Let’s start with the definition and types of Fluid first.
A fluid is any substance that flows or deforms under applied shear stress. or The substances which have the tendency to flow is also called as fluid.
Types of Fluids:
There are five different types of fluid has been classified:
- Ideal fluid
- Real fluid
- Newtonian fluid
- Non-Newtonian fluid, and
- Ideal plastic fluid
The fluid which cannot be compressed and have no viscosity falls in the category of an ideal fluid. Ideal fluid is not found in actual practice but
It is an imaginary fluid because all the fluid that exists in the environment have some viscosity. So, there is no ideal fluid in reality.
A fluid which is having some viscosity is called real fluid. Actually, all the fluids existing or present in the environment are called real fluids.
The Fluid which obeys Newton’s law of viscosity is known as the Newtonian fluid.
The Fluid which does not obey Newton’s law of viscosity is called Non-Newtonian fluid.
Ideal Plastic Fluid:
A fluid having the value of shear stress more than the yield value and shear stress is proportional to the shear strain (velocity gradient) is known as ideal plastic fluid.
So now I hope you have a basic idea on what is Fluid and their types, now let’s dive into our main topic that is Types of Fluid Flow.
There are two approach to study fluid.
- Lagrangian Approach: In this approach, a single fluid particle is taken and its behavior is analyzed at different sections (with respect to space).
- Eulerian Approach: In this approach, a certain section is taken in space and the behavior of fluid particles passing through this section is analyzed at a different instant. We mainly use this approach in Fluid Mechanics [With respect to Time].
Types of Fluid Flow:
There are Six different types of fluid flow:
- Steady and Unsteady
- Uniform and Non-Uniform
- Laminar and Turbulent
- Compressible and In-compressible
- Rotational and Ir-rotational and
- One, Two, and Three -dimensional Fluid Flow
We will study one by one,
1. Steady and Unsteady flows:
The steady flow is defined as that type of flow in which the fluid characteristics like velocity, density, pressure, etc at a point do not change with the time.
The Unsteady flow is defined as that type of flow in which the fluid characteristics like velocity, density, pressure, etc at a point change respected to time.
2. Uniform and Non-uniform fluid flow:
This uniform fluid flow is defined as the type of flow in which the velocity at any given time does not change with respect to space (i.e length of direction of the flow).
Whereas the Non-uniform flow is defined as,
This non-uniform fluid flow is defined as the type of flow in which the velocity at any given time changes with respect to space (i.e length of the direction of the flow).
3. Laminar, and Turbulent fluid flow:
This laminar fluid flow is defined as the type of flow in which the fluid particles move along well-defined paths or streamline and all the streamlines are straight and parallel.
Thus the particles move in laminas or layers gliding smoothly over the adjacent layer. This type of fluid is also called as streamline flow or viscous flow.
This Turbulent fluid flow is defined as the type of flow in which the fluid particles move in a zig-zag way, the eddies formation takes place which is responsible for high energy loss.
For pipe flow, The type of flow is determined by a non-dimensional number [(VD) / (ν) nuo] called the Reynolds number.
- D = Diameter of pipe
- V = Mean velocity flow in a pipe
- ν = Kinematic viscosity of the fluid.
- If the Reynold Number is less than 2000, the flow is called Laminar flow.
- Reynold Number is more than 4000, the flow is called Turbulent flow.
- If the Reynold Number is lies between 2000-4000, the flow may be laminar or turbulent.
4. Compressible and Incompressible fluid flow:
Compressible fluid flow is defined as the flow in which the density is not constant which means the density of the fluid changes from point to point.
The density notation is ρ but here i have used J.
J ≠ constant
Incompressible fluid flow is defined as the flow in which the density is constant which means the density of the fluid does not change from point to point.
J = constant
Gases are compressible fluid flow but whereas the liquid is incompressible fluid flow.
5. Rotational and irrotational Fluid flow:
The rotational fluid flow is defined as the type of fluid flow in which the fluid particles while flowing along streamline and also rotate about there own axis.
Whereas, The Ir-rotational fluid flow is defined as the type of fluid flow in which the fluid particles while flowing along streamline and do not rotate about there own axis.
6. One, Two and Three-dimensional fluid Flow:
One dimensional flow is that type of flow in which the flow parameter such as velocity is a function of time and one space co-ordinate only, say x.
u=f(x), v=0 and w=0
Where u,v and w are velocity component in x,y and z directions respectively.
Two-dimensional fluid flow is the type of flow in which velocity is a function of time and two rectangular space co-ordinate say x,y.
u= f1(x,y,), v= f2(x,y,) and w= 0.
Three-dimensional fluid flow is the type of 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).
Here you can read the Properties of fluid.
There are Six different types of fluid flow:
Steady and Unsteady
Uniform and Non-Uniform
Laminar and Turbulent
Compressible and In-compressible
Rotational and Ir-rotational and
One, Two, and Three -dimensional Fluid Flow
A fluid is any substance that flows or deforms under applied shear stress. Fluid has tendency to flow.
The properties of fluid are:
Density or Mass Density
Weight Density or Specific Weight
Specific Volume and
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References [External Links]:
- FLUID | meaning in the Cambridge English Dictionary
- Lecture 1 BASIC CONCEPTS AND PROPERTIES OF FLUIDS
- All the images used in this paper are made by Learn Mechanical under Creative Common License [Attribution Needed].
- Feature Image: Designed by the author.
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