This project is concerned with the general problem of nano-pollutant removal.
In particular, it aims at studying how ultra-fine solid particles dispersed in water can be captured and aggregated in order to be removed more easily. Recent investigations have shown that nanobubbles (referred to as NBs hereinafter) can be used to promote aggregation of suspended solids (referred to as particles hereinafter).
The underlying mechanisms are still unclear because they depend on the interaction between the NBs and the particles, which occurs at a scale that cannot be accessed optically.
An additional difficulty is due to the large scale separation between the NBs, which have size O(10) nanometers, and the particles, which are of micrometer size.
Here, The team proposes to develop a novel numerical framework to improve current physical understanding of NB-promoted aggregation and, in turn, to quantify this effect on the aggregation growth rate.
The final objective is to provide a reliable framework for the study of aggregation and removal of suspended solids by means of NBs.
The framework is based on Direct Numerical Simulation of the flow, coupled with a Direct-Forcing Immersed Boundary Method for the particles and Lagrangian Tracking of the NBs. Four DNS of the three-phase flow problem are planned: three of homogeneous isotropic turbulence and one of open-channel flow.
The interest in such processes comes from their huge practical importance in a wide variety of applications, from wastewater treatment and oxygenated irrigation to hetero-coagulation and medical applications related to targeted drug delivery.
All these applications aim at exploiting the long-time (meta)stability of the NBs in aqueous solutions, which is particularly persistent when the n-bubbles are made of insoluble gas.
Cristian Marchioli, University of Udine - Italy