A Wiener-Laguerre Model of VIV Forces Given Recent Cylinder Velocities

摘要

Slender structures immersed in a cross flow can experiencevibrations induced by vortex shedding (VIV), whichcause fatigue damage and other problems. VIV modelsthat are used in structural design today tend to assumeharmonic oscillations in some way or other. A time domainmodel would allow to capture the chaotic nature ofVIV and to model interactions with other loads and nonlinearities. Such a model was developed in the presentwork: for each cross section, recent velocity history iscompressed using Laguerre polynomials. The compressedinformation is used to enter an interpolation function topredict the instantaneous force, allowing to step the dynamicanalysis. An offshore riser was modeled in this way:some analyses provided an unusually fine level of realism,while in other analyses, the riser fell into an unphysicalpattern of vibration. It is concluded that the concept ispromising, yet that more work is needed to understandorbit stability and related issues, in order to produce anengineering tool.