## What is Fluid? Types of Fluid? How does fluid flow? Types of flow? Laminar | Turbulent | Compressible | Incompressible

Last updated on March 20th, 2023 at 11:59 am

## What is fluid?

Anything which can flow is called fluid like liquids and gas because of its weak intermolecular forces.

**What are Static and Dynamic fluid?**

**Static fluid:** A fluid at rest is known as static fluid, it has no shear stress.

**Dynamic fluid:**** **A fluid that is in motion is known as dynamic fluid.

Example: Take a glass of water when the water in the glass is not moving, it is a static fluid. When you move the glass in a circular motion the water inside it starts moving or rotating. It is a dynamic fluid. River is an example of dynamic fluid. A pond is settled water that is a static fluid.

**How does a fluid flow?**

Fluid flows due to two reasons:

- Difference between pressure
- Difference between potential energy

**Types of flow**

- Steady and unsteady flow
- 1D, 2D, 3D flow
- Laminar and turbulent flow
- Uniform and non-uniform flow
- Compressible and incompressible flow

**1. Steady and unsteady flow: **

Steady flow is defined as the type of flow in which fluid characteristics like velocity, pressure, density, etc. at a point do not change with time.

Unsteady flow is a type of flow in which the velocity, pressure, and density at a point change with time.

**2. 1D, 2D, 3D flow**

1D flow is a type of flow in which the flow parameter such as velocity is a function of one space coordinate only. The variation of velocities in the other two mutually perpendicular directions is assumed negligible.

2D flow is a type of flow in which velocity is a function of two space coordinates only. The variation of velocity in the third direction is negligible.

3D flow is the type of flow in which velocity is a function of three mutually perpendicular directions.

**3. Laminar and turbulent flow:**

A flow of fluid where each particle of fluid follows a smooth path, paths which never interfere with one another, and the velocity of the fluid is constant at any point in the fluid is called laminar flow.

Turbulent flow is an irregular flow where the velocity of a fluid is not constant at every point. In the case of turbulent flow liquid flowing in the pipe has no fixed speed or direction.

**4. Uniform and non-uniform flow**

Uniform flow is defined as the type of flow in which the velocity at any given time has the same magnitude and direction. Non-uniform flow is the type of flow in which velocity changes from time to time at any given instant of time.

**5. Compressible and incompressible flow**

Compressible flow is the type of flow in which the density of the fluid changes from point to point. In other words, density is not constant like in gases. Incompressible flow is the type of flow in which the density does not change from point to point. In other words, density is constant, Generally, liquids are incompressible.