Mean temperature field reconstruction of non-isothermal flow using Wollaston interferometry

This study investigates natural convection in a differentially heated cylindrical annulus using Wollaston shearing interferometry. Temperature-induced refractive index variations in silicone oil B5 are recorded as interferograms and processed with a windowed Fourier transform to reconstruct the two-dimensional line-of-sight mean temperature field, providing the general objective of this study, a quantitative description of the mean temperature distribution. To validate the approach, complementary three-dimensional numerical simulations are performed. The resulting temperature fields are used to generate synthetic interferograms. A qualitative and quantitative comparison shows moderate agreement in fringe structure, fringe density and flow features, including the characteristic crescent-shaped convective pattern, with reconstructed mean temperature fields consistent with numerical results. Remaining discrepancies are attributed to optical distortions, non-ideal thermal boundary conditions and light deflection in regions of strong gradients. Overall, the results demonstrate a robust framework and non-intrusive method for quantitative temperature reconstruction in convective flows.