In fact it isĮasier to find a turbulent flow than a flow that is really laminar. Turbulence occurs nearly everywhere: in the oceans, in the atmosphere, in rivers, even in stars and galaxies. Turbulent motions are very common in Nature. In a turbulent flow, however, the molecules in a fluid move in many different directions and at many different Smoothly in the same direction and at the same speed. In a laminar flow all the molecules in the fluid move more or less Now we are able to define the terms laminar and turbulent in a more precise fashion. In order to see how complicated the turbulent motions are look at the picture of the boiling kettle. In this particular case the turbulence is due to If you wait a bit longer bubbles will start to rise from theīottom to the surface and the motions of the water become very complicated or turbulent. You wait for a short while, the water will start to move in a laminar fashion, i.e. Put water in a pot and heat it up on your electric cooker. This is due to the fact that now the water molecules tend to move in different directions at differentĪnother example of turbulence you can easily observe at home is the flow of water in a boiling pot of water. Although the stream is still laminar, theįlow pattern of the water in the sink has become very complicated. Now place a cup under the stream of water emerging from the faucet. The water will also flow down the drain in a laminar flow. Furthermore, if you did not open the faucet too much, The flow of water is smooth becauseĪll the water molecules move, at more or less the same speed, in the same direction. The stream of water that emerges from your faucet is very smooth and very regular. Go to your kitchen sink and open the faucet. We will illustrate what we mean by 'simple' and 'complicated' using the following, simple experiment. 'simple' flow while a turbulent flow is a 'complicated' flow. Roughly speaking we can say that a laminar flow is a Basically there exist two types of flows, namely laminar flows and turbulent flows. either a liquid or a gas, from one place toĪnother. This is an annimation to perform the Reynolds Experiment.Let us first define what a flow is: a flow is the continuous movement of a fluid, i.e. Have preserved laminar flow at very high Reynolds number through Transitional Flow prevailsīetween these two limits. Number (based on diameter of the pipe) is less than 2100 and is It is also found that a flow in a pipe is laminar if the Reynolds While laminar flow is "orderly" turbulent flow is "Random" andįigure 7.3: Hot Wire Signals for Turbulent flow (top), Transitional flow (middle) and Laminar Flow (bottom) Significant component of velocity in the flow normal direction. Velocity in the main flow direction, turbulent flow has a It is clear that while the laminar flow has a predominant The traces of velocity at the three regimes of flow are shown inįig.7.3. Ī similar experiment may be conducted today using Hot WireĪnemometer, which measures instantaneous velocities at a point. These are what we call Laminar, Transitional and Turbulent Flows. As the flow speed is further increased the dye is blurred and seems to fill the entire pipe. As the flow speed was increased the dye fluctuates and one observes intermittent bursts. When the speeds were small the flow seemed to follow a straight line path (with a slight blurring due to dye diffusion). ) he injected a dye to observe the nature of flow. Into a flow through a glass tube (Fig.7.2. This becomes a very important classification of flows and is brought out vividly by the experiment conducted by Osborne Reynolds (1842 - 1912). Next: Entrance Length Up: Viscous Flow in Pipes Previous: Viscous Flow in PipesĬlassification of Flows, Laminar and Turbulent Flows A flow can be Laminar, Turbulent or Transitional in nature.
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