Comparison of two parameterizations of a turbulence-induced flocculation model through global sensitivity analysis

This paper describes a global sensitivity analysis of a fractal-based turbulence-induced flocculation model. The quantities of interest in this analysis are related to the floc diameters in two different configurations. The input parameters with which the sensitivity analyses are performed are the floc aggregation and breakup parameters, the fractal dimension and the diameter of the primary particles. Two related versions of the flocculation model are considered, evenly encountered in the literature: (i) using a dimensional floc breakup parameter, and (ii) using a non-dimensional floc breakup parameter. The main results of the sensitivity analyses are that only two parameters of model (ii) are significant (aggregation and breakup parameters) and that the relationships between parameter and quantity of interest remain simple. Contrarily, with model (i), all parameters have to be considered. When identifying model parameters based on measures of floc diameters, this analysis hence suggests the use of model (ii) rather than (i). Further, improved models of the fractal dimension do not seem to be required when using the non-dimensional model (ii).