Multiple concentrated vortices are often produced in the wake of lifting surfaces and downstream of pumps, turbines, and propulsors. The roll-up of multiple vortex strands is a common feature of these flows. In this study, we are examining the interaction of two vortices of variable strength and relative rotation (e.g. co-rotating or counter-rotating). A pair of equal-strength co-rotating vortices will merge to form a single vortex. However, as the relative strength of the vortices is decreased, the weaker vortex can wrap around the stronger vortex, causing the weaker vortex to be stretched. This stretching process can lead to cavitation inception. In the present work, we will examine this inception process. 德國LaVision PIV/PLIF粒子成像測速場儀 Imager SX PIV相機(jī) 用于粒子成像測速(PIV)的熒光示蹤粒子