Flow instability occurring in the collision of jets of an ideal incompressible fluid

Fourier method in the problem of small perturbations of colliding jets

“…Though the solutions found are physically meaningful (the growth of perturbations at infinity means instability of a single jet in Lagrangian coordinates), the analysis of the eigenvalues λ found does not allow us to conclude whether a given jet configuration is stable or unstable, i.e., the issue of stability in Eulerian coordinates is not clear. The statement on instability of all jet configurations proved in [1,5,6] on the basis of presentation (1) …”

“…The basic result of [1] was determining the eigenvalues λ. Presentation (1) was used to solve a number of various jet problems (see, e.g., [2][3][4][5][6]). At the same time, there are some publications whose authors doubt the applicability of presentation (1) or state that Eq.…”