An axisymmetric non-hydrostatic model for double-diffusive water systems

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Abstract

The three-dimensional (3-D) modelling of water systems involving double-diffusive processes is challenging due to the large computation times required to solve the flow and transport of constituents. In 3-D systems that approach axisymmetry around a central location, computation times can be reduced by applying a 2-D axisymmetric model set-up. This article applies the Reynolds-averaged Navier–Stokes equations described in cylindrical coordinates and integrates them to guarantee mass and momentum conservation. The discretized equations are presented in a way that a Cartesian finite-volume model can be easily extended to the developed framework, which is demonstrated by the implementation into a non-hydrostatic free-surface flow model. This model employs temperature- and salinity-dependent densities, molecular diffusivities, and kinematic viscosity. One quantitative case study, based on an analytical solution derived for the radial expansion of a dense water layer, and two qualitative case studies demonstrate a good behaviour of the model for seepage inflows with contrasting salinities and temperatures. Four case studies with respect to double-diffusive processes in a stratified water body demonstrate that turbulent flows are not yet correctly modelled near the interfaces and that an advanced turbulence model is required.
Original languageEnglish
Pages (from-to)521-540
JournalGeoscientific Model Development
Volume11
DOIs
Publication statusPublished - 6 Feb 2018

Keywords

  • axisymmetric model
  • CFD modelling
  • density-driven flow
  • double diffusion
  • double-diffusive convection
  • heat transport
  • non-hydrostatic model
  • numerical modelling
  • salt transport
  • salt-fingers
  • SWASH (Simulating WAves till SHore)

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