Juan A. Sillero

One-point statistics for turbulent wall-bounded flows at Reynolds numbers up to δ+ ≈ 2000

One-point statistics are presented for new direct simulations of the zero-pressure-gradient turbulent boundary layer in the range Reθ = 2780–6680, matching channels and pipes at δ+ ≈ 1000–2000. For tripped boundary layers, it is found that the eddy-turnover length is a better criterion than the Reynolds number for the recovery of the largest flow scales after an artificial inflow. Beyond that limit, the integral parameters, mean velocities, Reynolds stresses, and pressure fluctuations of the new simulations agree very well with the available numerical and experimental data, but show clear differences with internal flows when expressed in wall units at the same wall distance and Reynolds number. Those differences are largest in the outer layer, independent of the Reynolds number, and apply to the three velocity components. The logarithmic increase with the Reynolds number of the maximum of the streamwise velocity and pressure fluctuations is confirmed to apply to experimental and numerical internal and ext...

Two-point statistics for turbulent boundary layers and channels at Reynolds numbers up to δ+ ≈ 2000

Two-point statistics are presented for a new direct simulation of the zero-pressure-gradient turbulent boundary layer in the range Re θ = 2780–6680, and compared with channels in the same range of Reynolds numbers, δ+ ≈ 1000–2000. Three-dimensional spatial correlations are investigated in very long domains to educe the average structure of the velocity and pressure fluctuations. The streamwise velocity component is found to be coherent over longer distances in channels than in boundary layers, especially in the direction of the flow. For weakly correlated structures, the maximum streamwise length is O ( 7 δ ) for boundary layers and O ( 18 δ ) for channels, attained at the logarithmic and outer regions, respectively. The corresponding lengths for the spanwise and wall-normal velocities and for the pressure are shorter, O ( δ -2δ). The correlations are shown to be inclined to the wall at angles that depend on the distance from the wall, on the variable being considered, and on the correlation level used to define them. All these features change little between the two types of flows. Most the above features are also approximately independent of the Reynolds number, except for the pressure, and for the streamwise velocity structures in the channel. Further insight into the flow is provided by correlations conditioned on the intensity of the perturbations at the reference point, or on their sign. The statistics of the new simulation are available in our website.

Direct simulation of a zero-pressure-gradient turbulent boundary layer up to Re? = 6650

A direct simulation of an incompressible zero-pressure-gradient turbulent boundary layer over a flat plate is performed in Re? = 1100?6650 (Re? ? 2025), matching the range of the available numerical channels. The logarithmic region and the separation of scales are clearly observed. Proper turbulent inflow conditions, key in boundary layers, are generated by an auxiliary simulation at lower resolution and Reynolds number. Results are in agreement with existing numerical and experimental data sets.

Proposed stochastic parameterisations of subgrid turbulence in large eddy simulations of turbulent channel flow

Stochastic and deterministic subgrid parameterisations are developed for the large eddy simulation (LES) of a turbulent channel flow with friction-velocity-based Reynolds number of Reτ = 950 and centreline-based Reynolds number of Re0 = 20,580. The subgrid model coefficients (eddy viscosities) are determined from the statistics of truncated reference direct numerical simulations (DNSs). The stochastic subgrid model consists of a mean-field shift, a drain eddy viscosity acting on the resolved field and a stochastic backscatter force of variance proportional to the backscatter eddy viscosity. The deterministic variant consists of a net eddy viscosity acting on the resolved field, which represents the net effect of the drain and backscatter. LES adopting the stochastic and deterministic models is shown to reproduce the time-averaged kinetic energy spectra of the DNS within the resolved scales.

Direct numerical simulation of a self-similar adverse pressure gradient turbulent boundary layer at the verge of separation

The statistical properties are presented for the direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation. The APG TBL has a momentum thickness based Reynolds number range from

Stochastic self-energy subgrid model for the large eddy simulation of turbulent channel flows

Re_{\delta_2}=570

Hybrid openMP-MPI turbulent boundary layer code over 32k cores

to

Towards the Direct Numerical Simulation of a Self-similar Adverse Pressure Gradient Turbulent Boundary Layer Flow

13800

Public Dissemination of Raw Turbulence Data

, with a self-similar region from

Scale Dependent Stochastic Self-energy Model of the Energy Transfers in Turbulent Channel Flows

Re_{\delta_2} = 10000