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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/gmd-2016-176
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Model description paper
13 Sep 2016
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Geoscientific Model Development (GMD).
An axisymmetric non-hydrostatic model for double-diffusive water systems
Koen Hilgersom1, Marcel Zijlema2, and Nick van de Giesen1 1Water Resources Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, P.O. Box 5048, 2600 GA, The Netherlands
2Environmental Fluid Mechanics Section, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, P.O. Box 5048, 2600 GA, The Netherlands
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 systems that approach axisymmetry around a central location, computation times can be reduced by applying a quasi 3-D axisymmetric model setup. This article applies the 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 this quasi 3-D 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. Four qualitative case studies demonstrate a good behaviour with respect to expected density and diffusivity driven flow and stratification in shallow water bodies. A fifth case study involves a new validation method that quantifies the radial expansion of a dense water layer developing from a central inflow at the bottom of a shallow water body.

Citation: Hilgersom, K., Zijlema, M., and van de Giesen, N.: An axisymmetric non-hydrostatic model for double-diffusive water systems, Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2016-176, in review, 2016.
Koen Hilgersom et al.
Koen Hilgersom et al.

Data sets

An axisymmetric hydrodynamical model: model code and data
K. P. Hilgersom, M. Zijlema, and N. C. Van de Giesen
https://doi.org/10.4121/uuid:c0dce972-5a04-476f-8f3f-4ac34f40da1b
Koen Hilgersom et al.

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Short summary
This study models the local inflow of groundwater at the bottom of a stream with large density gradients between the groundwater and surface water. Modelling salt and heat transport in a water body is very challenging, as it requires large computation times. Due to the circular local groundwater inflow and a negligible stream discharge, we assume axisymmetry around the inflow, which is easily implemented in an existing model, largely reduces the computation times, and still performs accurately.
This study models the local inflow of groundwater at the bottom of a stream with large density...
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