Boundary layers in turbulent vertical convection at high Prandtl number

Many environmental flows arise due to natural convection at a vertical surface, from flows in buildings to dissolving ice faces at marine-terminating glaciers. We use three-dimensional direct numerical simulations of a vertical channel with differentially heated walls to investigate such convective, turbulent boundary layers. Through the implementation of a multiple-resolution technique, we are able to perform simulations at a wide range of Prandtl numbers Pr. This allows us to distinguish the parameter dependences of the horizontal heat flux and the boundary layer widths in terms of the Rayleigh number Ra and Prandtl number Pr. For the considered parameter range 1 ≤ Pr ≤ 100, 10⁶ ≤ Ra ≤ 10⁹, we find the flow to be consistent with a ‘buoyancy-controlled' regime where the heat flux is independent of the wall separation. For given Pr, the heat flux is found to scale linearly with the friction velocity V_∗. Finally, we discuss the implications of our results for the parameterisation of heat and salt fluxes at ice-ocean interfaces.