On the different contributions of coherent structures to the spectra of a turbulent round jet and a turbulent boundary layer

This paper examines and compares spectral measurements from a turbulent rou nd jet and a turbulent boundary layer. The conjecture that is examined is t hat both flows consist of coherent structures immersed in a background of i sotropic turbulence. In the case of the jet, a single size of coherent stru cture is considered, whereas in the boundary layer there are a range of siz es of geometrically similar structures. The conjecture is examined by compa ring experimental measurements of spectra for the two flows with the spectr a calculated using models based on simple vortex structures. The universali ty of the small scales is considered by comparing high-wavenumber experimen tal spectra. It is shown that these simple structural models give a good ac count of the turbulent flows.