An Advanced Measurement System for Vortex-Induced-Vibrations: Characterization in Large-Scale Risers

This paper presents the development of an advanced measurement system for real-time characterization of Vortex Induced Vibrations (VIV) in large-scale marine risers. Marine risers play a critical role in offshore oil and gas operations by transporting mud, debris, and hydrocarbons from the reservoir to the surface platform. The mechanical structure of the riser is constantly subject to the effect of vortex shedding produced by seawater flow, which may result in severe oscillations known as VIV. At present, the prediction of this potentially destructive phenomenon is a challenging area of research that has gained special attention. While there have been significant research contributions on vortex induced vibrations on small riser models (8-10 m in length), the number of experiments on large-scale risers is limited, mainly due to technical complexity, logistics, and cost involved in large scale testing. Furthermore, the experiments that have been carried out are often proprietary and their publication in scientific literature has been limited. High mode results have been a challenge since it is generally accepted that at least five accelerometers are required to accurately map a cycle, and most of the riser models have been instrumented with no more than ten or twenty accelerometers due to the associated technical challenges. The advanced system described herein is modular and has been tested with sixty-four accelerometers, theoretically capable of mapping 25 modes of vibration. This is, therefore, a significant development towards understanding the vortex shedding phenomenon at high modes. A complete description and design considerations for this advanced measurement system is presented in this paper. This includes aspects such as system architecture, hardware and software design, mounting procedure, and communication protocol for an actual application.