Machines Theory

Understanding the different types of fluid flow

Previously I explained fluid mechanics where I stated that fluid dynamics is one of its branches, it deals with a fluid flow. This means it involves the motion of a fluid subjected to unbalanced forces. This motion continues as long as the unbalanced forces are exerted. Well, that is not our purpose here.

types of fluid flow


Today you’ll get to know the different types of fluid flow since the fluid itself can be classified into different types depending on the variation of the fluid characteristics such as velocity, density, etc. The analysis method varies in fluid mechanics, depending on the type of flow. Let get into our topic of discussion, different types of fluid flow. You’ll also get to know the different types of fluid.

Read more: Understanding fluid mechanics


Different types of fluid flow

Steady and Unsteady flow:

A flow is said to be steady when its fluid characteristics such as density, velocity, and pressure at a point do not change with time. It can be mathematically expressed as:

Where V is the velocity of the fluid

P is the pressure of the fluid, and

J is the density of the fluid.

A flow can also be known to be unsteady when the fluid characteristics like velocity, pressure, and density at a point change with respect to time. It is mathematically expressed as:

Diagram of steady and unsteady flow in fluid mechanics:

steady and unsteady fluid flow

Uniform and Non-uniform flow:

The uniform flow is a type of fluid flow in which the velocity of the flow at a given time does not change with respect to space (along the length direction of the flow). It can also mathematically express as:

On the other hand, non-uniform flow is a type of fluid flow in which its flow velocity at a given time changes with respect to space. Mathematically, a non-uniform flow can be expressed as:

Diagram of a uniform and non-uniform flow:

uniform and non-uniform flow

Read more: Difference between dynamic and positive displacement pump

Laminar and turbulent flow

Laminar types of fluid flow are flow in which their fluid particles move along a well-defined streamline or paths. This happens in a way all the streamlines are straight and parallel to each other. In this type of flow, fluid particles are said to move in laminas. The layers in laminar flow glide smoothly over the adjacent layer. The flow is said to be laminar when the Reynolds number is more than 4000.

Nevertheless, turbulent flow is a type of flow in which the fluid particles move in a zig-zag manner. This zig-zag movement forms high turbulence and eddies, leading to high energy loss. The flow is turbulent when the Reynolds number is also greater than 4000. Well, a fluid flow in a pipe that has a Reynolds number between 2000 and 4000 is said to be in a transition state. Now you can see laminar and turbulent flow in pipe flow is characterized base on Reynold number.

Diagram of laminar and turbulent flow:

laminar and turbulent flow

Compressible and incompressible flows

In a compressible flow, its fluid density changes from one point to another point. That is, density is not constant. For instance, J not constant.

On the other hand, incompressible flow is a type of flow in which the density of the fluid is constant from a point to another. i.e., liquids are generally incompressible and gases are compressible. J=constant. Where J is the density of the fluid.

Rotational and irrotational flows

A rotational flow is a type of flow in which the fluid particles rotate about their own axis while flowing along the streamlines. Irrotational flow occurs if the fluid particles do not rotate while flowing along the streamline about their own axis. Finally,

One-, two-, and three-dimensional flows

One dimensional fluid flow is a type of fluid flow in which its flow parameter like velocity is expressed as a function of time and one space coordinates. It can be express as,

u = f (x, y), v=0; w=0;

The velocity along y and z directions i.e., v and w are considered negligible.

Secondly, two-dimensional flow is a flow in which the velocity is a function of time and two rectangular space coordinates. It is considered to be negligible when the velocity flow along the third direction. That is,

u = f (x, y); v = g (x, y); w = 0;

Finally, three-dimensional flow is a kind of fluid flow in which the velocity is a function of time and three mutually perpendicular rectangular space coordinates (x, y, and z).  that is,

u = f (x, y, z); v = g (x, y, z); w = h (x, y, z)

Read more:  Difference between the centrifugal and reciprocating pump

Watch the video below to learn about the fluid flow in fluid mechanics

now let this opportunity discuss the various types of fluid.

Types of fluids

fluid types

Below are the various types of fluid:

Ideal fluid – these types of fluid cannot be compressed and its viscosity does not fall in the category of an ideal fluid. It is said to be imaginary, that is, the fluid doesn’t exist in reality.

Real fluid – these fluids are real because they possess viscosity.

Newtonian fluid – this is when a fluid obeys Newton’s law of viscosity.

Non-Newtonian fluid – when fluid does not obey Newton’s law of viscosity.

Ideal plastic fluid – these types of fluid are known when the shear stress is proportional to the velocity gradient and the shear stress is more than the yield value.

Incompressible fluid – this is when the density of the fluid does not change with the application of external force.

Compressible fluid – is when the density of the fluid changes with the application of external force.

The table below shows the density and viscosity of different types of fluids

Types of fluidDensity Viscosity 
Ideal fluidConstantZero
Real fluidVariableNon-zero
Newtonian fluidConstant/ VariableT=u(dudy)
Non-Newtonian fluidConstant/ VariableT≠u(dudy)
Incompressible fluidConstantNon-zero/ zero
Compressible fluidVariableNon-zero/ zero

Read more: Things you need to know about pump


That is all for the article “Various types of fluid flow” where we also listed the types of fluids available.

I hope you like the reading, if so, kindly share it with other students. Thanks for reading. See you next time!

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