Author(s): Andrea Zampiron; Bastien Cerino; Vladimir Nikora
Linked Author(s): Vladimir Nikora
Keywords: Coherent structures; Turbulence; Open-channel flow; Structure functions
Abstract: Large- (LSMs) and very-large-scale (VLSMs) motions in open-channel flows (OCFs) are turbulent coherent structures providing significant contributions to momentum exchange (>50%), and thus to flow drag. The most common method for the identification of LSMs and VLSMs relies on premultiplied velocity spectra, where they appear as two “spectral hills” at large streamwise wavelengths (or small wavenumbers). LSMs are low-momentum regions with a length λ ≈ 2-4 flow depths (H), whereas VLSMs are depth-filling counterrotating streamwise rotational motions that can reach lengths up to λ ≈ 50H (Cameron et al., 2017). In this work, we propose an approach for identifying LSMs and VLSMs using second-order structure functions, thereby unlocking possibilities for further analysis by employing higher-order structure functions.
Year: 2024