Chemistry Drives Convection

Convection occurs when lower density fluid is located below higher density fluid–the lower density material rises, and the higher density material sinks. The best known case is where the lower density fluid is warmer, but it need not be. Since the 1980s researchers have been studying convection triggered by “autocatalytic” reactions, which are self-promoting. But there has been little study of the effects of more common chemical reactions on fluid flow, which could be relevant to many areas of science, such as the geology of Earth’s mantle.

Anne De Wit and her colleagues at the Brussels Free University (ULB) looked at the general case where two reactants come together to produce a single product (A+B→C). They developed a hydrodynamic model and then performed several computer simulations in which a less dense solution containing reactant A was placed on top of a more dense solution with reactant B. This normally stable configuration was disturbed by the appearance of the product C at the boundary between the two solutions, which led to convective “fingers.”