2. Empirical models of excitation spectra

2.1 Frequency and wavenumber spectra

The pressure loading induced by a turbulent boundary layer is usually represented by :

• of a time correlation function at a point – or of the frequency spectrum, denoted Φ _pp (ω) or more simply Φ(ω) ;

• of a correlation spectrum in space and time – or of the wave-frequency number spectrum, denoted Φ _pp (k, ω) or more simply Φ(k, ω).

The spectra were constructed from experimental data from the early 1960s to the present day. The data are obtained for simple configurations, in most cases for flat-plate boundary layer flows, with no opposing pressure...