On the directionality of thermal and salinity gradients in double diffusive convection

Double diffusive convection is a phenomenon that describes a new form of convection driven by two different density gradients (having different molecular diffusivities). The formation of horizontal double diffusive layers (DDLs) has been explained as a result of interaction between thermal and salinity gradients. DDLs can be formed both by creating a vertical or horizontal thermal gradient on a pre-existing vertically stable salinity gradient. The proposed work focusses mainly on the major differences between the characteristics of DDLs formed by imposing vertical and horizontal thermal gradient. The development of a fluent model for the investigation of the aforesaid phenomena has been proposed, explaining the flow behavior inside DDLs. The presence of a specially oriented convective rolls has been found in the case where the fluid particles move due to the buoyancy created by lateral thermal gradient. Compared to this, the characteristics of DDLs found in the presence of vertical thermal gradient are different, where, elements from same horizontal plane move vertically and mix with surrounding, creating a horizontal layer. A combination of Rayleigh numbers (solutal and thermal) and different analytical scales have been quantified to support the understanding of different DDLs.