Impact of Lens Angle and Nozzle Geometry on Aerodynamic Focusing: A Numerical Study

Straight-edge thin plate orifices (90° half angle) are used as the focusing elements in most aerodynamic lenses. They are simple to fabricate and have fewer boundary layer effects as compared to other geometries such as capillaries, converging nozzles, and diverging nozzles. The focusing performance of these other geometries has not been systematically evaluated. This study used computational fluid dynamics (CFD) simulations and Lagrangian particle tracking to investigate aerodynamic focusing of converging and diverging orifices with half angles ranging from 30° to 150° at two Reynolds numbers (50 and 100) and three Mach numbers (0.03, 0.1, and 0.3). The results show that the optimal Stokes number (Sto) for near-axis particles have small differences between the straight-edge orifice and the converging or diverging orifices, indicating small changes in focusing behavior for different lens geometries. This study also investigated the effects of varying dimensions of the exit nozzle on particle terminal trajectories into the vacuum chamber. The nozzle has a cylindrical constriction upstream of the exit orifice. Several nozzle radial aspect ratios and lengths of the constriction were simulated in a two-dimensional axisymmetric domain. The nozzle geometry that generates the least divergent particle path in the vacuum chamber as well as geometry that maintains the highest transmission efficiency for particles in the size range of 10 nm - 10 μm is identified.

Level thesis:degree_level

M.E.

Year dc:date.issued

2025

Author dc:creator

• Vannavong, Apolo

Advisor dc:contributor.advisor

• Hadj-Nacer, Mustafa

Committee members dc:contributor.committeemember

• Greiner, Miles
• Wang, Xiaoliang

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11435

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11435