Coherent structures refer to organized patterns or structures within fluid flows that persist over time and space. These structures play a crucial role in the dynamics and transport processes of fluid flows, as they can greatly influence momentum and energy transfer within the flow. Coherent structures can take various forms, such as vortices, jets, or large-scale eddies, and can be observed in both natural and engineered fluid systems. Studying coherent structures helps researchers better understand and predict the behavior of complex fluid flows, leading to advancements in various fields such as aerospace engineering, environmental science, and oceanography.