In the present study, mesopycnal flows are investigated using direct numerical simulations. In particular, intrusive density- and particle-driven gravity currents in the lock exchange setup are simulated with the high-order finite-difference framework Xcompact3d. To account for the settling velocity of particles, a customized Fick's law for the particle-solution species is used with an additional term incorporating a constant settling velocity proportional to the concentration of particles. A general energy budget equation is presented, for which the energy can migrate across the domain's boundaries. The relevant main features of intrusive gravity currents, such as front velocity, energy exchanges, sedimentation rate, deposit profile, and deposit map are discussed with the comparison between two- and three-dimensional simulations. In particular, the influence of the Grashof number, the interface thickness, the energy exchanges, the sedimentation process, and how the presence of more than one particle fraction may change the flow dynamics are investigated. The results are in good agreement with previous experiments and theoretical work, in particular for the prediction of the front velocity. For the particle-driven case, the suspended mass evolution along with the sedimentation rate suggests the occurrence of three different stages. In the first stage after the lock release, the particle mixture tends to suspend itself due to gravitational forces. Once most of the particle-mixture mass is suspended, the current intrudes while increasing its velocity, reaching its kinetic energy peak. In the last stage, the particles are deposited at a nearly constant sedimentation rate. As a result, the front velocity constantly decelerates.
Bibliographical noteKAUST Repository Item: Exported on 2022-05-20
Acknowledgements: This publication was made possible in part by the Commonwealth Scientific Industrial Research Organisation Professorial Chair in Computational Geoscience at Curtin University and the Deep Earth Imaging Enterprise Future Science Platforms of the Commonwealth Scientific Industrial Research Organisation, CSIRO, of Australia. This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 777778 (MATHROCKS). The Curtin Corrosion Centre and the Curtin Institute for Computation kindly provide ongoing support. Additionally, this work was conducted using resources and services at the Visualization Core Lab at King Abdullah University of Science and Technology (KAUST).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
ASJC Scopus subject areas
- Condensed Matter Physics