Bureau Veritas is a company specialized in testing, inspection and certification founded in 1828. It operates in a variety of sectors, including Building & Infrastructure (27% of revenue), Agri-food & Commodities (23% of revenue), Marine & Offshore (7% of revenue), Industry (22% of revenue), Certification (7% of revenue) and Consumer Products (14% of revenue). Bureau Veritas is present in 140 countries through a network of over 1,500 offices and laboratories, and more than 78,000 employees. Bureau Veritas generated €5.1 billion in revenue in 2019. Didier Michaud-Daniel has been the CEO of Bureau Veritas since March 2012.
A benchmark study of 10 different numerical methods for ship motion and load assessment is presented. Pitch motions and midship vertical bending moments are compared to model test results for a containership at zero speed in head regular waves. The wave steepness is varied from 2.1% to 10.5%. The model tests show that pitch and the vertical bending moment (VBM) display nonlinear behavior even for low-steepness waves. It is demonstrated that computational fluid dynamics (CFD) methods can reproduce the ship responses with good accuracy, even in very steep waves, involving green water and parts of the ship going in and out of water. Weakly nonlinear potential-theory methods tend to overestimate the pitch motions and the sagging moments as the wave steepness increases. For the vertical bending moment in steep waves, the 3D panel methods did not give significantly better results than those obtained with the nonlinear strip theories.
Designing floating wind turbine systems requires integrated load assessments (ILA) using fully coupled hydro-servo-aero-elastic models. In most cases, floater hydrodynamics are represented using potential-flow models for mooring system design and motion estimation, while the floater itself is typically assumed to behave as a rigid body. However, this assumption can significantly affect tower eigenfrequency calculations, especially for large floaters. In this study, we investigate these effects using in situ sensor data from the Zefyros 2.3 MW spar wind turbine. We present a methodology to accurately determine the tower's eigenfrequencies. A rigid-floater model without added mass leads to an average error of 65 % for the first tower mode relative to measurements. Including hydrostatic added mass reduces the error to 40 %. Further incorporating floater flexibility decreases the error to 4.3 %, and accounting for blade flexibility lowers it to just 2.8 %. These discrepancies highlight the importance of refining the hydro-servo-aero-elastic model to align with eigenfrequencies derived from finite-element hydro-structural analyses. We present potential model adjustments, assess their impacts, and demonstrate the updated validation process.
Abstract This study investigates the computation of the added wave resistance in head seas based on the middle field formulation using either the Rankine source method (SEACAL) or the free surface Green function method (HydroStarV). These two approaches are detailed and compared to the classical encounter frequency approximation (HydroStar). Numerical results (motion and added wave resistance) are derived and compared to experimental data for two ships : the Wigley IV hull for two forward speeds and the DTMB5415 for three forward speeds.
Abstract Moored floating structures usually respond with horizontal resonant motions to wave drift loads. Wave-current interactions influence the wave drift forces. Most often, there is an increase of wave drift forces for waves and current moving in the same direction, compared to conditions with waves only. It is acknowledged that correct representation of the phasing and magnitude of wave drift loads requires full quadratic transfer functions (QTFs). However, there are presently no numerical tools available to the industry for solving the full second order problem accounting for wave-current interactions. This paper presents and validates a heuristic method to correct zero-current potential flow QTFs for wave-current effects. Validation is provided by comparing numerical results with model test data for a FPSO. Comparisons include diagonals of the surge QTF and time series and spectra of the low frequency motions. The results show that the zero current numerical QTF compares reasonably well with the empirical QTFs for the zero current model tests, while they significantly underestimate for the cases with current (the empirical QTFs are identified from the model test data). The heuristic correction method provides good estimates of the QTF as compared to the empirical ones. Time domain simulations of low frequency motions compared to measurements lead to similar conclusions – the heuristic correction significantly improves the numerical predictions.
The phase-velocity method is widely used to generate focused waves for studying extreme waves and their interactions with marine structures. However, this method utilizes only the steady-state components of generated wave trains, while the wavefront, which contains complex transient components, is ignored. In this paper, we propose a new method for generating focused waves based on the wavefront velocity, defined as the velocity of the maximum wave in the wavefront zone. Unlike the phase-velocity method, our approach accounts for both the steady-state and wavefront components of transient waves. Consequently, the maximum waves of transient wave components are superimposed to form focused waves. We derive an analytical transient solution for focused waves using the wavefront-velocity method, enabling rapid investigation of the evolution of this type of focused waves. Furthermore, we implement the wavefront-velocity method in a numerical wave flume to generate focused waves. Compared with the phase-velocity method, the wavefront-velocity method produces a larger focused-wave amplitude, a shorter focusing time, and reduced long-wave reflections from the ends of wave flumes. It provides an alternative approach for generating extreme waves, thereby holding significant value for investigating the interactions between extreme waves and marine structures.
