Experimental investigation on vortex/wake-induced force of double unequal-diameter flexible cylinders in tandem

An experimental investigation on the vortex/wake-induced force of double unequal-diameter cylinders in tandem was performed. In the experiment, the upstream-to-downstream cylinder diameter ratio was 1.569, and the gap spacing ratio between the cylinder models ranged from 3 to 8. Under uniform flow with Reynolds number up to 11 328, the strains caused by the vortex/wake-induced vibrations were measured for the double flexible cylinders. Based on the measured strains, the displacements were reconstructed with the mode superposition method. Then, the vortex/wake-induced forces were obtained inversely. Subsequently, the time-varying excitation and added mass coefficients were identified by the forgetting factor least squares method. The results show that the wake-induced force coefficient and excitation coefficient of the downstream cylinder are smaller than those of the single cylinder, while the added mass coefficient becomes larger. In addition, the downstream cylinder under frequency capture can absorb a higher proportion of energy from the wake to excite larger vibration amplitudes, especially in the in-line direction.

Automated summary

An experimental investigation was conducted on the vortex/wake-induced force of double unequal-diameter cylinders in tandem. The results revealed that the downstream cylinder has smaller wake-induced force and excitation coefficients compared to a single cylinder, while the added mass coefficient increases. Furthermore, the downstream cylinder can absorb a higher proportion of energy from the wake and exhibit larger vibration amplitudes, particularly in the in-line direction.