Onset criteria for freely-decaying isotropic turbulence
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Direct numerical simulation (DNS) data for 3-dimensional forced and freely-decaying simulations
of homogeneous isotropic fluid turbulence. The data was obtained using the pseudospectral
code eDNS -- see the PhD thesis by S. R. Yoffe for details (https://arxiv.org/abs/1306.3408)
This dataset contains the spectra and derived statistical quantities for
all of the simulations performed.
Please see the header for each file for a description of what each data column contains.
For files containing spectra, different time snapshots are separated by a blank line,
with a # comment to give the timestep and plot number.
Decay:
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Data from our decaying simulations may be found in the subfolder 'decay'. The naming convention
is as follows:
d_.avg_spectra -- time evolution of the ensemble-averaged spectra (averaged over multiple runs)
d_.avg_stats -- time evolution of the statistical quantities derived from the ensemble-averaged spectra
where is the grid size and the kinematic viscosity.
Forced:
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Data from our forced simulations may be found in the subfolder 'forced'. The naming convention
is as follows:
f_.spectra -- time evolution of the spectra
f_.stats -- time evolution of the statistical quantities derived from the spectra
f_.avg_spectra -- ensemble-averaged spectra (averaged over multiple snapshots)
f_.avg_stats -- statistical quantities derived from the ensemble-averaged spectra
where is the grid size and the kinematic viscosity. For averaged quantities, the ensemble
is generated from uncorrelated snapshots from the stationary state. The spectra and single-value statistics
represent the average once turbulence has developed from the initial condition.
Note that all simulations except d1024_0.0002 started from an initially Gaussian field with energy spectrum
going as k^4 at low wavenumber (spectrum S5). The decaying simulation d1024_0.0002 started from an initial
field taken from an evolved forced simulation, f1024_0.0002.
Please see the PhD thesis by S. R. Yoffe for details on initial conditions (Section 2.2.5, p42), calculation of
statistics (Section 2.5, p57), code benchmarking (Chapter 3, p69), and a description of the simulations:
-- Decay: Section 4.1, p102;
-- Forced: Section 5.1, p120.
Thesis available online at:
--- https://arxiv.org/abs/1306.3408
--- https://www.era.lib.ed.ac.uk/handle/1842/7541