  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.
