Inlet grid-generated turbulence for large-eddy simulations

Abstract

A new technique of generating turbulence in large-eddy simulations (LES) has been investigated and results compared with previous studies for validation. The proposed gridInlet technique uses a grid pattern on the inlet boundary patch to produce grid-generated turbulence as used in wind tunnel experiments. This allows the turbulence integral length scale to be controlled by changing the grid size, while the turbulence intensity is controlled by changing the inlet distance. The objective of this paper is to investigate domain and mesh requirements to implement the gridInlet technique. This technique is most suited to studies on the influence of high-intensity isotropic turbulence on objects, particularly if comparisons are to be made to experimental data obtained with grid-generated turbulence.

Keywords:

• LES
• inlet turbulence
• inlet boundary patch
• grid-generated turbulence
• CFD

Acknowledgements

The authors acknowledge the use of the IRIDIS High Performance Computing Facility and associated support services at the University of Southampton in the completion of this work.

Notes

Notes: ^aThe inlet flow is calculated using the grid porosity, θ, and mean flowrate velocity, U _o , such that .

Figure 1 Numerical domain and boundaries for single, double and triple period inlets

^bSwitches between zero value and zero gradient, allowing vortices to exit the domain.

Notes: ^aNumber of cells per grid spacing.

^bSize of domain cross-section, i.e. double period is a domain of 2M by 2M and triple period, 3M by 3M.

Notes: ^a Re = Flow Reynolds number; Re _λ = Taylor microscale Reynolds number; λ = Taylor microscale.

Figure 9 Resolved and modelled components of turbulence intensity (logarithmic axes) for the M = 40 mm grid and Re = 36,000

^bSimulations in the limit of an infinite Reynolds number such that dissipation is from the sub-grid model only.

^cAt x/M = 10.