混合層の大規模渦構造制御における速度比の影響

抄録

To clarify the effect of velocity ratio on the control of large-scale structures in mixing layers, two-dimensional spatially developing mixing layers perturbed periodically were studied using direct numerical simulation. The perturbation consists of fundamental and subharmonic modes of the most unstable wave based on linear stability theory. The results show that it is possible to control the development of large-scale structures by controlling the initial phase difference between two modes, and that there exists a certain initial phase difference which suppresses vortex pairing. This initial phase difference varies with the velocity ratio. The downstream variations of the phase difference between fundamental and subharmonic modes of streamwise velocity fluctuation were also investigated. In the linear growth region, the local phase difference increases at a constant rate which varies with the velocity ratio. This linear increase of phase difference is explained by the dependence of phase velocity on the velocity ratio, which is derived from the linear stability theory. Because of this linear increase of phase difference, the initial phase difference which suppresses the pairing varies with the velocity ratio.