On the Spanwise Structure of a Plane Mixing Layer

In the plane mixing layer, mixing is accomplished by nominally two-dimensional entrainment of irrotational fluid from both streams by spanwise vorticesl, and three-dimensional motion induced by packets of streamwise counter-rotating vortex pairs2 which loop between adjacent spanwise vortices (the “braids”). These vortical structures originate in two- and three-dimensional instabilities of the mean flow, and hence may be manipulated by small-amplitude excitation at the flow partition.