he effects of different levels of static and oscillatory gravities on the thermal diffusion phenomenon or Soret effect in binary and ternary mixtures were numerically investigated. A two dimensional square cavity is considered with lateral heating conditions. The Navier-Stokes equations, coupled with energy and mass transfer equations were solved numerically using finite element method. A ternary hydrocarbon mixture consisting of methane - n-butane and dodecane and binary mixture made of water - isopropanol were analyzed to validate the applicability of the numerical method of various mixtures. The concentration , temperature and fluid flow distributions have been thoroughly analyzed for different gravity levels. The influence of gravity on the thermal diffusion process in a ternary mixture is further discussed. From the results obtained, it can be inferred that the effects of the static gravity on thermal diffusion is very significant and buoyancy convection affects the Soret separation.