Volume 6: Polar and Arctic Sciences and Technology
Popov et al. (1967) proposed an approach to evaluate the ice loads during ship-ice impact. The ap... more Popov et al. (1967) proposed an approach to evaluate the ice loads during ship-ice impact. The approach firstly calculates the reduced mass and velocity of ship-ice system based on the principle of conservation of momentum. Secondly, it predicts the ice loads by assuming that the reduced kinetic energy is absorbed by the work of contact crushing stress. The added mass used at the first stage of Popov approach is estimated with simplified empirical formulas. This paper attempts to introduce an improved method for the prediction of ice loads by accounting for the influence of the added mass, calculated by potential flow theory, in Popov’s approach. The evaluation of ice loads involves the effects of: 1) ship and ice geometry; 2) waves; and 3) hydrodynamic cross coupling between ship and ice. A potential flow theory model, consisting of a ship and an ice floe, is built to calculate the added mass, wherein the ship is approaching the free-floating ice at a constant speed in random waves...
IOP Conference Series: Materials Science and Engineering
Rogue waves pose a significant risk to marine safety, emphasizing the need to accurately predict ... more Rogue waves pose a significant risk to marine safety, emphasizing the need to accurately predict their occurrence in the open ocean. However, the complexity of their evolution, which may involve nonlinear physical phenomena such as wave-wave interaction and modulation instability, makes this task challenging. Currently the reconstruction of rogue waves involves generating focused waves through the superposition of different spectral components of irregular waves that are in phase at the focusing point. Despite its effectiveness, this approach is limited. The paper introduces a deep learning method based on Long short-term memory (LSTM) to predict focused waves generated in a Computational Fluid Dynamics (CFD) flume in the time domain. The model is trained on 60% of the generated wave time series, with the remaining 40% used for both validation and testing. The results demonstrate that the proposed method can assist with the prediction of focused waves at various observation points, ...
Despite the rapid development of Computational Fluid Dynamics (CFD) the demand for potential flow... more Despite the rapid development of Computational Fluid Dynamics (CFD) the demand for potential flow hydrodynamics in ship design remains relevant. This is because 2D and 3D Boundary Element Methods (BEM) can be applied for rapid prediction of motions and wave loads. This paper compares results from linear 2D strip-theory and 3D Green function methods with empirical forward speed correction factors in terms of ship motions, radiation forces and wave loads. The former approach applies a “Frank Close-fit” method to solve the radiation problem in 2D. The latter utilizes a pulsating “Green function” source distribution method to solve the radiation problem in 3D. Results are validated against experimental data available for a container ship. It is shown that the motion RAOs obtained by both methods are similar and agree with the experimental values. However, responses in terms of longitudinal distribution of wave loads show discrepancies which increase with wave length shortening and close...
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment
This paper presents a semi analytic time domain method for the analysis of the symmetric hydroela... more This paper presents a semi analytic time domain method for the analysis of the symmetric hydroelastic response of a container ship subject to slamming and green water loads. An Impulse Response Function (IRF) is adopted for the calculation of radiation, diffraction and wave excitation forces. Local hydrodynamic forces associated with green water on decks and slamming loads are respectively modelled by the Buchner’s Dam Break Model and a Generalised Wagner Model. The structural responses are captured by Euler-Bernoulli beam theory and solved by the modal superposition method. The Duhamel Integral technique is used to evaluate the dynamic response. A parametric study demonstrates how external forces may affect the global wave induced vertical bending moments and shear forces. Numerical simulations are compared against a hybrid method that combines computational fluid dynamics, boundary element and finite element methods for low to medium frequency induced dynamic response. It is concl...
The paper presents a Fluid Structure Interaction (FSI) method for hydroelastic water entry. The m... more The paper presents a Fluid Structure Interaction (FSI) method for hydroelastic water entry. The method assumes that the momentum exchange between the fluid and solid body can be used for the calculation of pressure, deformation and stresses arising during impact. The flexible fluid–structure interactions of flat plates entering water are solved using a computational code that employs the finite volume method to discretise both fluid and solid equations. This provides a better matching of momentum on the fluid–solid interface. The momentum arising in the solid body that emerges after the impact is defined as the momentum exchange, and is shown to increase linearly under the increase of non-dimensional impact speed. The ratio of the maximum pressure arising in an elastic body entering water to that of a rigid body is termed relative pressure and is shown to decrease linearly as a function of momentum exchange. The latter verifies the main hypothesis of this paper, namely that ‘the pre...
Journal of Offshore Mechanics and Arctic Engineering
For ships navigating in ice floe fields, ship–ice–wave interactions may affect ship performance a... more For ships navigating in ice floe fields, ship–ice–wave interactions may affect ship performance and ice impact forces. This paper presents an approach to evaluate the cross-coupling added mass and hydrodynamic damping between a passing ship and a free-floating small/medium size ice floe based on the boundary element method (BEM). The influences of added mass and hydrodynamic damping are explored for different wave frequencies and headings. Results are presented for a regular waves scenario whereby a tanker progressing at a slow speed is passing by a free-floating ice floe modeled as a round disk. Radiation and diffraction potentials of the interacting floating bodies are linearly superimposed to reflect the influence of hydromechanical coupling on responses. Parametric analysis of response amplitude operators (RAOs) indicates that the cross-coupling terms of added mass and hydrodynamic damping are of the same order of magnitude as those of the ice floe but smaller by one or two orde...
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment
This paper presents a deep learning method for the prediction of ship motions in 6 Degrees of Fre... more This paper presents a deep learning method for the prediction of ship motions in 6 Degrees of Freedom (DoF). Big data streams of Automatic Identification System (AIS), now-cast, and bathymetry records are used to extract motion trajectories and idealise environmental conditions. A rapid Fluid-Structure Interaction (FSI) model is used to generate ship motions that account for the influence of surrounding water and ship-controlling devices. A transformer neural network that accounts for the influence of operational conditions on ship dynamics is validated by learning the data streams corresponding to ship voyages and hydro-meteorological conditions between two ports in the Gulf of Finland. Predictions for a ship turning circle and motion dynamics between these two ports show that the proposed method can capture the influence of operational conditions on seakeeping and manoeuvring.
While landing Wing-in Ground Effect (WIG) craft are exposed to large hydrodynamic forces which ca... more While landing Wing-in Ground Effect (WIG) craft are exposed to large hydrodynamic forces which can lead to structural damages. Sea loads can be predicted by solving the free surface problem, known as water entry. The problem has been studied for rigid bodies until most recently, when researchers hypothesized that the structural response of the body can also influence the hydrodynamic pressures. This paper aims to provide deeper understanding of the impact loads during the water entry process of a hard chine section for the case of a common WIG Craft section. A Finite Volume Method (FVM) based computational fluid-structure interaction model is used to solve multi-physics and quantitative comparisons are made between experimental and computational data. Simulations demonstrate that structural dynamics can attenuate the pressure acting on body walls. The deadrise angle, speed in way of water entry and rigidity of the solid body are shown to affect the dynamic response with equivalent s...
Recent market trends in the cruise industry aim to provide land-based attractions on mega-cruise ... more Recent market trends in the cruise industry aim to provide land-based attractions on mega-cruise liners deck amusements. The structures used are mega-lightweight structures that comprise of slender beams to reduce added weight. They may be subject to dynamic wind-induced resonance as a result of fluctuating forces due to vortex shedding occurring close to the natural frequency of the structure. This paper investigates the structural responses due to wind-induced vibrations in the context of a ship deck outfitting by coupling CFD and FEA. The simulations are performed using one- and two-way coupling FSI to gain insights into the differences between the predicted responses. A deck amusement structure is idealized as an aluminum portal frame subjected to a constant head wind. Transient one- and two-way coupled simulations, based on Reynolds-Averaged Naiver-Stokes (RANS) and linear elastic 3D FEA are conducted. The predictions are compared against quasi-dynamic beam element idealizations.
Mitigating flooding risk through passive and active measures is a key step in further increasing ... more Mitigating flooding risk through passive and active measures is a key step in further increasing the safety of shipping, reducing loss of life and damage to the environment. This paper presents key findings from the EU Horizons 2020 project FLARE (FLooding Accident REsponse) that introduces a novel risk-based methodology beyond the state-of-the-art for “live” flooding risk assessment and control, with potential application to new and existing ships. The project develops a flooding accident model – based on statistics and first-principles tools – that aims to assess the frequencies of flooding events whilst accounting for pertinent environmental conditions and design parameters including ship crashworthiness. Cost-effective risk control options are under evaluation and possible recommendations and/or amendments to the regulatory framework will be submitted to the IMO.
Proceedings of the International Seminar on Safety and Security of Autonomous Vessels (ISSAV) and European STAMP Workshop and Conference (ESWC) 2019, 2020
Volume 6: Polar and Arctic Sciences and Technology
Popov et al. (1967) proposed an approach to evaluate the ice loads during ship-ice impact. The ap... more Popov et al. (1967) proposed an approach to evaluate the ice loads during ship-ice impact. The approach firstly calculates the reduced mass and velocity of ship-ice system based on the principle of conservation of momentum. Secondly, it predicts the ice loads by assuming that the reduced kinetic energy is absorbed by the work of contact crushing stress. The added mass used at the first stage of Popov approach is estimated with simplified empirical formulas. This paper attempts to introduce an improved method for the prediction of ice loads by accounting for the influence of the added mass, calculated by potential flow theory, in Popov’s approach. The evaluation of ice loads involves the effects of: 1) ship and ice geometry; 2) waves; and 3) hydrodynamic cross coupling between ship and ice. A potential flow theory model, consisting of a ship and an ice floe, is built to calculate the added mass, wherein the ship is approaching the free-floating ice at a constant speed in random waves...
IOP Conference Series: Materials Science and Engineering
Rogue waves pose a significant risk to marine safety, emphasizing the need to accurately predict ... more Rogue waves pose a significant risk to marine safety, emphasizing the need to accurately predict their occurrence in the open ocean. However, the complexity of their evolution, which may involve nonlinear physical phenomena such as wave-wave interaction and modulation instability, makes this task challenging. Currently the reconstruction of rogue waves involves generating focused waves through the superposition of different spectral components of irregular waves that are in phase at the focusing point. Despite its effectiveness, this approach is limited. The paper introduces a deep learning method based on Long short-term memory (LSTM) to predict focused waves generated in a Computational Fluid Dynamics (CFD) flume in the time domain. The model is trained on 60% of the generated wave time series, with the remaining 40% used for both validation and testing. The results demonstrate that the proposed method can assist with the prediction of focused waves at various observation points, ...
Despite the rapid development of Computational Fluid Dynamics (CFD) the demand for potential flow... more Despite the rapid development of Computational Fluid Dynamics (CFD) the demand for potential flow hydrodynamics in ship design remains relevant. This is because 2D and 3D Boundary Element Methods (BEM) can be applied for rapid prediction of motions and wave loads. This paper compares results from linear 2D strip-theory and 3D Green function methods with empirical forward speed correction factors in terms of ship motions, radiation forces and wave loads. The former approach applies a “Frank Close-fit” method to solve the radiation problem in 2D. The latter utilizes a pulsating “Green function” source distribution method to solve the radiation problem in 3D. Results are validated against experimental data available for a container ship. It is shown that the motion RAOs obtained by both methods are similar and agree with the experimental values. However, responses in terms of longitudinal distribution of wave loads show discrepancies which increase with wave length shortening and close...
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment
This paper presents a semi analytic time domain method for the analysis of the symmetric hydroela... more This paper presents a semi analytic time domain method for the analysis of the symmetric hydroelastic response of a container ship subject to slamming and green water loads. An Impulse Response Function (IRF) is adopted for the calculation of radiation, diffraction and wave excitation forces. Local hydrodynamic forces associated with green water on decks and slamming loads are respectively modelled by the Buchner’s Dam Break Model and a Generalised Wagner Model. The structural responses are captured by Euler-Bernoulli beam theory and solved by the modal superposition method. The Duhamel Integral technique is used to evaluate the dynamic response. A parametric study demonstrates how external forces may affect the global wave induced vertical bending moments and shear forces. Numerical simulations are compared against a hybrid method that combines computational fluid dynamics, boundary element and finite element methods for low to medium frequency induced dynamic response. It is concl...
The paper presents a Fluid Structure Interaction (FSI) method for hydroelastic water entry. The m... more The paper presents a Fluid Structure Interaction (FSI) method for hydroelastic water entry. The method assumes that the momentum exchange between the fluid and solid body can be used for the calculation of pressure, deformation and stresses arising during impact. The flexible fluid–structure interactions of flat plates entering water are solved using a computational code that employs the finite volume method to discretise both fluid and solid equations. This provides a better matching of momentum on the fluid–solid interface. The momentum arising in the solid body that emerges after the impact is defined as the momentum exchange, and is shown to increase linearly under the increase of non-dimensional impact speed. The ratio of the maximum pressure arising in an elastic body entering water to that of a rigid body is termed relative pressure and is shown to decrease linearly as a function of momentum exchange. The latter verifies the main hypothesis of this paper, namely that ‘the pre...
Journal of Offshore Mechanics and Arctic Engineering
For ships navigating in ice floe fields, ship–ice–wave interactions may affect ship performance a... more For ships navigating in ice floe fields, ship–ice–wave interactions may affect ship performance and ice impact forces. This paper presents an approach to evaluate the cross-coupling added mass and hydrodynamic damping between a passing ship and a free-floating small/medium size ice floe based on the boundary element method (BEM). The influences of added mass and hydrodynamic damping are explored for different wave frequencies and headings. Results are presented for a regular waves scenario whereby a tanker progressing at a slow speed is passing by a free-floating ice floe modeled as a round disk. Radiation and diffraction potentials of the interacting floating bodies are linearly superimposed to reflect the influence of hydromechanical coupling on responses. Parametric analysis of response amplitude operators (RAOs) indicates that the cross-coupling terms of added mass and hydrodynamic damping are of the same order of magnitude as those of the ice floe but smaller by one or two orde...
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment
This paper presents a deep learning method for the prediction of ship motions in 6 Degrees of Fre... more This paper presents a deep learning method for the prediction of ship motions in 6 Degrees of Freedom (DoF). Big data streams of Automatic Identification System (AIS), now-cast, and bathymetry records are used to extract motion trajectories and idealise environmental conditions. A rapid Fluid-Structure Interaction (FSI) model is used to generate ship motions that account for the influence of surrounding water and ship-controlling devices. A transformer neural network that accounts for the influence of operational conditions on ship dynamics is validated by learning the data streams corresponding to ship voyages and hydro-meteorological conditions between two ports in the Gulf of Finland. Predictions for a ship turning circle and motion dynamics between these two ports show that the proposed method can capture the influence of operational conditions on seakeeping and manoeuvring.
While landing Wing-in Ground Effect (WIG) craft are exposed to large hydrodynamic forces which ca... more While landing Wing-in Ground Effect (WIG) craft are exposed to large hydrodynamic forces which can lead to structural damages. Sea loads can be predicted by solving the free surface problem, known as water entry. The problem has been studied for rigid bodies until most recently, when researchers hypothesized that the structural response of the body can also influence the hydrodynamic pressures. This paper aims to provide deeper understanding of the impact loads during the water entry process of a hard chine section for the case of a common WIG Craft section. A Finite Volume Method (FVM) based computational fluid-structure interaction model is used to solve multi-physics and quantitative comparisons are made between experimental and computational data. Simulations demonstrate that structural dynamics can attenuate the pressure acting on body walls. The deadrise angle, speed in way of water entry and rigidity of the solid body are shown to affect the dynamic response with equivalent s...
Recent market trends in the cruise industry aim to provide land-based attractions on mega-cruise ... more Recent market trends in the cruise industry aim to provide land-based attractions on mega-cruise liners deck amusements. The structures used are mega-lightweight structures that comprise of slender beams to reduce added weight. They may be subject to dynamic wind-induced resonance as a result of fluctuating forces due to vortex shedding occurring close to the natural frequency of the structure. This paper investigates the structural responses due to wind-induced vibrations in the context of a ship deck outfitting by coupling CFD and FEA. The simulations are performed using one- and two-way coupling FSI to gain insights into the differences between the predicted responses. A deck amusement structure is idealized as an aluminum portal frame subjected to a constant head wind. Transient one- and two-way coupled simulations, based on Reynolds-Averaged Naiver-Stokes (RANS) and linear elastic 3D FEA are conducted. The predictions are compared against quasi-dynamic beam element idealizations.
Mitigating flooding risk through passive and active measures is a key step in further increasing ... more Mitigating flooding risk through passive and active measures is a key step in further increasing the safety of shipping, reducing loss of life and damage to the environment. This paper presents key findings from the EU Horizons 2020 project FLARE (FLooding Accident REsponse) that introduces a novel risk-based methodology beyond the state-of-the-art for “live” flooding risk assessment and control, with potential application to new and existing ships. The project develops a flooding accident model – based on statistics and first-principles tools – that aims to assess the frequencies of flooding events whilst accounting for pertinent environmental conditions and design parameters including ship crashworthiness. Cost-effective risk control options are under evaluation and possible recommendations and/or amendments to the regulatory framework will be submitted to the IMO.
Proceedings of the International Seminar on Safety and Security of Autonomous Vessels (ISSAV) and European STAMP Workshop and Conference (ESWC) 2019, 2020
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