The effect of numerical errors and turbulence models in large-eddy simulations of channel flow, with and without explicit filtering

Abstract

Turbulent channel flow simulations are performed using second- and fourth-order finite difference codes. A systematic comparison of the large-eddy simulation (LES) results for different grid resolutions, finite difference schemes, and several turbulence closure models is performed. The use of explicit filtering to reduce numerical errors is compared to results from the traditional LES approach. Filter functions that are smooth in spectral space are used, as the findings of this investigation are intended for application of LES to complex domains. Explicit filtering introduces resolved subfilter-scale (RSFS) as well as subgrid-scale (SGS) turbulence terms. The former can be theoretically reconstructed; the latter must be modelled. The dynamic Smagorinsky model, the dynamic mixed model, and the new dynamic reconstruction model are all studied. It is found that for explicit filtering, increasing the reconstruction levels for the RSFS stress improves the mean velocity as well as the turbulence intensities. When compared to LES without explicit filtering, the difference in the mean velocity profiles is not large; however the turbulence intensities are improved for the explicit filtering case.

Numerically induced high-pass dynamics in large-eddy simulation

“…In practice, one frequently observes that the subfilter resolution r is taken as low as 1 or 2. 8,15,25,26 In such cases the smallest retained flow features are only marginally resolved and one may anticipate a significant effect from the numerical discretization. 9,16 Hence, even though the numerical filtering component can be controlled in principle by choosing r sufficiently large, virtually all large-eddy studies reported in literature contain dynamic contributions arising from the coarseness of the discretization.…”

Computational Methodology of Sodium-Water Reaction Phenomenon in Steam Generator of Sodium-Cooled Fast Reactor

“…Inside the inner vessel, a pin bundle of 43 straight tubes, the alignment of which was the same as that of the Japanese prototype fast breeder reactor 'Monju' but rotated by an angle of 24 , was implemented. Figure 2 depicts the test section of the pin bundle.…”

“…The angle of 24 was chosen so as to maximize the influence of the reacting zone on the neighboring tubes based on the previous observation.…”

Grid filter models for large‐eddy simulation

“…Indeed, the filter G to consider in practical simulations is a composition of the convolution filter L and the projective grid filter, referred to as P such that G = (L • P) , thereby embodying the explicit LES filter L and the implicit projective grid filter P [2,3], represented by a hat. In the sequel, the focus is put on the particular case where implicit grid filtering is the only effective filter.…”