Numerical investigation on flow-induced vibration response of the cylinder inspired by the honeycomb

Abstract

The honeycomb-shaped structure has been proved to have good mechanical properties, and is it possible combining its good mechanical properties together with its flow characteristics? This will determine whether the honeycomb-shaped cylinder can be further extended to the practical application in ocean engineering or wind engineering. Therefore, the flow-induced vibration (FIV) responses of the three-dimensional cylinders inspired by the honeycomb are numerically investigated. Three different structures are considered, including the smooth cylinder (P0), the P60 cylinder corresponds to the direct impingement of the freestream on the saddle point, and the P30 cylinder corresponds to the vertical impingement of the freestream on the one edge of the structural element. The Reynolds number ranges of the simulations are 0.8 × 104 ≤ Re ≤ 8.0 × 104. Compared with the maximum cross-flow amplitude of P0, it is reduced by 59.33% for P60. The maximum mean-drag coefficients of P60 and P30 are about 1.85 and 2.10, which are reduced by about 38.33% and 30% compared with that of P0. The slope (β) of the actual lift coefficient (CT(t)) and the actual angle of attack (α(t)) is defined. For P60, β is greater than 0, so galloping doesn't occur. However, as for sample P30, β is less than 0 and thus galloping happens in the high reduced velocity range. Especially, the maximum in-line amplitude ratio reaches 0.6 when Ur = 20 for P30. Due to the existence of two boundary-layer separation points and the concave structure, the flow of P60 is weakened, so that the FIV response of P60 is suppressed. The flow separation and the flow reattachment are the fundamental causes of galloping response for P30. The critical angle of attack (θ) at which galloping response occurs is 40° for the honeycomb-shaped cylinder. When θ ≥ 40, β ≥ 0, the large-amplitude motion will not occur in the high reduced velocity range. When θ < 40, β < 0, and the negative damping phenomenon is observed and the galloping occurs.