What Is a Convection Model?

The Benard Rayleigh convective model is a qualitative to quantitative experiment on the formation mechanism of thermal convection and its influencing factors by experimental studies by Benard and Benal vortex Rayleigh. .

Bernal-Rayleigh convection model

A more detailed basic experiment conducted by the French scholar Benal in 1906 proved that only when the temperature increases to a certain degree, the heated parts will rise from everywhere, and their surroundings will fall. After that, there will be numerous regular regular hexagons, the temperature increasing part will rise in the center of the hexagon, and the cooling part will fall along the edge of the hexagon. This is the so-called Bénard's hive or Bénard vortex "(B'enard cells). It also shows that the Bénard's hive is stable; the ratio of the thickness of the fluid layer to the side length of the regular hexagon is close to 1.

In 1916, Rayleigh published a new research result showing that convection can only form when the lower heating speed is so large that it cannot be fully discharged by heat conduction outwards. The condition for generating convection is Ra = gh4kV. In the formula: Ra is the Rayleigh number; h is the thickness of the fluid layer; is the expansion coefficient; is the temperature gradient of the ground; g is the acceleration of gravity; When Ra reaches a certain value (about 1000), thermal convection can occur.