WAVE RUN-UP SIMULATIONS WITH A MOVING LARGE VOLUME SEMI-SUBMERSIBLE PLATFORM

Author(s)

Watai, Rafael de Andrade ; Matsumoto, Fabio Tadao ; Sparano, Joao Vicente ; Simos, Alexandre Nicolaos ; Ferreira, Marcos Donato A. S. ; ASME

• Document type: Journal article
• Source: OMAE2011: PROCEEDINGS OF THE ASME 30TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, VOL 1; v. N/A, p. 4-pg., 2011-01-01.

Abstract

Since July 2008, the Numerical Offshore Tank (TPN) of the University of Sao Paulo and Petrobras have been working on a research project intended to improve knowledge and modeling of advanced hydrodynamics topics, such as the wave run-up phenomenon. Among other activities, wave basin tests were performed with small-scale model of a large volume semi-submersible designed to operate in Campos Basin. These tests evidenced significant run-up effects on its squared-section columns for the steepest waves in several design conditions. In order to evaluate the difficulties involved in modeling the wave run-up phenomenon, simplified tests were also carried out with the model fixed and moored in regular waves with varying steepness. Previous studies using a 2nd order BEM model and a VOF CFD code to predict free-surface elevations below the deck under regular waves were presented in Matsumoto et al. (2010). The studies illustrated considerable differences between the wave elevation results in fixed and moored model setup; however, by that time, the analysis of the moored model by a VOF CFD code was not yet complete. This paper, therefore, presents wave run-up estimations with a moving large volume semi-submersible platform performed with the CFD code ComFLOW, which solves the Navier-Stokes equations employing a local height function to the free surface displacement. The phenomenon is investigated by simulating the flow around the semi-submersible model under the influence of high steepness regular waves on a non-uniform grid. Platform motions, derived from a first order BEM code, are imposed and synchronized with the incoming wave. Aiming at avoiding numerical wave reflections, a damping zone is also applied and positioned downstream the platform model. Predicted results are compared to experimental data, measured by seven vertical wave probes located in different positions below the model deck. Although considerably time-consuming, it will be shown that simulations present very good agreement with the experimental results. (AU)

• FAPESP's process: 07/05858-2 - Modeling of Second-Order Effects in the Roll Motion of FPSO Units
• Grantee: Fabio Tadao Matsumoto
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 10/08778-2 - Time domain boundary elements method for seakeeping analysis of marine systems
• Grantee: Rafael de Andrade Watai
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)