Advances in the Hydrodynamics of Side-by-Side Moored Vessels

Abstract

In this paper a comparison between model basin experiments and results of diffraction computations on side-by-side moored LNG carriers is presented. The computations are based on a new lid method in diffraction codes to suppress non-realistic high wave elevations between the two floating objects. This lid method was originally formulated by Chen (2005). In this method a damping value is added to the free surface by means of a damping parameter. Since no theoretical solution can be found to establish the required value of the damping parameter, model basin experiments have been performed to determine this value. However from the results of the model basin experiments it is shown that it is difficult to obtain one unique value of the lid damping (for the 4m or small gap). The way of tuning the damping value of the lid is crucial. Tuning the damping based on first order results, like motions or wave height RAO’s will lead to a much larger variation in the estimate of the second order sway wave drift force transfer function.

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

“…This improvement is less noticeable for motions. In all configurations probably an unique value of the damping factor might not be sufficient to fully cover the different measurements of the model tests as reported also in Pauw et al (2007). Regarding Configuration 3, the results in terms of motion and wave elevation are very good and also in this case the = 0.125 1/s (or α = 0.5 if one consider AQWA code) seems to reproduce better the experimental results.…”

“…In this way, the aforementioned frequency shift pointed out by Pauw et al (2007) was corrected and the results reached a better agreement with the experimental curves. Lu and Chen (2012) evaluated (using a CFD code) the energy dissipation when the wave elevation in the gap between two bodies presents a resonant behavior.…”

“…As mentioned in Molin (2001), Lewandowski (2008) and Pauw et al (2007), different resonant modes might appear in the gap between two vessels in a side-by-side arrangement. The most basic ones are longitudinal and transversal sloshing modes.…”

“…Following the same approach, Pauw et al (2007) applied the damping lid method comparing their results with experimental measurements in terms of wave elevation in the gap, first order Response Amplitude Operators (RAOs) and wave drift Quadratic Transfer Functions (QTFs). They concluded that an unique value of damping term is not enough to provide a fair agreement with the test data.…”

Um método de elementos de contorno do domínio do tempo para análise de comportamento no mar de sistemas oceânicos.

“…A first attempt for applying this method is presented in Fournier, Naciri and Chen (2006), where comparisons between numerical and experimental results for a Floating Storage and Regasification Unit (FSRU) and a LNG carrier positioned in side-by-side attested that the method was effective in attenuating the wave elevation in the confined zone, which consequently led to a better reproduction of the first order motions and drift forces. Following the same approach, Pauw, Huijsmans and Voogt (2007) applied the damping lid method for the investigation of resonant effects for LNG carriers. Experimental tests were conducted considering only one ship model, which was positioned at half-gap witdh from the lateral tank wall.…”