Hull Resistance Research Articles

Numerical Simulation of the Viscous Flow around High-Speed Ship Hull Considering the Free Surface

Over the last decade, considering the influence of the viscous free water surface, the numerical simulation of the flow around the hull is one of the focuses in ship research. Currently, the precision of numerical simulation results need to be enhanced. In this paper, Computational Fluid Dynamics (CFD) method is used, for a real high-speed ship model, to simulate the flow around the hull and to calculate the total hull resistance with FLUENT software. The Volume of Fraction (VOF) method of two-phase fluid is used to deal with the free surface tracking. The results of resistance are compared with the ship model experimental results. It is shown that the total resistance results calculated accord with the experimental results well, and the numerical method can simulate the profile of the ship wave-making.

CFD Simulation for the Resistance Performance of 1000 Dwt Deep-Vee Vessels on Bulbous Bow

Resistance influence factors of bulbous bow are analyzed with three 1000dwt displacement types Deep-vee forms provided. The free surface viscous flow of these forms is calculated by air-water two phases RANS equations with RNG turbulence model and volume of fraction method. Total resistance, pressure distribution and wave profile of hull are presented. Some results can be taken as follows: Adopted longer protruding length can improve the resistance character at medium high speed and ameliorate the resistance performance in calm water at low speed to design a 1000dwt deep-vee vessel; the bulbous bow wavemaking is only one of the reasons to influence the wavemaking resistance of hull. The importance influence factor of hull wavemaking resistance is how to form advantage disturbance or least disadvantage disturbance between the bulbous bow wave and hull wave.

쇄빙연구선 ARAON호를 이용한 북극해 해빙의 재료특성 (1) - 해빙의 두께, 온도, 염도, 밀도 계측 -

A field trial in an ice-covered sea is one of the most important tasks in the design of icebreaking ships and offshore structures. To correctly estimate the ice load and ice resistance of a ship's hull, it is essential to understand the material properties of sea ice during ice field trials and to use the proper experimental procedure for gathering effective ice data. The first Korean-made icebreaking research vessel, "ARAON," had her second sea ice trial in the Arctic Ocean during the summer season of 2010. This paper describes the test procedures used to obtain proper sea ice data, which provides the basic information for the ship's performance in an ice-covered sea and is used to estimate the correct ice load and ice resistance of the IBRV ARAON. The data gathered from the sea ice in the Chukchi Sea and Beaufort Sea during the Arctic voyage of the ARAON includes the temperature, density, and salinity of the sea ice, which was believed to be from two-year old ice floes. This paper analyses the gathered sea ice data in comparison with data from the first voyage of the ARAON during her Antarctic Sea ice trial.

船底防汚塗料の実船評価

The evaluation examination of self-polishing anti-fouling bottom paint has been carried out by training ship Fukae-maru (449G/T) of the graduate school of maritime sciences, Kobe University. For these past three years, 3 kinds of bottom paint of types low-friction coating, improved conventional paint and conventional paint have been evaluated by speed trials at Harima-Nada of the Seto Inland Sea. The frictional resistance of hull based on the viscosity of sea water accounts for 70-80% of all resistance at low speed range and accounts for 40-50% at high speed. The improvement of the frictional resistance of bottom shell plating reduces fuel consumption of a ship and leads to a reduction of the greenhouse gas emission at the same time. As a result of the speed trials, 3% or more of fuel-saving was effected with improved conventional paint and 9% or less of fuel-saving with low friction paint, compared to conventional anti-fouling bottom paint.

Frictional Resistance Calculations on a Ship using CFD

In the present study, we conducted propeller open water test, resistance test, and propeller, ship hull interaction for a ship‟s resistance and propulsion performance, using computational fluid dynamics techniques, where a K-epsilon, K-omega turbulence viscous models were employed. For convenience of mesh generation, unstructured meshes were used in the propeller region of a ship, where the hull shape is formed of delicate curved surfaces. On the other hand, structured meshes were generated for the remaining part of the hull and its domain, i.e., the region of relatively simple geometry. To facilitate the rotating propeller for propeller a moving reference frame motion type technique was adopted. The computational results were validated by comparing with the existing experimental data. In this work we are interested in predicting the frictional resistance offered to a ship during is motion. To this effect we start off with a consideration of the resistance offered to the bare hull in the absence of the propeller and later extend to the case where the propeller is in-place. The thrust generated by the propeller alone without considering the ship (called open water analysis) is also performed using CFD. FLUENT 6.0®, was used for CFD analysis and for modeling and meshing the packages used are CATIA – V5® and ICEM-CFD® respectively. The open water analysis of the 4-bladed propeller predicted a thrust of 346 kN at 30 rps. The bare hull resistance at 228 kN at 18 m/s, and resistance with propeller in place at 18 m/s was found to be 245 kN. The results predicted by the CFD analysis were found to be suitable for the present HSDS and it is believed that the hydrodynamics design of the propeller is acceptable for the problem at hand.

Estimation of hull-propeller interaction of a self-propelling model hull using a RANSE solver

Viscous flow around the self-propelled hull was investigated at model scale with a RANSE solver using k-ϵ turbulence model by coupling the flow around the hull model with the flow generated by the rotating propeller. Hence, the challenges involved in the coupling of flow past ship hull with propeller flow of lower-order scale have been brought out and addressed here. Propeller rotation is accounted for by mesh motion; the solution domain is represented by a rotating cylindrical domain encompassing the propeller and a fixed rectangular domain around the hull for the remaining part of the solution domain; both these domains are interfaced by sliding interfaces. Comparisons are made between the simulated results and corresponding experimental results for hull resistance, propeller thrust and propeller RPM. It is shown that the flow field in the self-propelling condition is well reproduced in the simulation, and the estimated thrust deduction factor and RPM agree well with the measured ones. Among the various turbulence modelling schemes available, the present study uses the Realizable k-ϵ turbulence model.

マシウ関数を用いた級数展開法による制約条件下における最適横截面積曲線について

When a high speed vessel is designed, it is important how we make her sectional area curve effectively on purpose to minimize the hull resistance. But on a sectional area curve, there are, in general, some constraints caused by the requirement of ship arrangement and we cannot reject them simply because we must build not only a small resistance ship but also an easily operable ship. A sectional area curve under these constraints is usually made from the experience of designers by referring one of a type ship, but we don't think we can get a true optimal curve easily only by the experience.In this report, we introduce the linear wave-making resistance theory into the optimal problem and Series 64 model 4793 is chosen as the object for analysis. The sectional area curve of Series 64 model 4793 is expanded into Mathieu function series and the performance is evaluated from the viewpoint of the wave-making resistance. Then we make the optimal curve for the improved hull form theoretically using calculus of variation under some constraints which are established artificially by us.Finally, we carry out resistance experiment of the improved hull form to evaluate our optimal method and it shows good result that the residual resistance of improved hull form becomes around the half of that of the original hull form.

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

After signing ship building contract shipyard’s design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of three parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics After signing ship building contract shipyard's design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of three parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

"Inclined Keel" 컨테이너선의 조파저항 최소화를 위한 선형최적화

Ever increasing fuel prices, almost doubled in the last three years, and global pressure to reduce their environmental impact have been enforcing commercial vessel operators and designers to re-assess current vessel designs with emphasis on their propulsion systems and operational practices. In this paper the Inclined Keel (IKH) concept, which facilitates to use larger propeller diameter in combination with lower shaft speed rates and hence better transport efficiency, is explored for a modern 3600 TEU container vessel with the aim of fitting an 13 % larger diameter propeller (and hence resulting 20% lower rpm) to gain further power saving over the similar size basis container ship with conventional level configuration. It appears that successful application of the inclined keel Hull concept is a fine balance amongst the maximum gain in propulsive efficiency, minimum increase in hull resistance and satisfaction of other naval architectural and operational requirements. In order to make the concept economically more viable, this paper concentrates on the fore body design with the possible combination of increase of volume in its fore body to recover the expected volume loss in the aft body due to the space for larger propeller and its low wave-making resistance to minimize the efficiency loss using a well-established optimization software. ※Keywords: Inclined keel(경사용골), IKH(Inclined Keel Hull, 경사용골선체), Container(컨테이너), Stern form(선미형상), Trim(트림), form(선형), A large and slow turning propeller(대직경 저회전 프로펠러)

Submarine hull integrity under blast loading

The paper deals with numerical methodologies to model and study the structural resistance of submarine hull against explosions, where fluid and solid phenomena interact. Explosion Crack Starter Tests (ECST), which are a standard procedure to study submarine materials and weldments with respect to blast loading, are modelled using an explicit FE code that solves Fluid/Structure (F/S) interactions within the same computation. The proposed numerical methods aim at computing the structural response of a target subjected to sequential explosions. Numerical results are compared to the corresponding explosion tests (ECST) performed by DGA (French Ministry of Defence).

Numerical analysis of influence of ship hull form modification on ship resistance and propulsion characteristics

After signing ship building contract shipyard’s design office orders performance of ship resistance and propulsion model tests aimed at, apart from resistance measurements, also determination of ship speed, propeller rotational speed and propulsion engine power for the designed ship, as well as improvement of its hull form, if necessary. Range of ship hull modifications is practically very limited due to cost and time reasons. Hence numerical methods, mainly CFD ones are more and more often used for such tests. In this paper consisted of 3 parts, are presented results of numerical calculations of hull resistance, wake and efficiency of propeller operating in non-homogenous velocity field, performed for research on 18 hull versions of B573 ship designed and built by Szczecin Nowa Shipyard.

Practical evaluation of resistance of high-speed catamaran hull forms—Part II

This study attempts to extend the analysis of several resistance prediction procedures based on experimental work carried out by researchers and, subsequently, wave resistance estimation as illustrated in Part I of this study by Sahoo et al. (2007). All the methods used have been analysed and compared with results obtained from towing tank tests, CFD analysis by use of SHIPFLOW and a computational analysis is software package CATRES, whose operation is based around thin ship theory. The results obtained from each of the resistance prediction methods have been investigated, and the limitations and areas of effectiveness for each of the resistance methods have been determined in relation to the vessels tested. Throughout this study, the primary objective of validating the resistance equations developed in Part I of this study has been achieved. The level to which the resistance prediction tool can be utilized during the designing of high-speed catamarans was further determined through the analysis of the results.

Wave-Making Resistance of a Catamaran Hull in Shallow Water Using a Potential-Based Panel Method

The aim of this paper is to investigate the influence of the water depth and the wave interference effects on the first- and second-order wave-making resistance of a catamaran hull using a potential-based boundary element method. Since the interior flow of each monohull of a catamaran is different from the exterior flow, both monohulls must be considered as lifting bodies. The pressure Kutta condition is imposed at the trailing edge of the lifting body to determine the dipole distribution, which generates required circulation on the lifting part. The effects of hull separation and water depth on the hydrodynamic characteristics of a catamaran hull are analyzed and the validity of the computer scheme is examined by comparing the wave resistance with others' numerical results. The present method could be a useful design tool for screening the suitable combinations of hull parameters and hull spacing at the preliminary design stage of a catamaran hull.

A parametric method for evaluation of resistance of swath ships

A parametric method for evaluation of resistance of swath ships This paper contains formulation of a parametric method for evaluation of SWATH ship's hull resistance. The method was elaborated on the basis of numerical calculation results obtained by using structural methods based on ship hydrodynamic theory and performed for sufficiently large series of body forms with systematically changing ship form parameters. Also, results of verifying investigations dealing with features of the method in question are presented by comparing the obtained resistance characteristics with those achieved by other authors as well as with ship model experimental test results. The obtained results of the verification indicate that the elaborated method can be useful in preliminary designing the SWATH ships.

Practical evaluation of resistance of high-speed catamaran hull forms—Part I

Although catamaran configuration has been around for a longtime, it is only in the recent past that such hull forms have seen unprecedented growth in the high-speed ferry industry. One of the design challenges faced by naval architects is accurate prediction of the hydrodynamic characteristics of such vessels primarily in the areas of resistance, propulsion and seakeeping. Even though considerable amount of research has been carried out in this area, there remains a degree of uncertainty in the prediction of calm water resistance of catamaran hull forms. This paper attempts to present the research work carried out so far and what needs to be undertaken in future for a reasonably accurate prediction of catamaran resistance characteristics. The authors have examined the deep water wave resistance characteristics of a series of transom stern, semi-displacement slender catamaran hull forms of round bilge as well as single chine hull forms, which are of utmost importance to the high-speed ferry industry. The accuracy of the established regression equation has been seen to deviate appreciably by various sources of uncertainties. Verification of the equation with experimental database is also lacking to a certain extent. Further research is, therefore, needed to refine the accuracy as well as to complete the selection of crucial parameters employed. However, the results obtained have shown considerable promise, and a regression equation for predicting wave resistance of catamarans in calm water can be seen as achievable.

A method for selection of parameters of ship propulsion system fitted with compromise screw propeller

A method for selection of parameters of ship propulsion system fitted with compromise screw propeller This paper concerns an algorithmic method for preliminary selection of parameters of ship propulsion system fitted with fixed screw propeller in the case when the ship's operation is associated with significant changes of waterway depth and width, hull resistance of the ship and its service speed. Mathematical model arguments of the considered design problem are main ship design parameters identified in the preliminary design stage. Structure of the formulated model complies with formal requirements for continuous- discrete mathematical optimization problems. The presented examples of application of the method concern an inland waterways ship fitted with compromise screw propeller optimized in the sense of minimization of fuel consumption for passing a given route distance within a given time. The elaborated method may be especially useful in designing such ships as: coasters, inland waterways ships, tugs, pushers, trawlers, mine sweepers, icebreakers etc.

국내 연안어선의 저항 최소화 선형설계에 관한 연구

In this study the hull form design with minimum resistance of domestic coastal fishing boat using a computer design procedure is carried out. The target boat is G/T 4.99 ton class fishing boat. which is one of the most popular boat in the coastal sea. For the task, the design parameters needed in preliminary stage are selected or determined from the existing boat. which has excellent resistances characteristics. In the EHP estimation during the design procedure, the main objective function is the hull resistance, and the initial hull forms before the optimization are selected from the boats that are in operation now. The EHP values from the hull after optimization process are also compared with those of the original hull to confirm its effect. Also, optimizing is investigated for the hull form to reestimate such factors as stability, laboring environment for the best design. it is expected that the results of this study here can be effectively used to improve the present design status of domestic small fishing boats.

Analysis of hull resistance of pushed barges in shallow water

Analysis of hull resistance of pushed barges in shallow water These authors performed a set of numerical calculations of water flow around pushed barges differing to each other by bow forms. The calculations were executed by means of FLUENT computer software. Turbulent free-surface flow of viscous liquid was considered. In this paper the calculated values of barge hull resistance split into bow, cylindrical and stern part components, have been compared and presented.

Inclusion of Whisker Spray Drag in Performance Prediction Method for High-Speed Planing Hulls

The planing hull performance prediction method published by Savitsky in the October 1964 issue of SNAME's Marine Technology included only the viscous drag and pressure drag components in the bottom area aft of the stagnation line. While discussing the existence of an additional component of viscous drag in the whisker spray region forward of the stagnation line, a method to quantify this drag component was not developed in Savitsky (1964). Earlier studies by Savitsky and Ross (1952) and Savitsky and Neidinger (1954) discuss the potential whisker spray drag component but do not present a complete analytical derivation of its magnitude nor verification of the results by comparison with experimental data. The present study fills this void by developing a method for quantifying the whisker spray contribution to total hull resistance as a function of deadrise angle, trim angle, and speed, and incorporating the results into the SNAME published hull performance prediction method. The analytical results are compared with data from model tests conducted at three separate towing tank facilities and show fairly good agreement with these data. It is shown that for high-speed planing hulls, the whisker spray drag component can be as much as 15% of the total drag. In addition, (1) procedures are provided for the proper location, size, and geometry of spray strips to deflect the whisker spray away from the hull bottom; (2) the aerodynamic drag of the hull cross-sectional area above the waterline is also quantified and included in the final performance prediction method; and (3) the equilibrium trim angle identified in the prediction program (for prismatic hull forms) is, for nonprismatic hulls, related to the trim angle of the v4 buttock line (relative to the level water surface) when measured at the forward edge of the mean wetted length.