Abstract
Shipping water, the flow washing over and impacting the upper decks of ships and offshore structures, occurs frequently during their service life and often causes structural problems. For engineers to design safe floating structures subjected to shipping water it is essential to gain an in-depth understanding of its depth and flow field, and the resulting impact forces. In this work, Computational Fluid Dynamics (CFD) is applied to understand the physics of shipping water washing over a stepped platform. We find that the most accurate solutions are obtained with the k−ε turbulence closure. The hydrodynamic load generated by the shipping water is found to strongly depends on the kinematic energy of the water hitting the step. It is shown that with smaller values of the freeboard a more dynamic flow ensues, with a stronger vortex and larger velocity gradient resulting in deeper shipping water and a larger impact force.
Highlights
Shipping water, known as green water, is the water flow washing the upper deck of ships and offshore structures, which can exert large forces and result in motions (Dillingham, 1981; Greco et al, 2015), de formations (Buchner, 1995), and the loss of transverse stability as the centre of gravity can be shifted upwards (Ersdal and Kvitrud, 2000)
Shipping water washing the upper surface of a fixed object was numerically modelled to improve our understanding of the physics of the flow as it impacts the deck and runs forward
Numerical results were compared against the experimental data, and it was found that the turbulent simulations provide more accurate re sults of the shipping water phenomenon
Summary
Known as green water, is the water flow washing the upper deck of ships and offshore structures, which can exert large forces (responsible for 10% of sea loads, see Hirdaris et al, 2014) and result in motions (Dillingham, 1981; Greco et al, 2015), de formations (Buchner, 1995), and the loss of transverse stability as the centre of gravity can be shifted upwards (Ersdal and Kvitrud, 2000). Computational Fluid Dynamics (CFD) can be used to simulate the washing of shipping water over any floating object (Stern et al, 2001) This method has shown significant potential in modelling sea loads (Izadi et al, 2018a), dynamic responses (Zhou et al, 2019; Esfandiari et al, 2019), resistance (Tezdongan et al, 2015; Kim et al, 2017; Demirel et al, 2017; Khojasteh and Kamali, 2017; Ghadimi et al, 2019; Huang et al, 2019b, 2020; Nazmand Bilandi et al, 2020; Dash timanesh et al, 2020) and wave energy (Bayoumi et al, 2015; Khojasteh and Kamali, 2016; Khojasteh et al, 2018a; Khojasteh et al, 2018b; Lopez et al, 2014; Masida et al, 2019) in the last three decades, and its application has become ever more common in recent years (Larsson et al, 2013).
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