DNS analysis on turbulence modulation by cavitation

The two-way interaction between cavitation and turbulence was investigated by the direct numerical simulation of a spatially-developing mixing layer. Namely, the vortical structure and Reynolds stress components were compared between cavitating and non-cavitating conditions. Cavitation mainly occur in the regions of low pressure which are corresponding to vortices. Under cavitating condition, instability of mixing layer is caused more easily due to disturbance by cavitation to the flow field. Therefore, the onset of the instability is shifted into upstream. In more developed region, pitch of roll-cell vortices get longer than non-cavitating condition as a result of shift of pairing process. Longer pitch of roll-cell vortices results in the decreasing of Reynolds stress component which is corresponding to one of the circumferential components of roll-cell vortices. Circumferential component of streamwise vortices, on the other hand, tends to increase in comparison with non-cavitating condition. This is explained by volume fluctuation by cavitation. The modulation of Reynolds stress is consistently described by these changes in vortical structures.