Estudo sobre a ocorrência de ressonâncias paramétricas numa plataforma TLWP próxima a um FPSO em ondas irregulares

Abstract

The present dissertation is a continuation of studies done on observed phenomena during experimental tests of a TLWP platform coupled with a FPSO. The tests were performed on scaled models. The results from regular sea states show that the system presents excessive amplifications for a band of wave periods and heights in the yaw direction. These phenomena were studied by Cruz (2010) and Rivera (2012). Rivera showed that the unstable behavior is caused by internal system excitations of the TLWP-FPSO induced by sway movement. A test was also performed in an irregular sea. The results of this test pointed out that the yaw motion does not present increments of amplitude like in the regular sea state tests, which led to the hypothesis that the experimental tests in irregular sea was not sufficient to draw conclusions. To verify this, a numerical model was developed capable of reproducing the platforms´ responses for a given sea state. Various numerical analyses were done with the same sea state, that is, same significant wave height and peak period, but with different random phases. The obtained results show that the system is strongly non ergodic and also presents parametric resonances.