CONVECTIVE HEAT-TRANSFER COEFFICIENT IDEN TIFICATION BEHIND A BACKWARD-FACING STEP BY ACTIVE INFRARED THERMOGRAPHY

Convective heat transfer coefficient identification behind a backward- facing step by active infrared thermography. A methodology for measuri ng mean and unsteady local heat transfer coefficient, based on the thi n film method, is presented. It consists in following the evolution of the surface temperature of a sensible surface submitted to a perturbe d pow. The temperature field along the time is acquired by an infrared thermography system synchronized with velocity and fluctuating pressu re measurements. A thermal modelisation of this wall allows us to char acterize and identify the local value of the mean and unsteady heat tr ansfer coefficient. This measurement method has been validated by stud ying the impact of a pulsed turbulent air jet on a pat plate. It is no w applied to the study of the heat transfer in the aerodynamical reatt achment zone present in the pow downstream a backward-facing step. A f irst correlation, for the mean heat transfer, is proposed for the back ward-facing step setup of the DERMES (Departement d'Etudes et de Reche rches en Mecanique et Energetique des Systemes). The unsteady results are analysed in time evolution in a thermal point of view and compared to the tomographic visualizations of this pow. Finally, the contribut ion of synchronised measurements and infrared thermography ave discuss ed as for their efficiencies and future developments.