COMPARISON OF STREAMING FLOW PRODUCED BY A CYLINDER AND A V-SHAPED ROD

摘要

Practical concerns led to the need for a device that would use an oscillating motion to produce a steady flow of fluid. Such a flow can be produced by oscillation of a bluff object. For example, a cylindrical rod oscillated along its diameter produces a steady flow-this phenomenon is called "steady streaming." This work compares the streaming flow produced by two bluff objects: a long rod with a cylindrical shape, and a long rod with a V-shape. The aims were to compare the flow fields and the flow rates. The methods were experimental. We oscillated various rods in a water tank and used particles to visualize the flow. From digitized images, fluid velocity was found and then flow rates were determined. During the experiments, the Keulegan-Carpenter number was varied from about 0.2 to 12 and the Stokes number (which was not independently controlled) typically had values from 1000 to 10,000. Results showed that the V-shape produced up to 10 times more flow than did the cylinder. Regarding high flow rates, the best operating condition occurred at a Keulegan-Carpenter number associated with shedding of one mature vortex pair per half cycle of oscillation.