Direct numerical simulations of particle-laden density currents with adaptive, discontinuous finite elements
High-resolution direct numerical simulations (DNSs) are an important tool for the detailed analysis of turbidity current dynamics. Models that resolve the vertical structure and turbulence of the flow are typically based upon the Navier–Stokes equations. Two-dimensional simulations are known t...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-09-01
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| Series: | Geoscientific Model Development |
| Online Access: | http://www.geosci-model-dev.net/7/1945/2014/gmd-7-1945-2014.pdf |
| Summary: | High-resolution direct numerical simulations (DNSs) are an important tool for
the detailed analysis of turbidity current dynamics. Models that resolve the
vertical structure and turbulence of the flow are typically based upon the
Navier–Stokes equations. Two-dimensional simulations are known to produce
unrealistic cohesive vortices that are not representative of the real
three-dimensional physics. The effect of this phenomena is particularly
apparent in the later stages of flow propagation. The ideal solution to this
problem is to run the simulation in three dimensions but this is
computationally expensive.
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This paper presents a novel finite-element (FE) DNS turbidity current model
that has been built within Fluidity, an open source, general purpose,
computational fluid dynamics code. The model is validated through re-creation
of a lock release density current at a Grashof number of 5 × 10<sup>6</sup> in
two and three dimensions. Validation of the model considers the flow energy
budget, sedimentation rate, head speed, wall normal velocity profiles and the
final deposit. Conservation of energy in particular is found to be a good
metric for measuring model performance in capturing the range of dynamics on a
range of meshes. FE models scale well over many thousands of processors and do
not impose restrictions on domain shape, but they are computationally
expensive. The use of adaptive mesh optimisation is shown to reduce the
required element count by approximately two orders of magnitude in comparison
with fixed, uniform mesh simulations. This leads to a substantial reduction in
computational cost. The computational savings and flexibility afforded by
adaptivity along with the flexibility of FE methods make this model well
suited to simulating turbidity currents in complex domains. |
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| ISSN: | 1991-959X 1991-9603 |