NUMERICAL ANALYSIS OF FLOW INTERACTIONS WITHIN A BANK OF TUBES WITH CLOSE SPACE RATIO

The flow within a tube bank is characterized by multiple concurrent interaction mechanisms, contributing to a complex response. To gain a better understanding of these mechanisms, it can be helpful to simplify the problem by focusing on fixed rows to apply the free-to-vibrate approach later. This study conducts a numerical analysis of the fundamental characteristics of crossflow in five rows of stationary cylinders. Our goal is to establish a connection between the variations in velocity fields, the forces acting on the cylinders, and the expected vibration response. Simulations of cylinder rows were executed within a domain featuring a cross-section of 0.193 m x 0.146 m and a length of 0.8 m. The cylinders, with an external diameter of 25 mm, were placed with a longitudinal and transverse spatial ratio of 1.26. The governing equations, including continuity and Navier-Stokes equations, were solved using Large Eddy Simulation with the Smagorinski-Lilly subgrid model, employing dynamic stress modeling within Ansys Fluent 19. The Reynolds number was set at 8.4 x 10^3, based on the gap flow velocity and the diameter of a single cylinder. The results from the transient field indicate interactions between the gap flow and the cylinders following literature experimental visualizations and numerical simulations. Variations in velocity within the gaps between the cylinders highlight the dynamic redistribution of flow. This flow pattern significantly influences the forces acting on the cylinders, demonstrating an increase in force coefficients at specific cylinder positions. The sudden increase in the lift force in one of the cylinders can be the main factor related to the fluid-elastic instability occurrence.