Mean Flow Characteristics of a Pulsating Round Jet

Abstract

The mean velocity and root-mean-square value of the turbulence component in pulsating round jets of low pulsation frequency were measured in the axial range of z/d≤30 by means of a hot wire anemometer, where z is the distance from the nozzle and d is the nozzle diameter. The measured values were approximated by the finite Fourier series. The time-averaged velocity on the jet axis decayed faster than the steady value. The time-averaged width of the pulsating jet, represented by the half-value radius of the time-averaged velocity, was slightly greater than the steady value. However, the time-averaged flow rate did not differ from that of the steady jet. The profiles of the time-averaged velocity and the amplitude of the fundamental velocity component became similar downstream at about z/d=5 and 10, respectively. A quasi-steady model for predicting the instantaneous velocity and turbulence on the jet axis was proposed.