Laser Anemometer Measurements of Turbulence in Non‐Newtonian Pipe Flows

Abstract

The structure of turbulence for pipe flows of dilute polyethylene oxide and polyacrylamide solutions is investigated using a laser anemometer technique. The instrumentation of the optical system and signal processing needed to satisfy the optical requirements and the signal‐to‐noise ratio are presented. The spatial requirement of the beam signal is described with regard to the lens, aperture, wavelength, and the angular alignment of the scattered and reference beams. A gravity‐flow system is used to minimize the degradation of polymer solutions. The measurements of wall pressure drops indicate that the polymer additives used give a consistent delay of transition from laminar flow to turbulence, as compared with Newtonian fluids. The axial turbulence intensities for polymer solutions are found to be substantially reduced, compared with results obtained for water.