Whether or not this phenomenon is caused by an external fluid flow determines whether it is "forced" or "free."
This phenomenon can be modeled by examining individual parcels which lose their coherence after travelling the mixing length. This type of instability occurs when the adiabatic gradient is smaller than the actual gradient according to the Schwarzschild criterion. The nonlinear v dot grad v term in the Navier-Stokes equations is sometimes called this type of acceleration. One form of this phenomenon driven by buoyancy causes the formation of namesake (*) hexagonal cells. Whether or not this phenomenon is caused by an external fluid flow determines whether it is "forced" or "free." This phenomenon dominates at high values of the Nusselt number. For 10 points, name this mechanism of heat exchange in which heat transfer is caused by the motion of a fluid, which is contrasted with radiation and conduction.
This phenomenon can be modeled by examining individual parcels which lose their coherence after travelling the mixing length.
convection [accept word forms such as convective, accept both "thermal convection" or "mass convection"]