On the instability of a fluid when heated from below

Abstract

It has been known for some times that when a horizontal layer of fluid is heated from below the fluid stationary, if initially at rest, until a certain temperature difference, depending on the physical constant of the fluid and the depth of the fluid layer, is reached. The equilibrium, which becomes less and less stable as the temperature rises, then becomes unstable for infinitely small disturbances, so that the fluid begins to move. Rayleigh,* in 1916, put forward a theory which gave the temperature at which motion first occurs when the top and bottom layers are free surfaces. The results agreed qualitatively with previous experiments due to Bérnard. Later Jeffreys calculated a critical temperature for the stability of a fluid between two rigid horizontal conducting planes. The investigation has since been revised by Jeffreys§ and also by Low.¶