TY - JOUR
T1 - Double-diffusive transport in multicomponent vertical convection
AU - Howland, Christopher J.
AU - Verzicco, Roberto
AU - Lohse, Detlef
N1 - Funding Information:
We thank two excellent anonymous reviewers for improving the focus and clarity of the paper through their insightful and thoughtful comments. This project has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant No. 804283). We acknowledge PRACE for awarding us access to MareNostrum at Barcelona Supercomputing Center, Spain (Project No. 2020235589). This work was also carried out on the Dutch national e-infrastructure with the support of SURF Cooperative.
Publisher Copyright:
© 2023 American Physical Society.
PY - 2023/1
Y1 - 2023/1
N2 - Motivated by the ablation of vertical ice faces in salt water, we use three-dimensional direct numerical simulations to investigate the heat and salt fluxes in two-scalar vertical convection. For parameters relevant to ice-ocean interfaces in the convection-dominated regime, we observe that the salinity field drives the convection and that heat is essentially transported as a passive scalar. By varying the diffusivity ratio of heat and salt (i.e., the Lewis number Le), we identify how the different molecular diffusivities affect the scalar fluxes through the system. Away from the walls, we find that the heat transport is determined by a turbulent Prandtl number of Prt≈1 and that double-diffusive effects are practically negligible. However, the difference in molecular diffusivities plays an important role close to the boundaries. In the (unrealistic) case where salt diffused faster than heat, the ratio of salt-to-heat fluxes would scale as Le1/3, consistent with classical nested scalar boundary layers. However, in the realistic case of faster heat diffusion (relative to salt), we observe a transition towards a Le1/2 scaling of the ratio of the fluxes. This coincides with the thermal boundary layer width growing beyond the thickness of the viscous boundary layer. We find that this transition is not determined by a critical Lewis number, but rather by a critical Prandtl number Pr≈10, slightly below that for cold seawater where Pr=14. We compare our results to similar studies of sheared and double-diffusive flow under ice shelves, and discuss the implications for fluxes in large-scale ice-ocean models. By coupling our results to ice-ocean interface thermodynamics, we describe how the flux ratio impacts the interfacial salinity, and hence the strength of solutal convection and the ablation rate.
AB - Motivated by the ablation of vertical ice faces in salt water, we use three-dimensional direct numerical simulations to investigate the heat and salt fluxes in two-scalar vertical convection. For parameters relevant to ice-ocean interfaces in the convection-dominated regime, we observe that the salinity field drives the convection and that heat is essentially transported as a passive scalar. By varying the diffusivity ratio of heat and salt (i.e., the Lewis number Le), we identify how the different molecular diffusivities affect the scalar fluxes through the system. Away from the walls, we find that the heat transport is determined by a turbulent Prandtl number of Prt≈1 and that double-diffusive effects are practically negligible. However, the difference in molecular diffusivities plays an important role close to the boundaries. In the (unrealistic) case where salt diffused faster than heat, the ratio of salt-to-heat fluxes would scale as Le1/3, consistent with classical nested scalar boundary layers. However, in the realistic case of faster heat diffusion (relative to salt), we observe a transition towards a Le1/2 scaling of the ratio of the fluxes. This coincides with the thermal boundary layer width growing beyond the thickness of the viscous boundary layer. We find that this transition is not determined by a critical Lewis number, but rather by a critical Prandtl number Pr≈10, slightly below that for cold seawater where Pr=14. We compare our results to similar studies of sheared and double-diffusive flow under ice shelves, and discuss the implications for fluxes in large-scale ice-ocean models. By coupling our results to ice-ocean interface thermodynamics, we describe how the flux ratio impacts the interfacial salinity, and hence the strength of solutal convection and the ablation rate.
KW - 2023 OA procedure
UR - http://www.scopus.com/inward/record.url?scp=85146368499&partnerID=8YFLogxK
U2 - 10.1103/PhysRevFluids.8.013501
DO - 10.1103/PhysRevFluids.8.013501
M3 - Article
AN - SCOPUS:85146368499
VL - 8
JO - Physical review fluids
JF - Physical review fluids
SN - 2469-990X
IS - 1
M1 - 013501
ER -