Since the COVID-19 pandemic has been a global crisis that has posed enormous and diverse challenges to humanity, it has revealed the urgent need for further study into a variety of properties of viruses, including virus particle size. The virus particle size ranges from 0.1 μm to 0.3 μm. As a result, based on the size of the COVID-19 virus particle, this thesis addresses the challenges encountered in focussing sub-300 nm nanoparticles using an aerodynamic lens and introduces a procedure for developing aerodynamic lens systems that can be used for measuring nanoparticle size. Perhaps this research will serve as a starting point for finding a solution or assist in the discovery of a cure for the global epidemic. The research undertaken for this thesis has also demonstrated how ANSYS Fluent (2021R1) software can be used for simulating a computational fluid dynamic (CFD) for an effective lens and nozzle configuration.

Employing ANSYS Fluent enabled the creation of a computational technique for developing and evaluating an aerodynamic lens and a divergent nozzle for focussing a flow that transmits particles as small as 300 nm through a sharp-edged plate orifice. A two-dimensional CFD for gas-solid flow based on the Lagrangian model for measuring the size of nanoparticles is presented. This study also introduces an advanced aerodynamic lens configuration with two sharp orifices rather than a conventional flat orifice. Because of their low inertia and high diffusivity, the focussing performance of conventional aerodynamic lenses degrades dramatically as particle diameters drop below 300 nm. For this work, theoretical and computational analyses for concentrating nanoparticles smaller than 300 nm were conducted. Fluent software, which automates lens configuration, was utilized for simulating the gas flow field and assessing the possibility of focussing sub-300 nm nanoparticles. The initial step was to devise a method for optimizing the lens dimensions and operating conditions involved in nanoparticle focussing. It was discovered that lighter carrier gases aid in the focussing of smaller nanoparticles and that multiple lenses performing at suboptimal Stokes numbers can focus a diverse range of nanoparticle sizes.

Additional developments included expressions for the operating pressure and lens measurements that decrease particle diffusion while maintaining subsonic flow. A new technique was also introduced in this study:​ the utilization of a novel model of pipe containing inside grooves that incorporate the size of the diameter and thickness of the lenses used in focussing the nanoparticles. The benefit of these grooves is that they enable the position of the lenses inside the pipe to be changed in case the lens needs to be moved to the left or right, if other lenses need to be added, or if only one lens is used for the same pipe employed in the experiment. As well, a computational simulation methodology was established for analyzing the performance of aerodynamic lens systems. Particle trajectory CFD was applied as a means of enhancing the lens and nozzle configuration. A technique for measuring the diameter of the nanoparticle (sub-300 nm) passing through an aerodynamic lens and divergent nozzle was also devised:​ nanoparticles are injected into the inlet and then passed through the aerodynamic lenses, and the nozzle throws them at 1 atm pressure.

A further outcome of this research was the development of a computational methodology for determining the exact focus characteristics of aerodynamic lens systems based on the use of the Lagrangian method for tracing particle trajectories. This work also entailed a comprehensive summary of the advancements and challenges associated with measuring the minimum nanoparticle size in an aerodynamic lens from the simulation perspective compared to the available experimental, computational, and numerical perspectives. The initial assumption was that the flow was continuous and subsonic, and the investigation determined the smallest particle size that can be accurately focussed on an axis with two lenses when consideration of diffusion is neglected. A systematic procedure was then described for facilitating the determination of the smallest particles that can be focussed. The final conclusion of this study is that the use of the Lagrangian method and improved aerodynamic lens design for the focussing of sub-300 nm spherical particles using a carrier gas (air) as the primary phase and carbon particles as the secondary phase is effective.

The simulation conducted revealed that lens performance is similar to that predicted by the design guidelines, indicating that the aerodynamic lens and divergent nozzle can focus particles as small as 300 nm. A nanoparticle lens system was computationally and theoretically designed, developed, and evaluated. Focussing was observed for particles ranging in size from 3 nm to 300 nm. The simulation results were compared with those of further detailed trajectory simulations based on CFD calculations published by Middha and Wexler and by Wang et al.. The model results were validated computationally based on a comparison of the simulation output with the available experimental data from the work of Tan et al. in order to verify the validity and efficiency of using the aerodynamic lens for measuring the size of sub-300 nm nanoparticles.