Utilization of the second invariant of the velocity gradient tensor to visualize the vortex tubes. Increasing the AR from 1.2 to 2.5 intensifies the vortex tubes strength inside the impactor. There are two main vortex tube in side impaction chamber for small Reynolds numbers. The strength of vortices affects the undersize particles deposition in inertial impactors. For Collecting finer particles, an impactor with higher Reynolds number should be used.