This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic d...This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic disciplines. The present investigation was performed within the framework of the 2-D slender body method （SBM） by calculating the resistance of three symmetric trimaran series moving in a calm free surface of deep water. Each trimaran series comprises of 4681 configurations generated by considering 151 staggers （-50%≤a≤＋ 100%）, and 31 separations （100%≤β≤400%） for 81 Froude numbers （0.20≤Fn≤ 1.0）. In developing the three trimaran series, Wigley-st. AMECRC-09, and NPL-4a models were used separately for both the main and side hulls of each individu;d series models. A computer macro named Tri-PL was created using the Visual Basic for Applications~. Tri-PL~ sequentially interfaced Maxsurfe then Hullspeed to generate the models of the three trimaran series together with their detailed hydrostatic particulars, followed by their resistance components. The numerical results were partially validated against the available published numerical calculations and experimental results, to benchmark the Tri-PL macro and hence to rely on the analysis outcomes. A graph template was creaLed within the framework of SigmaPlot to visualize the significant results of the Tri-PL properlv.展开更多
The application of multi-hull ship or trimaran vessel as a mode of transports in both river and sea environments have grown rapidly in recent years.Trimaran vessels are currently of interest for many new high speed sh...The application of multi-hull ship or trimaran vessel as a mode of transports in both river and sea environments have grown rapidly in recent years.Trimaran vessels are currently of interest for many new high speed ship projects due to the high levels of hydrodynamic efficiency that can be achieved,compared to the mono-hull and catamaran hull forms.The purpose of this study is to identify the possible effects of using an unsymmetrical trimaran ship model with configuration（S/L） 0.1-0.3 and R/L=0.1-0.2.Unsymmetrical trimaran ship model with main dimensions： L=2000mm,B=200 mm and T=45 mm.Experimental methods（towing tank） were performed in the study using speed variations at Froude number 0.1-0.6.The ship model was pulled by an electric motor whose speed could be varied and adjusted.The ship model resistance was measured precisely by using a load cell transducer.The comparison of ship resistance for each configuration with mono-hull was shown on the graph as a function of the total resistance coefficient and Froude number.The test results found that the effective drag reduction could be achieved up to 17% at Fr=0.35 with configuration S/L=0.1.展开更多
A 3D rankine panel method was developed for calculating the linear wave-making resistance of a tri-maran with Wigley hulls. In order to calculate the normal vector and derivative of the body surface accurately, non-un...A 3D rankine panel method was developed for calculating the linear wave-making resistance of a tri-maran with Wigley hulls. In order to calculate the normal vector and derivative of the body surface accurately, non-uniform rational B-spline (NURBS) was adopted to represent body surface and rankine source density. The radiation condition is satisfied using the numerical technology of staggered grids. Numerical results show that the linear wave-making resistance of the trimaran can be calculated effectively using this method.展开更多
This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and...This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.展开更多
As a new type of hull form,trimaran has remarkable excellent performances and has drawn more and more attention.When the viscous CFD technology now available is applied to the research of resistance performance of tri...As a new type of hull form,trimaran has remarkable excellent performances and has drawn more and more attention.When the viscous CFD technology now available is applied to the research of resistance performance of trimaran,the spatial discretization would usually result in the grid error and uncertainty,and thus the considerable discrepancy between the numerical results and the experimental data.In order to ascertain how much the grid would affect the calculation,the grid convergence should be studied.A mathematical trimaran was chosen as an example,with the commercial code CFX for the simulation,VOF for surface treatment,and the grid study was carried out based on two different turbulence models.It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty,and indicating the direction of improving the credibility of the numerical calculation, and,in addition to grid errors and uncertainties,the turbulence modeling errors and uncertainties contribute to the simulation errors.展开更多
Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is ...Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is important and necessary for better hydrodynamic performance.This paper focuses on the numerical investigation of trimaran hydrodynamics.The trimaran model used in this study is a 1/80 scale high-speed displacement frigate-type concept developed by the Center for Innovation in Ship Design(CISD)at Naval Surface Warfare Center,Carderock Division(NSWCCD).The numerical simulations were conducted for different outrigger positions at low and moderate Froude numbers by using commercial CFD software solving URANS equations.A verification and validation study was carried out for the numerical method in one configuration and one ship velocity.The existing experimental results for the trimaran resistance in the literature were used for validation.Five different outrigger positions were analyzed and the form factor of each configuration was calculated by the Prohaska method.The total resistance was decomposed to its components using the form factor.The interference factor was calculated for each configuration in terms of total resistance,residual resistance and wave resistance.Also,wave profiles using the longitudinal wave cuts in different locations were obtained both numerically and experimentally.It was concluded that the outrigger position had different effects on the interference,total resistance and wave profile at different Froude numbers.It was also shown that the CFD results were in good agreement with the experimental data in all configurations.In conclusion,this study presents the results of interference effects for different trimaran configurations in terms of wave resistance in addition to the total resistance and residual resistance.The numerical method was validated not only with the total resistance test data but also the longitudinal wave profiles along the hull.展开更多
This paper presents experimental results on configuration hydrodynamics.Three models are used in the model tests,which are typical of hard,round,and soft chines.Although specific values are different,the influence pat...This paper presents experimental results on configuration hydrodynamics.Three models are used in the model tests,which are typical of hard,round,and soft chines.Although specific values are different,the influence patterns are similar in the three ship models.A set of different outrigger positions is investigated in calm water and regular waves.A variety of interesting phenomena are observed,among which the splash resistance is the dominant component for a trimaran at high speeds(with Froude number Fr>0.6).If two small outriggers are placed inside Kelvin’s wave systems of the main hull,a strong splash appears,resulting in a significant resistance increase.Moreover,short and long waves cannot be neglected,for they may excite the motions of much smaller outriggers.This condition leads to non-vanishing heaving at high-frequency and non-normalized pitches at low frequencies.Based on the tests,three spectra of optimum configurations for resistance,longitudinal motions,and transverse motions are presented.These results reveal the optimum configurations of a trimaran hull in terms of hydrodynamic performance,thus providing a very powerful tool for optimum design of trimaran ships.展开更多
To predict the wave loads of a flexible trimaran in different wave fields,a one-way interaction numerical simulation method is proposed by integrating the fluid solver(Star-CCM+)and structural solver(Abaqus).Differing...To predict the wave loads of a flexible trimaran in different wave fields,a one-way interaction numerical simulation method is proposed by integrating the fluid solver(Star-CCM+)and structural solver(Abaqus).Differing from the existing coupled CFD-FEA method for monohull ships in head waves,the presented method equates the mass and stiffness of the whole ship to the hull shell so that any transverse and longitudinal section stress of the hull in oblique waves can be obtained.Firstly,verification study and sensitivity analysis are carried out by comparing the trimaran motions using different mesh sizes and time step schemes.Discussion on the wave elevation of uni-and bi-directional waves is also carried out.Then a comprehensive analysis on the structural responses of the trimaran in different uni-directional regular wave and bi-directional cross sea conditions is carried out,respectively.Finally,the differences in structural response characteristics of trimaran in different wave fields are studied.The results show that the present method can reduce the computational burden of the two-way fluid-structure interaction simulations.展开更多
In recent years,demands for car transportation by a ship have been increasing with favorable economic conditions in auto sector,and the need of a pure car carrier(PCC) has grown quickly.A PCC needs huge parking space ...In recent years,demands for car transportation by a ship have been increasing with favorable economic conditions in auto sector,and the need of a pure car carrier(PCC) has grown quickly.A PCC needs huge parking space but smaller displacement since a car is comparatively light for its volume.As a result,almost all PCCs have wide breadth,shallow draft and huge structure above the water surface.These features cause some technical issues of a PCC,like lack of stability,effect of strong winds on its resistance,difficulty of course keeping in rough seas,difficulty of berthing in strong winds,and so on.To overcome these technical issues,one of the authors has proposed a new concept for a PCC.This is a trimaran PCC which has very limited transverse bulkheads in the center hull by using two side hulls as fenders.In the present research,wind forces acting on a scale model of the trimaran PCC were measured in the towing tank with a wind generator at Osaka Prefecture University.Furthermore,in order to clarify the characteristics of wind pressure on the trimaran,height and width of tunnels which are between a main hull and side hulls were changed.And then,in order to imitate a real ship,we used wind reduction technology of corner-cut design for accommodation house of the ship.Moreover,the wind pressure acting on the trimaran was compared with that on a mono-hull PCC.Using these experimental and theoretical results,an estimation method of wind pressure acting on the trimaran PCC is deduced.展开更多
In the present paper,a new trimaran Pure Car Carrier(PCC) is proposed and a feasibility study on the ship is carried out.In this study,first,the effective horse power(EHP)/car of the PCC running in still water is pred...In the present paper,a new trimaran Pure Car Carrier(PCC) is proposed and a feasibility study on the ship is carried out.In this study,first,the effective horse power(EHP)/car of the PCC running in still water is predicted.By comparing the predicted EHP/car with that of a conventional mono-hull PCC,it is found that the trimaran PCC is superior to the conventional mono-hull PCC at rather higher speed.As ship speed increases,the reduction of the resistance of the trimaran is bigger.It is also found that at common service speed of PCCs,the EHP/car of a small PCC is lower than that of a conventional PCC.Secondly,the optimal L/B of a main-hull of the trimaran PCC in still water is determined.The optimal L/B of the main-hull varies with ship speed and size because the wave resistance decreases but the frictional resistance increases as L/B of the hull increases.As ship size increases,the optimal L/B of the main-hull of the trimaran PCC decreases.Finally,the increase of the resistance of PCCs running in strong wind is predicted.The results show that drift angle and speed reduction of the trimaran PCC are much smaller than the conventional mono-hull PCC because of large side force created by three demi-hulls.展开更多
This paper illustrates the reasons behind the research strategy that has led to a new generation of trimaran hulls by minimizing the hull＇s drag-design approach. The objective of this study was to search for the opti...This paper illustrates the reasons behind the research strategy that has led to a new generation of trimaran hulls by minimizing the hull＇s drag-design approach. The objective of this study was to search for the optimal side-hull yaw and roll angle to minimize induced drag of trimarans a^d so to investigate the differences in the performance results of a trimaran hull. Specifically, this research has been based on a critical analysis of the diversity of ama yaw and roll angles and outriggers positioning. Then, the paper will be comparing the results of the test series of the yaw and roll angles of trimaran areas. Design and towing tank test of a scaled trimaran model will be illustrated and compared along with some key and relevant results. The term ＂ama＂ is a word in the Polynesian and Micronesian languages to describe the outrigger part of a canoe to provide stability.展开更多
Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their inter...Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt＇s work, the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory, using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems, with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear （Dawson） methods. Moreover, sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.展开更多
Based on the potential flow assumption, this paper outlines the formulation of the boundary-value problem governing the steady free surface flow around a trimaran advancing at a constant forward. A Rankine panel metho...Based on the potential flow assumption, this paper outlines the formulation of the boundary-value problem governing the steady free surface flow around a trimaran advancing at a constant forward. A Rankine panel method was developed for the solution of the problem. The side-hulls were treated as lifting bodies and circulation was introduced into the flow field to implement the asymmetrical flow around each side hull. The linearized free surface condition was used. The appropriate treatment for transom-stern ship was also discussed. Additionally, a test was performed to quantify the resistance and especially the interference between the main and side hulls. The numerical results are in good argeement with experimental data.展开更多
This paper studies the hydrodynamic performance of a channel type planing trimaran. A numerical simulation is carried out based on a RANS-VOF solver to analyze the hydrodynamic performance of the channel type planing ...This paper studies the hydrodynamic performance of a channel type planing trimaran. A numerical simulation is carried out based on a RANS-VOF solver to analyze the hydrodynamic performance of the channel type planing trimaran. A series of hydrodynamic experiments in towing tank were carried out, in which both the running attitude and the resistance performance of the trimaran model were recorded. Some hydrodynamic characteristics of the channel type planning trimaran are shown by the results. Firstly, the resistance declines significantly, with the forward speed across the high-speed resistance peak due to the combined effects of the aerodynamic and hydrodynamic lifts. Secondly, the resistance performance is influenced markedly by the longitudinal positio- ns of centre of the gravity and the displacements. Besides, the pressure distribution on the hull and the two-phase flow in the channel are discussed in the numerical simulations.展开更多
Due to the interaction between the main hull and side hulls, different layouts and lengths of side hulls affect the wave loads significantly. Based on three-dimensional potential theory and Green＇s function, this art...Due to the interaction between the main hull and side hulls, different layouts and lengths of side hulls affect the wave loads significantly. Based on three-dimensional potential theory and Green＇s function, this article gives the significant values for wave loads, including vertical shear forces and vertical bending moments at different locations on the main hull, and transverse bending moments at the junction of the cross structure and main hull. In addition, a parametric optimization of wave loads for different layouts and lengths of side hulls were perfomed. Several speeds and wave headings were also considered. Finally, spectral analysis was conducted to attain load distribution. The conclusions of this study are conducive to the design and optimization of this new type of ship展开更多
文摘This paper numerically investigates the influence of separation variation of the outriggers on the hydrodynamic performance of a high speed trimaran （HST） aiming at improving its applicability in diverse realistic disciplines. The present investigation was performed within the framework of the 2-D slender body method （SBM） by calculating the resistance of three symmetric trimaran series moving in a calm free surface of deep water. Each trimaran series comprises of 4681 configurations generated by considering 151 staggers （-50%≤a≤＋ 100%）, and 31 separations （100%≤β≤400%） for 81 Froude numbers （0.20≤Fn≤ 1.0）. In developing the three trimaran series, Wigley-st. AMECRC-09, and NPL-4a models were used separately for both the main and side hulls of each individu;d series models. A computer macro named Tri-PL was created using the Visual Basic for Applications~. Tri-PL~ sequentially interfaced Maxsurfe then Hullspeed to generate the models of the three trimaran series together with their detailed hydrostatic particulars, followed by their resistance components. The numerical results were partially validated against the available published numerical calculations and experimental results, to benchmark the Tri-PL macro and hence to rely on the analysis outcomes. A graph template was creaLed within the framework of SigmaPlot to visualize the significant results of the Tri-PL properlv.
基金supported by the Directorate for Research and Community Service,University of Indonesia(RUUI Utama 2012),Jakarta,Indonesia
文摘The application of multi-hull ship or trimaran vessel as a mode of transports in both river and sea environments have grown rapidly in recent years.Trimaran vessels are currently of interest for many new high speed ship projects due to the high levels of hydrodynamic efficiency that can be achieved,compared to the mono-hull and catamaran hull forms.The purpose of this study is to identify the possible effects of using an unsymmetrical trimaran ship model with configuration（S/L） 0.1-0.3 and R/L=0.1-0.2.Unsymmetrical trimaran ship model with main dimensions： L=2000mm,B=200 mm and T=45 mm.Experimental methods（towing tank） were performed in the study using speed variations at Froude number 0.1-0.6.The ship model was pulled by an electric motor whose speed could be varied and adjusted.The ship model resistance was measured precisely by using a load cell transducer.The comparison of ship resistance for each configuration with mono-hull was shown on the graph as a function of the total resistance coefficient and Froude number.The test results found that the effective drag reduction could be achieved up to 17% at Fr=0.35 with configuration S/L=0.1.
基金the National Natural Science Founda-tion of China (No. 10572094)the Special ResearchFund for the Doctoral Program of Higher Education(No. 20050248037)
文摘A 3D rankine panel method was developed for calculating the linear wave-making resistance of a tri-maran with Wigley hulls. In order to calculate the normal vector and derivative of the body surface accurately, non-uniform rational B-spline (NURBS) was adopted to represent body surface and rankine source density. The radiation condition is satisfied using the numerical technology of staggered grids. Numerical results show that the linear wave-making resistance of the trimaran can be calculated effectively using this method.
文摘This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.
文摘As a new type of hull form,trimaran has remarkable excellent performances and has drawn more and more attention.When the viscous CFD technology now available is applied to the research of resistance performance of trimaran,the spatial discretization would usually result in the grid error and uncertainty,and thus the considerable discrepancy between the numerical results and the experimental data.In order to ascertain how much the grid would affect the calculation,the grid convergence should be studied.A mathematical trimaran was chosen as an example,with the commercial code CFX for the simulation,VOF for surface treatment,and the grid study was carried out based on two different turbulence models.It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty,and indicating the direction of improving the credibility of the numerical calculation, and,in addition to grid errors and uncertainties,the turbulence modeling errors and uncertainties contribute to the simulation errors.
基金The second author was supported by the Scientific and Technological Research Council of Turkey(TUBITAK)2219 International Postdoctoral Research Fellowship Program。
文摘Trimaran hydrodynamics have been an important research topic in recent years.Trimarans have even been chosen for naval surface combatants.In this case,investigation of a trimaran with different outrigger positions is important and necessary for better hydrodynamic performance.This paper focuses on the numerical investigation of trimaran hydrodynamics.The trimaran model used in this study is a 1/80 scale high-speed displacement frigate-type concept developed by the Center for Innovation in Ship Design(CISD)at Naval Surface Warfare Center,Carderock Division(NSWCCD).The numerical simulations were conducted for different outrigger positions at low and moderate Froude numbers by using commercial CFD software solving URANS equations.A verification and validation study was carried out for the numerical method in one configuration and one ship velocity.The existing experimental results for the trimaran resistance in the literature were used for validation.Five different outrigger positions were analyzed and the form factor of each configuration was calculated by the Prohaska method.The total resistance was decomposed to its components using the form factor.The interference factor was calculated for each configuration in terms of total resistance,residual resistance and wave resistance.Also,wave profiles using the longitudinal wave cuts in different locations were obtained both numerically and experimentally.It was concluded that the outrigger position had different effects on the interference,total resistance and wave profile at different Froude numbers.It was also shown that the CFD results were in good agreement with the experimental data in all configurations.In conclusion,this study presents the results of interference effects for different trimaran configurations in terms of wave resistance in addition to the total resistance and residual resistance.The numerical method was validated not only with the total resistance test data but also the longitudinal wave profiles along the hull.
基金Supported by the Natural Science Foundation of China under Grant Nos.52171294 and 52192692。
文摘This paper presents experimental results on configuration hydrodynamics.Three models are used in the model tests,which are typical of hard,round,and soft chines.Although specific values are different,the influence patterns are similar in the three ship models.A set of different outrigger positions is investigated in calm water and regular waves.A variety of interesting phenomena are observed,among which the splash resistance is the dominant component for a trimaran at high speeds(with Froude number Fr>0.6).If two small outriggers are placed inside Kelvin’s wave systems of the main hull,a strong splash appears,resulting in a significant resistance increase.Moreover,short and long waves cannot be neglected,for they may excite the motions of much smaller outriggers.This condition leads to non-vanishing heaving at high-frequency and non-normalized pitches at low frequencies.Based on the tests,three spectra of optimum configurations for resistance,longitudinal motions,and transverse motions are presented.These results reveal the optimum configurations of a trimaran hull in terms of hydrodynamic performance,thus providing a very powerful tool for optimum design of trimaran ships.
基金financially supported by the State Key Laboratory of Structural Analysis,Optimization and CAE Software for Industrial Equipment,Dalian University of Technology(Grant No.GZ23112)the Shandong Provincial Natural Science Foundation,China(Grant No.ZR2021ME146).
文摘To predict the wave loads of a flexible trimaran in different wave fields,a one-way interaction numerical simulation method is proposed by integrating the fluid solver(Star-CCM+)and structural solver(Abaqus).Differing from the existing coupled CFD-FEA method for monohull ships in head waves,the presented method equates the mass and stiffness of the whole ship to the hull shell so that any transverse and longitudinal section stress of the hull in oblique waves can be obtained.Firstly,verification study and sensitivity analysis are carried out by comparing the trimaran motions using different mesh sizes and time step schemes.Discussion on the wave elevation of uni-and bi-directional waves is also carried out.Then a comprehensive analysis on the structural responses of the trimaran in different uni-directional regular wave and bi-directional cross sea conditions is carried out,respectively.Finally,the differences in structural response characteristics of trimaran in different wave fields are studied.The results show that the present method can reduce the computational burden of the two-way fluid-structure interaction simulations.
基金supported by the Sasakawa Scientific Research Grant from the Japan Science Society
文摘In recent years,demands for car transportation by a ship have been increasing with favorable economic conditions in auto sector,and the need of a pure car carrier(PCC) has grown quickly.A PCC needs huge parking space but smaller displacement since a car is comparatively light for its volume.As a result,almost all PCCs have wide breadth,shallow draft and huge structure above the water surface.These features cause some technical issues of a PCC,like lack of stability,effect of strong winds on its resistance,difficulty of course keeping in rough seas,difficulty of berthing in strong winds,and so on.To overcome these technical issues,one of the authors has proposed a new concept for a PCC.This is a trimaran PCC which has very limited transverse bulkheads in the center hull by using two side hulls as fenders.In the present research,wind forces acting on a scale model of the trimaran PCC were measured in the towing tank with a wind generator at Osaka Prefecture University.Furthermore,in order to clarify the characteristics of wind pressure on the trimaran,height and width of tunnels which are between a main hull and side hulls were changed.And then,in order to imitate a real ship,we used wind reduction technology of corner-cut design for accommodation house of the ship.Moreover,the wind pressure acting on the trimaran was compared with that on a mono-hull PCC.Using these experimental and theoretical results,an estimation method of wind pressure acting on the trimaran PCC is deduced.
文摘In the present paper,a new trimaran Pure Car Carrier(PCC) is proposed and a feasibility study on the ship is carried out.In this study,first,the effective horse power(EHP)/car of the PCC running in still water is predicted.By comparing the predicted EHP/car with that of a conventional mono-hull PCC,it is found that the trimaran PCC is superior to the conventional mono-hull PCC at rather higher speed.As ship speed increases,the reduction of the resistance of the trimaran is bigger.It is also found that at common service speed of PCCs,the EHP/car of a small PCC is lower than that of a conventional PCC.Secondly,the optimal L/B of a main-hull of the trimaran PCC in still water is determined.The optimal L/B of the main-hull varies with ship speed and size because the wave resistance decreases but the frictional resistance increases as L/B of the hull increases.As ship size increases,the optimal L/B of the main-hull of the trimaran PCC decreases.Finally,the increase of the resistance of PCCs running in strong wind is predicted.The results show that drift angle and speed reduction of the trimaran PCC are much smaller than the conventional mono-hull PCC because of large side force created by three demi-hulls.
文摘This paper illustrates the reasons behind the research strategy that has led to a new generation of trimaran hulls by minimizing the hull＇s drag-design approach. The objective of this study was to search for the optimal side-hull yaw and roll angle to minimize induced drag of trimarans a^d so to investigate the differences in the performance results of a trimaran hull. Specifically, this research has been based on a critical analysis of the diversity of ama yaw and roll angles and outriggers positioning. Then, the paper will be comparing the results of the test series of the yaw and roll angles of trimaran areas. Design and towing tank test of a scaled trimaran model will be illustrated and compared along with some key and relevant results. The term ＂ama＂ is a word in the Polynesian and Micronesian languages to describe the outrigger part of a canoe to provide stability.
基金Project supported by the National Defense Science Foundation Program (Grant No. 9140A14070306JB1114)
文摘Up to now, there are no satisfactory numerical methods for simulating wave resistance of trimarans, mainly due to the difficulty related with the strong nonlinear features of the piece hull wave making and their interference. This article proposes a numerical method for quick and effective calculation of wave resistance of trimarans to be used in engineering applications. Based on Wyatt＇s work, the nonlinear free surface boundary condition, the time domain concept, and the full nonlinear wave making theory, using the Rankine source Green function, the 3-D surface panel method is expanded to solve the trimaran wave making problems, with high order nonlinear factors being taken into account, such as the influence of the sinking and trim, transom, and ship wave immersed hull surface. And the software is successfully developed to implement the method, which is validated. Several trimaran models, including a practical trimaran with a sonar dome and the transom, are used as numerical calculation samples, their wave making resistance is calculated both by the present method and some other methods such as linear （Dawson） methods. Moreover, sample model resistance tests were carried out to provide data for comparison, validation and analysis. Through the validation by model experiments, it is concluded that present method can well predict the wave making resistance, sinking and trim, and the accuracy of wave making resistance calculation is significantly improved by taking the trim and sinking into account, especially at high speeds.
文摘Based on the potential flow assumption, this paper outlines the formulation of the boundary-value problem governing the steady free surface flow around a trimaran advancing at a constant forward. A Rankine panel method was developed for the solution of the problem. The side-hulls were treated as lifting bodies and circulation was introduced into the flow field to implement the asymmetrical flow around each side hull. The linearized free surface condition was used. The appropriate treatment for transom-stern ship was also discussed. Additionally, a test was performed to quantify the resistance and especially the interference between the main and side hulls. The numerical results are in good argeement with experimental data.
基金supported by the National Nature Science Foun-dation of China(Grant No.50879014)the Doctoral Program of Higher Education of China(Grant No.200802170010)
文摘This paper studies the hydrodynamic performance of a channel type planing trimaran. A numerical simulation is carried out based on a RANS-VOF solver to analyze the hydrodynamic performance of the channel type planing trimaran. A series of hydrodynamic experiments in towing tank were carried out, in which both the running attitude and the resistance performance of the trimaran model were recorded. Some hydrodynamic characteristics of the channel type planning trimaran are shown by the results. Firstly, the resistance declines significantly, with the forward speed across the high-speed resistance peak due to the combined effects of the aerodynamic and hydrodynamic lifts. Secondly, the resistance performance is influenced markedly by the longitudinal positio- ns of centre of the gravity and the displacements. Besides, the pressure distribution on the hull and the two-phase flow in the channel are discussed in the numerical simulations.
基金Project supported by the Eleventh Five Year Plan Defense Pre-Research Fund, China (Grant No. 40103060101)
文摘Due to the interaction between the main hull and side hulls, different layouts and lengths of side hulls affect the wave loads significantly. Based on three-dimensional potential theory and Green＇s function, this article gives the significant values for wave loads, including vertical shear forces and vertical bending moments at different locations on the main hull, and transverse bending moments at the junction of the cross structure and main hull. In addition, a parametric optimization of wave loads for different layouts and lengths of side hulls were perfomed. Several speeds and wave headings were also considered. Finally, spectral analysis was conducted to attain load distribution. The conclusions of this study are conducive to the design and optimization of this new type of ship
