First, any obstruction or sharp corner, such as in a faucet, creates turbulence by imparting velocities perpendicular to the flow. Streamlines are smooth and continuous when flow is laminar, but break up and mix when flow is turbulent. The lines that are shown in many illustrations are the paths followed by small volumes of fluids. When there is turbulence, the layers mix, and there are significant velocities in directions other than the overall direction of flow. Layers flow without mixing when flow is laminar. (credit: Creativity103)įigure 2 shows schematically how laminar and turbulent flow differ. If you watch the smoke (being careful not to breathe on it), you will notice that it rises more rapidly when flowing smoothly than after it becomes turbulent, implying that turbulence poses more resistance to flow. The smooth flow is called laminar flow, whereas the swirls and eddies typify turbulent flow. Smoke rises smoothly for a while and then begins to form swirls and eddies. Turbulent flow, or turbulence, is characterized by eddies and swirls that mix layers of fluid together. Laminarflow is characterized by the smooth flow of the fluid in layers that do not mix. Before we can define viscosity, then, we need to define laminar flow and turbulent flow. The precise definition of viscosity is based on laminar, or nonturbulent, flow. In this section, we will investigate what factors, including viscosity, affect the rate of fluid flow. In the previous sections we have considered ideal fluids with little or no viscosity. Juice has low viscosity, whereas syrup has high viscosity. We call this property of fluids viscosity. The difference is fluid friction, both within the fluid itself and between the fluid and its surroundings. But when you pour syrup on your pancakes, that liquid flows slowly and sticks to the pitcher. When you pour yourself a glass of juice, the liquid flows freely and quickly. Explain how pressure drops due to resistance.Calculate flow and resistance with Poiseuille’s law. Define laminar flow and turbulent flow.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. 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 layers of a fluid flowing with low velocity do not get mixed with each other, thereby resulting in a laminar flow. When a faucet is slightly opened, and the water is allowed to rush out, the flow of water appears to be static. Hence, the laminar flow can be used for decorative purposes. This is because the ordered and continuous flow of water through the fountain outlets provides a crystal look to the stream of water. 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.Ī major application of laminar flow can be seen in fountains. The water flowing in quiet rivers or other water bodies is slow and smooth. Stagnant rivers and canals are a prominent example of laminar flow. 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. When such fluids are poured into a container, the flow seems undisturbed and constant. Viscous fluids such as honey, glycerin, and other syrups exhibit laminar flow in the best possible way. 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. 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. Turbulent flow is the opposite of laminar flow. You must have experienced turbulence while travelling on an aeroplane. Hence, a water balloon can be used to display laminar flow in real life. The water flows through the resultant hole uniformly and appears to be not moving at all. The taped part of the balloon is then pierced with the help of a sharp object such as a knife. To observe the laminar flow in a water balloon, a square piece of tape is pasted on its surface. This is the reason why the blood within the veins appears to be flowing in a straight line. The adjacent layers of the blood get mixed with each other on a molecular level however, they remain separated on the macroscopic level. The blood flowing in our veins undergoes laminar flow.
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