Rayleigh-Bènard convection

(redirected from Benard cells)

Rayleigh-Bènard convection

[′rā·lē bā′när kən‚vek·shən]
(physics)
Convection of a fluid heated from below, characterized by a regular array of usually hexagonal cells.
References in periodicals archive ?
It prevents adequate flow-out and leveling (the resultant surface may be quite rough and/or bumpy), often produces streaks and blotches, prevents good color development, causes flooding, floating and Benard cells, and generally hurts appearance.
Visibly, Benard cells of a given medium are very similar to each other, as well as the subsequent cycles of the Belousov-Zhabotinsky (BZ) reaction.
Regarding the origin of order, we can distinguish between order arising in near-equilibrium thermodynamics, such as freezing, crystallization, snow-flake formation, spontaneous magnetization, superconductivity, laser, or Bose-Einstein condensation; and structure formation in thermodynamic systems maintained in a state far from equilibrium, like turbulence, Benard cells, or reaction-diffusion systems.
2) Flow currents within the film (9-10) -- In the wet film, as water volatilizes, the temperature, surface, and interfacial tension will decline, more hydrophilic pigments will be carried with water to the surface, and Benard cells are formed.
The addition of water also tends to raise the surface tension, inducing more severe Benard cell flows.
Flocculation can contribute to a number of defects, including poor gloss, poor leveling, flooding and floating, Benard cells, and poor color development (see the March 2006 issue of JCT COATINGSTECH for more information on flocculation).
It prevents adequate flow-out and leveling (the surface may be quite rough), often produces streaks and blotches, prevents good color development, causes flooding, floating and Benard cells, and generally hurts appearance.
Haze may be due to fine solvent pops or pinholes, fine orange peel, roughness (caused by dry spray, flocculation or poor coalescence), small Benard cells, material that has exuded to the surface, material that condensed on the surface in the oven, absorption or trapping of moisture (which may be a form of blushing), degradation by overbaking, or the effects of oven gasses on the surface.
Benard cells are defects that look as if someone has imprinted a series of hexagonal shapes on the surface of the paint film.
Benard cells may be quite large (several cm across) or so small that a microscope is needed to see them.
BYK-377 works on reducing surface tension and specifically optimizes the wetting of problematic substrates, preventing the formation of Benard cells.