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Artikel
Simulations of two-dimensional and quasi-geostrophic turbulence
| Författare: |
Vallgren, |
| Dokumenttyp: |
Rapport |
| Tillstånd: |
Okänd |
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| År: |
2010 |
AbstractThis report is devoted to the details of the two codes that have been developed aimed at studies of large-scale turbulent flows. For this purpose, a first approach has been to derive and implement a code (PNSE2D) that simulates two-dimensional turbulence by numerically solving the two-dimensional incompressible Navier-Stokes equation in a doubly periodic square domain. The second code (QGE3D) adds complexity by taking into account background rotation and a stable stratification. This latter code solves the QG equation for the potential vorticity derived by Charney (1971), and can be considered an extension from PNSE2D into three dimensions. The motivation for developing new codes instead of using existing codes is that it gives us full control of the codes while they solve the equations in a very simple geometry (periodic boundary conditions). Furthermore, the codes are portable and have been developed to give a high degree of flexibility. The two codes have in common, among other things, the need for high resolution, which required the codes to be parallelized for utilization on parallel machines. Experiments have shown that good speed-up is obtained when increasing the number of processes (essentially increasing the number of cpu:s). The codes rely on a message passing interface (MPI) and a fast FFT-library, FFTW. The codes have been validated by the conservation of the inviscid invariants, i.e. energy and enstrophy in two-dimensional turbulent flows, and energy and potential enstrophy in QG turbulence.
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