Vortex-Induced Vibrations on Flexible Cylindrical Structures Coupled With Non-Linear Oscillators Available to Purchase

The recent escalade of the oil prices encourages the search and exploration of new oil fields. This represents a challenge to engineers, due to more difficult conditions of operation in harsh environments and deeper reservoirs. The offshore industry faces, in the edge of technology with new necessities and limiting conditions imposed by the environment, an increase in the cost of production. It is, therefore, of vital importance to have the equipments operating at the most optimized conditions in order to reduce these costs. VIV software developed in the frequency domain was successful in designing risers and pipelines using large safety factors and making conservative assumptions. These tools only predict single-mode vibrations. In this perspective, the present paper describes the results obtained from a new time-domain code developed to assess the vortex-induced vibrations of a long flexible cylinder. A time-domain analysis was chosen because this suits the problem well, since it is able to predict and calculate different modes of vibrations. In the model, a cylinder is divided into elements that can be exposed to an arbitrary current profile. Each of these elements is free to oscillate parallel and transversely to the flow, and is coupled to a pair of van der Pol’s wake oscillators. This simulates the vortex shedding and, therefore, the fluctuating nature of drag and lift coefficient during the occurrence of VIV. The governing equations are solved by 4th-Order Runge-Kutta schemes in time domain. The new time-domain model is compared with small scale model test data from benchmarking.