LAUSR

Leveraging the high-resolution, noninvasive capabilities of digital holography, this study introduces a staged decoupling strategy to quantitatively investigate thermodiffusion (Soret effect) in a binary mixture of n-dodecane (C12) and 1,2,3,4-tetrahydronaphthalene (THN). The spatiotemporal evolution of the concentration and temperature fields in the C12-THN mixture is quantitatively analyzed, and the Soret coefficient is calculated. Experimental results demonstrate that under a temperature gradient, C12, with higher molecular weight and lower density, migrates toward the top heated end, while THN, which, contrary to C12, migrates toward the cooled end. In this study, this migration direction aligns with gravitational differentiation, accelerating the establishment of a steady state. By decoupling the contributions of temperature and concentration to phase variations, the steady-state concentration gradient along the gravitational direction is obtained. The measured Soret coefficient of C12 in the 1:1 mass fraction C12-THN system is 3.36±0.24×10−3  K−1, which matches theoretical predictions and space experiments but slightly exceeds microgravity reference data due to Earth gravity. The high-precision holography measurement method developed in this study successfully visualizes and quantifies thermodiffusion processes in fluid systems, providing ground validation for microgravity thermodiffusion research in the Fluid Physics Experimental Rack of the China Space Station. It also offers critical parameter support for refining Soret effect modeling in reservoir numerical simulations. The findings hold significant implications for optimizing deep oil and gas exploration, enhancing thermal recovery efficiency, and advancing studies on multi-component fluid mechanisms in space.