Meandering motions and their relation to the energy spectrum in turbulent shear flows

Abstract

This study presents the contribution of the large-scale motions to the turbulent energy using custom-made arrays of hot-wire probes arranged in the span-wise direction. Decomposing the stream-wise velocity fluctuations into large- and small-scale components through the Fourier transform in the span-wise direction and evaluating their scales using the two-point correlation, it is found that the large-scale components have a large contribution in the generation of the outer peak of the turbulent pre-multiplied spectrum (PMS). The outer peak remains even in the low Reynolds number, and it is related to the span-wise organization of large-scale structure of u fluctuations. The spatial correlation in the stream-wise direction shows the large scale of 10δ, where δ is the boundary layer thickness, which is consistent with the outer peak wavenumber of PMS.