Flow control of two tandem cylinders by a highly flexible filament: Lattice spring IB-LBM

Abstract

In the current study, the Lattice Spring Method (LSM) is combined with the Immersed Boundary-Lattice Boltzmann Method (IB-LBM) to investigate fluid-elastic body interaction problems in unsteady conditions. The combined method benefits from worthy features of all three methods. As compared to the conventional fluid-solid interaction models, this model needs no arbitrary spring parameters to determine the deformation of the flexible body. The method is first verified against the previous studies in which a thin, long filament flaps in the wake of a cylinder that attached to the filament. In the numerical results section, the problem of a highly deformable filament in a tandem configuration, two series of rigid cylinders, is studied in detail. The effects of several variables such as Capillary number, the filament's length, and location of the trailing edge on the lift and drag coefficients of two tandem cylinders are investigated. Based on the numerical results, the fluctuations of the lift coefficient on both cylinders are damped when filament capillary number gets its maximum value and the filament clamped edge is located in the middle of the cylinders. This is shown by a frequency analysis of the wake fluctuations downstream of the filament and cylinders Also, it is found that increasing the filament's length can halve the drag coefficient on the downstream cylinder due to the low-pressure region created at the filament's tip.