ME 322 Lecture Notes - Lecture 23: Reynolds Number, Electric Spark, Turbulence (Nsa)
13 Dec 2017
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Reynold"s experiment (1883): flow in a tube with a trumpet to eliminate disturbances at the inlet, injected colored water to visualize flow. For sufficiently small velocities colored streak is straight line (laminar flow) In the presence of (small) disturbances at the inlet and sufficiently small velocities: streak shift about the tube but remains undisturbed. Increasing the velocity, at some point in the tube away from the trumpet, the color band mixes with the surrounding water. Increasing the velocity shifts the mixing point closer to the inlet. Viewing the tube with light of an electric spark => colored mass resolved into a mass of distinct curls or eddies. Reynolds showed that mixing appeared after reaching a critical value of. Minimizing the disturbances at the intake, the critical re was as high as 13,000. More refined experiments pushed the critical re to 90,000.
