Flocculation Dynamics of cohesive sediment

摘要: Cohesive sediment suspended in natural waters is subject not only to transport and deposition processes but also reactions of flocculation, \textit{i.e.} aggregation fine particles, breakup aggregates. Although occur at small very length scales compared deposition, flocculation can effectively have an impact on the large scale as well. Some phenomena that are correlated (or find roots in) are, for instance, coastal morphodynamics, pollutant contaminant sedimentation rivers, estuaries, lakes, canals, harbours water basins general. Water environments accommodate a variety societal functions, like navigation fish culture, provide potable supply serve industrial waste demand. At same time, bear several ecosystem functions essential healthy environment. The complicated balance between human need safeguard one rationales studying waters. specific focus this thesis directed towards genesis flocs by cohesive behaviour population aqueous environments. Floc size distribution, floc structure models investigated means three methods: experiments, mathematical analysis numerical modeling. experimental activity has been carried out settling column Laboratory Environmental Fluid Mechanics, aimed collecting information under different conditions turbulence intensity. An optical system dedicated collect images comparable designed coupled column. This enabled innovative sight properties suspension sediment, allowing distribution individual flocs. collected with recording elaborated analysed numerically assess First, data processed extract black-and-white Second, characterised quantities, amongst which size, fractal dimensions disorder function. Third, statistics calculated. repeated conditions. result overall portrait time evolution response field produced various intensities. In general we observe grow from (nearly) monodisperse primary developing distributed over wider range sizes. On hand (the scales), appears adapt forcing, process decrease spatial entropy reshaping distributions into more complex population. other growth accompanied dimension and, increase geometrical complexity, disorder. results given pulse modelling suspensions new equation. implemented through model. equation full mechanisms examined. then ones evaluate predictive skills shows implementation kinematic enables proper prediction capability major aspects present study characterisation interaction among aggregates within source considerations dynamics particular flocculating systems However, could achieved without obtained column, unique respect involved, control parameters measuring techniques.