On the generation and transition of Coanda flow with coaxial triple swirler

In this study, the effects of five coaxial triple swirler configurations on mass flow rate distribution, swirling flow structure, and Coanda flow formation to transition were investigated. The study utilized a numerical investigation with the Re-Normalization Group k-ε Turbulence model to simulate the internal and external flow field. An experimental setup was also provided to validate the numerical results using a Particle Image Velocimetry system. The swirling flow structure was classified into three categories: Coanda, Transient, and no-Coanda flows. Results showed that the transient swirling flow from the Coanda flow occurred with a slight change in the outer recess length, which can control the three flow categories. Also, the study found two types of swirling flow structures with cylindrical and bubble shapes with the change in the inner recess length, a key variable in controlling the swirling flow structure. Additionally, the study presented quantitative results to predict the formation of the Coanda flow using dimensionless parameters composed of momentum ratios of swirlers. Overall, the findings of this study provide valuable insights into the design and optimization of coaxial triple swirler configurations for practical applications.