The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Francis Noblesse - One of the best experts on this subject based on the ideXlab platform.
-
Practical hydrodynamic optimization of a monohull
Transactions of the Society of Naval Architects and Marine Engineers, 2020Co-Authors: Dane Hendrix, Scott Percival, Francis NoblesseAbstract:An extremely simple CFD tool is used to define optimized monohull ships for which the total (Friction + wave) calm-water drag is minimized. The friction drag is estimated using the classical ITTC friction-drag formula.
-
Farfield waves created by a monohull ship in shallow water
European Journal of Mechanics B-fluids, 2020Co-Authors: Jiayi He, Chenliang Zhang, Huiyu Wu, Francis NoblesseAbstract:Abstract Interference effects between the dominant waves created by the bow and the stern of a monohull ship, of length L , that advances at constant speed V along a straight path in calm water of uniform finite depth D are considered. The largest waves due to constructive interference result in an apparent wake angle ψ max that can differ greatly from the cusp or asymptote angles associated with the wave pattern of a ship when interference effects are ignored, as in Kelvin’s classical analysis. Thus, wave interference has a very large effect on the wave signature of a ship in shallow water and cannot be ignored. Water-depth effects on the wake angle ψ max are found to be insignificant for water depths d L ≡ D / L greater than d deep L ≈ 0.89 or for Froude numbers F ≡ V / g L greater than F deep ≈ 0.5 / d L . Furthermore, the water depth d L has only a relatively small influence on the wake angle ψ max for 1.5 F , and the deep-water approximation ψ max ≈ 0.14 / F 2 can then be used.
-
A Practical Hydrodynamic Optimization Tool For the Design of a Monohull Ship
2020Co-Authors: Chi Yang, Rainald Löhner, Francis NoblesseAbstract:This paper presents a practical hydrodynamic optimization tool for the design of a monohull ship. The main components of this tool consists of a practical design-oriented CFD tool, a NURBS representation for the hull surface, and a gradient-based optimization procedure. The CFD tool, which is used to evaluate the steady flow about a ship, is based on a new theory, called NeumannMichell (NM) theory. The wave drag predicted by the NM theory is in fairly good agreement with experimental measurements. The hull surface is represented by NURBS, which allows for the large variation of hull form during optimization cycles. For purposes of illustration, the classical Wigley hull is taken as an initial hull and the hydrodynamic optimization tool is used to determine the optimal hull forms for three design speeds and for a given speed range with displacement constraint.
-
Practical Estimation of Sinkage and Trim for Common Generic Monohull Ships
Ocean Engineering, 2016Co-Authors: Chao Ma, Chenliang Zhang, Xi Chen, Yin Jiang, Francis NoblesseAbstract:Abstract Two practical approaches for estimating the sinkage and the trim experienced by a freely floating ship that advances at a constant speed in calm water are considered for common monohull ships at moderate Froude numbers F ≤ 0.45 : an experimental approach based on experimental data, given in the literature, for 22 ship models; and a numerical approach based on a practical linear potential-flow theory, the Neumann-Michell theory, that only requires simple flow computations. The experimental approach yields particularly simple analytical relations for the sinkage and the trim, and thus requires no flow computations. The numerical approach only involves flow computations for the ship hull in equilibrium position at rest; i.e., sinkage and trim effects on the position of the ship hull are ignored in these flow computations. Both approaches are found to yield reasonable predictions of sinkage and trim for a wide range of monohull ships at Froude numbers F ≤ 0.45 .
-
Interference effects on the Kelvin wake of a monohull ship represented via a continuous distribution of sources
European Journal of Mechanics B-fluids, 2015Co-Authors: Chenliang Zhang, Jiayi He, Chen-jun Yang, Wei Li, Francis NoblesseAbstract:Abstract Wave-interference effects on the wave pattern of a monohull ship that advances at constant speed along a straight path in calm water are considered. The flow around the ship is represented via a continuous distribution of sources over the hull surface, rather than via a point source at the bow and a point sink at the stern. A practical and realistic numerical method for determining the apparent wake angle ψ max , where the largest waves are found at high Froude numbers, for general ship hulls (including multihulls and/or distributions of pressure at the free surface) is considered. The method only involves elementary numerical computations that can be performed simply and efficiently. The method is therefore used here to perform systematic computations for seven ship hulls that correspond to broad ranges of main hull-shape parameters (beam/length, draft/length, beam/draft, waterline entrance angle) at ten Froude numbers. This numerical study shows that the apparent wake angle ψ max is only weakly influenced by the shape of the ship hull. A useful practical consequence of this numerical finding is that the wake angle ψ max can be estimated for general monohull ships via simple analytical relations. These relations provide relatively-accurate practical estimates (without computations) of the apparent wake angle ψ max ( F ) for arbitrary ship hull forms and Froude numbers. The explicit approximations for the wake angle ψ max ( F ) obtained here account for both longitudinal interference between the divergent waves created by the fore and aft regions of a monohull ship and lateral interference between the divergent waves created by the port and starboard sides of the hull. As expected, these relations yield an estimate of the wake angle ψ max ( F ) for a monohull ship that is more precise than the analytical estimate given by an elementary analysis of interference between the dominant waves created by the bow and the stern of a ship, which corresponds to a 2-point wavemaker approximation of the continuous hull-surface distribution of sources considered here.
P A Ghani - One of the best experts on this subject based on the ideXlab platform.
-
Resistance and wash measurements on a series of high speed displacement monohull and catamaran forms in shallow water
International Journal of Maritime Engineering, 2004Co-Authors: A. G. Molland, S Chandraprabha, P A Wilson, Dominic Taunton, P A GhaniAbstract:The paper summarises an experimental investigation into the resistance and wash waves of high speed displacement Monohulls and catamarans in shallow water. Measurements of total resistance, running trim, sinkage and multiple longitudinal wave cuts were carried out for three round bilge hulls derived from the NPL series and one from Series 64. Parametric changes included length/displacement ratios of 7.4, 8.5 and 9.5, and hull separation/length ratios of 0.2, 0.4 and infinity. The tests were carried out in two depths of shallow water over a length Froude Number range of 0.25 to 1.0 and a depth Froude Number range of 0.5 to 3.0. The wave resistance was derived using wave pattern analysis and the principal particulars of the generated wave system are presented as maximum wave height, period, distribution of energy and direction of wave propagation. The results of the investigation provide a better understanding of the performance of high speed displacement Monohulls and catamarans in shallow water, including the influences of speed, water depth, hull separation and length/displacement ratio. The data derived are very suitable for design applications and for the validation of theoretical analyses of ship wave resistance and wash waves.
-
Resistance and Wash Wave Measurements On A Series of High Speed Displacement Monohull and Catamaran Forms In Shallow Water
The International Journal of Maritime Engineering, 2004Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:The paper summarises an experimental investigation into the resistance and wash waves of high speed displacement Monohulls and catamarans in shallow water. Measurements of total resistance, running trim, sinkage and multiple longitudinal wave cuts were carried out for three round bilge hulls derived from the NPL series and one from Series 64. Parametric changes included length/displacement ratios of 7.4, 8.5 and 9.5, and hull separation/length ratios of 0.2, 0.4 and infinity. The tests were carried out in two depths of shallow water over a length Froude Number range of 0.25 to 1.0 and a depth Froude Number range of 0.5 to 3.0. The wave resistance was derived using wave pattern analysis and the principal particulars of the generated wave system are presented as maximum wave height, period, distribution of energy and direction of wave propagation. The results of the investigation provide a better understanding of the performance of high speed displacement Monohulls and catamarans in shallow water, including the influences of speed, water depth, hull separation and length/displacement ratio. The data derived are very suitable for design applications and for the validation of theoretical analyses of ship wave resistance and wash waves.
-
NUMERICAL ESTIMATION OF SHIP WASH WAVES IN DEEP AND SHALLOW
FAST 2003 The 7th International Conference on Fast Sea Transportation, 2003Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:A description is given of an extensive numerical and experimental investigation into the wash waves generated by high speed displacement monohull and catamaran forms in deep and shallow water. The objective of the research has been to identify and estimate numerically the characteristic content of the near-field wash waves, including their transverse and divergent wave components and direction of propagation, for different design and operating conditions such as the influence of length-displacement ratio, catamaran hull separation, speed, trim and shallow water. The principal part of the numerical method uses modified thin ship theory, which is found to be satisfactory for the relative slender hull forms employed for high speed Monohulls and catamarans. The numerical predictions are found to be in satisfactory agreement with extensive parametric model wave cut measurements which have been carried out recently in deep and shallow water.
A. G. Molland - One of the best experts on this subject based on the ideXlab platform.
-
Resistance and wash measurements on a series of high speed displacement monohull and catamaran forms in shallow water
International Journal of Maritime Engineering, 2004Co-Authors: A. G. Molland, S Chandraprabha, P A Wilson, Dominic Taunton, P A GhaniAbstract:The paper summarises an experimental investigation into the resistance and wash waves of high speed displacement Monohulls and catamarans in shallow water. Measurements of total resistance, running trim, sinkage and multiple longitudinal wave cuts were carried out for three round bilge hulls derived from the NPL series and one from Series 64. Parametric changes included length/displacement ratios of 7.4, 8.5 and 9.5, and hull separation/length ratios of 0.2, 0.4 and infinity. The tests were carried out in two depths of shallow water over a length Froude Number range of 0.25 to 1.0 and a depth Froude Number range of 0.5 to 3.0. The wave resistance was derived using wave pattern analysis and the principal particulars of the generated wave system are presented as maximum wave height, period, distribution of energy and direction of wave propagation. The results of the investigation provide a better understanding of the performance of high speed displacement Monohulls and catamarans in shallow water, including the influences of speed, water depth, hull separation and length/displacement ratio. The data derived are very suitable for design applications and for the validation of theoretical analyses of ship wave resistance and wash waves.
-
Resistance and Wash Wave Measurements On A Series of High Speed Displacement Monohull and Catamaran Forms In Shallow Water
The International Journal of Maritime Engineering, 2004Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:The paper summarises an experimental investigation into the resistance and wash waves of high speed displacement Monohulls and catamarans in shallow water. Measurements of total resistance, running trim, sinkage and multiple longitudinal wave cuts were carried out for three round bilge hulls derived from the NPL series and one from Series 64. Parametric changes included length/displacement ratios of 7.4, 8.5 and 9.5, and hull separation/length ratios of 0.2, 0.4 and infinity. The tests were carried out in two depths of shallow water over a length Froude Number range of 0.25 to 1.0 and a depth Froude Number range of 0.5 to 3.0. The wave resistance was derived using wave pattern analysis and the principal particulars of the generated wave system are presented as maximum wave height, period, distribution of energy and direction of wave propagation. The results of the investigation provide a better understanding of the performance of high speed displacement Monohulls and catamarans in shallow water, including the influences of speed, water depth, hull separation and length/displacement ratio. The data derived are very suitable for design applications and for the validation of theoretical analyses of ship wave resistance and wash waves.
-
NUMERICAL ESTIMATION OF SHIP WASH WAVES IN DEEP AND SHALLOW
FAST 2003 The 7th International Conference on Fast Sea Transportation, 2003Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:A description is given of an extensive numerical and experimental investigation into the wash waves generated by high speed displacement monohull and catamaran forms in deep and shallow water. The objective of the research has been to identify and estimate numerically the characteristic content of the near-field wash waves, including their transverse and divergent wave components and direction of propagation, for different design and operating conditions such as the influence of length-displacement ratio, catamaran hull separation, speed, trim and shallow water. The principal part of the numerical method uses modified thin ship theory, which is found to be satisfactory for the relative slender hull forms employed for high speed Monohulls and catamarans. The numerical predictions are found to be in satisfactory agreement with extensive parametric model wave cut measurements which have been carried out recently in deep and shallow water.
-
METHODS FOR ASSESSING THE SEAKEEPING PERFORMANCE OF COMPETING HIGH SPEED VESSEL DESIGNS
Hydrodynamics of High Speed Craft, 1999Co-Authors: A. G. Molland, D J TauntonAbstract:Seakeeping performance can have a significant influence on the choice of competing vessel types for a particular route. The criteria used in assessing the performance include motions and accelerations, operational limits, speed loss and passenger comfort. The paper describes methods which have been developed for estimating the seakeeping performance of high speed craft and, in particular, the application of suitable criteria for assessing the performance of alternative vessels at the design stage. The methods use a data base of motion transfer functions for high speed Monohulls and catamarans, together with assumed wave energy spectra for the relevant operational sea area. A data base of transfer functions has been developed from extensive head sea tank testing of Monohulls and catamarans and, more recently, model tests of high speed catamarans in oblique seas. These data are being enhanced by theoretical methods which are under development. Applications of the methods described are illustrated in case studies of competing high speed monohull and multihull vessels for particular routes.
Zhao Xiao-dong - One of the best experts on this subject based on the ideXlab platform.
-
Research on the application of hybrid monohull techniques to larger ships
Journal of Harbin Engineering University, 2020Co-Authors: Zhao Xiao-dongAbstract:The hybrid monohull technique was taken from ships with tonnages ranging from hundreds of tons to thousands of tons and even four thousand tons.Three hybrid Monohulls were created by installing built-up longitudinal-stabilizing appendage on the bottoms of ordinary ships.Regular wave and resistance experiments for the hybrid Monohulls and the original ship hulls were carried out in a tank.The longitudinal motion and resistance performance of each ship were analyzed.It was shown that the resistance of the hybrid Monohulls,which had properly moulded lines,dimension and locations,was close to the results for the original hull,but longitudinal motion was reduced considerably compared with the original ship.This hybrid monohull technique can be used on ships with tonnages up to four thousand tons.
-
Experimental study on 4000t deep-V hybrid monohull
Journal of Ship Mechanics, 2020Co-Authors: Zhao Xiao-dongAbstract:In this paper,the resistance and seakeeping test results about a new type 4 000t deep-V hybrid monohull were presented.A comparative study on deep-V hybrid monohull with built-up stabilizing appendage and ordinary deep-V ship was made.The effect of the resistance and seakeeping performance of the hybrid monohull with built-up stabilizing appendage was analyzed.The test results show that the resistance of the deep-V hybrid monohull is close to the ordinary deep-V ship,and the longitudinal motions of deep-V hybrid monohull,such as heave,pitch,and vertical acceleration,are reduced by the built-up stabilizing appendage considerably.It shows that the hybrid monohull technique can be used for more large tonnage ship.
-
The Test Research on High Seakeeping Performance Displacement Hybrid Monohull Ship
2020Co-Authors: Zhao Xiao-dongAbstract:The model tests of a hybrid monohull ship which is designed on basis of conventional rounded chine monohull ship are carried out.There is a stabilizing appendage on the bottom of the stem of the ship which consists of a semi-submerged hull and passive bow-fin.Three appendage schemes are selected.The purpose of the tests is to analyze the affect of the appendage on resistance and seakeeping of the ship and to find the optimal scheme.The test results show that the longitudinal motions of the hybrid monohull ship are reduced considerably compared with the conventional rounded chine monohull ship,and the resistance is the same nearly as one of the conventional rouded chine ship.
-
Motion prediction of hybrid monohull considering viscous and bow up state effect
Journal of Ship Mechanics, 2020Co-Authors: Zhao Xiao-dongAbstract:The theory and test researches indicate that hybrid monohull can greatly upgrade its seakeeping performance but with little influence to resistance in peace water.How to exactly predict the motion of this kind of ship is always the problem which people concern.In this paper,the longitudinal motion of deep-V and deep-V hybrid monohull is predicted using STF method.The researches indicate that traditional strip method can not reflect the viscous effect of built-up appendage because it bases on potential theory,so the predicted results are very different from test results.For this end,the hydrodynamic coefficients of ship sec-tions which have built-up appendage are computed using CFD software Fluent which calculates viscous effect.Lift force coefficients of built-up appendage are computed using RANS method,and the effect of bow up state is also calculated.The results show that the method can effectively improve the prediction preci-sion.
D J Taunton - One of the best experts on this subject based on the ideXlab platform.
-
Resistance and Wash Wave Measurements On A Series of High Speed Displacement Monohull and Catamaran Forms In Shallow Water
The International Journal of Maritime Engineering, 2004Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:The paper summarises an experimental investigation into the resistance and wash waves of high speed displacement Monohulls and catamarans in shallow water. Measurements of total resistance, running trim, sinkage and multiple longitudinal wave cuts were carried out for three round bilge hulls derived from the NPL series and one from Series 64. Parametric changes included length/displacement ratios of 7.4, 8.5 and 9.5, and hull separation/length ratios of 0.2, 0.4 and infinity. The tests were carried out in two depths of shallow water over a length Froude Number range of 0.25 to 1.0 and a depth Froude Number range of 0.5 to 3.0. The wave resistance was derived using wave pattern analysis and the principal particulars of the generated wave system are presented as maximum wave height, period, distribution of energy and direction of wave propagation. The results of the investigation provide a better understanding of the performance of high speed displacement Monohulls and catamarans in shallow water, including the influences of speed, water depth, hull separation and length/displacement ratio. The data derived are very suitable for design applications and for the validation of theoretical analyses of ship wave resistance and wash waves.
-
NUMERICAL ESTIMATION OF SHIP WASH WAVES IN DEEP AND SHALLOW
FAST 2003 The 7th International Conference on Fast Sea Transportation, 2003Co-Authors: A. G. Molland, D J Taunton, S Chandraprabha, P A Wilson, P A GhaniAbstract:A description is given of an extensive numerical and experimental investigation into the wash waves generated by high speed displacement monohull and catamaran forms in deep and shallow water. The objective of the research has been to identify and estimate numerically the characteristic content of the near-field wash waves, including their transverse and divergent wave components and direction of propagation, for different design and operating conditions such as the influence of length-displacement ratio, catamaran hull separation, speed, trim and shallow water. The principal part of the numerical method uses modified thin ship theory, which is found to be satisfactory for the relative slender hull forms employed for high speed Monohulls and catamarans. The numerical predictions are found to be in satisfactory agreement with extensive parametric model wave cut measurements which have been carried out recently in deep and shallow water.
-
METHODS FOR ASSESSING THE SEAKEEPING PERFORMANCE OF COMPETING HIGH SPEED VESSEL DESIGNS
Hydrodynamics of High Speed Craft, 1999Co-Authors: A. G. Molland, D J TauntonAbstract:Seakeeping performance can have a significant influence on the choice of competing vessel types for a particular route. The criteria used in assessing the performance include motions and accelerations, operational limits, speed loss and passenger comfort. The paper describes methods which have been developed for estimating the seakeeping performance of high speed craft and, in particular, the application of suitable criteria for assessing the performance of alternative vessels at the design stage. The methods use a data base of motion transfer functions for high speed Monohulls and catamarans, together with assumed wave energy spectra for the relevant operational sea area. A data base of transfer functions has been developed from extensive head sea tank testing of Monohulls and catamarans and, more recently, model tests of high speed catamarans in oblique seas. These data are being enhanced by theoretical methods which are under development. Applications of the methods described are illustrated in case studies of competing high speed monohull and multihull vessels for particular routes.