Fluid

Substance that continually deforms under an applied shear stress

For other uses, see Fluid (disambiguation).

A fluid is a substance that continually deforms (flows) under an applied shear stress, or external force. Fluids are a subset of the phases of matter and include liquids, gases, plasmas, and, to some extent, plastic solids. Fluids are characterized by their ability to flow and conform to the shape of their containers.

Properties

Fluids exhibit properties such as viscosity, density, and pressure. These properties are essential in understanding fluid behavior and are fundamental in the study of fluid dynamics and fluid statics.

Viscosity

Viscosity is a measure of a fluid's resistance to deformation at a given rate. It describes the internal friction of a moving fluid. A fluid with high viscosity, such as honey, resists motion because its molecular makeup gives it a lot of internal friction. A fluid with low viscosity, such as water, flows easily because its molecular makeup results in very little friction when it is in motion.

Density

Density is the mass per unit volume of a fluid. It is an important property in fluid dynamics as it affects buoyancy, pressure, and flow characteristics. The density of a fluid can change with temperature and pressure.

Pressure

Pressure is the force exerted by a fluid per unit area. It is a crucial concept in fluid statics and dynamics. Pressure in a fluid at rest is isotropic, meaning it acts equally in all directions. In a moving fluid, pressure can vary in different directions.

Types of Fluids

Fluids can be classified into several types based on their properties and behavior under different conditions.

Newtonian Fluids

Newtonian fluids have a constant viscosity that does not change with the rate of deformation or shear rate. Examples include water and air.

Non-Newtonian Fluids

Non-Newtonian fluids have a viscosity that changes with the rate of deformation or shear rate. Examples include ketchup, toothpaste, and blood.

Ideal Fluids

An ideal fluid is a theoretical fluid that is incompressible and has no viscosity. Ideal fluids are used in many theoretical models to simplify the analysis of fluid flow.

Real Fluids

Real fluids have viscosity and are compressible to some extent. All actual fluids are real fluids, and their behavior is more complex than ideal fluids.

Applications

Fluids play a crucial role in various fields such as engineering, medicine, meteorology, and oceanography. Understanding fluid behavior is essential for designing systems like pumps, turbines, aircraft, and ships.

See also

• Fluid dynamics
• Fluid statics
• Hydraulics
• Pneumatics
• Rheology
• Continuum mechanics

Related pages

• Viscosity
• Density
• Pressure
• Newtonian fluid
• Non-Newtonian fluid
• Ideal fluid
• Real fluid