Numerical simulations of confined vortex ring

• Main Author: Kwek, Wen Hao
• Other Authors: New Tze How, Daniel
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/167847
• Institution: Nanyang Technological University

The intricate interactions between the vorticities of the vortex rings and the boundary layers induced along the physical geometries will unveil comprehensive flow dynamics of the vortex rings. However, there has been limited research that study about the characteristics of circular vortex rings fully confined in between two no-slip parallel walls and in circular convergent walls despite their relevance and importance in engineering and biology. Hence, this project aimed to analyse the fundamental characteristics of a circular vortex ring fully confined in between two no-slip parallel flat plates and in a circular convergent pipe for three different convergent angles of 60°, 90° and 120°, through the utilisation of the Large Eddy Simulation model in Ansys Fluent to perform numerical simulations. The numerical simulation results highlighted the formation and deformation of the primary, secondary and tertiary vortex rings due to adverse pressure gradient, viscous diffusion and azimuthal instability, the formation of hairpin vortices from the secondary and tertiary vortex rings, and the entrainment of the secondary and tertiary vortex rings into the primary vortex ring. Furthermore, the variation in the vorticity and velocity of the vortex ring were observed to follow a downward trend, while the variation in the wall shear stress was observed to increase and reach a peak upon the formation of the secondary vortex ring before decreasing with fluctuations. Nevertheless, the accuracy and reliability of the results obtained in this project should be validated through conducting physical experiments and refining the mesh configurations for the aforementioned physical geometries.