Christian T. Jacobs

Surface-sampled simulations of turbulent flow at high Reynolds number

Summary A new approach to turbulence simulation, based on a combination of large-eddy simulation (LES) for the whole flow and an array of non-space-filling quasi-direct numerical simulations (QDNS), which sample the response of near-wall turbulence to large-scale forcing, is proposed and evaluated. The technique overcomes some of the cost limitations of turbulence simulation, since the main flow is treated with a coarse-grid LES, with the equivalent of wall functions supplied by the near-wall sampled QDNS. Two cases are tested, at friction Reynolds number Reτ=4200 and 20000. The total grid node count for the first case is less than half a million and less than two million for the second case, with the calculations only requiring a desktop computer. A good agreement with published DNS is found at Reτ=4200, both in terms of the mean velocity profile and the streamwise velocity fluctuation statistics, which correctly show a substantial increase in near-wall turbulence levels due to a modulation of near-wall streaks by large-scale structures. The trend continues at Reτ=20000, in agreement with experiment, which represents one of the major achievements of the new approach. A number of detailed aspects of the model, including numerical resolution, LES-QDNS coupling strategy and sub-grid model are explored. A low level of grid sensitivity is demonstrated for both the QDNS and LES aspects. Since the method does not assume a law of the wall, it can in principle be applied to flows that are out of equilibrium. This article is protected by copyright. All rights reserved.

Turbulent channel flow simulation at friction Reynolds number Re_tau = 20,000

Dataset supports: Sandham, N., Johnstone, R., and Jacobs, C. (2017). Surface-sampled simulations of turbulent flow at high Reynolds number. International Journal for Numerical Methods in Fluids.Dataset from a turbulent channel flow simulation at friction Reynolds number Re_tau = 20,000. The modelling approach considers a single large eddy simulation (LES) combined with an array of non-space-filling quasi-direct numerical simulations (QDNSs).

Solution field data from a three-dimensional Taylor-Green vortex simulation

Solution field data from a three-dimensional Taylor-Green vortex simulation, performed using the OpenSBLI code with a uniform grid of 256^3 points.

Enstrophy and kinetic energy data from 3D Taylor-Green vortex simulations

Enstrophy and kinetic energy data from four 3D Taylor-Green vortex simulations, using uniform grids of 64^3, 128^3, 256^3, and 512^3 solution points. The simulations were performed using the OpenSBLI code developed at the University of Southampton.Dataset to support: Jammy, Satya, Jacobs, Christian and Sandham, Neil (2016) Performance evaluation of explicit finite difference algorithms with varying amounts of computational and memory intensity. Journal of Computational Science, 1-15.