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During the lecture a new mechanical apparatus, specially designed for investigating fundamental aspects of VIV in a Towing Tank will be presented. An electrically driven movable spring-leaf system was devised and constructed to deal with elastic mounted cantilevered cylinders, either rigid or flexible ones. The apparatus has low structural damping and allows the excitation of VIV under continuously modulated spring rigidity, aiming at investigating the effect of natural frequency modulation on the response. The experiments were carried out at IPT Towing Tank, which is 280m long, 6m wide and 4m deep. Both rigid and flexible cantilevered cylinders mounted on the new apparatus were studied. Some results on the rigid cylinder are presented. A striking feature of such apparatus is the possibility to obtain the whole VIV amplitude and frequency response curves from a single run, under a single towing velocity, therefore at the same Reynolds number. The Hilbert-Huang spectral analysis technique, applicable to nonlinear and non-stationary signals, is used. This is possible as the reduced velocity varies along that particular constant velocity run, according to the natural frequency modulation.
- Speaker
- Professor Celso Pesce, University of Sao Paulo, Brazil
- Venue
- Seminar Room, Fraser Noble Building