Laminar Flow

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Introduction

You know that an ant releases an invisible, fragrant chemical called Pheromone. The successive ants smell this chemical and march-like an army. So, don’t you think this is a laminar flow? Yes, that’s true.

A laminar flow in fluid mechanics is the straight or linear flow of all the particles of the fluid that is similar to the marching of an ant. If in this case ants deviate from their path and make two directions, then it is the non-laminar flow.

This page discusses laminar fluid flow, lamellar flow, non-laminar flow, lumina flow, and laminar flux in detail.


Laminar Fluid

In a fluid, for laminar flow, all the particles carry constant attributes like velocity, pressure, and speed. These particles have a smooth movement as we walk on a smooth road. 

You can think of the laminar flow of liquid as the straight road (free of turns). While driving when you encounter a turn on the left or right of the road, the laminar flow becomes a non laminar flow.


Laminar Flow in Fluid Mechanics

In fluid dynamics, laminar flow is a smooth or regular movement of particles of the fluid. In Laminar flow, the fluid flows in parallel layers with lesser lateral mixing and no disruption between the layers. We call the laminar flow a streamline or viscous flow.

The terminology ‘streamlined flow’ is descriptive of the laminar fluid flow because, in laminar flow, layers of water flow over one another at varying speeds with virtually no mixing between layers, fluid particles move in definite and observable paths or streamlines just like the marching of Indian Army.

When a fluid flows via a closed channel such as a pipe or between two flat plates, the laminar flow may occur depending on the velocity, viscosity of the fluid, and the size of the pipe. Laminar flow occurs at lower velocities and high viscosity. 

Let’s look at the visual representation of the lumina flow:


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Laminar Flow in Liquid

A laminar flow in a liquid depends on the two following factors:

  1. Velocity

  2. Viscosity

Whenever a fluid flows in a pipe, the velocity of the laminar fluid flow remains to change that’s what we can observe in the above figure. So, when there is a pressure difference in the below and the above layer of the laminar fluid, the velocity difference also occurs.


Real-life Application of Laminar Flow

In aerodynamics, the same concept applies to dynamic lift. We see an airfoil, which carries a pressure difference; however, the flow remains laminar, and this pressure difference allows the wings of an aeroplane to lift up. So, here, laminar flow is one of the applications in the mechanics of air.

However, when the viscosity of the liquid is higher like honey, peanut butter, milk butter; they all have a higher viscosity and when they flow after melting, their layers remain intact, and therefore, all the particles to remain in close vicinity with each other, without leaving their exact lattice point (imaginary) while making movement in the forward direction. 

This smooth forward movement is the result of the laminar flow. So, the more is the viscosity, the more is the laminar flow, and the more is the laminar flux. So, do you know how laminar flux varies and turns to turbulence? If you don’t know, let’s understand this in detail:


Laminar Flow to Non-Laminar Flow

Do you know why a laminar flow turns to a non-laminar flow? In the above example, we discussed an application of aerodynamics for the laminar flow. 

In another example, we discussed honey, ghee, peanut butter, milk butter, and so on. These all eating items have high viscosity. Let’s suppose that you kept an opened ghee packet under the Sun. Now, on melting, it starts flowing very quickly in varying directions. So, when this variation in its laminar fluid flow occurs, this is the turbulent flow or turbulence nature. 

Turbulence occurs when the velocity of the fluid increases with the decrease in its velocity. We consider the turbulence flow as a non-laminar flow.

Let’s consider another example to understand the same:

When you are hurrying to your office, and you encounter heavy traffic after making a turn, you adjust the flow of your driving to whatever direction you can take to cross the traffic, here, your driving has a turbulent or a non-laminar flow because at each adjustment to drive ahead of all the vehicles, the property of your vehicle in motion like velocity, acceleration is changing. 

FAQ (Frequently Asked Questions)

1. What is Laminar-Turbulent Flow?

Ans: As you know that the blood flow through your veins has a laminar flow. Let’s suppose that a patient is injected with a thick needle to transmit the glucose. Now, by accident, that needle came out and the blood started falling at a high speed. So, the laminar blood flow turned to turbulent blood flow.

What happened here is, when the blood was having a streamlined flow under great pressure and when it came out with high releasing pressure, it built a turbulent nature.

2. State an Example of Laminar Flow.

Ans: Laminar flow in a straight pipe is considered the relative motion of a set of concentric cylinders (points) of the laminar flow, the outside end fixed at the pipe wall and the others moving at rising speeds as the centre of the pipe is approached. 

For instance, Smoke emitting in a straight path from a cigarette undergoes a laminar flow. However, after rising a small distance, the smoke changes to turbulent flow, as it eddies (makes circular movements) and swirls from its regular path.

3. State One Example of Non-Laminar Flow.

Ans: Non-laminar flow is more commonly known as turbulence. It is a problem as the introduction of air into the flow of water decreases the amount of energy it contains unlike water, which is a non-compressible fluid. 

Air can be compressed because of which, it acts much like a sponge/cushion within the water reducing its’ effect on the wheel and thus reducing its’ ability to efficiently rotate the wheel.