The spanwise spectra in wall-bounded turbulence
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The pre-multiplied spanwise energy spectra of streamwise velocity fluctuations are investigated in this paper. Two distinct spectral peaks in the spanwise spectra are observed in low-Reynolds-number wall-bounded turbulence. The spectra are calculated from direct numerical simulation (DNS) of turbulent channel flows and zero-pressure-gradient boundary layer flows. These two peaks locate in the near-wall and outer regions and are referred to as the inner peak and the outer peak, respectively. This result implies that the streamwise velocity fluctuations can be separated into large and small scales in the spanwise direction even though the friction Reynolds number \(Re_\tau \) can be as low as 1000. The properties of the inner and outer peaks in the spanwise spectra are analyzed. The locations of the inner peak are invariant over a range of Reynolds numbers. However, the locations of the outer peak are associated with the Reynolds number, which are much higher than those of the outer peak of the pre-multiplied streamwise energy spectra of the streamwise velocity.
KeywordsWall-bounded turbulence Streamwise/spanwise spectra Scale separation Inner/outer peak
This work was supported by the National Natural Science Foundation of China (Grants 11302238, 11232011, 11572331, and 11490551). The authors would like to acknowledge the support from the Strategic Priority Research Program (Grant XDB22040104), the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grant QYZDJ-SSW-SYS002), and the National Basic Research Program of China (973 Program 2013CB834100 : Nonlinear Science).
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