Fluid Physics Definition Equation Applications Bernoulli’s Formula


A fluid is a material that flows or is continuously deformed under shear (tangential stress). In other words, the fluid has zero shear modulus. A fluid is a biological material that flows across the surface. 

Liquids, Gases and Plasma Fluids. However, some solids also behave as liquids. For example, the pitch is a (very) slow-flowing high, viscosity solid. Silly putty flows but freezes with sudden force. Solids are not generally liquids because they resist tangential stress and deform only until they reach static equilibrium.

Fluid Physics

In biology, fluid means the physics definition but also refers to body fluids such as blood, plasma, and urine. In this context, fluids such as saline solution and juice are also given to replace body fluids.

Types of fluids

Liquids can be classified as:

Ideal fluid is a fluid that is in-compressible, & has no viscosity is called an ideal fluid. An ideal fluid is just an imaginary fluid because all fluids have some viscosity.

  1. A real liquid:

A fluid with viscosity is called a genuine fluid. All liquids are, in practice, actual liquids. Example: water, air etc.

  1. A Newtonian fluid:

A Newtonian fluid is called an accurate fluid in which the shear strain or velocity gradient is directly proportional.

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Example: Benzine, Water etc.

  1. Non-Newtonian Fluid:

A real fluid whose shear strain or velocity gradient is not directly proportional to the rate is called a non-Newtonian fluid.

Example: Plaster, slurries, pastes etc.

  1. An ideal plastic fluid is:

An ideal plastic fluid is a fluid whose shear stress is greater than the yield value and where the stress is directly proportional to the strain rate or velocity gradient.

  1. Insoluble liquid:

A fluid whose density does not change under external force or pressure is called an incompressible fluid. All liquids are considered in this category.

  1. Compressed Fluid:

A fluid whose density changes when an external force or pressure changes is called a compressible fluid. All gases are considered in this category.

fluid dynamics equations

Tabular representation of fluid types:

Types of fluidDensityViscosity
Ideal fluidConstantZero
Real fluidVariableNon zero
Newtonian fluidConstant/ VariableT = u(du/dy)
Non-Newtonian fluidConstant/ VariableT ≠
Incompressible fluidConstantNon-zero/zero
Compressible fluidVariableNon-zero/zero

Fluid Physics:

  • Fluid Physics is a highly empirical physics that deals with fixed and moving bodies affected by forces.
  • Fluid physics may be defined as the branch of engineering science that mainly deals with fluids’ behavior under conditions of rest and motion.
  • This includes liquids, gases, plasmas and, to some extent, plastic solids.

fluid dynamics vs fluid mechanics

· They may be divided into three parts:

  1. Statics 2. Kinematics 3. Dynamics

1. Statics

Hydrostatics studies compressible fluids under static conditions, and dealing with compressible fixed gases is called aerostatics.

2. Kinetics

It also handles instances of velocity, incremental velocities, and stream.

3. Dynamics

It deals with the relationships between velocities, forces and acceleration of fluids or the forces that cause them.


This article has gone through the fundamentals of fluids, their types, and fluid physics. Fluid physics is the branch of engineering science that applies the laws of force and motion to fluids, like liquids and gases.


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