1. 1 LES of Turbulent Flows: Lecture 4 (ME EN 7960-003) Prof. Rob Stoll Department of Mechanical Engineering University of Utah Fall 2014

2. 2 LES Filters and their transfer functions Real Space FiltersFilter Transfer Function Only the Gaussian filter is local in both real and wave space

3. 3 Filtering Turbulence (real space, cutoff filter) Note: here (and throughout the presentation) we are using DNS data from Lu et al. (International Journal of Modern Physics C, 2008).

4. 4 Filtering Turbulence (real space, Gaussian filter) Note: here (and throughout the presentation) we are using DNS data from Lu et al. (International Journal of Modern Physics C, 2008).

5. 5 Filtering Turbulence (real space, box filter) Note: here (and throughout the presentation) we are using DNS data from Lu et al. (International Journal of Modern Physics C, 2008).

6. 6 Filtering Turbulence (real space) Note: here (and throughout the presentation) we are using DNS data from Lu et al. (International Journal of Modern Physics C, 2008).

7. 7 Filtering Turbulence (wave space) π/Δ 2 π/Δ 1 π/Δ 2 π/Δ 1 π/Δ 2 π/Δ 1

8. 8 Filtering Turbulence (wave space) π/Δ 1 π/Δ 2 Comparison between different filters

9. 9 We can use our filtered DNS fields to look at how the choice of our filter kernel affects this separation in wavespace Decomposition of Turbulence for real filters π/Δ Resolved scales SGS scales Resolved SFS Resolved scales SGS scales