Laminar flow is the undisturbed and constant flow of fluids. When a fluid exhibits laminar flow, the adjacent layers of the fluid do not get mixed with each other on a macroscopic level. Hence, the fluid layers appear to be moving in straight lines parallel to each other. Reynolds number is used as a criterion that decides whether the flow of fluid is laminar or turbulent. If the Reynolds number of fluid is less than 2000, it is capable of exhibiting laminar flow. Typically, a laminar flow occurs when the fluid flows with low velocity, or the outlet of the container has a small diameter. It is also related to the viscosity of the fluid in such a way that the fluids having higher viscosity are much likely to exhibit laminar flow.
Examples of Laminar Flow
1. Blood Flow
The blood flowing in our veins undergoes laminar flow. The adjacent layers of the blood get mixed with each other on a molecular level; however, they remain separated on the macroscopic level. This is the reason why the blood within the veins appears to be flowing in a straight line.
2. Water Balloon
To observe the laminar flow in a water balloon, a square piece of tape is pasted on its surface. The taped part of the balloon is then pierced with the help of a sharp object such as a knife. The water flows through the resultant hole uniformly and appears to be not moving at all. Hence, a water balloon can be used to display laminar flow in real life.
You must have experienced turbulence while travelling on an aeroplane. Turbulent flow is the opposite of laminar flow. The laminar flow of air means that there exists little or no mixing of the gaseous particles, whereas the turbulent flow of air means that the particles of air move randomly and get mixed with each other. The laminar flow of air is an essential requirement to ensure a smooth flight because it allows a uniform flow of particles of air over the surface of aircraft.
4. Viscous Fluids
Viscous fluids such as honey, glycerin, and other syrups exhibit laminar flow in the best possible way. When such fluids are poured into a container, the flow seems undisturbed and constant. This is because the layers of the viscous fluids do not merge with each other easily and stay separated from each other, thereby flowing in straight lines, i.e., parallel to each other.
Stagnant rivers and canals are a prominent example of laminar flow. The water flowing in quiet rivers or other water bodies is slow and smooth. There exist no waves or swirls in the water body, which means that the different layers of water do not hamper each other and follow a straight pathway parallel to each other.
A major application of laminar flow can be seen in fountains. This is because the ordered and continuous flow of water through the fountain outlets provides a crystal look to the stream of water. Hence, the laminar flow can be used for decorative purposes.
When a faucet is slightly opened, and the water is allowed to rush out, the flow of water appears to be static. This is because the layers of a fluid flowing with low velocity do not get mixed with each other, thereby resulting in a laminar flow.
The smoke coming out of a burning incense stick appears linear near the stick; however, it disperses after a certain distance from the stick. This is because the particles of the smoke present close to the tip of a burning incense stick or a cigarette do not interfere with each other, thereby allowing the individual particles to follow a smooth path or exhibit laminar flow.