Two-dimensional numerical simulations of Marangoni–Bénard instabilities during liquid–liquid mass transfer in a vertical gap

Two-dimensional (2D) simulations of isothermal liquid–liquid mass transfer subject to surface tension- and buoyancy-driven hydrodynamic instabilities have been carried out. Simulation is based on the numerical solution of 2D equations of momentum and mass transport, using a combination of finite difference and finite volume methods. Two different cases have been considered: (1) buoyancy stable mass transfer, only surface tension-driven convection occurs; (2) surface tension-driven instability superseeded by buoyant convection. The faster attenuation of mass transfer coefficients in buoyancy stable situations is attributed to the merging of convection cells leading to a reduction in the number of renewal zones along the interface. Concentration profiles next to the interface reveal the diffusional nature of the mass transfer in the immediate interfacial neighbourhood.