# Types of Fluid Flow in Fluid Mechanics

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Types of Fluid Flow are the detailed categorization of various fluid flows that exist in nature. In this, we define fluid flow on various properties such as velocity change, pressure drop, density variation, routes, etc. Fluid Flow is a branch of fluid mechanics that deals with fluids. It involves the movement of fluid under the influence of unequal forces. As long as unbalanced forces are applied, this motion will persist. There are six different types of fluid flow in Fluid Mechanics.

Before we get into the specifics of the various types of flow in fluid mechanics, it’s important first to understand fluid. A fluid is a liquid, gas, or other material that constantly deforms (flows) due to applied shear stress or external force. They have a zero shear modulus, or in other words, they can’t resist any shear stress. Although the term fluid encompasses both the liquid and gas phases, its definition differs depending on the field of study. Let us now discuss the different types of fluid flow in Fluid Mechanics.

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## What is Fluid Flow?

Fluid Flow is a part of fluid mechanics that deals with the dynamics of fluids. The motion of a fluid subjected to imbalanced forces is the subject of this phenomenon. As long as unbalanced pressures are applied, this motion will continue. Let’s take a closer look at the various types of fluid flow.

There are five types of fluids that have been identified: Ideal fluid, Real fluid, Newtonian fluid, Non-Newtonian fluid, and Ideal plastic fluid. Fluid analysis can be done in two ways.

• Lagrangian Approach: In this method, a single fluid particle is selected, and its behavior is examined in several areas (with respect to space).
• Eulerian Approach: This method involves taking a segment of space and analyzing the behavior of fluid particles traveling through it at a different time. This method is mostly used in Fluid Mechanics [With Regard to Time].

## What are the Types of Fluid Flow?

Liquids, gases, and plasmas are examples of fluids that are one of the phases of matter. Fluids, according to one scientific definition, are substances with zero shear modulus or, to put it another way, substances that cannot resist the shear force applied to them.

The six different types of fluid flow are:

• Uniform and Non-Uniform
• Laminar and Turbulent
• Compressible and In-compressible
• Rotational and Irrotational
• One, Two, and Three -dimensional Fluid Flow

The term steady flow refers to a flow in which the fluid characteristics at a given point, such as velocity, pressure, density, and so on, do not fluctuate over time.

(δV/δT)x0,y0,z0= 0,(δP/δT)x0,y0,z0= 0,(δρ/δT)x0,y0,z0= 0

Unsteady flow is defined as a flow in which the fluid parameters at a given point change with time, such as velocity, density, and pressure.

(δV/δT)x0,y0,z0≠0,(δρ/δT)x0,y0,z0≠0

### Uniform and Non-uniform Fluid Flow

This uniform fluid flow is described as a flow in which the velocity does not change about space at any given moment (i.e., length of the flow’s direction).

(δV/δs)t=constant= 0

Non-uniform types of fluid flow are described as a type of fluid flow in which the velocity fluctuates about space at any given time (i.e., length of the flow’s direction).

(δV/δs)t=constant≠ 0

### Laminar and Turbulent Fluid Flow

Fluid particles move along well-defined routes or straight and parallel streamlines in this form of fluid flow. As a result, the particles move in laminas or layers, smoothly gliding over the next layer. This type of fluid flow is also known as viscous flow or streamline flow.

Turbulent fluid flow is defined as a flow in which the fluid particles travel in a zig-zag manner, forming eddies and wasting a lot of energy. The Reynolds number (VD/ν) is a non-dimensional number that determines the type of fluid flow in a pipe.

• Laminar flow occurs when the Reynold Number is less than 2000.
• When the Reynolds Number exceeds 4000, the flow is described as turbulent.
• The flow might be laminar or turbulent if the Reynolds Number is between 2000 and 4000.

### Compressible and Incompressible Fluid Flow

Compressible fluid flow is described as a flow in which the fluid density does not remain constant from one place to another.

ρ ≠ constant

Whereas incompressible types of fluid flow are described as a flow with a constant density, which means that the density of the fluid does not change from point to point.

ρ = constant

The fluid flow of gases is compressible, whereas the fluid flow of liquids is incompressible.

### Rotational and Irrotational Fluid Flow

Rotational fluid flow is a type of fluid flow in which the fluid particles spin about their axis while flowing along a streamline.

On the other hand, irrotational fluid flow is defined as a form of fluid flow in which the fluid particles do not rotate on their own axis while traveling along a streamline.

### One, Two, and Three-dimensional Fluid Flow

One-dimensional flow is when the flow parameter, such as velocity, is a function of time and only one space coordinate, say x.

u=f(x), v=0 and w=0

The x,y, and z velocity components are u,v, and w, respectively.

The velocity of a two-dimensional fluid flow is a function of time and two rectangular space coordinates, such as x and y.

u= f1(x,y,), v= f2(x,y,) and w= 0.

Three-dimensional fluid flow is a form of fluid flow in which velocity is a function of time and three mutually perpendicular directions. The function of 3 space coordinates (x,y,z).

u= f1(x,y,z), v= f2(x,y,z) and w= f3(x,y,z).

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