Identifying the wall signature of large-scale motions with extended POD

Abstract

This work analyzes the effect on the wall of large-scale motions (LSMs) in turbulent channel flows. We assess in which region of the channel the large-scale motions have more impact on the wall-shear stress. The proposed method is based on the extended proper orthogonal decomposition (EPOD), which can provide information about the temporal correlation coefficient between two quantities. In this study, the correlation between velocity fields in wall-normal planes and wall-shear-stress signal is analyzed. To test the method, a database obtained from a direct numerical simulation (DNS) is used. Results show that LSMs have a significant correlation with wall-shear stress located in the logarithmic region. Furthermore, it is found that the largest correlation occurs between the largest scales of the flow field and wall-shear stress signal.