Yuting Jin

URANS Prediction of Ship Hydrodynamics in Head Sea Waves at Zero Forward Speed With Model Testing Validation

The paper presents computations on predicting the hydrodynamics of a generic floating liquefied natural gas (FLNG) hull form in regular head sea waves using unsteady Reynolds-Averaged Navier-Stokes (URANS) solver StarCCM+. Initially, model scale simulations were conducted at model test basin water depth (d=0.8m), with detailed verification and validation study performed to estimate numerical uncertainties. The simulation results were compared with potential flow solutions and validated against experimental studies. Using the verified numerical setup, ship hydrodynamics including wave induced loads, moments as well as ship motion responses in deep water waves(d=8.0m) have been studied. The computed time history results were decomposed by Fourier series to obtain force/moment and motion transfer functions on the frequency domain. From the obtained results, the presented URANS approach demonstrates slightly better accuracy compared with potential flow (PF) solutions. It is also found that water depth has great influences on the computed wave force and ship motion transfer functions for certain range of wave frequencies.

Hydrodynamics of a conceptual FLNG system in side-by-side offloading operation

ABSTRACT This paper investigates the hydrodynamics of an floating liquefied natural gas (FLNG)–liquefied natural gas (LNG) offloading system in a side-by-side configuration using potential flow solver AQWA. The system is moored by an internal turret mooring system allowing itself to weathervane under external disturbances and is designed to operate in a sea environment close to that on the coast of Western Australia. Initially, validations are presented for the computed wave loads, representative motion responses and mooring loads. The results are compared against experimental data and those gathered from literatures. Time domain analyses are carried out for the FLNG–LNG system coupled with hawser, fender and mooring systems under the combination of wind, current and waves. The relative motions between the FLNG and LNG in the horizontal plane as well as the mechanical loads on the hawsers, fenders and moorings are computed. Furthermore, the effects of varying hawser pretension and stiffness on the hydrodynamic performance are investigated.

URANS prediction of berthed ship–passing ship interactions

ABSTRACT This paper investigates berthed ship–passing ship hydrodynamic interactions using unsteady Reynolds-averaged Navier–Stokes (URANS) solver StarCCM+ in both model scale and full scale. A double-body approximation method is adopted to investigate the hydrodynamic effects on the berthed ship when in close proximity with the passing ship. A benchmark experimental test condition is replicated for the verification and validation of the numerical simulation. Based on the validated numerical model, the interaction forces and moments are predicted for different passing ship speeds and lateral separations. The same conditions are repeated in full scale to quantify possible scale effects. The trends seen in the numerical results correlated well with past authors findings. The difference in the model-scale and full-scale interaction force and moment predications are not significant. Full scale berthed ship–passing ship interaction forces and moments can therefore be approximated (for similar cases) by model-scale tests with confidence. HIGHLIGHTS (1) URANS computations are conducted to study berthed ship–passing ship interactions in both full-scale and model-scale conditions.(2) Numerical results are validated against benchmark experimental data.(3) Relationship between interaction forces and moments acting on the berthed ship with respect to passing ship speed and lateral separation are identified.(4) Scale effects in berthed ship–passing ship interaction forces and moments are quantified.

Computational modelling of sloshing in liquefied natural gas tank

Sloshing in the tank of liquefied natural gas (LNG) carriers has recently attracted immense attention due to the rise in demand for LNG transportation. It occurs in partially filled tanks and is capable of inflicting severe damage to the tank’s interior. One effective method to dampen sloshing activities is by introducing baffles into the tank. In this paper, the nature of sloshing has been investigated using finite volume based unsteady Reynolds Averaged Navier-Stokes (URANS) method. Good correlation was achieved between the results obtained from the presented computations and past studies, demonstrating the feasibility of the established numerical modelling approach. Employing similar computational method, two-dimensional (2D) sloshing computations were performed or different baffle additions at varying filling levels. Observations were made in the baffled tanks where an increase in the number of baffles would cause the sloshing activities to magnify if the baffle height was significantly lower than the filling level. When comparing the 2D and 3D computational results, close resemblance of the average pressure profile and maximum impulsive loads had suggested that 2D simulations are feasible to model sloshing induced loads in a 3D tank.

URANS prediction of berthed ship - passing ship interactions

In this paper, the unsteady Reynolds-Averaged Navier-Stokes computational method has been employed for investigating the hydrodynamic interactions between berthed and passing ships. Initially, simulations in model-scale were performed for validating the numerical modelling technique using available benchmark experimental test cases. A formal study of verification and validation was carried out for quantifying the numerical uncertainties. Based on the validated numerical setup, systematic computations were conducted for further investigations on the influence of varying passing ship speeds and lateral separations on the interaction forces and moments. The same conditions were repeated in full scale to quantify possible scale effects. The numerical results demonstrate that the interaction forces and moments are proportional to the square of the passing ship speed and inversely proportional to the lateral separation between the two ships, which agrees well with the findings by Remery (1974) and Kriebel (1995) respectively. In addition, when comparing model and full scale results, the overall differences are not very significant and are within the simulation uncertainty for most cases

Sensitivity of Smoothed-Particle Hydrodynamic Parameters on Slamming Simulations

The oil and gas industry requires complex subsea infrastructure in order to develop offshore oil and gas fields. Upon installation, these components may encounter high slamming loads, stemming from impact with the water surface. This paper utilises Smoothed Particle Hydrodynamics to quantify these loads on a free-falling object. The investigation is interested in conducting a parameter study and determining the effect of varying simulation parameters on the prediction of slamming event kinematics and forces. The surface impact of a 2D freefalling wedge was simulated, with the results being compared to an experimental investigation. It was found through the parameters that particle resolution and the size of the SPH particle kernel are very important, whilst the diffusion terms do not play an important role. The latter is due to the very transient nature of slamming events, which do not allow sufficient time for diffusion in the domain. The close correlation of numerical and experimental results, along with the robustness and quick set up of SPH slamming simulations, indicate that SPH is a promising method of modelling more complicated slamming problems, which may involve more intricate impacting structures.

Experimental study of wave induced loads and motions on FLNG in head and oblique sea waves

In the past decade, an innovative concept, the floating liquefied natural gas (FLNG) system has been developed as a more effective solution over conventional pipelines for exploiting offshore natural gas resources. Understanding the hydrodynamic behaviour of such a mega structure in a real seaway is essential for determining its performance as well as evaluating the operabilities of on-board facilities and safe offloading. In this paper, experimental study on the hydrodynamic performance of a generic FLNG hull form has been presented. The 1:100 scale model was tested in the Australian Maritime College model test basin for head sea and oblique sea conditions at zero forward speed. The wave induced loads and motions were measured by load cells and linear variable differential transducers (LVDTs) respectively. Experimental uncertainties on each of the measured variables were studied by taking partial differentiations on the uncertainty sources. The time history measurements were decomposed by Fourier series for obtaining frequency domain force/moment and motion transfer functions. The results were compared with numerical solutions from potential flow and Reynolds-Averaged NavierStokes (RANS) solvers. A good correlation between the experimental and numerical results has been demonstrated

An experimental investigation of hydrodynamic impacts of marine growth on mid-water arch system

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