VIV and Hydrodynamic Forces of Circular Cylinders Attached under a Flat Spring with Forced Oscillation Tests in Still Water

摘要

This paper describes a model test to examine characteristics of vortex-induced vibration (VIV) of tubing in water, e.g. a marine riser, and also gives consideration of characteristics VIV from experimental results. Circular cylinders that were rigid were used for the model test because the authors assumed the model that was a part of a marine riser. The test models were suspended into still water through a flat spring so that VIV could be found with hydro elasticity in spite of a rigid circular cylinder. This was a forced oscillation test in still water. It was found that behaviors of a power spectrum of VIV could be approximately classified into three patterns according to the number of a peak frequency. The authors investigate characteristics of hydrodynamic force including drag force by separating measured in-line force in forced oscillation to two components of added mass and a damping coefficient. Power spectra of VIV behavior from the model tests are finally compared with two-dimensional CFD computations.