Lattice boltzmann method for investigation of flow through square in-line cylinders with transverse oscillation

A numerical research work is carried out to examine fluid-structure interaction in flow over six inline square cylinders undergoing transverse oscillations via the lattice Boltzmann method. The impact of the oscillation frequency ratio ([Formula: see text]), where imposed oscillation frequency is represented as [Formula: see text] and [Formula: see text]is the natural vortex shedding frequency of a stationary cylinder, on wake dynamics and flow patterns is examined. Simulations are performed at Reynolds number of Re = 80, with a non-dimensional gap spacing (s/d = 1.0) and an oscillation amplitude ratio of A/d = 0.2. The frequency ratio is varied in the range 0.1 < [Formula: see text]≤ 2.0. Three distinct flow patterns are identified: synchronous lock-on (0.8 ≤ [Formula: see text]≤ 1.4), quasi-periodic lock-on-I (1.6 ≤ [Formula: see text] ≤ 2.0) and quasi-periodic non-lock-on-I (0.1 ≤ [Formula: see text]≤ 0.6). The synchronization range is wider than that reported for single oscillating cylinder. A single coherent wake envelops the entire cylinder array, with wake recovery occurring at higher oscillation frequencies due to merging of vortex and formation of multi-polar vortices downstream of final cylinder. The first cylinder experiences highest mean drag, followed by a reduction and gradual increase along the downstream cylinders.