Two-dimensional unsteady incompressible flows in which the potential vorticity (PV) plays a key role are examined in this study. through the development of the evolution equation for the PV gradient. For the case where the PV is conserved. precise statements concerning topology-conservation are presented. https://www.bekindtopets.com/best-offer-Bilstein-53-264817-B8-5100-Series-Dual-Steering-Damper-Kit-2013-2022-Ram-2500-3500-super-value/