Numerical study flow-induced vibration of four two-degree-of-freedom circular cylinders in lozenge configuration using random vortex- boundary element scheme

Abstract

Flow-induced vibration around industrial structures is a significant factor contributing to the mechanical degradation of these structures exposed to fluid flow. Numerical simulation of such flows is challenging with conventional simulation methods due to the displacement of the structural boundaries and the complexity of defining and satisfying boundary conditions. In this research, the development and combination of random vortex and boundary element methods have been employed to address the aforementioned challenges. Two-dimensional flow at Reynolds numbers of 100, 200, and 1000 around four two-degrees-of-freedom circular cylinders in two lozenge configurations with different diameter ratios (parallel and vertical diameter to the flow direction) has been simulated. In configuration 1, the diameter ratio is 1.5, the horizontal and vertical diameters are equal to 3 times and 2 times the cylinder diameter, respectively. In configuration 2, the diameter ratio is 1, and the diameter of the lozenge is equal to 4 times the cylinder diameter. The changes in hydrodynamic force coefficients, and streamlines are depicted for each scenario. The oscillation amplitude of the rear cylinders, which is affected by the vortex shedding from the front cylinders, increases. In certain instances, especially at higher Reynolds numbers like Reynolds 1000, increasing in oscillation amplitude may even result in collisions between the cylinders. For configuration 2, both the average drag coefficient and the range of variation for all four cylinders are greater than those for similar cylinders in configuration 1. The results indicate that an increase in the Reynolds number from 100 to 200 and 1000 results in approximately 1.4 and 11.5 times amplification in the oscillations of the drag coefficient, and the maximum value of lift coefficient increases nearly 2.2 and 80 times, respectively.