Highly Turbulent Flow Laminarized by Hairy Pipe Walls

Abstract

Nature has found ways to laminarize turbulent flows, as demonstrated by the high swim speed of dolphins and the silent flight of owls. Owls locate their prey by hearing and need to fly silently. In both cases it has something to do with the soft pliable surface of the moving body and the wavy pattern that occurs on the dolphin skin and the owl feathers. Our objective was to investigate whether a pipe lined with a hairy soft carpet would “laminarize” air flows. The degree of laminarization was determined by the velocity profile. Manual pressure measurements were done to determine the air velocity at cross-sections along the pipe. Varying flow rates were tested before the hair was cut increasingly shorter. It was found that for some hair lengths the velocity profile approached the parabolic form of laminar flow at very high Reynolds number.