Analysis on L vortex development in a transitional boundary layer
Although plentiful research on L vortex can be found in literature, the mechanism of Lvortex generation is still in veil. Despite the difference in initial perturbation conditions in both experiments and numerical simulations, the following L vortex was found to be basically the same, which leads to an assumption that L vortex is an inherent characteristic of boundary layer equations. On the other hand, the initial disturbance or T S wave is believed to function as trigger and should not be viewed as an embryonic form of L vortex. The notion L vortex comes from wave growth according to primary and secondary instability theory is not convincing at all. In this paper, the shape of L vortex and its relation with initial disturbance is carefully investigated using direct numerical simulation (DNS) The mechanism of L vortex generation is the ultimate goal of this paper.