Oschillations of an impinging turbulent jet: Coherence characterization via conditional sampling
Abstract
By using zero crossing statistics, in conjunction with recursive digital filtering, to determine self and crossprobability densities of velocity and pressure, the degree of phase fluctuation of organized oscillations of turbulent jet flow through a cavity is characterized as a function of mean phase deviation from the "lockon" condition; "lockon", producing maximum pressure amplitude, corresponds to a timeaveraged phase difference between organized velocities at the exit and entrance of the cavity of 2 nπ. As a frequency jump is approached, there is mean phase deviation from this 2 nπ condition, and the degree of phase (or period) fluctuation increases; at the jump, crossprobability densities show no discernible coherence. Concerning the evolution of the jet in the streamwise direction, growth of the timeaveraged organized wave amplitude, obtained by using a waveeducation method, is shown to be associated with a decrease in phase fluctuation of the velocity. However, selfprobabilities of pressure, and crossprobabilities between pressure and exit velocity, are essentially invariant between cavity exit and inlet, reflecting dominance of the acoustic contribution to the unsteady pressure field at separation.
 Publication:

Journal of Sound Vibration
 Pub Date:
 July 1982
 DOI:
 10.1016/S0022460X(82)800795
 Bibcode:
 1982JSV....83..111R
 Keywords:

 Computational Fluid Dynamics;
 Oscillating Flow;
 Probability Density Functions;
 Sampling;
 Turbulent Jets;
 Coherence;
 Digital Filters;
 Flow Velocity;
 Pressure Distribution;
 Fluid Mechanics and Heat Transfer