Simultaneous Measurements of Unsteady Thermal and Flow Fluctuations Using High-Speed Infrared Thermography and PIV Over a Backward Facing Step

In order to investigate the flow and heat transfer fluctuations in the near-wall region downstream a backward facing step, a Time-resolved Stereoscopic Particle Image Velocimetry (TS-PIV) and a high-speed infrared thermography (IRT) combined system was constructed. Using this measurement system, the time series of the velocity in the vicinity of the heated wall and the heat transfer on the heated wall were measured at Reynolds number, which is based on the step height and inlet mainstream velocity, of 2.5 × 10³. It confirmed the validity of the velocity fluctuation obtained by using TS-PIV. The results showed that the forward and downwash flows correspond to the enhancement of the heat transfer in the near-wall region. Also, the vortex structure in the yz plane was detected by Q_yz-criterion, and the locational relationship between the vortex structure and the heat transfer enhancement was investigated.