Fluid flow can be observed in the flow of gases in pipes, in the Universe, flow of air around the wings of an aircraft, etc. and flow of liquids in pipes, the ocean, flow of blood in blood vessels, etc. and can be studied under various categories like Aerodynamics and Hydrodynamics. Usually these fluids flow inside or around a solid surface and both exert pressure on each other thus making it important to study the flow under the influence of these forces. And when forces are involved, the law of conservation of linear momentum, law of conservation of mass and law of conservation of energy can be applied to study the behaviour of the fluids.
Properties of the fluid in relation to time and space can be studied to know how they behave under certain circumstances. This knowledge about the behaviour of fluids can be applied in various fields to design and develop systems involving fluids. However, the behaviour of fluids depends on the characteristics of the fluid, the speed of the fluid and the shape of the solid surface in or around which it flows.
The three characteristics of the fluid like the viscosity, density and compressibility are important to study fluid behaviour. ...