WIV response of tapered circular cylinders in a tandem arrangement: An experimental study

Abstract

In practical situations, cylindrical structures are arranged in various configurations where they might show different flow induced responses as compared to that for an isolated cylinder. The current paper reports the results of an in-water experimental study dealing with the transverse and streamwise responses of tapered cylinders in tandem arrangements. The results are examined against those for equivalent tandem uniform cylinders. The study can be considered as the first of its kind reported in the open literature. In the present study the upstream cylinder is fixed while the downstream cylinder is elastically mounted. The single degree of freedom vibrating system has a low mass-damping parameter (m*ξ≈0.0408). The Reynolds number, based on the mean diameter of the cylinders, ranges from 1400 to 20,000 and the reduced velocities vary from 2 to 21. Various spacing ratios (S/D) from 2 to 7 are examined.For tapered cylinders in tandem arrangement it is found that unlike uniform cylinders, the amplitude of vibrations does not decrease with the increase of the spacing ratio. The amplitude of the transverse response in the tandem tapered cylinder is slightly higher than that for the uniform cylinder in a tandem arrangement. With a tandem arrangement, the three dimensionality of the flow field appears not to have any lessening effect on the transverse WIV response of cylinders. The spacing ratio at which the tapered cylinder acts more like a single tapered cylinder is noticed to vary from that for the equivalent uniform cylinders in a tandem arrangement. It appears that, because of the three dimensional nature of the wakes downstream of the tapered cylinder, the vortices shed from the upstream tapered cylinder grow weak at much closer distances.