Investigating multiscale empirical mode decomposition of density fluctuation near critical point of SF6

We use a multiscale approach to investigate the dynamics of fluctuations near the critical point of

sulfur hexafluoride (SF6) in microgravity. The multiple spatial and temporal fluctuations can be

effectively separated using the Bidimensional Empirical Mode Decomposition (BEMD)

technique. The resulting orthogonal decompositions for each spatial scale are represented by an

Intrinsic Mode Function (IMF) image. The thermophysical properties for each spatial scale were

extracted using the Dynamic Differential Microscopy (DDM), which allows the structure factor's

computation and the intermediate scattering function (ISF) of critical fluid. The ISF gives the

correlation time of fluctuation, which determines the thermal diffusion coefficient. Using these

image processing methods, we found the thermal diffusivity coefficient above the critical

temperature and effective diffusion coefficients below the critical temperature.