Construction of 2D-3C PIV and high-speed infrared thermography combined system for simultaneous measurement of flow and thermal fluctuations over a backward facing step

Highlights: • Simultaneous measurement system that combines 2D-3C PIV and high-speed IRT was established. • Flow and thermal fluctuations near wall region over a backward facing step were measured by this system. • High heat transfer coefficient corresponded to the increase in forward and the downwash flow near wall region. - Abstract: In the present study, simultaneous measurement of flow and heat transfer fluctuations downstream of a backward facing step in the near-wall region is presented. The instantaneous flow and convective heat transfer profiles were experimentally measured using two-dimension-three component (2D-3C) PIV and a high-speed infrared thermography (IRT) combined system at the same time. Using this measurement system, the unsteady flow behaviour in the vicinity of the heated wall and the heat transfer on the heated wall were investigated for the Reynolds number range from 2.5 × 10³ to 5.2 × 10³, which is based on the step height. The results showed that the forward and downwash flows appear to enhance the heat transfer in the near-wall region. It is confirmed that the simultaneous measurement of flow and heat transfer fluctuations is possible to be obtained by using this system.