Fluids are affluences that have the potential of flowing and undergo alterations in their shape when exposed to pressure. They incorporate liquids, gases, and some plastic solids. Just to say, owing to their capability to flow from one particular location to another, and also their non-rigid nature, the research of fluid properties has usually been far more demanding than rigid solids. Nevertheless, it’s this deformability, and fluid nature that has created several excellent advances in science achievable. The pumping of oil and water, their conveyance by piping, the advancement of the internalized combustion engine, and also modern day aviation technological innovation, all owe their actuality in one way or the other to the fluid properties’ exploitation.

Fluids can be efficiently transported via channels and pipes. In this kind of conveyance, pressure plays a quite important role. With modification of pressure, fluids can’t only be relocated from one place to another, but can be exploited to operate for us. It was found that even changing the diameter of a given pipe can have an impact on the pressure of the fluid flowing via it. Let’s look into this venture effect.

When a liquid or gas moving through a pipe encounters a constriction of the pipe, velocity of flow escalations at the constriction, with an equivalent drop in static pressure. This principle is known as the Venturi effect. With reference to Bernoulli’s principle, ‘fluid velocity is inversely proportional to its static pressure’. This implies that, when the fluid velocity increases, its pressure decreases. The Venturi effect is an edition of Bernoulli’s principle, but much more particularly suited to the fluids’ flow through a pipe.

When a liquid or gas flowing via a pipe is subjected to a constriction, it implies that the surface area at that stage has decreased, leading to a smaller sized opening. Nevertheless, the fluid’s flow rate can’t decrease, in accordance to the ‘Principle of Continuity’, the rate of mass flow into an isolated system, as well as out flow, stays constant. In order to sustain identical rate of flow, the molecules of the fluid rush out at a higher velocity through the constriction, in order to cover an identical distance in the same span. This to an increase in the velocity of flow. The fluid’s kinetic energy is:

KE = ½ × *p* × v^{2}

Where, *p* is the fluid’s mass density, and v is its flow velocity. Clearly, as the fluid velocity increases at the constriction, the kinetic energy increases. But, as learnt in our A Level Physics tuition class on Conservation of Energy Law, ‘energy can neither be created nor destroyed’. This implies that the entire energy has to stay constant. Therefore, as the fluid’s kinetic energy increases, its pressure proportionally decreases, such that the total energy remains constant.