bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Verification of Modelling Practice for CFD Calculations to Obtain Hydrodynamic Damping of Offshore Vessels
Authors: Koop Arjen , Loubeyre Sebastien , Yu Kai , Xu Haihua , Zheng Yingying , Huang Zhenjia (Jerry) 
Published: October 2022

Abstract
Estimates for hydrodynamic damping on offshore vessels are important input parameters for simulations studies on vessels operating at sea, e.g. moored vessels in waves, wind and current, workability and operability investigations, Dynamic Position studies, ship-to-ship operations and safety studies of vessels. To accurately predict the motions of vessels this quantity should be determined with confidence. Traditionally, model experiments in water basins using so-called decay or forced oscillation tests are carried out to determine the hydrodynamic damping. With recent advancements in CFD modelling, the offshore industry has started using CFD as an alternative method to compute the hydrodynamic damping of offshore vessels. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical Modelling Practice is developed within the Reproducible CFD JIP to obtain the hydrodynamic damping values using CFD simulations. The Modelling Practice describes the geometry modelling, computational mesh, model set-up and post-processing for these type of CFD calculations. This Modelling Practice is verified and validated by three independent verifiers against available model test data.
This paper provides an overview of the calculated CFD results from the verifiers when following the CFD Modelling Practice. The results are benchmarked against available model test results for a barge-shaped and tanker-shaped FPSO. The objective of the presented work is to obtain the hydrodynamic damping for the surge, sway and roll motions at low KC values and it is a continuation of the results presented in earlier papers OMAE2020-19173 and OMAE2021-62411. By following this Modelling Practice, the CFD predictions for the quadratic damping coefficients as well as the natural periods are consistent between the different verifiers, i.e. within 20% from each other, and within 20% of the model test results. Exceptions to this general statement are found for the surge direction where a large difference is found between the calculated CD values and the measured CD values as well as for the roll direction, where the CFD results between the various verifiers can show larger differences depending on the numerical settings.
Therefore, we conclude that when following the developed Modelling Practice for CFD simulations, consistent results can be obtained for the hydrodynamic damping of offshore vessels in surge, sway and roll direction, but that additional sensitivity studies still need to be carried out for specific situations.
Identification and Investigation of Extreme Events on Marine Structures Using ALE Approach and Hydrodynamic Coupling of Navier Stokes- and Laplace Equation-Based Models
Authors: Kamath Arun , Martin Tobias , Wang Weizhi , Pakozdi Csaba , Bihs Hans 
Published: October 2022

Abstract
Increased deployment of offshore wind turbines is seen as an important pathway to increase green renewable energy production. Improved and rapid identification of extreme events and evaluation of hydrodynamic loads due to such events is essential to reduce the cost of energy production. Numerical modelling to pre-screen sea states and identify the crucial events to prioritise model tests will make a major contribution to reduce design times and costs for such structures. In this effort, a highly efficient and nonlinear numerical model based on the Laplace equations is used to generate undisturbed wave kinematics. Such a simulation is used to identify extreme wave events in a sea state realisation and further, the wave loading due to such events are evaluated using Morison Formula. Events screened in this manner can then be transferred to a high-resolution model such as a Navier-Stokes equations-based solver to investigate the hydrodynamics in details. The implementation of such a method in the open-source hydrodynamic model REEF3D is presented in this work.
Analysis of the Influence of Opening Design Parameters on Cavity Flow Characteristics
Authors: Wang Luqun , Yu Jiawei , Wang Xianzhou , Deng Weihua , Feng Dakui 
Published: October 2022

Abstract
Cavities are widely used in marine vehicles and aircraft, the flow field inside these cavities is associated with strong acoustic effects, unsteadiness and turbulence. The flow characteristics and acoustic characteristics of cavities have become a hot research field, and the design parameters of openings are important factors affecting the flow characteristics of cavities. In this paper, some design parameters of openings are set to be variable, including the openings diameter, the opening spacing, the openings angle and the perforated plate thickness. A series of cavity structures with different opening design parameters are studied with large eddy simulation (LES) method. The numerical calculation is carried out by commercial CFD software FLUENT with structured grid. Large eddy simulation combined with acoustic analogy theory is used to study flow induced noise with different design parameters. The sound source is established based on the unsteady flow field in the cavity calculated by large eddy simulation (LES), then the far-field noise is predicted by the Fwowcs Williams Hawkings (FW-H) acoustic analogy theory, and the effects of various design parameters on the acoustic characteristics of the cavity are studied. The results show that the sound pressure level increases with the increase of the opening diameter, decreases with the increase of the opening angle, decreases with the increase of the opening spacing, and decreases with the increase of the perforated plate thickness.
Seakeeping of a Rectangular Barge With Skirts – From Model Tests to Numerical Wave Tank Simulations
Authors: Fernandez G. , Naciri M. 
Published: October 2022

Abstract
For decades now, wave basin model tests have been the cornerstone of the verification of new concept global performance. Model tests are also the preferred approach to shed light on complex hydrodynamics phenomena that cannot be correctly handled by the conventional seakeeping engineer’s toolbox. Two decades ago, model tests were performed on a seemingly simple geometry in the form of a rectangular barge with horizontal skirts fitted at its keel. The hull was held in place via a soft horizontal mooring system for simplicity and with a view to concentrating on the hydrodynamics. The objective was to investigate the likelihood of subharmonic resonance when the roll natural period is in the vicinity of twice the heave natural period (Ref. [1]). It is useful to revisit state of the art seakeeping toolbox and assess to what extent the beam regular and irregular wave tests can be reproduced numerically. Numerical Wave Tanks (NWT) are being considered as a possible substitute for model tests for well-defined scope of works. Such techniques based on Computational Fluid Dynamics (CFD) using Euler’s equations have been applied to the rectangular barge with skirts as a test case for this new verification approach excluding viscosity.
The paper briefly describes the scope of the model test campaign, documents performance of the ANSYS-AQWA suite of program in reproducing the key model tests (decay, monochromatic beam wave and irregular beam wave tests) and finally highlights the performance of the NWT for this specific geometry and abovementioned tests.
On Some Nonlinear Wave Diffraction and Refraction Solutions in Shallow Waters
Authors: Hayatdavoodi Masoud , Ertekin R. Cengiz 
Published: October 2022

Abstract
Diffraction and refraction of nonlinear shallow water waves due to uneven bathymetry is studied numerically in two and three dimensions. The numerical tank consists of a wavemaker at the upwave side of the domain, the submerged obstacles in the middle of the domain, and a numerical wave absorber on the downwave of the domain. The numerical wavemaker is capable of generating solitary and cnoidal waves as solutions of the Green-Naghdi (GN) equations. The nonlinear wave refraction and diffraction is studied by use of the Level I GN equations. The system of equations are solved numerically in time domain by use of a second-order finite difference approach, and in a boundary-fitted coordinate system. Various forms of three-dimensional bathymetry with large slopes, including flat and curved ramps from deep to shallow regions are considered. Results include solitary and cnoidal wave surface elevation and particle velocities and are compared with the existing solutions where possible. Overall very good agreement is observed. Discussion is provided on the nonlinearity and dispersion effects on the wave diffraction and refraction, as well as on the performance of the GN equations in solving these problems.
Response Mitigation of Floating Platform by Porous-Media Tuned Liquid Dampers
Authors: Tsao Wen-Huai , Chen Ying-Chuan , Kees Christopher E. , Manuel Lance 
Published: October 2022

Abstract
A porous-media tuned liquid damper (PMTLD) can serve as an eco-friendly, economical, and effective dynamic vibration absorber. Placing porous media within a water tank can improve the capacity for energy dissipation and optimize the performance by varying its material properties. The numerical simulations of the floating platform dynamics in waves coupled with the sloshing problem in PMTLD are emphasized. Two numerical methods are adopted for fluid computation. The first potential-based approach employs a mixed-type boundary value problem (BVP) solver, which is implemented by the boundary element method (BEM), coupled with a free surface particle tracker, which includes the nonlinear damping effects via a quadratic Forchheimer term for PMTLD. Another equivalent mechanical model is also used exclusively for solving the linear PMTLD. The coupling behavior between fluid and structure is solved by the Newmark method. The second viscous approach uses the finite element method (FEM) to spatially discretize the Navier-Stokes equations and handles the free surface via the volume of fluid (VOF) and the level set (LS) equations. The multiphase simulation is implemented by a computational modeling toolkit Proteus for the fluid phase and Chrono for the solid phase. The correlations between potential flow and Navier-Stokes (NS) models are presented. The PMTLD is designed for a floating platform by analogy with the tuned mass damper (TMD). Numerical results show that the PMTLD can effectively reduce the structure’s dynamic response in terms of vibration amplitude around resonance. Such damping devices have great potential for practical applications in offshore platforms and wind turbine design.
A Study on Safer New Optimal Route for Anti-Collision in Coastal Waters
Authors: Kim Won-Ouk , Kang Song-Jin , Kim Young-Rong , Kim Chang-Je 
Published: October 2022

Abstract
Although radar and AIS alarm functions have been used as support measures for collision prevention in many ships, they lacked the function to identify actual collision risk ships and inform the degree of risk and did not provide information on avoidance routes. This study aims to design a newly developed safer new optimal route for anti-collision based on the Collision Risk Zone assessment method, targeting mainly very small-sized ships that caused most of the collision accidents due to human errors. Designing a safer new optimal route is composed of three segments according to the ship’s characteristics. That is, empirical method for small-sized ships, collision risk zone method for larger ships and then combination method between empirical and collision risk method. In addition, this study analyzed the collision risk of various scenarios according to the navigation relationships and speed conditions between the two meeting ships. As a result, the model proposed in this study numerically calculated the risk of collision according to the navigation situation and could provide a safe optimal avoidance path accordingly. Therefore, this model can be applied to build the collision avoidance model of not only the current ship but remote-controlled ship, which is under compliance with COLREG regulations and involves the possibility of human error in an operation.
Analysis of Interference Characteristics of a Boat in Chasing a Large Ship
Authors: Deng Weihua , Yu Jiawei , Feng Dakui , Xiang Han , Yao Chaobang 
Published: October 2022

Abstract
Recovery of Unmanned Surface Vehicles (USV) is a typical multibody dynamics problem. When boat (that is USV) chases the large ship, the flow field around it will be affected by the wake of large ship, which will cause many difficulties for the maneuver of boat. In this paper, the model 4667-1 of the US series 62 planning craft is taken as the boat, and the 10x larger model of DTMB 5512 is taken as the large ship (named as 5512-MS). Numerical analysis on the performance of the boat affected by the wake field of the large ship in calm water is studied utilizing in-house CFD solver, coupled with multi-moving domain method and dynamic overset grid technology. The 2-DOF simulation is conducted to solve the resistance and attitude of the boat and DTMB 5512, and the simulation results are compared with the experimental data to verify the reliability of the numerical method. Numerical simulations of boat chasing the large ship along different paths are performed to analyze the interference characteristics in the chasing process. The study shows that along different paths, there are obvious differences in the motion and forces of the boat. Finally, the suggested route for recovery of USV is presented.
Assessment of the Power Obtained by a Multi Wind Turbine Floating Platform
Authors: Martín-San-Román Raquel , Azcona-Armendáriz José , Iribas-Latour Mikel , Cuerva-Tejero Alvaro 
Published: October 2022

Abstract
In order to reduce the cost of floating wind energy, several multi wind turbine floating platform designs have been proposed and are currently under development. Multi wind turbine configurations in onshore sites have been found to produce a combined blockage effect on the incoming flow that leads to a greater extraction of power compared to isolated rotors. The main objective of this study is to assess the power obtained by a multi wind turbine configuration with respect to a single turbine, both on a floating platform under wind and wave loading. In this study, the NREL 5MW OC4 semi-submersible floating wind turbine has been taken as reference. With this wind turbine model, three different configurations, in two operational cases, have been simulated using CENER’s in-house MUST (Multi wind tUrbine Simulation Tool), coupled to the aerodynamic module AeroVIEW (Aerodynamic Vortex fIlamEnt Wake). The configurations that have been analysed are: first, the single floating wind turbine; second, forced platform movements on a bi-wind turbine and finally a bi-wind turbine freely floating platform. The results of the comparisons show a positive effect of having two nearby side by side rotors on the same floating platform, with an increase in the generated power.
Experimental Investigation of Flow Around a Single Circular Cylinder Freely Vibrating in Two Degrees-of-Freedom
Authors: el Sheshtawy Hasan , el Moctar Ould , Tödter Simon , Schellin Thomas E. 
Published: October 2022

Abstract
Experimental investigations were performed for a single circular cantilevered cylinder located in a circulating water channel. The cylinder of mass ratio 1.78 and aspect ratio 17.8, vertically fixed at one end, was freely oscillating in the streamwise and lateral directions. Tests were performed at three reduced velocities of 1.29, 1.93, and 5.83, corresponding to Reynolds numbers 1.26 × 104, 1.88 × 104, and 5.65 × 104, respectively. At the inlet of the water channel, a Laser doppler velocimetry system measured mean velocities and turbulence intensities. Vortex shedding frequencies were compared with cylinder response frequencies in the streamwise and lateral directions. A particle image velocimetry technique analyzed the wake’s flow topology, and a triaxial accelerometer measured the cylinder response. Wake patterns of shed vortices caused by the flow around the cylinder were experimentally investigated. The main objective was to investigate wake patterns obtained for the stationary cylinder and for the cylinder oscillating with an elliptic trajectory and with a Lissajous trajectory. The PIV technique was used to capture vortex patterns on the mid plane along the cylinder’s length at three different time steps. The experiments provided reliable benchmark data suitable for numerical validation of vortex-induced vibration for circular cylinders oscillating in two degrees-of-freedom.
A Comparison of Different Numerical Methods to Simulate Forced Roll Oscillations of Floating Structures in Grid-Based Schemes
Authors: Meyer Jannik , Neufeldt Henrik , Hildebrandt Arndt 
Published: October 2022

Abstract
To accurately describe the motion of floating structures in waves using low-fidelity methods (Boundary Element Method, analytic methods), roll damping has to be determined with higher fidelity due to the influence of viscous effects. In these higher-fidelity estimations, either existing models like Ikeda’s model, which was validated using model test results, or Computational Fluid Dynamics simulations are frequently used. Forced roll tests are the main method to estimate the hydrodynamic properties (damping & added mass). In this study, three different numerical approaches to simulate structures in roll motions in grid based Finite Volume Method schemes are compared regarding their efficiency and numerical accuracy.
The results of this study show a good agreement between all three methods. While mesh morphing and Arbitrary Mesh Interface show similar results, the runtime of the Arbitrary Mesh Interface is increased by factor three. The most computationally challenging method is the overset method, which has its benefits in more complex motion environments and need further improvement to be a feasible alternative to the established methods mesh morphing and Arbitrary Mesh Interface.
Reconstruction of Fish Farm Model Tests in CFD for Detailed Analysis of Internal Sloshing and Wave Loading in Extreme Sea States
Authors: van der Plas P. , Serraris J. W. , Helder J. A. , Hanssen F.-C. W. , Bjar L. F. , Krogenes K. O. 
Published: October 2022

Abstract
In recent years fish-farming is gradually moving towards more exposed offshore environments. This makes the study of loading conditions in extreme sea states increasingly relevant. Sea farms often involve light and slender structures which typically include flexible components such as nets and other farming equipment. This poses a significant challenge in model tests when it comes to the installation of measurement equipment such as pressure inducers and force panels. Reconstruction in CFD provides a meaningful tool to complement model test data and to investigate design variations when model testing is unfeasible or financially unattractive. Combined model tests and CFD form a hybrid approach resulting in synergy for both methods.
The model tests are performed to determine the overall motion behavior of the fish cage and to produce a large amount of wave impact events. However, the overall pressure distribution and resulting loads on the supporting semi-submersible structure could not be measured.
CFD is used to reconstruct the flow in and around a fish-farm concept consisting of a fish cage supported by a circular semi-submersible ring. The CFD simulations are used to get more detailed information about the loads on the supporting semi-submersible structure during specific wave events that were observed in the model tests.
The incoming undisturbed waves from the model tests are reconstructed in CFD. Furthermore, the motions of the fish cage are included in CFD by imposing the (synchronized) motions as registered during the model tests. This paper describes the iterative wave matching procedure that was applied to reconstruct the wave events in CFD and presents a comparison of the full simulation setup with experiments.
Analysis of Structures in Very Shallow Water: CFD Analysis of Wave Propagation and Breaking Waves
Authors: Johannesen Magnus , Lande Øystein 
Published: October 2022

Abstract
Structures installed in very shallow water are experiencing forces from a very disturbed flow field, including rapidly changing gradients and breaking waves. Estimating loads on these structures usually involves running full 3D CFD analyses to predict the flow field and calculate the forces.
This paper is comparing a full 3D CFD simulation using OpenFOAM to a novel method of wave propagation with a multilayer solver based on Basilisk in order to establish the applicability of such a method in estimating loads on structures in shallow water. By applying the multilayer method the analysis time is reduced so much that one can estimate kinematics with a statistical approach where one analyses a wide range of sea states to estimate loading on the structure. This approach is common in deep water where much of the kinematics are simplified.
Structural Load Estimation of Downstream Wind Turbines in an Offshore Wind Farm
Authors: Xia Yiqing , Matsumoto Yosuke , Yousefi Iman , Oouchi Kazuyoshi , Kaneko Shunsuke , Nittouji Michio , Fujii Kenji , Machida Kaho 
Published: October 2022

Abstract
In this study, three IEA Wind 15MW offshore reference wind turbines with monopile support structures, are placed at a distance of eight rotor diameters in the prevailing wind direction. FAST. Farm responses are simulated under different wind conditions and sea states. The outputs suggest that for downstream turbines the effect of partial wake impingement is higher on tower bending moments than on blade bending moments. The downstream wind turbines have higher energy spectra around the tower natural frequency, which may potentially affect the fatigue loads and cut down the turbine lifetime. This study provides references for structural load analysis of downstream wind turbines in large-scale fixed-bottom offshore wind farms.
Offshore Wind Turbine Support Structures Along Indian Coast - Multi Criteria Analysis
Authors: Mallela Mounika , Saha Nilanjan , Alluri Satya Kiran Raju , Ramana Murthy M. V. 
Published: October 2022

Abstract
The selection of a feasible support structure for the site-specific environmental conditions helps in reducing the capital cost of the offshore wind turbines. As the study location falls under shallow water depth, the bottom fixed structures such as monopile, tripile and jacket have been considered as alternatives. The analysis of the alternatives has been carried out using API and DNVGL codal provisions in a finite element based framework, accounting for hydrodynamic and soil structure interaction effects. OWTs are simultaneously subjected to aerodynamic loads from the turbine blade rotations, estimated using blade element momentum theory based software and are coupled analysis is carried out. Multi criteria decision analysis (MCDA) is adopted to aid in the decision making regarding the choice of the feasible support structure. Multi-criteria evaluation problem consists of a viable set of alternatives for a given problem. MCDA explicitly evaluates the conflicting criteria involved in the decision making. It helps analyzing a complex problem using a predefined set of variables/criteria to derive at a logical solution. Among the various methods of MCDA for evaluating the alternatives against the criteria, the Analytical Hierarchy Process (AHP) has been adopted. In this, the pairwise comparison is made for the given alternatives using predefined criterion. The criteria considered for the study are structural configuration, fabrication, transportation and installation of the structure. The criterion again are classified into different sub criteria in order to sort out the priority of all the alternatives. The support structure with the highest priority has been identified as the optimal and feasible structure for the location under study.