9 types of fluids

Fluid is a substance that does not have a definite shape and yields easily to external pressure. It continually flows or deforms when it is subjected to shear stress or external force. Gases, liquids, and plasmas can be included in fluids. Fluids are widely used in industries, kitchens, our bodies, in the atmosphere, etc. Based on the properties of the fluid-like viscosity, and density, fluids can be of many types. In this article, we discuss the 9 types of fluids.

Types of fluid:

  1. Ideal fluid
  2. Ideal plastic fluid
  3. Real fluid
  4. Newtonian fluid
  5. Non-newtonian fluid
  6. Time dependant fluid
  7. Time independent fluid
  8. In compressible fluid
  9. Compressible fluid

Ideal fluid:

  • It is incompressible and is an imaginary fluid that does not exist in reality.
  • It does not have viscosity.
  • Density is constant and viscosity is zero.

Ideal plastic fluid:

  • When shear stress is proportional to velocity gradient and more than yield value and thus fluid is said to be ideal plastic fluid.

Real fluid:

  • Fluids that have viscosity are real fluids.
  • Density is variable and viscosity is non-zero.

Newtonian fluid:

  • The fluid which obeys newton’s law of viscosity is called a Newtonian fluid.
  • Density is constant /variable and viscosity is T=u(du/day)
  • Don’t have elastic properties.
  • They are isotropic and unreal.
  • Viscosity is temperature dependant and depends on various pressures.
  • When an increase in temperature of fluid viscosity decreases.
  • It was named after Sir Issac newton who defines viscous flow.
Glycerol – example of a Newtonian fluid
Danny S., CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Non-Newtonian fluid:

  • The fluid which does not obey newton’s law of viscosity is called a non-Newtonian fluid.
  • Density is constant/variable.
Paint-example of a Newtonian fluid

Time-dependent fluid:

  • The shear stress or viscosity decreases with time because of isothermal conditions and steady shear which is known as thixotropic.
  • And which increases with time under the same circumstances they are known as rheopectic or anti-thixotropic.

Time-independent fluids:

  • The rate of shear at a given point depends on instantaneous shear stress at that point and is also known as non-Newtonian viscous fluids.

They are further divided into two types:

      Fluids with yield stress.

      Fluid without yield stress 

Incompressible fluid:

  • When the density of fluid remains invariant with an application of the external force it is known as an incompressible fluid.

Compressible fluid:

  • When the density of fluid varies with an application of the external forces it is known as compressible fluid.

See Also