Hull Spacing Research Articles

Design for Copying Grouser and Bionic Convex Hull Patterns on Track Surfaces of Crawler Combine Harvesters

In the rainy season, which often has uncertain rainfall, crawler combine harvesters have difficulty traversing wet and soft rice fields. A large amount of clay is often accumulated on the track surfaces, resulting in frequent slipping and sinking, which greatly affects the operational performance and harvesting efficiency of crawler combine harvesters. To address this issue, this paper proposes a high-traction track grouser based on the structure of an ostrich’s foot sole. First, a traction force mathematical model is constructed to analyze the interaction between a track grouser and wet and soft rice fields, and parameter optimization is conducted. Then, the bionic information of a dung beetle’s non-smooth body surface is extracted, and the surface of the track is designed with biomimetic convex hull patterns based on the geometric similarity principle and adhesive experiments. Finally, the analysis results indicate that the optimized track grouser significantly improved the traction of the track in wet and soft rice fields. For the track plate with a bionic desorption convex hull pattern, a convex hull diameter of 6 mm, convex hull spacing of 8.25 mm, and convex hull height of 3 mm led to good adhesion reduction and desorption effects in wet and soft soil.

Characterizations of $L$-concavities and $L$-convexities via derived relations

This paper is to characterize $L$-concavities and $L$-convexities via some derived forms of relations and operators. Specifically, notions of $L$-concave derived internal relation space and $L$-concave derived hull space are introduced. It is proved that the category of $L$-concave derived internal relation spaces and the category of $L$-concave derived hull spaces are isomorphic to the category of $L$-concave spaces. Also, notions of $L$-convex derived enclosed relation space and $L$-convex derived hull space are introduced. It is proved that the category of $L$-convex derived enclosed relation spaces and the category of $L$-convex derived hull spaces are isomorphic to the category of $L$-convex spaces.

Multi-objective optimization for an autonomous unmoored offshore wind energy system substructure

Autonomous unmoored floating offshore wind energy systems are an unconventional but promising technological solution to access the greatest wind resource in deep waters far offshore. This study proposes a trimaran substructure for such an autonomous unmoored system producing green hydrogen, named the Wind Trawler, which serves as both a power generation system and an energy transport vessel. Using a multi-objective optimization approach founded on the non-dominated sorting genetic algorithm (NSGA-II), the principal geometric parameters of the trimaran substructure hulls (primary hull and two symmetrically-spaced equivalent outriggers) are optimized with respect to minimization of system steel mass and minimization of the average unit power consumption per unit generation. Three discrete cases of maximum allowable overturning angle in heel (5°, 10°, and 15°) are considered. The results show that outriggers provide the majority of stability while the primary hull is most significant in influencing power performance and steel mass. Constraints of system stability and minimum outrigger draught induce a tradeoff between the outrigger waterplane area and the outrigger spacing from the primary hull. Steel mass minimization correlates with small hull spacing, shallow hull draughts, and greater outrigger proportion of the total mass. Large hull spacing, deep hull draughts, and reduced outrigger size maximizes the proportion of total mass in the streamlined primary hull, and therefore minimizes power consumption relative to generation. The effect of increasing maximum allowable overturning angle is that outrigger draught is much deeper at equal spacing from the primary hull. This induces a much greater outrigger mass and less efficient system overall, which drives up power consumption relative to generation. Ultimately, the optimum Wind Trawler substructures yield steel mass results that promise to compete with that of conventional systems, especially considering the elimination of mooring and electrical transmission subsystems. Metrics of power consumption relative to generation are unique to this type of unmoored system and thus need to be translated to conventional units of net energy production. This can be performed by considering the varying expected duration and trajectories of each operational mode.

Design and Modeling of Catamaran Flat Plate Ship with Bottom Glass Concept to Improve Tourism Underwater in Bangsring Banyuwangi

The beauty of the beach and underwater of Bangsring beach make this beach one of the leading destinations in Banyuwangi Regency. However, until today how to enjoy the beauty of the underwater can exclusively be done by diving or snorkeling, which is quite troublesome and exhausting, especially for tourists who want to enjoy and looking entertainment in a simpler way. So the concept of bottom-glass in this design is offered as a problem solving in this study, while the concept of flat plate and flat-bottom is carried out to efficiently time and cost of shipbuilding, because with this flat plate concept, there is no rolling and other material bending process. The design of the main dimensions is made based on owner requirements are obtained based on field study and literature studies, then the main parameters are obtained (LOA = 12 m, total B = 5.6 m, B each hull = 0.94 m, hull spacing = 3.72 m, T = 0.7 m, H = 1.85 m, Vs = 10 knots). To maximize the design, 4 ship models were designed with these primary parameters, based on the analysis of resistance using Maxsurf Resistance, model 4 with a maximum resistance of 4.3 kN was chosen which tend to be more effective compared with the designs of model 1, model 2, and model 3 which has a maximum resistance of 8 kN, 4.9 kN and 5.3 kN. The results of the stability analysis carried out in this design with the load case 100%, 80%, 60%, 40%, and 20%, has met all requirements for intact stability IMO MSC.36 (63) for HSC multihull Annex 7.

O razvoju oblika trupa katamarana za brod za preradu ribe kao podršci nacionalnom ribarstvu u Indoneziji

Several advantages of multihull, such as catamaran, have been extensively discussed in the previous research. Therefore, this research focuses on developing a catamaran hull form for the fish processing vessel hull. The initial stage is determining the principal dimension and exploring the configurations of catamaran hull forms. The existing high-speed craft catamarans have been adopted to determine the parent model main dimensions using a linear regression equation model. Otherwise, the catamarans single demi-hull geometry was developed by converting and modifying the parent model hull form with enlarging the hull displacement to achieve the deadweight capacity and service speed requirements. The demi-hull spacing configuration with s/L 0.17, s/L 0.20, s/L 0.30, and s/L 0.40 on the resistance characteristics, intact stability, and sea-keeping behaviour were also explored. Furthermore, the comparisons with the previously proposed monohull were presented. Regarding the hull resistance performance, the analysis indicated that the catamaran hull form had better total resistance characteristics than the monohull on the service speed over 23 knots. In the case of intact stability, the analysis results presented that the catamaran hull form has better intact stability characteristics than the monohull. The dynamic stability of the catamarans also gave better dynamic stability at the heeling angle below 41.57°. Otherwise, the catamarans with s/L 0.17 and s/L 0.20 have lower dynamic stability than the monohull at the heeling angle larger than 41.57° and 58.03°, respectively. In the sea-keeping performance, the catamaran hull has shown an excellent rolling motion required for the offshore environment loading/unloading process. The large demi hull spacing of the catamarans hull can reduce the effect of the wave creating load on the roll motion response at the Beam Sea.

Study on Anti-Friction Mechanism of Canna-Leaf Biomimetic Micro-Textured Fruit Tree

Fruit tree pruning is an important part of orchard management. In this paper, the force on and the wear of the pruner in the pruning process were studied with a canna-leaf biomimetic convex-hull pruner. The pruner was formed by laser etching technology. The influence of laser power and scanning speed on the geometric dimensioning of the micro texture was analyzed. The shear force calculation model was built to obtain the positive pressure load during the pruning process, while the model accuracy was verified in the static pressure shear test, and the wear mechanism was analyzed in the wear test. The real pruning process was simulated to compare the worn areas of the textured and non-textured pruners and the number of cuts in fixed wear condition, for proving the wear reduction characteristics of the micro-textured pruner. The results show that: the optimal forming parameters are 70 W 1.6 mm/s (10 mm-diameter branches), 80 W 2.4 mm/s (15 mm-diameter branches) and 80 W 1.6 mm/s (20 mm-diameter branches), and the convex hull spacing is 300 μm. Laser power affects the depth and width of the texture, while scanning speed affects the depth of the texture. The positive pressure on the pruner is proportional to the modulus of elasticity, moment of inertia, cut depth, and bevel angle, whilst it is inversely proportional to the distance from the fixed point of the blade to the positive pressure. The wear test shows that the anti-wear performance of the textured pruner is not obvious at the load of 300 g, while the anti-wear performance of the textured pruner is significant at the loads of 1000 g and 2000 g. The wear mechanism shifts from the abrasive wear in the early stage to more complex oxidative wear and adhesive wear. The actual shear test shows that the textured pruner wears less than the non-textured pruner and enters the stable shear faster.

Fuzzy generalized convex spaces

On completely distributive lattice, the notion of fuzzy generalized convex space is introduced. It can be characterized by many means including fuzzy generalized hull space, fuzzy generalized restricted hull space, fuzzy generalized convexly enclosed relation space and fuzzy generalized derived hull space.

Research and Design of Wind and Solar Complementary Electric Sightseeing Boat

To solve the problem of rapid development of domestic water tourism and water pollution in scenic waters, windsurfing technology and solar photovoltaic technology are applied to small and medium-sized sightseeing cruise ships. While optimizing the hull design and component coordination, the application of automatic control technology further improves the utilization efficiency of wind and light energy, and achieves the adaptation of the sail angle of attack and the efficient coupling of the two energies. The ship mainly uses the natural resources of solar energy and wind energy. It will not burn fossil fuels during the ship’s travel, thus reducing the emission of toxic and harmful substances, which has positive significance for environmental protection. In short, the solar wind-assisted power generation ship studied in this project has remarkable features such as zero emission, high degree of intelligence, significant wind-assisted effect, high efficiency of light energy utilization, and low hull space occupation. Compared with the ordinary lake area cruise ship, the energy-saving and emission reduction effect of the power generation ship is very obvious[1].

Influence of the Tensor Product Model Representation of qLPV Models on the Feasibility of Linear Matrix Inequality Based Stability Analysis

AbstractThe paper investigates and proves the statement, that the convex hull of the polytopic tensor product (TP) model representation influences the feasibility of linear matrix inequality (LMI) based stability analysis methods. The proof is based on a complex stability analysis example of a given quasi linear parameter varying (qLPV) state‐space model. Specifically, the three degree of freedom (3‐DoF) aeroelastic wing section model including Stribeck friction is used as the tool for the example model. The proof is achieved by utilizing TP model transformation and LMI based tools. As a first step, numerous TP model type control solutions holding different convex hulls are systematically derived of the qLPV model via LMI based control design methods. As a second step, each control solution is further equivalently transformed for different TP model representations holding different convex hulls. Finally, the stability of all solutions over all TP model representations are checked via LMI based stability analysis methods. As a result of the two steps, a two dimensional (2D) convex hull space is attained for the 3‐DoF aeroelastic wing section model. The two dimensions are denoted by the LMI based control design and the LMI based stability analysis for different convex hulls. Based on the numerical results, a detailed, comprehensive analysis is provided. The paper as a novelty proves the statement, that the polytopic TP model representation of a given control solution strongly influences the feasibility of LMI based stability analysis methods.

Hydrodynamics of single-deadrise hulls and their catamaran configurations

Asymmetric planing hulls are often used on high-speed catamarans. In this study, a linearized potential-flow method is applied for modeling steady hydrodynamics of single asymmetric hulls and their catamaran setups. Numerical results are validated with available experimental data and empirical correlations. Parametric calculation results are presented for the lift coefficient and the center of pressure for variable hull geometry, spacings, and speed regimes. The lift coefficient is found to increase at smaller hull spacings and decrease at higher Froude numbers and higher deadrise angles.

Ship resistance of quadramaran with various hull position configurations

Multihull ships are widely used for sea transportation, and those with four hulls are known as quadramarans. Hull position configurations of a quadramaran include the diamond, tetra, and slice. In general, multihull vessels traveling at high speeds have better hydrodynamic efficiency than monohull ships. This study aims to identify possible effects of various quadramaran hull position configurations on ship resistance for hull dimensions of 2 m length, 0.21 m breadth, and 0.045 m thickness. We conducted a towing test in which we varied the hull spacing and speed at Fr values between 0.08 and 0.62 and measured the total resistance using a load cell transducer. The experimental results reveal that the lowest total resistance was achieved with a diamond quadramaran configuration at Fr = 0.1-0.6 and an effective interference factor of up to 0.35 with S/L = 3/10 and R/L = 1/2 at Fr = 0.62.

Observations and computations of narrow Kelvin ship wakes

Computations of far-field ship waves, based on linear potential flow theory and the Hogner approximation, are reported for monohull ships and catamarans. Specifically, far-field ship waves are computed for six monohull ships at four Froude numbers F≡V/gL=0.58, 0.68, 0.86, 1.58 and for six catamarans with nondimensional hull spacing s≡S/L=0.25 at two Froude numbers Fs≡V/gS=1 and 2.5. Here, g is the gravitational acceleration, V and L denote the ship speed and length, and S is the separation distance between the twin hulls of a catamaran. The computations show that, although the amplitudes of the waves created by a ship are strongly influenced by the shape of the ship hull, as well known, the ray angles where the largest waves are found are only weakly influenced by the hull shape and indeed are mostly a kinematic feature of the flow around a ship hull. An important practical consequence of this flow feature is that the apparent wake angle of general monohull ships or catamarans (with arbitrarily-shaped hulls) can be estimated, without computations, by means of simple analytical relations; these relations, obtained elsewhere via parametric computations, are given here. Moreover, the influence of the two parameters Fs and s that largely determine the ray angles of the dominant waves created by a catamaran is illustrated via computations for three catamarans with hull spacings s=0.2, 0.35, 0.5 at four Froude numbers Fs=1, 1.5, 2, 2.5. These computations confirm that the largest waves created by wide and/or fast catamarans are found at ray angles that only depend on Fs (i.e. that do not depend on the hull spacing s) in agreement with an elementary analysis of lateral interference between the dominant waves created by the bows (or sterns) of the twin hulls of a catamaran. The dominant-waves ray angles predicted by the theory of wave-interference effects for monohull ships and catamarans are also compared with the observations of narrow Kelvin ship wakes reported by Rabaud and Moisy, and found to be consistent with these observations.

Interference effects on the Kelvin wake of a catamaran represented via a hull-surface distribution of sources

Wave-interference effects on the far-field waves created by a catamaran, with identical twin hulls of length L at a lateral separation distance S, that advances at constant speed V along a straight path in calm water of large depth are considered. Systematic computations are performed for 125 Froude numbers Fs≡V/gS (where g denotes the acceleration of gravity) within the range 0.4≤Fs≤3.5, 25 hull spacings s≡S/L within the range 0.2≤s≤0.8, and seven simple mathematically-defined hulls that correspond to a broad range of main hull-shape parameters (beam/length, draft/length, beam/draft, waterline entrance angle), i.e. for 21,875 distinct cases in all. The two dominant wake angles ψi and ψo that correspond to the ray angles ψ=±ψi and ψ=±ψo where the largest divergent waves are found within the Kelvin wake −ψK≤ψ≤ψK with ψK≈19∘28′ are determined numerically via a realistic yet practical method. This practical method, used previously for monohull ships, is based on the numerical determination of the two major peaks of the amplitude function in the Fourier-Kochin representation of far-field ship waves, evaluated via the Hogner approximation and the stationary-phase approximation. The computations show that the hull shape only has a relatively small influence on the wake angles ψi and ψo associated with the dominant waves. A useful practical consequence of this numerical finding is that the two wake angles ψi and ψo can be estimated, without computations, for general catamarans in terms of the Froude number Fs and the hull spacing s via simple analytical approximations, obtained here via parametric computations. The computations also show that lateral interference effects are dominant if s and/or Fs are sufficiently large, i.e. for ‘wide’ and/or ‘fast’ catamarans. Moreover, the computations reported here for catamarans represented via hull-surface distributions of sources show that the basic two-point wavemaker model of interference between the waves created by the twin bows of a catamaran is realistic for wide and/or fast catamarans. However, wave-interference effects are more complicated if both s and Fs are small, i.e. for ‘narrow slow’ catamarans. The numerical analyses of dominant waves considered earlier for monohull ships and here for catamarans show that, although the amplitudes of the waves created by a ship are strongly influenced by the shape of the ship hull, the ray angles where the largest waves are found are mostly a kinematic feature that is only weakly influenced by the hull shape and the related wave amplitude.

Numerical analysis of the interference effects on resistance, sinkage and trim of a fast catamaran

The purpose of the present paper is the numerical investigation of the interference phenomena between the waves generated by the individual hulls of a catamaran. The study focuses on the effects of both Froude number and demi-hull separation distance on resistance and on sinkage and trim. The numerical simulations are carried out by the URANS solver CFDShip-Iowa V.4 and, to assess the capability for prediction of resistance, sinkage and trim of the URANS code for twin-hull configuration vessels, a verification and validation study is performed for global as well as for local variables. A very good agreement between the numerical results and the experimental data is obtained, and the validation study demonstrates the high level of accuracy of the current predictions, which are used to have a better insight into the interference phenomena. In accordance with the experiments, within Fr = 0.45–0.65, the catamaran has a significantly higher resistance coefficient compared to the mono-hull; furthermore, the C T value increases with decreasing the separation distance between the twin hulls. On the contrary, at Fr lower than 0.45 and at Fr higher than 0.65, the effects of hull spacing on resistance as well as on sinkage and trim can be neglected. The flow field characteristics, wave pattern, wave cuts and pressure distributions are analyzed through the CFD analysis. Finally, the effects of the Reynolds number on resistance are also investigated and results show a small decrease in interference with increasing the Reynolds number.

Experimental investigation of interference effects for high-speed catamarans

We have performed an experimental investigation aimed at assessing the relevance of hull interference effects on the total resistance of a catamaran model advancing in calm water. To this purpose, drag and attitude measurements have been carried out for several values of the hull separation, as well as for the monohull, at changing the Froude number in the range 0.1–0.8. Data concerning the two-dimensional wave field around the models have also been collected. Our results indicate that, except for a narrow range of conditions where favorable interference is observed, the interaction between the catamaran hulls usually results in a marked increase of the total resistance as compared to the monohull case. This penalization can be as large as 30% for the narrowest hull spacing at Fr≈0.5. At larger hull spacings, the effect is attenuated and occurs at smaller Froude numbers. Interference effects are less evident both in the small and large Froude number range, namely when Fr<0.3 and Fr>0.7 respectively. Insight into the mechanisms underlying this behavior is obtained by examining the relational dependence between the resistance variation and the data concerning attitude of the vessel and wave-field elevation.

Optimal module layout for a generic offshore LNG liquefaction process of LNG-FPSO

Constraints related to offshore projects such as liquefied natural gas floating, production, storage, and offloading (LNG-FPSO) have been considered more important than those in onshore areas because topside process systems are located on the limited hull space. Therefore, the layout of the LNG-FPSO topside equipment shall be designed as multi-deck instead of single-deck, and this layout shall be optimised in order to reduce the area occupied by the topside equipment at the front-end engineering design stage. In this study, an optimal module layout for a generic offshore LNG liquefaction process system is derived, considering the deck penetration of long-length equipment across several decks. By considering the above, we formulate a mathematical model, which consists of 1652 unknowns, 1624 equality constraints, and 1048 inequality constraints. This mathematical model can be regarded as the optimisation problem, in which the number of unknowns is larger than the total number of equality constraints and given variables. To obtain the optimal layout, the minimisation of the total layout cost was defined as an objective function. The optimal module layout was then obtained using a mixed integer nonlinear programming.

Reducing the cost of ballast tank corrosion: an economic modeling approach

One of the most relevant problems in ship construction and maintenance nowadays concerns the corrosion in the double hull space ballast tanks of modern merchant vessels. On the one hand, there is a general consensus that the economic life span of such a vessel depends primarily upon the corrosion state of its ballast tanks, while on the other hand, the position of these tanks, squeezed between the outer hull and the loading tanks, makes routine inspection and maintenance almost impossible.Today, ship's ballast tanks are usually constructed in grade A steel and protected with a standard epoxy coating, backed up with sacrificial zinc anodes. Such a construction has been applied without significant alterations for many years. However, the objective of this economic study is to compare this construction method with some feasible alternatives. The considered alternatives are: (1) an increase of the scantlings, eliminating the necessity to replace corroded steel but diminishing the cargo carrying capacity of the ship, (2) application of the novel and more durable TSCF25 coating (3), the use of corrosion resistant steel in ship construction or (4) a standard PSPC15 coating combined with lifetime lasting aluminum sacrificial anodes. After running each alternative through a cost model including an extensive sensitivity analysis, it is concluded that the durable coating and the use of lifetime lasting aluminum anodes are bound to improve the actual basic tank concept. Corrosion resistant steel becomes attractive depending upon the evolution of the international steel market.

Two-dimensional modeling of stepped planing hulls with open and pressurized air cavities

A method of hydrodynamic discrete sources is applied for two-dimensional modeling of stepped planing surfaces. The water surface deformations, wetted hull lengths, and pressure distribution are calculated at given hull attitude and Froude number. Pressurized air cavities that improve hydrodynamic performance can also be modeled with the current method. Presented results include validation examples, parametric calculations of a single-step hull, effect of trim tabs, and performance of an infinite series of periodic stepped surfaces. It is shown that transverse steps can lead to higher lift-drag ratio, although at reduced lift capability, in comparison with a stepless hull. Performance of a multi-step configuration is sensitive to the wave pattern between hulls, which depends on Froude number and relative hull spacing.

Wave-Induced Motions of Gas Cat: A Novel Catamaran for Gas Processing and Offloading

The preliminary development of the novel concept of using a large catamaran, known as Gas Cat, as a floating natural gas processing and offloading facility is outlined. The proposed system is based on two ship-shaped hulls joined by a spanning superstructure. For off-loading purposes a carrier may dock with or be tethered to the catamaran. A concept design has been developed based on two retrofitted VLCCs allowing for the processing and storage of 1 × 106 bbls of condensate and approximately 240,000 m3 of liquefied natural gas. A key aspect of the development of this concept is the accurate estimation of the motions of the catamaran in a variety of operational scenarios. Model experiments were conducted in the Model Test Basin of the Australian Maritime College using a 1:78 scale model of two full-form hulls converted into a catamaran configuration. Tests were conducted in head, beam, and oblique seas for two hull spacings and a range of wave heights. The experimental results show that for the range of wave conditions tested good linearity of the motions can be expected with respect to wave height. An increase in demihull separation was found to significantly reduce the sway, heave, and roll motions in beam seas. However, a change in demihull separation had little influence on the motions in oblique seas. A change in heading angle from head seas to beam seas significantly increased the sway, heave, and roll motions while reducing pitch motions. Bow quartering seas were seen to be the worst heading angle for yaw. The results from the experiments allowed the expected motions of the Gas Cat to be determined in extreme weather conditions.

Experimental investigation into wave-induced design loads on a large moored catamaran

A new concept uses a large catamaran, Gas Cat, as a floating natural gas processing, storage and offloading facility. The concept design of the vessel is based on two retrofitted very large crude carriers allowing for the processing and storage of 1 million bbls of condensate and approximately 240,000 m3 of liquid natural gas. Key to the development of this concept is the accurate estimation of the wave-induced cross-demi-hull loads experienced by the catamaran in a variety of operational scenarios. Model experiments were conducted in the model test basin of the Australian Maritime College using a 1:78 scale model of two full-form hulls, converted into a catamaran configuration, to measure the wave-induced forces and moments. Tests were conducted in head, beam and oblique seas for two hull spacings and a range of wave heights. The experimental results show that for the range of wave conditions tested, good linearity of the forces and moments can be expected with respect to wave height. This allows the results to be used to determine expected loads for a range of wave conditions. Changes in demi-hull separation were found to have little influence on the measured cross-demi-hull loads. Forces and moments were the least for the head sea condition; therefore, in order to minimise the wave-induced loads on the vessel, it is recommended that it be allowed to weathervane with the prevailing swell direction. The forces and moments which may be expected in Timor Sea 10,000-year return storm conditions have been estimated based on the model results. These provide valuable data for the preliminary design of an appropriate structural configuration for the vessel.