Proper Orthogonal Decomposition of the Unsteady Pressure Field in the Three-Dimensional Wall Jet

—The streamwise variation in the unsteady wall pres- sure of a turbulent three-dimensional wall jet was examined using Proper Orthogonal Decompostion. Based on the exit velocity and the nozzle diameter, the Reynolds number of the wall jet was 140,000. The fluctuating wall pressure was measured using a two-dimensional lateral-streamwise array of 89 condenser microphones from x/D=5 to 15. The instantaneous pressure fluctuations showed strong lateral antisymmetry, which appeared to be linked to the lateral development of the flow. Instantaneous intermittent events convected downstream through the entire measurement region but were observed to change speed, slow down, surge forward, and convect laterally. The first two POD modes were antisymmetric and the next few higher modes appeared to be associated with lateral meandering of the jet. Low-order reconstructions of fluctuating wall pressure displayed the intermittency and meandering observed in the unsteady pressure field.