Quantitative evaluation of spatio-temporal heat transfer to a turbulent air flow using a heated thin-foil

Spatial and temporal variation of heat transfer to a turbulent air flow was evaluated experimentally, employing a technique from high-speed infrared thermography that records temperature fluctuation on a heated thin-foil. Although the temperature variation on the foil attenuated in time and space due to the thermal inertia and lateral conduction, it was possible to restore the quantitative heat transfer by solving the inverse heat conduction equation. In this paper, the experimental technique and the procedure to evaluate the heat transfer coefficient are described which includes low-pass filtering to reduce measurement noise and inverse heat conduction analysis inside the test surface. The time-spatial variation of the heat transfer evaluated here was confirmed to be reliable by comparing the statistics with the existing experimental and numerical results. In addition, a unique feature of the spatio-temporal heat transfer for the turbulent boundary layer is observed that correlates with flow features in the near-wall region such as the streak structure.