Numerical modeling and simulation of aggregation and clogging phenomena in Microfluidic devices

Simulations are dominant and essential tools for achieving understanding into microfluidics processes. Eventually, experimental work could be substitute by simulations. Therefore, more precise modeling approach is required to describe the particles behavior in the system. The aim of this study was to understand the particle-particle, particle-aggregate, particle-wall, aggregate-aggregate and aggregate-wall mechanism which lead to microfluidics clogging. In the first part of this thesis, aggregation/fragmentation dynamics of hard-gel single size microparticles suspended in a Newtonian liquid owing through a straight channel is studied by numerical simulations. A one-way Discrete Element Method is employed to simulate the motion and the adhesion of the particles. The formation and fragmentation of aggregates, and their deposition at the channel walls are investigated by varying the Reynolds number and the strength of the adhesive force. In addition, a non-periodic channel is considered to simulate the start-up phase of aggregate formation till a `pseudo steady-state' condition. Results in terms of micro-structures, particle velocity profiles, and spatial and temporal evolution of aggregates in 2D and cylindrical (3D) channels are presented and discussed, respectively. In the second part, I studied the two different size microparticles suspended in a Newtonian fluid in laminar flow, by implementing all the above condition except that different adhesive forces combination is used to test various condition in microfluidics in cylindrical (3D) channels. My results show that variation in adhesion forces and Reynold number have a dominating influence on the whole system i.e., at very high adhesion and Reynolds number, the rate of large aggregates generation and wall attachment rate increase tremendously and in case of different size particles big size particle have strong influence in aggregation and wall attachment. Our model can easily explain the agglomeration, fragmentation and clogging phenomena in microfluidics.