Vortex Induced Vibrations of cylinders : experiments in reducing drag force and amplitude of motion

Abstract

Reducing the deleterious effect of Vortex Induced Vibrations (VIV) in marine risers is an important task for ocean engineers; and many competing factors exist in the design of VIV suppression devices. This thesis explores the experimental minimization of the drag force and the disruption of vortex formation by utilizing VIV suppression devices. Two series of tests are conducted-both utilizing separate testing designs. The first tests are the flexible cylinder experiments, detailed in Chapter 2, which determine the drag force and vibration amplitude of numerous, original testing configurations. The second series of tests are the rigid cylinder, PIV experiments, detailed in Chapter 3. These tests measure both the drag force on the cylinder and the oscillating component of the lift force, the latter of which is a good indication of vortex formation. The Chapter 3 tests also image the test section wake-providing helpful insight into the physical process of vortex formation. In brief, this thesis presents a detailed description and results of the two series of original VIV suppression tests. Many original configurations are tested, and the results are contained herein.