Image resection and heat transfer measurements by IR thermography in hypersonic flows

This study describes a data reduction technique to estimate heat fluxes in hypersonic flows based on measurements of the temperature distribution on the surface of the model by means of infrared (IR) thermography. IR images are registered using a camera model based on perspective projection approach taking into account lens distortion. Relative displacements between model and IR camera, due to sting mechanical vibrations, can increase the noise. An approach to reduce it, based on single-step discrete Fourier transform and Speed-Up Robust Features methods, is presented. Heat flux is computed with an inverse heat transfer problem applying the trust region reflective algorithm. The proposed data reduction technique is numerically validated and applied to an experimental test carried out in the Hypersonic Test Facility Delft (HTFD) at Mach number equal to 7.5.