Evaluation of the frequency characteristics of cntTSP measurement for unsteady low-speed flow

Carbon nanotube temperature-sensitive paint (cntTSP) is a fluid measurement technology that utilizes temperature-sensitive paint (TSP). It works as an optical temperature sensor, with a thin layer of carbon nanotubes to heat the TSP layer. This study investigated the frequency characteristics of cntTSP measurements in low-speed flow. The flow field on the flat plate was periodically changed by introducing intermittent local disturbances to the flat plate in a low-speed wind tunnel test. cntTSP measurement was conducted behind the local disturbance to evaluate changes in the temperature associated with periodic changes in the flow. The amplitude of the temperature change decreased approximately linearly with the frequency in a double-logarithmic graph. Moreover, the temperature amplitude at 25 Hz was 0.008 K, and it was necessary to detect a very small temperature change to evaluate high-frequency phenomena.