# Types of fluid flow – Fluid Mechanics

**Based on different conditions, fluid flow is divided into following types :-****1) Steady and Unsteady Flow:****i) Steady Flow:**

A flow is said to be steady flow if different fluid properties and fluid velocity does not change with respect to time.

If R is the set of fluid properties and V is the set of fluid particles, then for a steady flow.

**ii) Unsteady Flow:**

A flow is said to be unsteady flow if different fluid properties and fluid velocity changes with respect to time.

For unsteady flow,

dR/dt **≠** 0 and dV/dt **≠** 0

**2) Uniform and non-uniform flow:****i) Uniform flow:**

In this type of flow, different fluid poperties and fluid velocity does not varies with respect to space (or directions).

Eg:- Constant discharge through a constant diameter pipe.

**ii) Non-uniform flow:**

In this type of flow, different fluid poperties and fluid velocity varies with respect to space (or directions).

Eg:- Constant discharge through a variable diameter pipe.

**3) Steady and Uniform Flow:**

In steady and Uniform flow, the fluid properties as well as the fluid velocity neither changes with respect to time nor changes with respect to space ( or direction).**4) Compressible and Incompressible flow:****i) Compressible Flow:**

The flow in which density of fluid varies with respect to change in pressure is called **Compressible flow**.**ii) Incompressible Flow:**

The flow in which density of fluid does not varies with respect to change in pressure is called **Incompressible flow**.**5) One, two and three dimensional flow:****i) One dimesnsional flow:**

In this type of flow the fluid flows only in one dimension (either x,y or z ).**ii) Two dimensional flow:**

In two dimensional flow, the fluid flows only in any of the two

dimension ( either xy,yx or xz).**iii) Three dimensional flow:**

In this type of flow, the fluid flows in all of the three

dimension (x,y and z).**6) Natural and Forced Flow:****i) Natural Flow:**

In natural flow, fluid flows due to natural means like gravity, buoyancy etc. It is also known as **unforced flow**.**ii) Forced Flow:**

The flow in which fluid flows with the help some external unnatural power like pump or fan is known as **forced flow**.**7) Laminar and Turbulent flow:****i) Laminar flow:**

In a laminar flow, the flow of fluid is smooth and highly ordered. In this flow, the fluid layers move parallel to each other and do not cross each other.**ii) Turbulent flow:**

In a turbulent flow, the flow of fluid is chaotic and not in any order. In this flow, the fluid layers cross each other and do not move parallel to each other.

Image Source :https://www.mechanicalbooster.com/2016/08/difference-between-laminar-and-turbulent-flow.html

**8) Internal and External Flow:****i) Internal flow:**

When the fluid flows inside a closed surface like pipe or duct, it is called an **internal flow.****ii) External flow:**

when does not flow inside any closed surface or flows on the outer surface of body then it is called **external flow.****9) Viscous and Inviscid flow:****i) Viscous flow:**

The flow in which the resistance provided by viscosity is considerable is known as **Viscous Flow**. In this type of flow, the frictional effects are significant.**ii) Inviscid or Non – Viscous Flow:**

The flow in which the resistance provided by viscocity is negligible is known as **Inviscid or Non- Viscous Flow**.

In this type of flow, the frictional effects are not significant.