Double-diffusive transport in multicomponent vertical convection

Motivated by the ablation of vertical ice faces in salt water, we use three-dimensional direct numerical simulations to investigate heat and fluxes two-scalar convection. For parameters relevant ice-ocean interfaces convection-dominated regime, observe that salinity field drives convection is essentially transported as a passive scalar. By varying diffusivity ratio (i.e., Lewis number $Le$), identify how different molecular diffusivities affect scalar through system. Away from walls, find transport determined turbulent Prandtl $Pr_t\approx 1$ double-diffusive effects are practically negligible. However, difference plays an important role close boundaries. In (unrealistic) case where diffused faster than heat, salt-to-heat would scale $Le^{1/3}$, consistent with classical nested boundary layers. realistic diffusion (relative salt), transition towards $Le^{1/2}$ scaling fluxes. This coincides thermal layer width growing beyond thickness viscous layer. We this not critical number, but rather $Pr\approx 10$, slightly below for cold seawater $Pr=14$. compare our results similar studies sheared flow under shelves, discuss implications large-scale models. coupling interface thermodynamics, describe flux impacts interfacial salinity, hence strength solutal rate.