Thermosolutal Natural Convection under the Dufour and Soret Effects: Aiding and Opposing Cases

An unsteady numerical investigation of thermosolutal natural convection is conducted within a square cavity, considering the effects of Dufour ( $$Du$$ ) and Soret ( $$Sr$$ ) for both aiding and opposing cases. The vertical walls of the cavity are maintained at constant but different temperatures and concentrations, while the other walls are adiabatic and impermeable. The finite volume method is used to solve the governing equations, and the SIMPLER algorithm is used in the solution process. The primary objective is to identify the flow regime for flows dominated by thermal and solutal effects, while also examining the impact of $$Du$$ and Sr coefficients on this process. Results are presented for several parameters, such as the buoyancy ratio, thermal Rayleigh number ( $$R{{a}_{t}})$$ , $$Du$$ , and Sr coefficients on flow pattern, and heat and mass transfer. The results show that the presence of $$Du$$ and $$Sr~$$ coefficients notably influences the structure flow. Furthermore, $$Du~$$ can increase the heat transfer rate more than the mass transfer rate. Conversely, the $$Sr~$$ coefficient increases the mass transfer rate more than the heat transfer rate. Additionally, the effects of $$Du$$ and $$Sr$$ on the oscillatory regime have been studied, revealing a significant impact on oscillation flow when the parameters are increased by delaying their appearance.