Reasons for the roughness of turbulent pressure-fluctuation spectra

Various reasons for the jagged nature of the spectra of pressure pulsations in the turbulent boundary layer on a surface immersed in a flow are investigated. Preliminary statistical analysis of spectra obtained for flow around a body of revolution at Reynolds numbers ranging from 40,000,000 to 126,000,000 reveals the existence of a series of families of vortex scales, with the scales in each family standing in a geometric progression with common ratio of 0.5. This suggests that the production of smaller-scale vortices takes place when larger-scale vortices lose stability and divide in two.