Bernoulli’s Principle in Aviation

Mr Daniel Bernoulli, a Swiss mathematician explained the how pressure of a fluid varies with speed of motion. In simple terms he said that in as the velocity of a fluid increases the pressure exerted by the fluid decreases. The best and most common example of Bernoulli’s principle is: if you put your thumb in front of a garden hose, you will notice that only the velocity of the water coming out, has increased but the pressure will reduce. Do remember its important to understand where is the pressure reduction happening.Lets go deeper into this subject, but before that we need to understand some basics.

First, what is a fluid? In this case we are considering Air as a fluid, we are also assuming it to be incompressible and it behaves as a so-called ideal fluid. Bernoulli’s principle showed that in a streamline flow for an ideal fluid the total energy (or pressure) remains a constant. Now, a fluid in motion has two types of energy:

1. static pressure energy

2. dynamic pressure energy (this can be related to kinetic energy)

Static pressure at any point in a fluid very simply is the pressure acting equally in all directions. The kinetic energy of a parcel of air in motion relative to an object allows it to exert a force on the object.This force when calculated per unit surface area is called Dynamic pressure. We know,

kinetic energy = 1/2 x mass x square of velocity

and dynamic pressure is equal to kinetic pressure, but mass equates to air density,

therefore , Dynamic pressure = 1/2 x rho x square of velocity.

where q = dynamic pressure, rho = air density and v = velocity

These forms of energy can change from one form to another but the total energy remains the same. Its denoted by :

Pressure energy(Static pressure) + Kinetic energy (Dynamic pressure) = Constant Total Energy

So, if you increase dynamic pressure then, static should reduce.

This very principle is important because have you ever wondered why the aircraft’s wing is curved? and in that very shape? Its for this basic principle.Bernoulli’s principle showed whats and whys that causes a plane to fly.Do remember what to take from all this, you need to know Bernoulli’s basic principle and what we explained there after.