Detuned secondary instabilities in three-dimensional boundary-layer flow

A three-dimensional boundary layer is the seat of a spatially amplified instability, the crossflow instability, which is encountered for example on swept wings. Beyond a certain amplitude, the flow destabilizes again through a secondary instability. The objective of this work is to show that by using a discrete spatial Floquet method (Block method) from a certain transversally periodic elementary pattern, there can exist a large-scale modulation linked to amplification mechanisms involving detuned modes.