An experimental study of pulsating turbulent flow in a pipe

Abstract

An experimental study of pulsating turbulent flow in a pipe is reported in which measurements of instantaneous velocity were made using a two-component Laser Doppler Anemometer system. Local values of ensemble-averaged axial velocity, and radial and axial components of root-mean-square turbulent velocity fluctuation were obtained from the measurements. The frequency of the imposed pulsation of flow rate was varied systematically over a wide range covering inner scale dimensionless frequency ω ν / u τ 2 from 0.004 to 0.04. In terms of outer scale frequency ω D / u τ the corresponding values varied from 1.8 to 18. In addition, effects of changing the mean flow rate and the amplitude of flow rate pulsation were studied. Radial distributions of the amplitude of the modulation of ensemble-averaged axial velocity and the axial and radial components of RMS turbulent fluctuation, and their phase shifts relative to the imposed flow pulsation, are presented for conditions which include the low, intermediate and high frequency ranges. These add to and reinforce the body of information available from earlier experimental work and have enabled useful progress to be made in evaluating and validating approaches used for correlating such data. By relating observed behaviour to the fundamental processes of turbulence production, redistribution of turbulence energy between its components and radial propagation of turbulence, a good understanding of the results has been obtained.