated in the figure below. The
experiment clearly proves Bernoulli's principle and shows how a pressure differential
generates lift.
Bernoulli's principle demonstration. (a) A person
holds two curved sheets of paper The pressure between the sheets in (b) is lower than the
surrounding pressure causing the sheets to get closer. (c) The same result is obtained by
using a single sheet. The pressure above the sheet in (d) is lower than the pressure below,
thus causing the sheet to lift.
*Daniel Bernoulli (1700-1782), a Swiss Mathematician and Physician.
**Robert Boyle (1627-1691)
Return to Principles of Flight
Return to pilotsweb.com
Last update May 17, 2005
Copyright © pilotsweb.com All Rights Reserved
