Periodic turbulent channel flow

The periodic turbulent channel flow is a well-known benchmark in CFD, to study wall-bounded turbulence. It is attractive as a test case due to its simple setup, and it is well documented in the literature with plenty of database available.

DNS Reτ= 180

Have a look at the following video to see how to run a turbulent channel flow simulation with Xcompact3d and post-process the data with Py4Incompact3d.

In the video, it is shown how to perform a Direct Numerical Simulation of the turbulent channel flow case with a Reynolds number equal to 180. The simulation should take few hours on a dozen of CPU cores to collect converged statistics. The idea is to reproduce figure 4 of Bartholomew, P., Deskos, G., Frantz, R. A., Schuch, F. N., Lamballais, E., & Laizet, S. (2020). Xcompact3D: An open-source framework for solving turbulence problems on a Cartesian mesh. SoftwareX, 12, 100550., web link, but with a lower spatial resolution.

You will see how to use Paraview to visualise the snapshots and Py4Incompact3d to generate the statistics (mean streamwise velocity profiles and rms of the velocity fields). The key parameters in the input file are also discussed.

For this case, input_DNS_Re180_LR_explicittime.i3d from the examples/Channel-Flow directory is used. Information is also provided on how to use the small Fortran file stretching_parameter_channel.f90 which can be use for: (i) determine the stretching intensity close to the wall via the beta parameters (see Laizet, S., & Lamballais, E. (2009) High-order compact schemes for incompressible flows: A simple and efficient method with quasi-spectral accuracy. Journal of Computational Physics, 228(16), 5989-6015, web link); (ii) determine the input Reynolds number of the simulation (the Reynolds number in the input file in Xcompact3d is based on the centreline velocity of a Poisseuille profile and half the height of the channel flow).

The statistics generated with Py4Incompact3d are compared with two sets of reference data (available in ``examples/Channel-Flow` directory of Py4Incompact3d):

1-Lee, M., & Moser, R. D. (2015). Direct numerical simulation of turbulent channel flow up to Reτ=5,200. Journal of fluid mechanics, 774, 395-415.

2-Vreman, A. W., & Kuerten, J. G. (2014). Comparison of direct numerical simulation databases of turbulent channel flow at Reτ= 180. Physics of Fluids, 26(1), 015102.