The mixing layer between non-parallel streams

Compared to the classical two-dimensional plane mixing layer, the mixing layer between non-parallel streams has an additional degree of freedom: the angle between the streams and the direction perpendicular to the trailing edge. Consequently the mean vorticity vector, which depends on these angles, is no longer by necessity parallel to the trailing edge of the flow. The ensuing coherent structures are generally helices with components normal to the trailing edge. They can be controlled by different mechanisms, depending on the velocity vectors.