Johns Hopkins Turbulence Databases

Forced Isotropic Turbulence

Forced MHD Turbulence

Channel Flow

HB Driven Turbulence

Dataset
descriptions

1. Forced isotropic turbulence:

Simulation data provenance: JHU DNS code (see README-isotropic for more details).

- Direct numerical simulation (DNS) using 1,024
^{3}nodes. - Navier-Stokes is solved using pseudo-spectral method.
- Energy is injected by keeping constant the total energy in shells such that |k| is less or equal to 2.
- After the simulation has reached a statistical stationary state, 5,028 frames of data with 3 velocity components and pressure are stored in the database. Extra time frames at the beginning and at the end have been added to be used for temporal-interpolations.
- The Taylor-scale Reynolds
number fluctuates around R
_{λ}~ 433 - There is one dataset ("coarse") with 5028 timesteps available, for time t between 0 and 10.056 (the frames are stored at every 10 time-steps of the DNS). Intermediate times can be queried using temporal-interpolation.
- There is another dataset ("fine") that stores every single time-step of the DNS, for testing purposes. Times available are for t between 0.0002 and 0.0198).
- A table with the time history of the total kinetic energy and Taylor-scale Reynolds number as function of time can be downloaded from this text file.
- Radial spectrum E(k) averaged over time can be downloaded from this text file.

2. Forced MHD turbulence:

Simulation data provenance: JHU DNS code (see README-MHD for more details).

- Direct numerical simulation (DNS) using 1,024
^{3}nodes. - Incompressible MHD equations are solved using pseudo-spectral method.
- Energy is injected by using a Taylor-Green flow stirring force.
- After the simulation has reached a statistical stationary state, 1,024 frames of data with 3 velocity components, pressure, 3 magnetic field and magnetic vector potential components are stored in the database.
- The Taylor-scale Reynolds
number fluctuates around R
_{λ}~ 186. - 1024 timesteps are available, for time t between 0 and 2.56 (the frames are stored at every 10 time-steps of the DNS). Intermediate times can be queried using temporal-interpolation.
- A table with the spectra of the velocity, magnetic field, Elsasser variables, cross-helicity and magnetic helicity can be downloaded from this text file.
- A table with the time histories of energy and dissipation, both kinetic and magnetic, as well as of magnetic and cross helicity, can be downloaded from this text file.

3. Channel flow:

Simulation data provenance: Collaboration of UT Texas and JHU, using the UT Texas DNS code (see README-CHANNEL for more details).

- Direct numerical simulation (DNS) of channel flow in a domain of size 8π x 2 x 3π , using 2048 x 512 x 1536 nodes.
- Incompressible Navier-Stokes equations are solved using the pseudo-spectral (Fourier-Galerkin) method in wall-parallel (x, z) planes, and the 7th-order B-spline collocation method in the wall-normal (y) direction.
- Simulation is run and equilibrated using prescribed bulk velocity=1, then switched to imposed pressure gradient (dP/dx = 0.0025) and further equilibrated.
- After the simulation has reached a (nearly) statistical stationary state, 4,000 frames of data with 3 velocity components and pressure are stored in the database. The frames are stored at every 5 time-steps of the DNS. This corresponds to about one channel flow-through time. Intermediate times can be queried using temporal-interpolation.
- The friction velocity is u
_{τ}= 0.0499. - The viscosity is ν = 5 x 10
^{-5}. - The friction velocity Reynolds number is Re
_{τ}~ 1000. - The y-locations of the grid points in the vertical direction can be downloaded from this text file; the corresponding B-spline knot locations can be obtained from this text file.
- A table with the time history of friction velocity Reynolds number can be downloaded from this text file.
- A table with the vertical profiles of mean velocity, Reynolds shear stresses, viscous stress, normal stress, mean pressure, pressure variance and pressure-velocity covariance in viscous units, can be downloaded from this text file.
- Files with tables of the streamwise (k
_{x}) spectra of u, v, w, p at various heights can be downloaded for the following y+ values: 10.11, 29.89, 99.75, 371.6, and 999.7. - Files with tables of the spanwise (k
_{z}) spectra of u, v, w, p at various heights can be downloaded for the following y+ values: 10.11, 29.89, 99.75, 371.6, and 999.7. - GetPosition and Filtering functions not yet implemented for the channel flow dataset.

4. Homogeneous buoyancy driven turbulence:

Simulation data provenance: Los Alamos National Laboratory using the LANL DNS code (see README-HBDT for more details).

- Direct Numerical Simulation (DNS) of homogeneous buoyancy driven turbulence in a domain size 2π x 2π x 2π,
using 1,024
^{3}nodes. - The incompressible two-fluid Navier-Stokes equations are solved using a pseudo-spectral method. These equations represent the large speed of sound limit for the fully compressible Navier-Stokes equations with two fluids having different molar masses and obeying the ideal-gas equation of state.
- The domain is triply periodic and the homogeneity of the fluctuating quantities is ensured by imposing mean zero velocity and constant mean pressure gradient. These conditions are similar to those encountered in the interior of the Rayleigh-Taylor mixing layer.
- The two fluids are initialized as random blobs, with a characteristic size of about 1/5 of the domain. The flow starts from rest, in the presence of a constant gravitational acceleration, and the fluids start moving in opposite direction due to differential buoyancy forces. Turbulence fluctuations are generated and the turbulent kinetic energy increases; however, as the fluids become molecularly mixed, the buoyancy forces decrease and at some point the turbulence starts decaying.
- Due to the change in specific volume during mixing, the divergence of
velocity is not zero, but related to the density field. This leads to a
variable coefficient Poisson equation for pressure, which is decomposed in two
parts, for the gradient and curl components of ∇
*p*/ρ. These are solved using direct solvers to ensure mass conservation and baroclinic generation of vorticity to machine precision. - The 1015 time frames stored in the database cover both the buoyancy driven increase in turbulence intensity as well as the buoyancy mediated turbulence decay. Each time frame contains the density, 3 velocity components, and pressure at the grid points. The frames are stored at a constant time interval of 0.04, which represents between 20 to 50 DNS time steps.
- Schmidt number: 1.0
- Froude number: 1.0
- Atwood number: 0.05
- Maximum turbulent Reynolds number: Re
_{τ}~ 17,765. - Minimum turbulent Reynolds number during decay phase: Re
_{τ}~ 1,595. - A file with the time history of the Favre turbulent kinetic energy,

k^{˜}= <ρu_{i}^{''}u_{i}^{''}> ⁄ 2<ρ>, Reynolds stresses, R_{ii}= <ρu_{i}^{''}u_{i}^{''}> (no summation over i), vertical mass flux, a_{v}= <ρ u_{1}^{'}> ⁄ <ρ>, turbulent Reynolds number, Re_{t}= k^{˜2}⁄ νε, eddy turnover time, τ = k^{˜}⁄ ε, kinetic energy dissipation, ε, density variance and density-specific volume correlation can be found here.(Note: Until July 22, 2015, the time-history file that was posted on this site included the total kinetic energy instead of the Favre turbulent kinetic energy. The file posted since July 22, 2015 lists the Favre turbulent kinetic energy) - Files with tables of the power spectra of density, 3 velocity components, and mass flux can be downloaded at the following times: 6.56, 11.4, 15.0, 20.0, 30.0, and 40.0.
- Files with tables of the density PDF can be downloaded for the following times: 0.0, 6.56, 11.4, 15.0, 20.0, 30.0, and 40.0.

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