Response amplitude mitigation of the offshore structures like tension leg platform (TLP) is important since these structures are always exposed to environmental loads such as waves, and in the case of TLP, reduction in response amplitude of platform causes reduction in stress range in tendons; this would increase the fatigue life of tendons, and therefore, increases the structural safety. Also providing stable conditions for machinery and crew increases the efficiency and functionality of the platform. This article thus aims to investigate the possibility and effectiveness of applying tuned mass damper (TMD) as a passive structural control system to suppress the surge motion of TLP that is exposed to wave load. Both numerical and experimental studies were carried out to assess the performance of the TMD. A close agreement is obtained between the numerical simulations and experimental results. The results of numerical and experimental investigations in this study indicate that applying the TMD, tuned to the surge natural frequency of the platform or frequencies close to the surge natural frequency of the platform, doesn’t have efficiency in reducing the surge responses of TLP in the range of probable waves in seas and oceans.
{"title":"Numerical and Experimental Study on Dynamic Response Mitigation of Tension Leg Platform Using Tuned Mass Damper","authors":"M. R. Tabeshpour, Latif Nikmehr","doi":"10.5957/josr.06200039","DOIUrl":"https://doi.org/10.5957/josr.06200039","url":null,"abstract":"Response amplitude mitigation of the offshore structures like tension leg platform (TLP) is important since these structures are always exposed to environmental loads such as waves, and in the case of TLP, reduction in response amplitude of platform causes reduction in stress range in tendons; this would increase the fatigue life of tendons, and therefore, increases the structural safety. Also providing stable conditions for machinery and crew increases the efficiency and functionality of the platform. This article thus aims to investigate the possibility and effectiveness of applying tuned mass damper (TMD) as a passive structural control system to suppress the surge motion of TLP that is exposed to wave load. Both numerical and experimental studies were carried out to assess the performance of the TMD. A close agreement is obtained between the numerical simulations and experimental results. The results of numerical and experimental investigations in this study indicate that applying the TMD, tuned to the surge natural frequency of the platform or frequencies close to the surge natural frequency of the platform, doesn’t have efficiency in reducing the surge responses of TLP in the range of probable waves in seas and oceans.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41493301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High-speed ferries of around 100 m length cruising at around 40 knots can cause significant passenger discomfort in head waves. This is due to the frequencies of encountering waves, of maximum hull response to encountered waves and of maximum passenger discomfort all falling within a similar range. In this paper, the benefit obtained by fitting active T-foils and stern tabs to control heave and pitch in head waves is considered. Ship motion responses are computed by numerical integration in the time domain including unsteady control actions using a time domain, high-speed strip theory. This obviates the need to identify transfer functions, the computed time responses including nonlinear hull immersion terms. The largest passenger vertical accelerations occur at forward locations and are best controlled by a forward located T-foil acting in combination with active stern tabs. Various feedback control algorithms have been considered and it is found that pitch damping control gives the greatest improvement in passenger comfort at forward positions. Operation in adaptive and nonlinear modes so that the control deflections are maximized under all conditions give the greatest benefit and can reduce passenger motion sickness incidence (MSI) by up to 25% in a 3-m head sea on the basis of International Organization for Standardization (ISO) recommendations for calculation of MSI for a 90-minute seaway passage.
{"title":"Operation of T-Foils and Stern Tabs to Improve Passenger Comfort on High-Speed Ferries","authors":"M. Davis","doi":"10.5957/josr.07200047","DOIUrl":"https://doi.org/10.5957/josr.07200047","url":null,"abstract":"High-speed ferries of around 100 m length cruising at around 40 knots can cause significant passenger discomfort in head waves. This is due to the frequencies of encountering waves, of maximum hull response to encountered waves and of maximum passenger discomfort all falling within a similar range. In this paper, the benefit obtained by fitting active T-foils and stern tabs to control heave and pitch in head waves is considered. Ship motion responses are computed by numerical integration in the time domain including unsteady control actions using a time domain, high-speed strip theory. This obviates the need to identify transfer functions, the computed time responses including nonlinear hull immersion terms. The largest passenger vertical accelerations occur at forward locations and are best controlled by a forward located T-foil acting in combination with active stern tabs. Various feedback control algorithms have been considered and it is found that pitch damping control gives the greatest improvement in passenger comfort at forward positions. Operation in adaptive and nonlinear modes so that the control deflections are maximized under all conditions give the greatest benefit and can reduce passenger motion sickness incidence (MSI) by up to 25% in a 3-m head sea on the basis of International Organization for Standardization (ISO) recommendations for calculation of MSI for a 90-minute seaway passage.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43354496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. White, Dominic J. Piro, Bradford G. Knight, K. Maki
The maneuvering characteristics of a surface ship play a critical role in the safety of navigation both in port and in an open seaway, and are vital to the overall operational ability of the ship. The vast majority of maneuvering analyses for ships have been performed under the assumption of calm water, yet ships mostly operate in waves. Understanding of maneuvering in waves is limited by the complexity of the problem and the challenges of performing physical experiments and numerical simulations. In this work, a new fast-running method that allows for the study of maneuvering in waves is formulated. The newly formulated approach is categorized as a “hybrid method,” taking its name from the multiple numerical methods and force models used to predict the total hydrodynamic force acting on the vessel maneuvering in waves. The framework presented here uses a combination of Computational Fluid Dynamics, a linear time-domain boundary element method, and a propeller-force model for efficient computation of the total hydrodynamic force.
{"title":"A Hybrid Numerical Framework for Simulation of Ships Maneuvering in Waves","authors":"P. White, Dominic J. Piro, Bradford G. Knight, K. Maki","doi":"10.5957/josr.06200037","DOIUrl":"https://doi.org/10.5957/josr.06200037","url":null,"abstract":"The maneuvering characteristics of a surface ship play a critical role in the safety of navigation both in port and in an open seaway, and are vital to the overall operational ability of the ship. The vast majority of maneuvering analyses for ships have been performed under the assumption of calm water, yet ships mostly operate in waves. Understanding of maneuvering in waves is limited by the complexity of the problem and the challenges of performing physical experiments and numerical simulations. In this work, a new fast-running method that allows for the study of maneuvering in waves is formulated. The newly formulated approach is categorized as a “hybrid method,” taking its name from the multiple numerical methods and force models used to predict the total hydrodynamic force acting on the vessel maneuvering in waves. The framework presented here uses a combination of Computational Fluid Dynamics, a linear time-domain boundary element method, and a propeller-force model for efficient computation of the total hydrodynamic force.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48752424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-20DOI: 10.5957/JSR.1995.39.3.225
J. Kvalsvold, O. Faltinsen
Slamming against the wet deck of a multihull vessel in head sea waves is studied analytically and numerically. The theoretical slamming model is a two-dimensional, asymptotic method valid for small local angles between the undisturbed water surface and the wet deck in the impact region. The disturbance of the water surface as well as the local hydroelastic effects in the slamming area are accounted for. The elastic deflections of the wet deck are expressed in terms of dry normal modes. The structural formulation accounts for the shear deformations and the rotatory inertia effects in the wet deck. The findings show that the slamming loads on the wet deck and the resulting elastic stresses in the wet deck are strongly influenced by the elasticity of the wet deck structure.
{"title":"Hydroelastic Modeling of Wet Deck Slamming on Multihull Vessels","authors":"J. Kvalsvold, O. Faltinsen","doi":"10.5957/JSR.1995.39.3.225","DOIUrl":"https://doi.org/10.5957/JSR.1995.39.3.225","url":null,"abstract":"Slamming against the wet deck of a multihull vessel in head sea waves is studied analytically and numerically. The theoretical slamming model is a two-dimensional, asymptotic method valid for small local angles between the undisturbed water surface and the wet deck in the impact region. The disturbance of the water surface as well as the local hydroelastic effects in the slamming area are accounted for. The elastic deflections of the wet deck are expressed in terms of dry normal modes. The structural formulation accounts for the shear deformations and the rotatory inertia effects in the wet deck. The findings show that the slamming loads on the wet deck and the resulting elastic stresses in the wet deck are strongly influenced by the elasticity of the wet deck structure.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"39 1","pages":"225-239"},"PeriodicalIF":1.4,"publicationDate":"2021-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47832718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The submarine H. L. Hunley conducted the first successful submarine attack on an enemy vessel, USS Housatonic, during the American Civil War but was lost with all hands because of unknown circumstances. The submarine has been recovered, and recent archeological findings have uncovered that a spar torpedo was used as opposed to a standoff torpedo that was commonly assumed to have been used. As a result, the submarine would have been in close proximity to the weapon when it exploded than previously thought. A multipart investigation has been conducted with the goal of determining if this reduced standoff distance could explain the mysterious loss of the vessel in the minutes or hours after the attack. Here, the results of a bottom-up naval architectural and weapons-effects analysis are reported. Together, the experimental, computational, and analytical results provide new insight to the vessel’s stability characteristics, propulsion, and dynamic loading environment during the attack. In addition, a discussion of possible loss scenarios, informed by both calculation results and inspections of vessel’s hull, is presented. Although the story of what happened to H. L. Hunley that night remains shrouded in mystery after this work, several important new research questions emerge.
{"title":"Investigating the Role of Weapon Effects and Flooding on the Loss of H. L. Hunley","authors":"M. Collette, K. Nahshon","doi":"10.5957/JOSR.03180017","DOIUrl":"https://doi.org/10.5957/JOSR.03180017","url":null,"abstract":"The submarine H. L. Hunley conducted the first successful submarine attack on an enemy vessel, USS Housatonic, during the American Civil War but was lost with all hands because of unknown circumstances. The submarine has been recovered, and recent archeological findings have uncovered that a spar torpedo was used as opposed to a standoff torpedo that was commonly assumed to have been used. As a result, the submarine would have been in close proximity to the weapon when it exploded than previously thought. A multipart investigation has been conducted with the goal of determining if this reduced standoff distance could explain the mysterious loss of the vessel in the minutes or hours after the attack. Here, the results of a bottom-up naval architectural and weapons-effects analysis are reported. Together, the experimental, computational, and analytical results provide new insight to the vessel’s stability characteristics, propulsion, and dynamic loading environment during the attack. In addition, a discussion of possible loss scenarios, informed by both calculation results and inspections of vessel’s hull, is presented. Although the story of what happened to H. L. Hunley that night remains shrouded in mystery after this work, several important new research questions emerge.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":" ","pages":"1-18"},"PeriodicalIF":1.4,"publicationDate":"2021-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48441749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article investigates the radiated sound power from idealized propeller noise sources, characterized by elemental monopole and dipole acoustic sources near the sea surface. The free surface of the sea is modeled as a pressure-release surface. The ratio of sound power of the near surface sources to the sound power from the same sources in an unbounded fluid is presented as a function of source immersion relative to sound wavelength. We herein show that the sound power radiated by submerged monopole and horizontal dipole sources is greatly reduced by the effect of the free surface at typical blade passing frequencies. By contrast, the sound power from a submerged vertical dipole is doubled. A transition frequency for the submerged monopole and horizontal dipole is identified. Above this transition frequency, the radiated power is not significantly influenced by the sea surface. Directivity patterns for the acoustic sources are also presented. The principal sources contributing to underwater radiated noise (URN) over a wide frequency range are propellers and onboard machinery (Urick 1983; Ross 1987; Collier 1997; Carlton 2007). Propeller sources are highly complex, but simplification is possible at low frequencies where the wavelength of underwater sound is much larger than propeller dimensions. The propeller may then be regarded as a set of fluctuating forces at the propeller hub and a stationary monopole source that represents the growth and collapse of a cavitation region as each blade passes through the region of wake deficit. This type of model was used by Kinns and Bloor (2004) to examine the net fluctuating forces on a cruise ship hull due to defined propeller sources. The nature of the monopole source was considered by Gray and Greeley (1980), who focused on singlescrew merchant ships where cavitation is dominant at operational speeds. Nonuniformity in the wake, as well as static pressure that falls toward the sea surface, causes this monopole source to be located near top dead center, closer to the surface than the propeller hub. It introduces cyclic components at multiples of propeller blade passing frequency (bpf) as well as broadband noise over a wide frequency range. These components create a pressure field that acts on nearby hull surfaces, but the URN is controlled by the presence of the pressure release surface that corresponds to the free surface of the sea. The aim of this article was to investigate how idealized propeller noise sources are influenced by the surface of the sea.
{"title":"Radiated Sound Power from Near-Surface Acoustic Sources","authors":"M. Karimi, R. Kinns, N. Kessissoglou","doi":"10.5957/JOSR.04200025","DOIUrl":"https://doi.org/10.5957/JOSR.04200025","url":null,"abstract":"\u0000 \u0000 This article investigates the radiated sound power from idealized propeller noise sources, characterized by elemental monopole and dipole acoustic sources near the sea surface. The free surface of the sea is modeled as a pressure-release surface. The ratio of sound power of the near surface sources to the sound power from the same sources in an unbounded fluid is presented as a function of source immersion relative to sound wavelength. We herein show that the sound power radiated by submerged monopole and horizontal dipole sources is greatly reduced by the effect of the free surface at typical blade passing frequencies. By contrast, the sound power from a submerged vertical dipole is doubled. A transition frequency for the submerged monopole and horizontal dipole is identified. Above this transition frequency, the radiated power is not significantly influenced by the sea surface. Directivity patterns for the acoustic sources are also presented.\u0000 \u0000 \u0000 \u0000 The principal sources contributing to underwater radiated noise (URN) over a wide frequency range are propellers and onboard machinery (Urick 1983; Ross 1987; Collier 1997; Carlton 2007). Propeller sources are highly complex, but simplification is possible at low frequencies where the wavelength of underwater sound is much larger than propeller dimensions. The propeller may then be regarded as a set of fluctuating forces at the propeller hub and a stationary monopole source that represents the growth and collapse of a cavitation region as each blade passes through the region of wake deficit. This type of model was used by Kinns and Bloor (2004) to examine the net fluctuating forces on a cruise ship hull due to defined propeller sources. The nature of the monopole source was considered by Gray and Greeley (1980), who focused on singlescrew merchant ships where cavitation is dominant at operational speeds. Nonuniformity in the wake, as well as static pressure that falls toward the sea surface, causes this monopole source to be located near top dead center, closer to the surface than the propeller hub. It introduces cyclic components at multiples of propeller blade passing frequency (bpf) as well as broadband noise over a wide frequency range. These components create a pressure field that acts on nearby hull surfaces, but the URN is controlled by the presence of the pressure release surface that corresponds to the free surface of the sea. The aim of this article was to investigate how idealized propeller noise sources are influenced by the surface of the sea.\u0000","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-8"},"PeriodicalIF":1.4,"publicationDate":"2021-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44089216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soonseok Song, S. Dai, Y. Demirel, M. Atlar, S. Day, O. Turan
Hull roughness increases ship frictional resistance and thus results in economic and environmental penalties. Its effect has been prevalently predicted using the similarity law scaling procedure, presented by Granville (1958; 1978). However, this method has not yet been validated with experimental data using a model ship. This paper presents an experimental investigation into the effect of roughness on ship resistance and provides a validation of the similarity law scaling, by using tank testing of a flat plate and a model ship. Both the plate and the ship were tested in smooth and rough surface conditions, respectively. For the rough surface conditions, sand grit (aluminium oxide abrasive powder) was applied on the surfaces of the flat plate and the ship model. The roughness functions of the rough surface were derived by using the results obtained from the flat plate tests. Using the roughness function and the flat plate towing test, the frictional resistance was extrapolated to the length of the model ship following the similarity law scaling procedure. The total resistance of the rough ship model was first predicted using the extrapolated frictional resistance and the result of the smooth ship model, and then compared with the results from the rough ship model. The predicted total resistance coefficients for the rough ship model showed good agreement with the measured total resistance coefficient of the rough ship model; thus proving the validity of using Granville’s similarity law scaling to extrapolate the roughness effect on ship resistance.
{"title":"Experimental and Theoretical Study of the Effect of Hull Roughness on Ship Resistance","authors":"Soonseok Song, S. Dai, Y. Demirel, M. Atlar, S. Day, O. Turan","doi":"10.5957/JOSR.07190040","DOIUrl":"https://doi.org/10.5957/JOSR.07190040","url":null,"abstract":"Hull roughness increases ship frictional resistance and thus results in economic and environmental penalties. Its effect has been prevalently predicted using the similarity law scaling procedure, presented by Granville (1958; 1978). However, this method has not yet been validated with experimental data using a model ship. This paper presents an experimental investigation into the effect of roughness on ship resistance and provides a validation of the similarity law scaling, by using tank testing of a flat plate and a model ship. Both the plate and the ship were tested in smooth and rough surface conditions, respectively. For the rough surface conditions, sand grit (aluminium oxide abrasive powder) was applied on the surfaces of the flat plate and the ship model. The roughness functions of the rough surface were derived by using the results obtained from the flat plate tests. Using the roughness function and the flat plate towing test, the frictional resistance was extrapolated to the length of the model ship following the similarity law scaling procedure. The total resistance of the rough ship model was first predicted using the extrapolated frictional resistance and the result of the smooth ship model, and then compared with the results from the rough ship model. The predicted total resistance coefficients for the rough ship model showed good agreement with the measured total resistance coefficient of the rough ship model; thus proving the validity of using Granville’s similarity law scaling to extrapolate the roughness effect on ship resistance.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"65 1","pages":"1-10"},"PeriodicalIF":1.4,"publicationDate":"2021-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48772577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Verification and validation of computational fluid dynamic simulations are performed at model and full scales for the high-speed littoral combat ship (LCS) surface combatant, including the effects of hook, interceptors, and water-jet propulsion. Predictions of the body force thrust, sinkage, and trim use a speed controller for attaining self-propulsion. Two methods for water-jet performance are used: 1) evaluation of forces based on integration of the stress over the wetted area of the hull and water-jet duct, pump casing, and nozzle (integral method) and 2) ITTC (2005) water-jet test procedure (control volume method). The comparison errors at model (resistance, sinkage, and trim) and full (power and trim) scales are satisfactory using both Froude (Fr) scaled model- and full-scale trial data, including the effects of the interceptors and water jets (WJ) on resistance/power, sinkage, and trim. For the model-scale model without WJs, the negative bottom hydrodynamic pressure near the water-jet inlets are observed without and with the hook simulations, and experiments with the hook. The negative bottom vertical force near the water-jet inlets for the simulations without the hook supports Savitsky’s (2014) assertion that semi-displacement monohulls do not exhibit hydrodynamic lift and disproves Giles’ (1992) assertion to the contrary. The hook and interceptors do not affect the pressure distribution significantly near the water-jet inlets. For the full scale model, the WJs induce bow up trim for the simulations and interpolated (between conditions)- and Fr scaled model-scale experiments. The negative bottom pressure and vertical force near the water-jet inlet for the simulations disprove Giles’ (1992) assertion that the WJs provide additional hydrodynamic lift. This is further supported by the comparisons of the vertical force % thrust vs. inlet velocity ratio for the LCS, with results shown in Bulten (2005) for a high-speed motor yacht. Bulten (2005) shows positive vertical force for inlet velocity ratios ≥ 1.25. However, LCS operates in the regime of an inlet velocity ≤ 1.2; thus, consistent with Bulten (2005), the vertical force is negative. The nonlinear effects between the interceptors and WJs are small such that a linear combination can provide a reasonable approximation.
{"title":"Effects of Hook, Interceptor, and Water Jets on LCS Resistance/ Power, Sinkage, and Trim","authors":"T. Dogan, Hamid Sadat-Hosseini, F. Stern","doi":"10.5957/JOSR.04200027","DOIUrl":"https://doi.org/10.5957/JOSR.04200027","url":null,"abstract":"Verification and validation of computational fluid dynamic simulations are performed at model and full scales for the high-speed littoral combat ship (LCS) surface combatant, including the effects of hook, interceptors, and water-jet propulsion. Predictions of the body force thrust, sinkage, and trim use a speed controller for attaining self-propulsion. Two methods for water-jet performance are used: 1) evaluation of forces based on integration of the stress over the wetted area of the hull and water-jet duct, pump casing, and nozzle (integral method) and 2) ITTC (2005) water-jet test procedure (control volume method). The comparison errors at model (resistance, sinkage, and trim) and full (power and trim) scales are satisfactory using both Froude (Fr) scaled model- and full-scale trial data, including the effects of the interceptors and water jets (WJ) on resistance/power, sinkage, and trim. For the model-scale model without WJs, the negative bottom hydrodynamic pressure near the water-jet inlets are observed without and with the hook simulations, and experiments with the hook. The negative bottom vertical force near the water-jet inlets for the simulations without the hook supports Savitsky’s (2014) assertion that semi-displacement monohulls do not exhibit hydrodynamic lift and disproves Giles’ (1992) assertion to the contrary. The hook and interceptors do not affect the pressure distribution significantly near the water-jet inlets. For the full scale model, the WJs induce bow up trim for the simulations and interpolated (between conditions)- and Fr scaled model-scale experiments. The negative bottom pressure and vertical force near the water-jet inlet for the simulations disprove Giles’ (1992) assertion that the WJs provide additional hydrodynamic lift. This is further supported by the comparisons of the vertical force % thrust vs. inlet velocity ratio for the LCS, with results shown in Bulten (2005) for a high-speed motor yacht. Bulten (2005) shows positive vertical force for inlet velocity ratios ≥ 1.25. However, LCS operates in the regime of an inlet velocity ≤ 1.2; thus, consistent with Bulten (2005), the vertical force is negative. The nonlinear effects between the interceptors and WJs are small such that a linear combination can provide a reasonable approximation.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"87 9","pages":"1-24"},"PeriodicalIF":1.4,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41283612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Green water on the ship deck in rough sea conditions may induce extreme impulsive wave impacts on superstructures and result in severe structural damage. It is of great importance to consider green water loads in ship structure design. However, there are many challenges in predicting green water loads due to the strongly nonlinear wave-ship interactions and the multiphase, multi-scale nature of the wave impact phenomena. In this article, a three-dimensional hybrid Eulerian-Lagrangian approach is proposed for simulating green water loads on the ship deck. It is extended from an efficient and accurate two-dimensional method developed for fluid-structure interaction problems. In this method, the flow field is solved on a fixed regular Cartesian grid system in an Eulerian framework, whereas the solid body motion is tracked with a set of markers immersed in the fluid and solved in a Lagrangian framework. Two benchmark cases, green water on a fixed simplified Floating Production Storage and Offloading (FPSO) model and green water on ship, are simulated. Comparison between experimental data and numerical results shows that our method is a viable choice for predicting green water loads.
{"title":"Numerical Simulation of Green Water on Deck with a Hybrid Eulerian-Lagrangian Method","authors":"K. Liao, W. Duan, Q. Ma, Shan Ma, Jianming Yang","doi":"10.5957/JOSR.03190015","DOIUrl":"https://doi.org/10.5957/JOSR.03190015","url":null,"abstract":"Green water on the ship deck in rough sea conditions may induce extreme impulsive wave impacts on superstructures and result in severe structural damage. It is of great importance to consider green water loads in ship structure design. However, there are many challenges in predicting green water loads due to the strongly nonlinear wave-ship interactions and the multiphase, multi-scale nature of the wave impact phenomena. In this article, a three-dimensional hybrid Eulerian-Lagrangian approach is proposed for simulating green water loads on the ship deck. It is extended from an efficient and accurate two-dimensional method developed for fluid-structure interaction problems. In this method, the flow field is solved on a fixed regular Cartesian grid system in an Eulerian framework, whereas the solid body motion is tracked with a set of markers immersed in the fluid and solved in a Lagrangian framework. Two benchmark cases, green water on a fixed simplified Floating Production Storage and Offloading (FPSO) model and green water on ship, are simulated. Comparison between experimental data and numerical results shows that our method is a viable choice for predicting green water loads.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-18"},"PeriodicalIF":1.4,"publicationDate":"2021-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46548255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jeonghwa Seo, Hoe-Seong Jeong, S. Rhee, Kyogun Chang
The present study aims to examine the resistance and propulsion performance of an amphibious vehicle with waterjet propulsion by conducting a series of towing tank model tests. The test model was an armored vehicle consisted of a box-shaped chassis, two flush-type waterjets, a bow flap, and a trimtab. Following the powering prediction procedure of a conventional ship, the resistance test, waterjet system and bollard pull test, and self-propulsion test were performed. The Froude number based on the characteristic length and advance speed for the model test ranged from 0.883 to 1.275. The effect of the track deployment conditions was also investigated by conducting a test with the retracted and normal track condition. In the bollard pull and self-propulsion test where two waterjets were installed onto the chassis, the flow rate of the waterjet was higher than that in the single waterjet system test, resulting in high thrust. The propulsive efficiency increased in high advance speeds as the transom was exposed to air.
{"title":"Towing Tank Model Tests for Propulsive Performance Analysis of a Waterjet-Propelled Amphibious Vehicle","authors":"Jeonghwa Seo, Hoe-Seong Jeong, S. Rhee, Kyogun Chang","doi":"10.5957/JOSR.09190055","DOIUrl":"https://doi.org/10.5957/JOSR.09190055","url":null,"abstract":"The present study aims to examine the resistance and propulsion performance of an amphibious vehicle with waterjet propulsion by conducting a series of towing tank model tests. The test model was an armored vehicle consisted of a box-shaped chassis, two flush-type waterjets, a bow flap, and a trimtab. Following the powering prediction procedure of a conventional ship, the resistance test, waterjet system and bollard pull test, and self-propulsion test were performed. The Froude number based on the characteristic length and advance speed for the model test ranged from 0.883 to 1.275. The effect of the track deployment conditions was also investigated by conducting a test with the retracted and normal track condition. In the bollard pull and self-propulsion test where two waterjets were installed onto the chassis, the flow rate of the waterjet was higher than that in the single waterjet system test, resulting in high thrust. The propulsive efficiency increased in high advance speeds as the transom was exposed to air.","PeriodicalId":50052,"journal":{"name":"Journal of Ship Research","volume":"1 1","pages":"1-17"},"PeriodicalIF":1.4,"publicationDate":"2020-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44071142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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