Reconstruction of the spatial phase and temperature structure of a candle flame using Hilbert optics and shear interferometry methods

The study of the structure of the candle flame is discussed in the work. The optical diagnostics adapted to the study of combustion problems is based on the visualization of phase disturbances induced in the probe light field by the medium under study with using Hilbert optics and interferometry methods combined with pixel-by-pixel processing of the dynamic structure of the recorded images. The diagnostic complex is implemented on the basis of the IAB–463M device with modified blocks of optical filtration, light source, registration and information processing. The dynamic phase structure of the candle flame was visualized. The temperature was measured using thermocouples at the reference points. The phase function was restored on axisymmetric sections from the obtained hilbertograms. The temperature field of flame was reconstructed using the inverse Abel transform.

Hilbert diagnostics of convective structures and phase transition in super cooled water

The evolution of the crystallization wave front and convective structures in a horizontal layer of supercooled water bounded by tempera- ture-controlled flat surfaces is visualized using methods of Hilbert optics. The phase transition is manifested by the occurrence of a crys- tallization wave and is accompanied by a positive energy release, which, in turn, affects the dynamic distribution of the optical phase density gradient in supercooled water and induces phase perturbations in the probing light field. The results of measurements of the phase velocity and the shape of the crystallization front approximated by Bezier curves are presented. The wave front velocity is obtained using modified time-of-fight method. The phase velocity field is found to exhibit spatio-temporal quasi-periodicity that can be related to the existence of oscillatory phenomena in the crystallization process.

Optical Hilbert Diagnostics of the Vortical Structures Induced by the Pressure Front on an Aperture

The methods of Hilbert optics widely use in tasks of visualization and measurement of phase optical density in fluids. In this work, the problem of vortex rings generation upon sudden opening of a cylindrical chamber containing a gas at elevated pressure is considered. At diffraction of pressure front on an aperture in a wall the vortical rings propagated in the opposite directions from the wall have been detected by optical Hilbert methods.