Two-Point Cross-Spectral and POD Analysis of High Reynolds Number Zero Pressure Gradient Turbulent Boundary Layer*

This study reports some of the two-point cross-spectral and proper orthogonal decomposition analyzes performed on the zero pressure gradient flat plate turbulent boundary layer experiments at R$_{\theta}=$9800 and 19,100. They are based on hot-wire measurements using a rake of 143 single wire probes placed in the LML wind tunnel, which has a 20 m long test section with approximately 30 cm of boundary layer thickness. Elongated correlations and their variation across the boundary layer are shown using two-point space-time correlations computed over very long records. The possible interaction between the inner and outer layer is discussed using the cross-correlations analysis and also a POD-based reconstruction of the velocity fields on a plane normal to the streamwise direction. Organization of the large scale structures on the same plane is also demonstrated using a combination of different spanwise Fourier and POD modes.