Experimental studies on dispersion processes in periodic flows

The aim of this thesis Experimental studies on dispersion processes in periodic flows is to study the hydrodynamics and asses the mixing properties of periodic flows, through extensive experimental campaigns. With mixing, we refer to the field of environmental fluid mechanic that seeks to provide tools to assess the flow of nutrients needed for the survival of an ecosystem, limit toxic pollutants and minimize the anthropic impact. Over the last twenty years, a lot of literature had been devoted to asses mixing processes occurring in uniform flows but less on periodic ones. A periodic flow is an oscillatory flow whose characteristics assume the same sequence of values exactly after a fixed length of time, known as the period. These repetitive velocity patterns produce in the hydrodynamics a periodical occurrence and, eventually, destruction of flow structures responsible for the dispersion or the entrainment of pollutants/ nutrients within the domain considered. Coastal areas provide a typical example of regions dominated by period flows, such as those induced by tidal currents and sea waves. These areas are also characterised by a massive human development, and biodiverse ecosystems, making the study of the mixing of paramount importance for their sustainment and preservation.