The acoustic-particle velocity in the vicinity of a liner: a PIV-CAA comparison

Abstract

A comparison between measurements and simulations of the acoustic-particle-velocity field in a rectangular duct in the near field of a single-degree-of-freedom, Helmholtz-resonator liner is presented. For the measurements, at low-velocity (Ma=0.01) grazing flow condition, the non-intrusive measurement technique particle-image velocimetry (PIV) is applied. The computational aeroacoustic (CAA) simulation is performed by solving the linearised Euler equations in the time domain, without background flow (Ma=0). The CAA solution uses an extended-Helmholtz-resonator acoustic-impedance model to represent the liner. A strong similarity between the simulated and the measured acoustic-particle-velocity distributions is observed. This suggests that the PIV-based technique enables the visualisation of the acoustic-velocity field, on the one hand. On the other hand, it confirms that the given acoustic-impedance model effectively simulates the response of a liner, in terms of the near-field acoustic-particle velocity.