thermosolutal

Thermosolutal refers to phenomena in fluids and materials where temperature gradients and solute concentration gradients interact to influence density and transport, producing buoyancy-driven flows and mixing. The concept extends beyond simple thermally driven convection to include solutal buoyancy, so that the density depends on both temperature and solute concentration. In many systems the competing effects can stabilize or destabilize the flow depending on the sign and relative magnitude of thermal and solutal expansions.

The governing framework is the Navier–Stokes equations under the Boussinesq approximation, coupled to transport equations for heat and solute concentration. A composite Rayleigh number, incorporating thermal and solutal contributions, characterizes stability. When gradients oppose each other, double-diffusive or thermosolutal instabilities can arise, leading to structures such as salt fingers or layered convection.

Thermosolutal processes appear in oceanography (thermohaline circulation), geophysics, and industrial contexts such as alloy solidification, crystal growth, and chemical reactors, where temperature and composition control mixing, phase boundaries, and transport rates. The term is sometimes used descriptively in studies focusing on the combined effect of temperature and solute fields, and is related to but distinct from “thermohaline” and from phenomena described by the Soret effect or purely thermal convection.

Because the term is not uniformly standardized, definitions may vary by discipline, but the core idea is the joint influence of temperature and solute gradients on buoyancy-driven transport.