Search

The Floating Drilling Production Storage and Offloading (FDPSO) Platform is functionally a non-propelled vessel and belongs to a subset of a wider group of vessels called Floating Production Systems (FPS). The FDPSO, besides its unique attribute of drilling capability, has all the functionalities of FPSOs. Given the remote offshore locations of oil fields, FDPSOs provide viable economic solution for drilling, production, storage and offloading to smaller vessels for transportation of oil. This paper addresses the designer's concern in the critical role of positioning of the moonpool since it has a direct bearing on the dynamic effects experienced by the platform. The investigation provides valuable quantitative insights into the important effects on drag during towing, sloshing effect within the moonpool and motion dynamics due to the liquid oscillation. The results of this investigation using numerical and experimental tools, is expected to give key inputs for the designer towards the design of better performing FDPSO platform and benefit the industry. This paper investigates the vessel dynamics including the liquid oscillation behaviour inside the moonpool as a function of the moonpool location in the vessel. The results of the study are important inputs to a designer for consideration of new designs. The FDPSO is a dedicated design of a large capacity platform, different from the conventional FPSO which is usually a retrofitted ship for the purpose. The investigation is based on computational simulation using a commercial RANSE solver namely, STAR-CCM+. Comparison with results from towing tank tests serves to initially validate the numerical simulation-based results. The study performs hydrodynamic diffraction analysis using a potential flow-based solver, namely ANSYS – AQWA. A simplified hull form represents the FDPSO, considering that it is a platform predominantly stationary in operation. However, drag and interactive effects with the moonpool as well as a liquid oscillation in the moonpool are important dynamic conditions for investigation in stationary as well as transit conditions during the tow. The focus of the investigation is on moonpool dynamics in calm water and regular sea conditions and ship motion in waves. The moonpool is vertical circular cylindrical shaped and the investigation considers three moonpool locations namely, at the forward, the midship and the aft, respectively. The water column in the moonpool experiences large oscillatory motions in the piston mode or the sloshing mode. The analysis captures the flow physics, amplitude of oscillations, hydrodynamics resistance and the vessel motion response. The results obtained establish that the location of the moonpool contributes to the augmentation of the cavity drag in the FDPSO. For the selected parameters, the study indicates that the moonpool located in the forward region gives better performance as compared to responses in the other locations. [ABSTRACT FROM AUTHOR]

This study examines land-based oscillating water column (OWC) devices numerically and experimentally subjected to the action of regular and irregular waves. The higher-order boundary element method was used to develop the numerical model for the simulation of a single- and dual-chamber OWC. A comparison of the performance of both structures is presented. The JONSWAP spectrum method was employed to generate the irregular waves. Physical experiments were conducted to validate the accuracy of the numerical results and demonstrate the variation of aerodynamic and viscous damping effects in the two device configurations. The dual-chamber configuration is proved to broaden the effective frequency bandwidth. The addition of the internal wall reduces the higher-order wave components inside the chamber. The single-chamber OWC efficiency in irregular wave conditions is approximately 5–12 % lower than in regular wave conditions. The dual-chamber OWC efficiency is reduced at the resonance condition in irregular waves but improved in the low wave-frequency region. It is shown that partial sloshing inside the chambers always occurs under the action of the irregular waves, and this phenomenon is more frequently observed in short period waves. A bottom slope is introduced to enhance the dual-chamber converter peak efficiency in the low-frequency, irregular wave conditions whilst the flat-bottomed OWC demonstrates a wider overall effective frequency bandwidth. The hydrodynamic efficiency of the individual chambers in the OWC is less sensitive to significant wave heights; a finding which contrasts with the case of regular waves. • Hydrodynamics of single- and dual-chamber OWCs subjected to irregular waves is studied experimentally and numerically. • Partial sloshing in the chamber frequently occurs in the action of the irregular waves. • The effective frequency bandwidth of the dual-chamber OWC under irregular waves is broadened effectively. • The hydrodynamic efficiency of the dual-chamber OWC under irregular waves is less sensitive to wave nonlinearity. [ABSTRACT FROM AUTHOR]

The violent fluid motion in a partially filled vessel is called sloshing. Resonance occurs when the natural frequency of the fluid oscillation approaches that of its container. This result may lead to structural failure. In this study, a Smoothed Particle Hydrodynamics (SPH) model is established to investigate the sloshing motion in a shallow water reservoir. Sloshing in a submerged obstacle, cylinder array, rectangular and wall-inclined topography is considered. In terms of results, the cylinder array is more effective than the other models to reduce the impact force due to the sloshing wave in a rectangular tank. The results prove that the proposed SPH model is capable of simulating sloshing in the shallow water tank. [ABSTRACT FROM AUTHOR]

This paper presents a comparative numerical study on liquefied natural gas (LNG) pump tower loads, while focusing on two aspects. First, are impact loads relevant for the structural design of LNG pump towers and, second, in which way does fluid-structure interaction influence these loads? Numerical simulations of the multiphase problem were conducted using viscous field methods. First, unsteady Reynolds-averaged Navier-Stokes (URANS) equations, extended by the volume of fluid (VoF) approach, were used to simulate, at model scale, the flow inside a three-dimensional LNG tank without the tower structure. Then, these results were used to validate the numerical method against model test measurements. Afterward, motion periods and amplitudes were systematically varied in the flow simulations. Flow velocities and accelerations along the positions of the main structural members of the pump tower were extracted and used as input data for load approximations based on the Morison equation. Finally, these load approximations were compared with loads determined from solving the delayed detached eddy simulation (DDES). Time histories as well as statistical measures of global loads acting on the entire and the simplified tower structure were of the same order of magnitude. However, their time evolution differed, especially at their peaks, and this was considered significant for structural design. [ABSTRACT FROM AUTHOR]

The aim of this work is to simulate the complex 3D hydrodynamics inside free-surface anti-roll tanks with obstacles and side sub-compartments. The case studies comprise a rectangular tank, a tank with a C-shaped section and a rectangular tank with baffles, for which experimental results are provided. The simulations have been performed for 3 and 6 degrees of roll, and for various filling levels. The Open Source Computational Fluid Dynamics (CFD) tool OpenFOAM has been used to carry out the simulations. Various turbulence models and boundary condition implementations have been used. It is shown in the paper that the k-ω SST model with slip boundary condition is the one that provides the best trade-off between accuracy and computational efficiency. In order for present results to be easily reproducible, the simulations files, also including the geometrical ones, are provided as supplementary material. [ABSTRACT FROM AUTHOR]

In the present work, the sloshing phenomenon in a rectangular tank with non-Newtonian Bingham fluid is modeled. The numerical method used is the Incompressible Smoothed particle Hydrodynamics (ISPH) method. In the present study, first, a proper algorithm has been developed for modeling the Bingham fluid with the free surface. The method is validated by the famous previous works and experimental results. Then, to investigate the behavior of Bingham fluid, first, a proper Bingham number for sloshing phenomena is defined and the results are extracted according to this number. Three different Bingham numbers are considered and sloshing phenomena are analyzed and discussed for each of them. Finally, the effect of the baffle on the control of the sloshing phenomenon for the Bingham fluid is examined. The results show that increasing the Bingham number decreases the amplitude of the sloshing phenomenon. Also, the vertical baffle significantly controls the sloshing phenomenon. [ABSTRACT FROM AUTHOR]

With more recent discoveries of oil and gas reserves in the deep ocean locations like Guyana and Ghana, floating vessels such as floating production storage and offloading (FPSO) and floating liquified natural gas (FLNG) are in high demand. Good seakeeping characteristics of floating vessels are relevant because they are expected to be in operation all year round regardless of the weather conditions they may encounter. One phenomenon that affects the motion responses of floating vessels in severe weather conditions is sloshing in the cargo tanks. Vessel wave responses and sloshing may, individually and combined, cause damaging and dangerous motions. The availability of fast and accurate techniques for predicting and analyzing the motions and tank behavior in extreme weather conditions plays a significant role in the design and operations of floating vessels. Over the years, investigations have been carried out on the hydrodynamics of vessel motions, sloshing as a separate phenomenon as well as coupled vessel motions with sloshing analysis. This study reviews the existing techniques that are applicable for analyzing coupled vessel motions and sloshing in the tanks of floating vessels moored offshore. The pros and cons of each technique have been discussed, with the aim to help future researchers and engineers select the most appropriate method for design and analysis. This paper also identifies methods that are yet to be fully applied for coupled seakeeping--sloshing analysis. [ABSTRACT FROM AUTHOR]

In the present paper, an improved multiphase weakly compressible smoothed particle hydrodynamics model for balancing the accuracy and stability of the long‐term simulations is proposed to model the forced liquid sloshing in a tank. The governing equations of the multiphase flow are discretized by considering the density discontinuity over the interface. To suppress the pressure oscillation, a previous density correction term suitable only for single‐phase problems is modified and incorporated into the discrete continuity equation to suit multiphase problems. The modified density reinitialization algorithm is implemented to calculate the pressure of the boundary particles, and the coupled dynamic solid boundary treatment (SBT) is employed to determine the rigid wall condition. For convenience, a numerical probe algorithm is also proposed to accurately measure the wave height. The present model exhibits a better numerical stability than the previous multiphase smoothed particle hydrodynamics model, and its results well confirm with the experimental data of the forced sloshing of liquid excited by swaying or rolling. [ABSTRACT FROM AUTHOR]

Optimum safe design through numerically investigation and simulation of FSI due to seismic loading on acid tank with piping attachment is presented. A nonlinear FSI based on the FEM is performed on a full-scale 3D model. Investigations are supplemented by a CFD to simulate the fluid motion inside the tank using acceleration time history of Kocaeli earthquake, the response of the maximum stress, deformation, and displacement of rigidly restrained fixed and flexible tanks at different fill levels and thickness are evaluated. The results are compared and analyzed with design codes and the difference observed in hydrostatic pressure is less than 0.08%, and in maximum values of hydrodynamic pressure are less than 4.3%, 0.8%, and 1.5% at three fill level while the average difference in transient time history total pressure is less than 0.4%. Finally, the provision given in the design codes and response of parameters is computed and polynomial correlation is proposed with an accuracy of above 0.99 and average difference less than 5% in fixed tank and less than 2% in the flexible tank for designing a safe tank by analysis. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian, particle method, which combines the advantages of Euler and Lagrangian method and has special advantages in simulating violent non-linear fluid–structure interaction problems. In this study, an improved SPH method is used to simulate four fluid–structure interaction cases. Firstly, the violent flow in the mould filling process is simulated to validate that the SPH model can obtain accurate flow patterns with any complex solid boundaries. Secondly, the dam-break flow against a vertical wall is simulated, and the pressure curves are compared with the experiment. Then liquid sloshing problems under different external excitations are simulated, and the complex coupling characteristics can be captured. Finally, the interactions between fluid and floating bodies are researched. The obtained numerical results show good agreement with the results from other sources, and clearly demonstrate the effectiveness of the presented SPH method in modelling fluid–structure interaction problems.

Smoothed particle hydrodynamics (SPH) is a meshfree, Lagrangian, particle method, which combines the advantages of Euler and Lagrangian method and has special advantages in simulating violent non-linear fluid–structure interaction problems. In this study, an improved SPH method is used to simulate four fluid–structure interaction cases. Firstly, the violent flow in the mould filling process is simulated to validate that the SPH model can obtain accurate flow patterns with any complex solid boundaries. Secondly, the dam-break flow against a vertical wall is simulated, and the pressure curves are compared with the experiment. Then liquid sloshing problems under different external excitations are simulated, and the complex coupling characteristics can be captured. Finally, the interactions between fluid and floating bodies are researched. The obtained numerical results show good agreement with the results from other sources, and clearly demonstrate the effectiveness of the presented SPH method in modelling fluid–structure interaction problems. [ABSTRACT FROM AUTHOR]

Abstract Oscillating Water Column (OWC) is one of the pioneer devices in harnessing wave energy; however, it is not fully commercialized perhaps due to the complicated hydrodynamic behavior. Previous studies are significantly devoted to OWC devices located in nearshore and coastal regions where incident wave energy would experience dissipation more than offshore. In this paper, a 1:15 scaled fixed offshore OWC model is tested in a large towing tank of National Iranian Marine Laboratory. Wave spectrum shape effect on the efficiency of the OWC model is addressed. Moreover, the paper investigates the effects of the geometric and hydrodynamic factors on OWC device efficiency and uncovers new points in nonlinear interaction occurring inside the chamber; i.e. sloshing. The results indicate that shape of the spectrum inside the chamber is affected by the type of incident wave spectrum, especially for long waves. Pierson–Moskowitz spectrum leaded to higher efficiency rather than JONSWAP spectrum at longer incident wave periods. According to efficiency analysis, increasing wave height may lead to air leakage from the chamber followed by vortex generation, which is a reason for decreasing the efficiency of the OWC device. Furthermore, no shift in the resonant period of the OWC model, due to wave height increase, was observed at the opening ratios equal or smaller than 1.28%. Spectral analysis of water fluctuation inside the OWC chamber illustrates two modes of sloshing. The first mode can be seen at short period waves while the second mode is visible at long period waves. The sloshing modes approximately vanish by increasing draft value. [ABSTRACT FROM AUTHOR]

Abstract Hydrodynamics of an anti-sloshing technique using floating foams in a rectangular liquid tank is investigated. A series of experiments are conducted. An analytical potential-flow solution is derived to help explain the experimental observations. Effects of various layers of floating foams on both the wave profiles and dynamic pressure histories in sloshing tanks are analyzed. It shows that even a single layer of floating foams can help reduce the sloshing amplitude due to energy dissipation. If multiple layers of floating foams are further applied, the sloshing amplitude can be further reduced. The amplitude of dynamic pressure in the tank is also found to decrease as the number of foam layers increases. Besides, anti-sloshing effects of floating foams in tanks of different depths are discussed. Floating foams are found to work more efficiently for larger amplitude sloshing waves. Highlights • An anti-sloshing technique based on floating foams is introduced. • Hydrodynamics of sloshing tanks with floating foams is investigated. • Both analytical and experimental investigations are carried out. • Effects of floating foams on wave elevation and sloshing pressure are discussed. [ABSTRACT FROM AUTHOR]

Abstract Integrated dynamic responses of FLNG system in side-by-side offloading operation are investigated numerically and experimentally in this paper. A numerical code is developed based on potential flow theory to predict the interactions between connected vessels' motions and liquid sloshing in the time domain. The impulsive response function (IRF) method is adopted in the resolution for 6 DOF vessels' motions, nonlinear sloshing in liquid tanks is solved using boundary element method (BEM), and connection system including hawsers and fenders is numerically modeled as linear response system. A series of model tests are conducted to validate the feasibility of the numerical code. Hydrodynamic interaction between the vessels and shielding effects under different wave directions are analyzed; sloshing effects on the vessels' motions and on the loads of connection system are investigated; the sensitivities of the vessels' motions and loads to connection system stiffness are discussed. It is found that the vessels' motions are significantly affected by the hydrodynamic interactions between vessels and sensitive to wave directions for shielding effects. The radiation forces of the adjacent vessel tend to amplify vessel's motions and LNG carrier is more likely to be affected by FLNG's radiation forces for their difference in displacement. In addition, compared with solid loading condition, liquid loading vessel tends to have decreased natural roll frequency and have increased sway motions in the frequency region that higher than the natural sloshing frequency. The two sloshing responses peaks appear in the natural roll frequencies and natural sloshing frequencies, which are respectively mainly excited by vessels' roll and sway motions. Besides, in low fill conditions, the sloshing loads contribute to larger sway motions in low fill conditions for the natural sloshing frequencies are closer to the main response frequency region of vessels. Sloshing nonlinearity gets obvious in the conditions with low fill conditions and large wave amplitude, while the motion responses of vessels have slight nonlinearity with the increases of sloshing nonlinearity when no violent sloshing with wave break is excited. Furthermore, small stiffness of the connection system has slight influences on the vessels' motions, and resonant motions can be excited when the natural frequency of the connection system located in the wave frequency region. Highlights • A numerical code is developed to predict the integrated dynamic responses in side-by-side offloading FLNG system. • Experimental tests are conducted to validate the numerical code. • Comparative studies are carried out to investigate the coupling mechanism. • The effects of filling levels and wave directions on FLNG performances are investigated. [ABSTRACT FROM AUTHOR]

Abstract Tuned liquid dampers (TLDs) are economical dynamic vibration absorbers which are increasingly being used for structural response control. Nevertheless, a thorough understanding of the sloshing behavior inside the TLD is essential for efficient design. In this paper, a truly incompressible smoothed particle hydrodynamics (ISPH) method is employed to circumvent the difficulties regarding the simulation of fully nonlinear sloshing motion induced by large amplitude excitations. The behavior of the TLD with damping screens is studied numerically over a wide range of excitation frequencies and amplitudes. It is found through comparison with the existing experimental data that the ISPH model is a powerful tool for accurate predictions of the TLD behavior. The amplitude-dependent properties of an equivalent tuned mass damper (TMD) model, which is capable of reproducing the energy dissipation characteristics of the TLD, are derived from the simulations results. Good agreement between the numerical and experimental results is indicative of the equivalent model's ability to predict the response of structure–TLD systems, suggesting that the ISPH model can properly simulate the TLD behavior. The effect of screen placement on the performance of structure–TLD systems is also investigated. Findings reveal that improved performance of TLD can be realized under high amplitude excitations by placing the damping screens in the locations corresponding to the higher sloshing modes. [ABSTRACT FROM AUTHOR]

The offloading of LNG from a ship-shaped FLNG facility to a carrier in a side-by-side configuration in the open sea is a new operation in the offshore industry. Its novelty means that there is limited guidance available for potential FLNG operators when undertaking operability assessments. The criteria for design of side-by-side offloading operations at sea are reviewed, largely based on the pioneering work by Shell. Whilst many advances have been made, several areas of uncertainty remain, particularly associated with the underlying complex non-linear hydrodynamics. To this end, a review of the relevant hydrodynamics associated with side-by-side offloading is presented. Within this scope, the key factors that are likely to play an important role in determining side-by-side offloading operability include roll motions of LNG carriers, liquid cargo sloshing and free surface motions in the gap between vessels. Each of these phenomena can exhibit resonance, with the response amplitude of roll motions, sloshing and free surface motions in the gap being sensitive to damping levels and excitation frequencies. To explore the present understanding of the hydrodynamic excitation and damped response of these phenomena, recent developments have been reviewed and critiqued; these encompass numerical simulations, physical model tests and full scale measurements. Recommendations for future work directions to expand the current understanding and address shortcomings are also provided. [ABSTRACT FROM AUTHOR]

Ship dynamics in presence of sloshing is addressed in time-domain through a co-simulation approach. A nonlinear blended 6-DOF ship motion solver, addressing rigid body dynamics and external fluid-structure interaction, is coupled with a 3D Weakly Compressible Smoothed-Particle Hydrodynamics (WC-SPH) solver, addressing the internal fluid dynamics. The coupling is carried out by means of network communication, which is suitable for grid computing. The resulting co-simulation approach is able to address nonlinear ship motions together with nonlinear sloshing in internal tanks. The two solvers and the co-simulation strategy are presented, together with two example applications. One example application addresses the roll motion of a vessel, with and without an anti-rolling tank, in regular beam waves. The effect of varying the anti-rolling tank length and the effect of varying the forcing wave steepness are investigated. Simulations disclose nonlinear phenomena and indicate the capability of the developed approach of identifying the reduction of anti-rolling tank effectiveness for too small tank lengths and/or too large forcing wave steepnesses. A second application is presented, for validation purposes, where simulations are compared with experimental data from literature regarding roll and heave for a tanker hull form in regular beam waves, with and without a partially filled tank. [ABSTRACT FROM AUTHOR]

An improved smoothed particle hydrodynamic (SPH) model is developed to study the complex hydrodynamic behaviour of an onshore oscillating water chamber. The improvements include adding a diffusive term to the continuity equation and incorporating the corrective smoothed particle method (CSPM). A modified boundary condition is implemented to better simulate the pressure field near the solid boundary. The SPH model is first verified by comparing the numerical results with analytical solutions and the available experimental data. The verified model is then applied to study the hydrodynamic behaviour of an onshore oscillating water chamber. The free surface elevations inside the water chamber and the total forces acting on the front wall of the water chamber are studied for different wave conditions. The turbulence energy distribution and the sloshing phenomenon in the water chamber are also investigated. [ABSTRACT FROM AUTHOR]

Dam breaking and sloshing are hydrodynamic phenomena of great importance in the assessment of progressive flooding of ships and offshore platforms. Recent experimental tests have generated more data with different configurations of openings and flooded compartments. The internal geometry of the compartments is important on the behavior and impact of the flooded water on the vessel motion. In this paper, a computational code is validated to simulate dam breaking and sloshing with two different configurations. Numerical results were obtained for recent experiments on transfer of water between connected neighboring compartments with two configurations of openings. The comparison with experimental data validated the numerical code and showed some important details of the flow field. The two configurations of sloshing are excited in sway motion, where certain amount of water flows from one side to the other through an opening and the other way round. The implemented numerical scheme is based on the finite difference method, where the Euler equations are solved using an upwind total variation diminishing scheme with a structured computational mesh. [ABSTRACT FROM AUTHOR]

A rectangular barge with partially filled rectangular tank is considered. The sloshing motions in tank and coupling motions of floating body are discussed in both frequency domain and time domain. In frequency domain, the superposition of natural sloshing modes is adopted for modelling liquid sloshing in tank and eigen-functions expansion is used for the motions of barge. In time domain, nonlinear Boussinesq-type approach in terms of velocity potential is used for simulating internal liquid motions. An impulse response function is introduced for solving the motions of floating body and the hydrodynamic coefficients in the equations of motions are obtained from the results in frequency domain. The quadratic damping term in roll is taken into account for both numerical approaches. The numerical results in both frequency domain and time domain are compared with experimental results in basin. [ABSTRACT FROM AUTHOR]

Floating liquefied natural gas (FLNG) facilities are a game changer in offshore hydrocarbon development. One of the key challenges associated is offtake of LNG from FLNG to LNG carriers. Side-by-side offloading is considered a promising method, but one which may be sensitive to LNG carrier roll response. During an offload the sloshing of the cargo at intermediate load conditions could couple with the global vessel response i.e. coupling of sloshing with the higher harmonics (double or triple value) of the roll natural frequency. An experimental study is conducted with a barge-like vessel carrying two spherical tanks. These tanks are filled with water to different volumes to simulate different load conditions. For comparison, same tests were performed for which the tanks were empty, but the vessel properties modified to a ‘frozen’ approximation of an intermediate load condition. The effects of the internal liquid cargo motions on global roll motions are clarified, for the first time, for vessels with spherical tanks. The roll response of the vessel with liquid cargo inside spherical tanks is greater than observed for the equivalent ‘frozen-cargo’ case. This study also provides a foundation for improved numerical modelling with relevancy for side-by-side offloading operations. [ABSTRACT FROM AUTHOR]

Characterizing the movement of space propellant in the tank subjected to maneuvers and predicting its damping is a fundamental requirement for the success of space missions. In this work, we evaluate the capabilities of the smoothed particle hydrodynamics method (SPH) of characterizing liquid sloshing motion. SPH simulations are performed using the open-source code DualSPHysics, which employs a weakly compressible assumption to simulate incompressible flows. We verify the SPH scheme by showing that the calculated boundary layer matches the analytical solution of the Stokes problem. The methodology is then validated against an open-access experimental database involving sloshing experiments on partially-filled cylindrical tanks subject to horizontal excitations. We present a study of two regimes: (a) a forced, periodic regime and (b) a transient regime where we compare the full liquid interface elevation, the corresponding frequency content and the full liquid interface damping maps. The simulations are able to capture the relevant flow physics with a good level of accuracy. In particular, the simulations fairly accurately reproduced the elevation of the full free surface, predicting a 3D crescent shape of the rising wavefronts, as well as damping rates under free sloshing. Analysis of the frequency range further showed good agreement of the dominant frequencies between the experimental, simulated and analytical values given by the linearized sloshing theory. [ABSTRACT FROM AUTHOR]

The aim of this work is to carry out numerical simulations in the time domain of seakeeping problems taking into account internal flow in tanks, including sloshing. To this aim, a Smooth Particle Hydrodynamics (SPH) solver for simulating internal flows in tanks is coupled in the time domain to a Finite Element Method (FEM) diffraction–radiation solver developed for seakeeping problems. Validations are carried out comparing against available experimental data. Good agreement between obtained numerical results and experimental data is found. [ABSTRACT FROM AUTHOR]

This paper describes a formulation of a nonlinear sloshing problem based on the Hamiltonian mechanics. In particular, we focus on behavior of a liquid surface and a hydrodynamic force arising from the nonlinear sloshing in shallow water depth. It is well known that the water wave in shallow water depth shows the characteristic behaviors such as the solitary wave by inherent nonlinearities. Therefore, the effect of nonlinearity is significantly crucial for accurate predictions of the wave height and the hydrodynamic force. Although many researches have been studied for the feature of the nonlinear sloshing in shallow water depth, the theoretical analysis is essentially difficult because a lot of higher order nonlinear terms and sloshing modes have to be taken into account for accurate numerical predictions. Consequently, it yields complicated algebraic procedures. This study presents a formulation of nonlinear sloshing based on the canonical theory for constrained systems. In addition, the Dirichlet–Neumann operators developed by Craig and Sulem (1993) is introduced to obtain an asymptotic description for the kinematic boundary condition of the liquid surface. The proposed approach facilitates the consideration of the nonlinearity in the formulation. This study demonstrates analytical predictions considering up to the fourth-order nonlinear terms and higher-order sloshing modes and discusses adequate truncation orders for them. Moreover, experiments are conducted to measure time histories of the wave height and the nonlinear hydrodynamic force due to the sloshing in a rectangular tank subjected to a horizontal excitation. As the results of frequency analyses for the time histories, many frequency spectra with the integral multiples of the dominant frequency were observed. In particular, the only odd multiples of the dominant frequency were involved in the results of hydrodynamic force. These features were also obtained by the analytical predictions by the proposed method. [ABSTRACT FROM AUTHOR]

The damping effect of the vertical baffles inside a liquid storage tank is studied in this paper. A numerical model based on the finite volume method is established and used to evaluate the accuracy of an analytical model developed to estimate the hydrodynamic damping caused by the vertical wall bounded baffles. For this purpose, several full scale baffled tanks with different aspect ratios are numerically analyzed. The numerical results were then used to validate the analytical model. The reduction in sloshing wave height caused by the baffles is estimated for selected tanks subjected to the seismic excitations. Finally, a simple procedure to estimate the reduction in sloshing amplitude due to the presence of baffles is proposed and validated using the time history numerical results. [ABSTRACT FROM AUTHOR]

A multi-physics computational method is presented to model the effect of internally and externally-carried fuel on aeroelastic behaviour of a pitch–plunge aerofoil model through the transonic regime. The model comprises three strongly coupled solvers: a compressible finite-volume Euler code for the external flow, a two-degree of freedom spring model and a smoothed particle hydrodynamics solver for the fuel. The smoothed particle hydrodynamics technique was selected as this brings the benefit that nonlinear behaviour such as wave breaking and tank wall impacts may be included. Coupling is accomplished using an iterative method with subcycling of the fuel solver to resolve the differing timestep requirements. Results from the fuel-structural system are validated experimentally, and internally and externally-carried fuel is considered using time marching analysis. Results show that the influence of the fuel, ignoring the added mass effect, is to raise the flutter boundary at transonic speeds, but that this effect is less pronounced at lower Mach numbers. The stability boundary crossing is also found to be less abrupt when the effect of fuel is included and limit cycles often appear. An external fuel tank is seen to exhibit a lower stability boundary, while the response shows a beating effect symptomatic of two similar frequency components, potentially due to interaction between vertical and horizontal fuel motion. [ABSTRACT FROM AUTHOR]

Understanding how fuel sloshes in a fuel cell, as a vehicle races around a circuit, is an important but mostly unexplored factor when designing fuel containment systems. Cell designs are based on knowledge of how liquids slosh in other containers, with the design and placement of structures, such as weirs, based on engineering judgement. This work aims to provide better understanding for this difficult problem with a view to improve future designs. A Graphics Processing Unit (GPU) based Smoothed Particle Hydrodynamics (SPH) model is presented to simulate the fuel sloshing problem, with results from a simplified and real fuel cell geometry shown and compared against real data recorded in a vehicle. The vehicle motion and accelerations are included in the SPH simulations using a body force within the momentum equation. Results show good agreement between the simulation and the real fuel movement, with bulk motion captured well for accelerations up to 5 times gravity. Focus is placed on the practicality of the method for use as part of an industrial design process, therefore the amount of time needed to compute results is considered throughout. Computational performance is found to be within acceptable limits, while numerical accuracy is actively considered through the use of Kahan compensated summation. It is concluded that the model is successful in capturing the necessary fluid dynamics for it to be useful in fuel cell design. It is expected that the method will provide insight into current cell designs and highlight where improvements can be made. [ABSTRACT FROM AUTHOR]

Risks related to sloshing of liquid metal coolant due to seismic excitation need to he investigated. Sloshing effects on reactor performance include first, fluid-structure interaction and second, gas entrapment in the coolant with subsequent transport of void to the core region. While the first can hypothetically lead to structural damage or coolant spill, the second increases the risk of a reactivity insertion accident and/or local dryout of the fuel. A two-dimensional computational fluid dynamics study is carried out in order to obtain insights into the modes of sloshing depending on the parameters of seismic excitation. The applicability and performance of the numerical mesh and the Eulerian volume of fluid method used to track the free surface are evaluated by modeling a simple dam break experiment. Sloshing in the cold plenum free surface region of the European Lead-cooled SYstem (ELSY) conceptual pool-type lead-cooled fast reactor (LFR) is studied. Various sinusoidal excitations are used to imitate the seismic response at the reactor level. The goal is to identify the domain of frequencies and magnitudes of the seismic response that can lead to loads threatening the structural integrity and possible core voiding due to sloshing. A map of sloshing modes has been developed to characterize the sloshing response as a function of excitation parameters. Pressure forces on vertical walls and the lid have been calculated. Finally, insight into coolant voiding has been provided. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the operation of a new design of wave energy converter. The design consists of a buoyant tethered submerged circular cylinder which is allowed to pitch freely about an axis below its centre. Within the body of the cylinder a fluid half fills an annular tank whose shaped inner walls allow the fundamental sloshing mode of the fluid be to tuned to any period of interest. The pitching motion of the cylinder in waves induces a sloshing motion inside the annular tank which in turns drives an air turbine connecting air chambers above the two isolated internal free surfaces. The concept behind this design is to couple resonances of the pitching cylinder with natural sloshing resonances of the internal water tank and thus achieve a broadbanded power response over a wide range of physically-relevant wave periods. Mathematically, the problem introduces new techniques to solve the series of complex internal forced sloshing problems that arise and to efficiently determine key hydrodynamic coefficients needed for the calculation of the power from the device. The results show that practical configurations can be found in which the efficiency of a two-dimensional cylindrical device is close to its maximum theoretical limit over the target range of periods from to s. [Copyright &y& Elsevier]

Abstract: A series of two-dimensional model tests has been carried out to study the hydrodynamic performance of a floating liquefied natural gas (FLNG) section including internal sloshing oscillations. The reference FLNG section is ballasted with fresh water and equivalent solid weights respectively, to clarify the coupling effects. In addition, five different ballasting conditions of the FLNG section were considered, to investigate the influence of filling levels and natural frequencies. Response amplitude operators (RAOs) of both motion responses and internal sloshing flows are calculated based on measured data. The inner-tank sloshing exhibits obvious effects on sway and roll motions, while little effects on heave motion. It is observed that the first mode of sloshing can significantly affect the global motions of the vessel, while that in higher modes shows little effects. The coupling effects are found to be sensitive to the filling levels of the tank and the roll frequencies of the vessel. Whether the internal sloshing amplifies or reduces the global motions is related to the difference between the first mode of sloshing frequency and the roll frequency of the vessel. The outcome of this study would offer better understanding on the coupled hydrodynamics of ship motions and sloshing flows. [Copyright &y& Elsevier]

This study presents a new model for predicting the response of a two-dimensional tuned liquid damper (TLD) tank with a variable fluid depth. A simple finite element method is presented, which is used to calculate the sloshing mode shapes. From the mode shapes, the equivalent mechanical properties of the sloshing fluid are estimated. Three tanks (flat-bottom, triangular-bottom, and circular-bottom), which have closed-form expressions for their equivalent mechanical properties are used to evaluate the model. The proposed model is in agreement with the closed-form expressions. Subsequently, a parametric study is conducted on tanks with a chamfered-bottom, boxed-bottom, and ramped-bottom to assess how their properties change as the shape of the tank bottom is altered. The model provides TLD designers with greater flexibility when selecting a tank shape. Moreover, the model could be used to optimize the shape of a TLD tank to maximize its performance for a given liquid mass, allowing construction cost savings to be realized. [ABSTRACT FROM AUTHOR]

The seismic behavior of partially filled rigid rectangular tank with bottom-mounted submerged block is numerically simulated. Six different ground motions characterized on the basis of low-, intermediate-, and high-frequency contents are used to investigate the dynamic behavior of tank-liquid-submerged block system. A velocity potential-based Galerkin finite element model is developed for the analysis. The effect of submerged block on impulsive and convective response components of hydrodynamic behavior manifested in terms of base shear, overturning base moment, and pressure distribution along the tank wall as well as the block wall has been quantified. [ABSTRACT FROM AUTHOR]

Effects of inner-tank sloshing on the global motion responses of a floating liquefied natural gas (FLNG) vessel has been investigated through a series of model tests. Decay tests with the FLNG vessel subjected to a forced excitation in heave, roll and pitch motions in still water were carried out. The FLNG vessel was also subjected to band-limited white noise wave excitations under head, quartering and beam sea conditions. Three filling levels of 20%, 40% and 60% were included. To clarify the influence of the inner-tank sloshing, model tests were also carried out for the FLNG vessel with the inner-tank liquid treated as frozen mass (substitute the inner-tank liquid with equivalent solid weight) corresponding to each filling level. Based on the experimental results, we conclude that the effects of the inner-tank sloshing on the responses of FLNG are sensitive to wave excitation frequencies. The inner-tank sloshing can obviously affect the wave frequency motions of the vessel, in particular the roll motions can be most pronouncedly affected, while it is insignificant on low frequency motions. In addition, the influence of the filling levels has also been investigated through the comparison of the three filling conditions. [ABSTRACT FROM AUTHOR]

An overview of the actual status of the modelling of hydro-structure interactions which occur during the severe sloshing impacts in the tanks of LNG Carriers of membrane type is presented. This problem still appears to be open and there are no fully satisfactory methodologies and methods available to solve this problem fully consistently within the so called direct calculation approach. That is why, for the time being, we still have to rely on simplified procedures. The paper first summarizes the main technical difficulties associated with this problem and then discusses the different methods which are employed in practice. [ABSTRACT FROM AUTHOR]

Abstract: A RANS based CFD solver with VOF modeling of free surface is employed to investigate the effects of sloshing and flooding on damage ship hydrodynamics. The numerical study includes three research works, i.e. the simulations of forced roll motion of an intact ship, sloshing of water in tank and forced roll motion of a damage ship. The computed roll moments in the tank and at opening were compared. The coefficient of roll damping was obtained and validated against model test data. The results show that the impact of sloshing on damage ship hydrodynamics is frequency dependent. It becomes significant near natural roll frequency of the tank. The phase differences between hydrodynamic and hydrostatic components are increasing with frequency. The flooding at opening of a damage ship tends to alleviate the sloshing impact. [Copyright &y& Elsevier]

Abstract: Free-surface flows are of significant interest in Computational Fluid Dynamics (CFD). However, modelling them especially when the free-surface breaks or impacts on solid walls can be challenging for many CFD techniques. Smoothed Particle Hydrodynamics (SPH) has been reported as a robust and stable method when applied to these problems. In modelling incompressible flows using the SPH method an equation of state with a large sound speed is typically used. This weakly compressible approach (WCSPH) results in a stiff set of equations with a noisy pressure field and stability issues at high Reynolds number. As a remedy, the incompressible SPH (ISPH) technique was introduced, which uses a pressure projection technique to model incompressibility. Although the pressure field calculated by ISPH is smooth, the stability of the technique is still an open discussion. An alternative approach is to use an acoustic Riemann solver and replace the particle velocities and pressures by pressures and velocities determined from a Riemann solver. This technique is equivalent to the Godunov method in Eulerian techniques and so will be called the Godunov SPH method (GSPH). However, since the acoustic Riemann solver is a first order approximation of the Riemann solution, it is highly dissipative and cannot be employed in energetic free-surface flows without modification. In this paper, the GSPH method is modified by using the HLLC (Harten Lax and van Leer-Contact) Riemann solver. The accuracy of the modified GSPH technique is further improved by utilising the MUSCL (Monotone Upstream-centred Schemes for Conservation Laws) scheme with Slope–Limiter. This modified GSPH method along with the WCSPH and ISPH techniques are used to study non-linear sloshing flow. The accuracy, stability and efficiency of the techniques are assessed and the results are compared with experimental data. [Copyright &y& Elsevier]

Abstract: In this paper, an experimental and an analytical investigation of the hydrodynamic damping due to lower and upper mounted vertical baffles as well as horizontal baffles in partially filled rectangular tanks are conducted. The analytical model earlier provided to estimate the hydrodynamic damping ratio of lower mounted vertical baffles is extended for upper mounted baffles. The semi-empirical Miles expression, which was originally developed to evaluate damping ratio of ring baffles in cylindrical tanks is also formulated for horizontal baffles in rectangular tanks. The comparisons between maximum hydrodynamic damping cased by various baffle configurations (upper and lower mounted vertical arrangements, as well as horizontal arrangements) are made and the validity of extended analytical models is discussed. [Copyright &y& Elsevier]

The present research focuses on experimentally clarifying the effect of inner-tank sloshing on the hydrodynamics of an Floating Liquefied Natural Gas (FLNG) system. Through the comparisons of the results obtained from the model tests carried out with the vessel model ballasted with liquid and solid cargo separately, the effects of the inner-tank sloshing on the hydrodynamics of an FLNG system are highlighted and presented. Statistical languages of the maximum, minimum, mean values and the standard deviations and power density spectra calculated with the help of the algorithm of Fast Fourier Transformation (FFT) are provided. It is concluded that the effects of the inner-tank sloshing on the responses of the FLNG system are sensitive to wave excitation frequencies, and that the effects of the inner-tank sloshing play an important role, particularly in the roll motion of the FLNG hull. The outcome of the proposed technique would offer constructive feedback, which can lead to more practical applications and can serve as a reference for the verification of the potential numerical simulations by other researchers. [ABSTRACT FROM AUTHOR]

Abstract: FLNG (Floating Liquid Natural Gas) is a new type of floating LNG (Liquid Natural Gas) platform that consists of a ship-type FPSO hull equipped with LNG storage tanks and liquefaction plants. This new platform type has been developed as an alternative to long pipelines running to an onshore LNG liquefaction plant from stranded offshore fields (i.e., ). This study provides a comprehensive review of recent research developments on the hydrodynamics of FLNG. Research results based on numerical calculations and model tests are summarized, existing problems are discussed, and further research topics regarding FLNG are suggested. [Copyright &y& Elsevier]

Sloshing is one of the major concerns for liquid storage tanks and the vibration characteristics of the contained liquid require lot of research attention. Simulated experimental investigations using triaxial shake tables are rare in this field and the non linear dynamic behavior of the structure is of interest, be it during transportation of liquids or during earthquakes. The paper presents an experimental cum analytical investigation on lateral sloshing behavior under simulated vibrating conditions on a fixed base rectangular container with water. The tank has been designed to suit experimental requirements and the walls were made of Perspex sheets in order to view the sloshing phenomena and for image capturing purposes. The behavior of the system is identified during dynamic loading under lateral sweep sine excitation and simulated random vibration studies were carried out further on the 3D shaking table. Sloshing natural frequencies, wave amplitudes and dynamic pressures on the tank walls are measured during the investigation which throws light into the nonlinear dynamic characteristics due to large amplitude sloshing. CFD modeling has been carried out on the experiments conducted and the results are discussed. [ABSTRACT FROM AUTHOR]

By using Kelvin's inversion, we construct analytical harmonic functions satisfying the zero-Neumann condition on the inner spherical wall everywhere except a single point where the velocity is infinite. This set of functions can be used to construct approximate velocity potentials associated with liquid sloshing in a spherical tank, and in other hydrodynamic problems. By using Kelvin's inversion, we construct analytical harmonic functions satisfying the zero-Neumann condition on the inner spherical wall everywhere except a single point where the velocity is infinite. This set of functions can be used to construct approximate velocity potentials associated with liquid sloshing in a spherical tank, and in other hydrodynamic problems. [ABSTRACT FROM AUTHOR]

The driving stability of transport vehicles is significantly affected by the type of cargo that is transported and the design of the tank. Cargo motion can have both beneficial and negative aspects in terms of driving stability and braking performance. Neglecting the influence of the dynamically moving cargo in driving simulations leads to significant errors in the simulation results. We propose a new method for the dynamic simulation of tank trucks carrying fluids and silo vehicles carrying granulates. The method couples Lagrangian particle methods, such as smoothed particle hydrodynamics for fluids or the discrete element method for granular media, and multibody systems using co-simulations. The capability of the new approach is demonstrated by providing simulation results of two benchmark manoeuvres and the behaviour of fluid and granular cargo is compared. [ABSTRACT FROM AUTHOR]

This study considers the motion responses of floating bodies in waves coupled with sloshing-induced internal forces and their effects on sloshing-induced impact loads. The linear ship motion is solved using an impulse-response-function (IRF) method, while the nonlinear sloshing flow is simulated using a finite difference method. The considered models are a liquid natural gas floating production, storage, and offloading unit (LNG FPSO) with two partially filled tanks and a modified S175 hull with an antirolling tank. In the case of the LNG FPSO model, both numerical and experimental studies are carried out. Three degree-of-freedom motion responses are allowed in the presence of regular waves, and the measured response amplitude operators (RAOs) are compared with computational results. For the modified S175 hull, the computational results are compared with other existing computational results. It is observed that the present method provides a fair agreement with experimental and other numerical results, showing significant coupling effects on both motion responses and sloshing flows. The numerical study extends to the observation of pressure field inside the tanks, and a significant difference in internal pressure is also shown. [ABSTRACT FROM AUTHOR]