Self-similarity of wall-attached turbulence in boundary layers

An assessment of the turbulent boundary layer flow structure, which is coherent with the near-wall region, is carried out through a spectral coherence analysis. This spectral method is applied to datasets comprising synchronized two-point streamwise velocity signals at a near-wall reference position and a range of wall-normal positions spanning a Reynolds-number range Re-tau similar to O(10(3))-O(10(6)). Within each dataset, a self-similar structure is identified from the coherence between the turbulence in the logarithmic region and at the near-wall reference position. This self-similarity is described by a streamwise/wall-normal aspect ratio of lambda(x)/z approximate to 14, where lambda(x) and z are the streamwise wavelength and wall-normal distance respectively.