Development of a time domain boundary element method for numerical analysis of floating bodies’ responses in waves

Abstract

This article presents the development of a numerical tool for seakeeping simulations of marine systems using a time domain boundary element method based on Rankine sources. The formulation considers two initial boundary value problems defined for the velocity and acceleration potentials, the last being used to avoid numerical problems in calculating the time derivatives of the velocity potential. A fourth-order Runge-Kutta method is used for the time marching of the problem, which consists in the integration of the free surface conditions and body equations of motion. Numerical test cases are presented for bodies with simplified geometries, such as an hemisphere and a circular section cylinder. Exciting forces, added mass and radiation damping coefficients, and motions response amplitude operators are compared to analytical and numerical data, presenting a very good agreement. Furthermore, the numerical method is applied to a floating production storage and Off-loading unit and the results are verified with experimental data carried out in the hydrodynamic calibrator of the University of Sao Paulo. By means of these investigations, we have verified that the developments performed so far are correct and new extensions, therefore, may be planned for more complex applications.

Rankine time-domain method with application to side-by-side gap flow modeling

“…A novel linear TDRPM developed by the Numerical Offshore Tank of the University of Sao Paulo [28] is also applied for calculating the first order geosim motions and wave elevations in the gap. Details of the method are presented in Appendix A, so only the main features of the method will be described next, for the sake of conciseness.…”

“…Currently, TDRPM neglects the nonlinear effects originated from the presence of unknown free surface and body surface positions [28]. TDRPM is being developed in the context of a research project that aims at coupling the time domain hydrodynamic solver to the dynamic simulator of the Numerical Offshore Tank of the University of Sao Paulo (TPN-USP), which also takes into account the effects of wind, current, mooring lines and risers.…”

A 3d Isogeometrical Boundary Element Analysis for Non-Linear Gravity Wave Propagation

“…These models have been applied to simulated tsunami generation and [1] overturning waves [2][3][4], to design breakwaters [5,6], to predict the wave pressure impact on structures [7], or to study radiation and diffraction waves produced by a wave-maker [8][9][10][11]. Nowadays, because of the increasing interest on the ocean renewable energy, in which the generation systems are installed near-shore or off-shore, new applications of such models are being used to study the fluid-structure interaction considering the effect of the waves [12][13][14][15][16].…”

Analysis of wave resonant effects in-between offshore vessels arranged side-by-side

“…In order to reproduce the experimental behavior, a numerical technique to model a numerical beach has been used in-between the floating bodies. Frequency domain (AQWA-Ansys) and time domain (TDRPM -Time Doman Rankine Panel Method, by Watai et al (2014)) numerical codes have been used. The numerical approach of the beach in both codes is the same.…”

“…A novel linear TDRPM developed by the Numerical Offshore Tank of the University of Sao Paulo Watai et al (2014) has been also applied for calculating the first order geosim motions and wave elevations in the gap. The code is based on the three-dimensional low order panel method and applies the Rankine source as Green function.…”