convect

Convect is a verb used in physics and engineering to describe the transfer of heat or mass by convection. Convection refers to the transport caused by the bulk motion of a fluid, as opposed to conduction through stationary matter or radiation. When a fluid is heated, it becomes less dense and rises, while cooler fluid sinks, creating convective currents that distribute energy or material.

In thermodynamics and heat transfer, convective heat transfer is characterized by a convective heat transfer coefficient and a temperature difference between the surface and the fluid. Convection can be natural, driven by buoyancy forces arising from density variations, or forced, driven by external means such as a pump or a fan. The relative importance of convection versus conduction is often described by the Biot number and the Nusselt number, and by dimensionless numbers such as the Grashof and Rayleigh numbers for natural convection.

In astrophysics and geophysics, convection is a major energy transport mechanism. In stars, convective zones move plasma and transport energy from hotter to cooler regions. In planetary atmospheres and oceans, convective processes contribute to weather systems, cloud formation, and large-scale circulation.

In mathematical modeling, the convective term appears in the governing equations as a non-diffusive transport term, typically written as (u · ∇)T for temperature or (u · ∇)φ for other scalars, and is often coupled with diffusion and sources.