Time-resolved phase-lock pressure-sensitive paint measurement of trailing edge noise dynamics

TL;DR

This study introduces a novel time-resolved phase-locking method using pressure-sensitive paint and laser pulses to measure and analyze trailing edge noise dynamics on an airfoil, overcoming sensor noise limitations.

Contribution

The paper presents a new phase-locking technique that enables high-accuracy measurement of weak pressure fluctuations associated with trailing edge noise.

Findings

Resolved pressure fluctuations at 679 Hz with 50 Pa amplitude

Achieved measurement accuracy of about 15 Pa at 19.2 kHz

Demonstrated suppression and redevelopment of pressure fields related to TE noise

Abstract

Pressure-sensitive paint (PSP) was applied to the surface of a NACA0012 airfoil to investigate pressure fluctuations associated with trailing edge (TE) noise under low-velocity flow conditions. The primary focus is to assess the feasibility of employing laser pulses exposed at the airfoil surface to mitigate TE noise. However, the weak pressure fluctuations accompanying TE noise pose a challenge, as they are overshadowed by image sensor noise in high-speed cameras capturing PSP emission changes. A novel time-resolved phase-locking technique was introduced to address this issue, utilizing the signal from a semiconductor pressure transducer at the trailing edge as a phase-lock trigger source. By repetitively conducting phase-locked measurements (1150 times), time series ensemble-averaged data based on PSP emission images were obtained, enabling the capture of these subtle pressure fluctuations. Quantitatively, fluctuations with a dominant frequency of 679 Hz and an amplitude of 50 Pa are resolved within an accuracy of about 15 Pa, achieved at a recording rate of 19.2 kHz. Both the suppression and subsequent redevelopment of the pressure field with the TE noise offer valuable insights into the dynamics of TE noise and open avenues for targeted noise reduction strategies in aerodynamic applications.