Secondary instability of large scale structure in free turbulent shear layer

The secondary instability theory is used to study the behavior of spatially growing disturbance in free turbulem shear layer. The numerical results indicate that secondary instability of subharmonic mode shows a strong choice of spanwise wavenumber and the maximum growth rate occurs in two dimensional case. In contrast to that secondary instabilities of the fundamental mode occur in a wide scope of spanwise wavenumber. We have found so called translative instability at β=0 and bifurcation phenomenon for an amplitude of the KH wave larger than 0.06. Project supported by the National Natural Science Foundation of China