convection libre

CONT: [La] convection naturelle [...] est causée par le réchauffement diurne de la surface terrestre, résultant souvent en la formation de nuages Cumulus.

CONT: Free convection is the rising of heated air and the sinking of cooler air without the need of external forces.
CONT: Convection ... is a principal means of energy transfer. Distinction is made between free convection (gravitational or buoyant convection), motion caused only by density differences within the fluid; and forced convection, motion induced by mechanical forces such as deflection by a large-scale surface irregularity, turbulent flow caused by friction at the boundary of a fluid, or motion caused by any applied pressure gradient. Free and forced convection are not necessarily exclusive processes. On a windy day with overcast sky, the heat exchange between ground and air is an example of forced convection. On a sunny day with a little wind where the ground temperature rises, both kinds of convection take place.