Numerical Investigation on Drag and Vortex Induced Vibration Characteristics of Multiple Cylinders

Abstract

The drag and vortex induced vibration (VIV) characteristics of a multiple cylinder are investigated using the detached eddy simulations. The multiple cylinders consist of a single main cylinder and twin auxiliary cylinders for a deep sea mining riser. Tandem and side-by-side arrangements are tested and compared with the single cylinder. The drag characteristics are investigated with the stationary case in the range of 0.5∼2.0 × 105 in Reynolds number (Re). The drag of the tandem arrangement shows smaller drag than those of the single cylinder while it’s consisted with the three cylinders. The stationary vortexes are observed at the clearance between the main and auxiliary cylinder which make the tandem arrangement become airfoil-like section as a total which induce the smallest drag than the other cases. The VIV characteristics are studied with the cases of forced oscillation in the cross-flow direction. The damping and added mass coefficients in cross-flow direction are estimated from the time series of the lift forces. Flow field analysis reveal the difference in VIV characteristics due to the variety of the arrangements and the single pipe.