Abstract
The wall-attached structures of velocity fluctuations over a traveling wavy boundary are explored here by performing large eddy simulation (LES) at a moderate Reynolds number (). The wave slope is , where is the wave amplitude and is the wave number. The prescribed wave age is where is the wave phase speed and is the friction velocity. For comparison, the results of a LES over a smooth wall are also discussed. The wall-attached structures are self-similar with respect to their heights, and in particular the population density of their streamwise components scales inversely with their heights, which is reminiscent of a hierarchy of attached eddies. The wall-attached structures in the flow over the traveling wavy boundary retain geometric self-similarity; however, their streamwise length scale is decreased by the wavy boundary while their spanwise length scale is increased. By conditionally averaging the streamwise velocity fluctuations within the wall-attached structures, the reconstructed streamwise turbulent intensity was found to exhibit logarithmic behavior. The turbulent intensity carried by the small-scale wall-attached structures in the near-wall region is weakened by the traveling wavy boundary, while that of the large-scale wall-attached structures in the outer region is enhanced. The streamwise velocity corresponding to the highest uniform momentum zone for the large-scale wall-attached structures in the presence of the wavy boundary is larger than that for the smooth wall.
6 More- Received 20 August 2020
- Accepted 16 December 2020
DOI:https://doi.org/10.1103/PhysRevFluids.6.034611
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