Daniel Bernoulli (8 February 1700 – 17 March 1782) was one of the many prominent mathematicians in the Bernoulli family.
He discovered several essential theory in the fields on physic, mathematics & calculus.
Bernoulli Force/Effect/Principle/Law: (bɛrnuji)
n
1. Physics. The principle that in a liquid flowing through a pipe, the pressure difference that accelerates the flow when the bore changes is equal to the product of half the density times the change of the square of the speed, provided friction is negligible.
2. The effect of a change in air pressure depending on the state & position of the vocal folds.
3. The Bernoulli Effect also comes in to play in sailing & aeronautics due the differences in air pressure in front/behind the sail or under/over the wing.
The following is quoted from Johan Sundberg’s ‘The Science of the Singing Voice’ Published 1987 by Northern Illinois University Press.
“When an air stream is forced through a sufficiently narrow glottis, the vocal folds start to vibrate. In this process, the so-called Bernoulli force plays an important role. The Bernoulli force is activated when an object prevents a flowing substance, such as air, from streaming freely, so that certain layers of the stream have to travel a longer distance than the rest of the stream. Under these conditions the velocity is greater in that layer, which is forced to travel the longer way than in the freely streaming part. Such a difference between the layers’ velocities generate an under-pressure, which is greatest in a direction perpendicular to the direction of the freely traveling stream. In the glottis, the middle later of the air stream goes undisturbed through the slit. The lateral layers of the air stream are deflected by the vocal folds, so that they have to travel a longer distance than the middle later. Thus, the condition for generating the Bernoulli force is met, and hence an under-pressure results along the vocal folds. This under-pressure strives to move the vocal fold tissues toward the midline of the glottis slit. This is equivalent to saying that the Bernoulli force strives to close the glottis as soon a there is a transglottal air stream.”