Total Ship Resistance Research Articles

Multi-objective hull form optimization utilizing sequential sampling optimization method

With advancements in computer technology, Computational fluid dynamics (CFD) theory provides a numerical tool for evaluating the comprehensive hydrodynamic performance of ships. On this basis, the Simulation-based design (SBD) technology based on the static sampling method (SSM) which is termed as SBD-SSM in this paper is recognized as a hull form optimization method with significant advantages. However, in the SBD-SSM method, the excessive pursuit of the global accuracy of the surrogate model leads to the need for more CFD evaluations. Consequently, this demands the substantiality of computing resources and diminishes optimization efficiency. We apply a novel hull form optimization method based on the Sequential Sampling-based Optimization (SBO) method to address this challenge. Furthermore, to strike an appropriate balance between prediction value and uncertainty while finding optimal solutions, we employ the adaptive sampling method known as Pseudo Expected Improvement Matrix (PEIM). By integrating SBO with PEIM, we introduce the SBO-PEIM optimization method, initially applied through mathematical optimization functions to verify its feasibility in optimization. Subsequently, we apply this method to optimize the total resistance and wake performance of the KCS ship. Our findings demonstrate that the SBO-PEIM method achieves higher prediction accuracy in near-optimal solutions than the SBD-SSM method, enhancing optimization efficiency by at least 17.5%. It validates the efficacy of the SBO-PEIM approach in addressing real-world engineering optimization challenges.

NUMERICAL STUDY OF THE RESISTANCE REDUCTION IN HYBRID MINI-SUBMARINE

Hybrid mini-submarine is a single innovative ship combining the concepts of conventional fast ships, hydrofoils, and submarine with the specific mission of safeguarding national sovereignty. This study was conducted to analyze the reduction of resistance in this mini-submarine by examining the positioning and shape of NACA hydrofoils. The process involved adjusting the positions of NACA hydrofoils and incorporating different configurations. This was indicated by the inclusion of nine speed configuration in the hydrofoil mode, eight in the conventional mode, and five in the submarine mode. Moreover, Computational Fluid Dynamics (CFD) simulation was applied for analysis using the Ansys CFX software. The results showed that the positioning of the NACA hydrofoils at close proximity reduced the resistance. The selection of symmetrical and slender configuration was also observed to optimize the reduction of resistance. Moreover, the combination of position and NACA hydrofoil 0012 produced an average resistance reduction of up to 12.52%. The configured model successfully reduced the total ship resistance and also identified the optimal position and shape configuration for the NACA hydrofoils. These findings provided valuable insights into the components and characteristics of total ship resistance and served as a valuable reference for further research on the development of maritime security technology.

Investigating Fishing Vessel Hydrodynamics by Using EFD and CFD Tools, with Focus on Total Ship Resistance and Its Components

The aim of this work is to gain a better understanding of the hydrodynamics of a typical Argentinian fishing vessel in calm water. It is focused on the evaluation of total ship resistance and its components for different draughts. The 1978 ITTC Power Prediction method is used to predict total ship resistance from experiments carried out at the University of Buenos Aires towing tank. To conduct a more detailed evaluation of the flow around this hull, numerical studies at model scale are carried out with the open-source code OpenFOAM V10 and validated against experimental results. The Reynolds-Averaged Navier–Stokes (RANS) method together with Volume of Fluid (VOF) are used for the numerical procedure. The validated CFD model not only can provide more detailed information about the ship’s hydrodynamics than the EFD results but also allows for the exploration of the improvement in ship power prediction by using combined CFD-EFD methodologies. This work numerically calculates the form factor by using a double-body configuration and discusses the possibility of combining EFD results with this CFD form factor in order to improve total force prediction for this kind of ships.

Computational Investigation into Predicting Total Resistance of Axe-Bow Ship’s in Calm Water

Computational Investigation into Predicting Total Resistance of Axe-Bow Ship’s in Calm Water

The use of a set of artificial neural networks to predict added resistance in head waves at the parametric ship design stage

During the parametric ship design stage, added ship resistance, a component of total ship resistance is analysed to estimate the required propulsive power. The determination of added resistance at this design stage is problematic because the added resistance is calculated using hull shape, which is unknown at this stage. At the parametric design stage, only basic ship parameters, such as length, breadth, draught, block coefficient and Froude number are defined and known. Therefore, the focus of this research was to develop an effective tool to solve this problem. The article presents a set of five Artificial Neural Networks (ANNs) to predict added resistance using basic design parameters. Only model test data was used to train the ANNs in order to obtain reliable results. The research showed that using an ANN set consisting of five ANNs developed using different segregated data resulted in slightly more reliable and accurate estimates than using an individual ANN. To facilitate implementation, the developed ANNs were provided in the form of mathematical functions and open source software code from the Mendeley Data repository. A practical example of how an ANN set can be used to solve a design task was demonstrated in this article.

Numerical Investigation of Length to Beam Ratio Effects on Ship Resistance Using Ranse Method

Abstract The paper discusses the length to beam (L/B) ratio effects on ship resistance at three different Froude numbers using unsteady RANSE simulation. First, the JBC ship model was used as an initial hull form for verification and validation of predicted ship resistance results with measured data, and then the influence of the L/B ratio on ship resistance was carried out. Ship hull forms with different L/B ratios were produced from the initial one by using the Lackenby method. The numerical results obtained show the L/B ratio’s effect on ship resistance. Increases of the L/B ratio led to gradual reduction of the total ship resistance and vice versa. Analysis of the changing of the resistance components indicates that the pressure resistance changes are considerably larger than the frictional one. Finally, the paper analyses the difference in the flow field around the hull of the ship with variation of the L/B ratio to fully understand the physical phenomenon in the change of ship resistance at different L/B parameters.

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Comparative Analysis of Faired-In Bulb and Bulbous Bow Ram Bow's Bulbous Bow Shape On Total Ship Resistance

A General Cargo Ship is a ship that carries various kinds of cargo in the form of goods. The goods transported are usually packaged goods. Using a bulbous bow on the ship's bow is the best alternative. Bulbous bows are installed on ships with high speed to reduce drag, whose nature depends on the function of the block coefficient and Froude number of ships. Ships with particular Cb and Fn can use a Bulbous bow due to considering the advantages of a significant enough resistance reduction, or vice versa. This research is a general cargo ship model with a bulbous bow. They are using the main dimensions of the ship with Length Over All (LOA) 153.45 m, Length Between Perpendicular (LBP) 144.2 m, Length On Load Waterline (LWL) 147.8 m, and Breadth (B) 25.27 m. height (H) 13.5 m, Draft (T) 9.52 m, Speed ​​(V) 14.75 Knots. The magnitude of the resistance and practical power of the ship required to reach a speed of 14.75 knots on a ship with the Faired-in Bulb type obtained from maxsurf 431.9 kN and 4096, 548 HP. For Bulbous bow type Ram Bow ships, the resistance and adequate power obtained are 431.3 kN and 4090,683 Hp. The ship's power using the Bulbous bow Faired-in Bulb is more significant than using the Bulbous bow of the Ram Bow type.

Multi-objective hull form optimization of a SWATH configuration using surrogate models

The present study introduces a surrogate-based multi-objective hull form optimization of a SWATH configuration, enabling optimal hull design compromises between seakeeping performance and ship resistance. A parametric model of a SWATH ship is built, which has variable horizontal torpedoes semi-axis and strut angle of inclination. The displacement is assumed to be constant and is balanced with the vertical semi-axis of torpedoes. The objective seakeeping function is the amplitude of vertical movement on the ship’s gangway, calculated in irregular waves. As the energy dissipation of SWATH ships are mainly generated by viscous effects, these are estimated using empirical formulas and are added to the equations of motion. The ship resistance is computed with a finite volume solver using a RANS model. Three levels of fidelity, having increasing computation costs, are considered to model ship resistance. The first low fidelity level concerns the wetted surface of the hull. Due to their geometry, SWATH ships can be destabilized by the Munk moment and be dynamically unstable, which can lead to instabilities in resistance calculations. The medium-fidelity level then considers a free sinkage and a fixed pitch to ensure the stability of the calculations. The third higher-fidelity level considers stabilizing fins to counterbalance the destabilizing moment. Trim angles of fins are solved to reach moment equilibrium and the fins drag is included in the total ship resistance, which is to be minimized. The multi-objective optimization problem is solved for these three degrees of fidelity. Results differences between fidelity level approaches are also compared, in order to highlight the impact on the optimal hull designs of using a low-fidelity method, with regard to the computational costs.

Design and Cost Multi-Objective Optimization of Small-Scale LNG Carriers using the Value Engineering Approach

Nowadays, liquefied natural gas (LNG) carriers are the main merchant fleets for the transport of natural gas for energy. The large LNG carrier has a more efficient freight cost (approximately 7.8 USD/MMBTU) than a small-scale LNG carrier (SSLNGC; approx. 12,8 USD/MMBTU). Another method must be introduced to make SSLNGCs more cost-efficient. As such, this work conducted an experiment to improve the design of SSLNGCs via design and cost optimization by combining a value engineering approach and multi-objective optimization to decrease hull resistance and lower construction material costs by adjusting the ship dimension ratio. By improving the conceptual design and using semi-integrated numerical simulations, the final result showed improvements in SSLNGCs by decreasing the hull shell area by 1.57% to reduce the construction material needed and total ship resistance by 8.3%.

Experimental and Numerical Investigation into the Effect of the Axe-Bow on the Drag Reduction of a Trimaran Configuration

Using the axe-bow to reduce total ship resistance on monohull ships has been well-known. This advantage has been further applied to a trimaran configuration together with its space-to-length (S/L) ratio differences. The investigation was carried o

Benchmark Study of FINETM/Marine CFD Code for the Calculation of Ship Resistance

Benchmarking can be used to test CFD programs for selecting turbulence models, grid dependency studies, testing different numerical schemes and source codes, and testing different boundary conditions. CFD simulation in this study uses FINE™/Marine 7.2-1 software. The solver process at NUMECA uses the ISIS-CFD flow solver developed by EMN, which uses the incompressible unsteady Reynolds-average Navier stoke equation (RANSE). The solver is based on the finite volume method, and Turbulence models use SST k-ω models. The free surface flow around a model surface ship (DTMB 5415) advancing in calm water under steady conditions is numerically simulated. The geometry of the DTMB 5415 ship hull was provided in igs file format. The 1996 International Towing Tank Conference has recommended the DTMB 5415 combatant as a benchmark case for CFD computations of ship resistance and propulsion. The results compare well with the available experimental data. They allow an understanding of the differences that can be expected from vicious and potential flow methods due to their different mathematical formulations. It is demonstrated that the complementary application of these methods allows good predictions of the total ship resistance.

A reduced order data-driven method for resistance prediction and shape optimization of hull vane

Hull Vane (HV) is an energy-saving appendage introduced by Hull Vane BV company to reduce total ship resistance. Shapewise, HV is a hydrofoil wing transversely fixed at the transom bottom of the hull.In this paper, a data-driven shape optimization method is proposed for HV. To avoid the time-consuming resistance evaluation of designs via a viscous flow solver, we develop a Machine-Learning (ML) based model that predicts the hull's total resistance in the presence of an HV. For this purpose, Principal-Component Analysis (PCA) is first implemented to reduce the dimensionality of the problem, and then the prediction model is trained with the most influential of the Principal Components (PCs). Given that these PCs capture the maximum geometric variance of the original design space, higher accuracy can be achieved at the expense of a few training samples. After the training phase, the model is integrated with an optimizer, which searches in a dimensionally-reduced design space for the optimal design of the HV. The obtained results achieved a 70% dimensionality reduction with the aid PCA and an approximately 98% accuracy for predicting total resistance. Compared with the reference HV, the optimized one reduced the total resistance by 1.2%.

Numerical investigation on the effect of trim on ship resistance by RANSE method

This paper presents the results of study effect of trim on resistance of US Navy Combatant DTMB 5415 model at three different drafts and two Froude numbers by using unsteady RANSE method in conjunction with towing tank tests. Firstly, the numerical results at zero trim condition were verified and validated with experimental data. Then, a series of resistance curves for different trim conditions at different drafts and speeds were performed to produce data source to evaluate the influence of trim on ship resistance. Results denote that the changing tendency of total ship resistance at different trim conditions varying with speed and draft combinations, and the variation of pressure resistance component due to trim is considerably larger than frictional resistance component. Finally, the paper provides details of flow characteristics around ship like wave patterns on free surface, pressure distribution and skin friction on the hull surface, and free water surface in order to explain the physical phenomenon of changing ship resistance at different trim condition.

Achieving Drag Reduction with Hullform Improvement in Different Optimizing Methods

In general, evaluation of ship hydrodynamic efficiency could be produced by an energy-efficient and concentrated cost function. An optimization method with the representation of hull geometry is one of the preliminary design steps that are most appropriate for evaluating hydrodynamic performance. This work presents a comparison of two numerical methods for optimizing the shape of the hull concerning the minimization of total ship resistance in calm water conditions. The optimization method uses a theoretical approach based on Michell's integral and Rankine source methods. The discussion of the two methods emphasizes the comparison of wave resistance, total resistance, wave profiles, and wave contour. The optimized hull form comparison of total resistance between Michell's integral and Rankine source methods decreased by 3.79% and 4.0%, respectively. Comparing wave resistance with decreases by 5.52% based on Michell's integral method and 13.33% by the Rankine source method, the wave profiles generated by these two methods present a fair amount of compatibility. The wave contour illustrates a reasonably straightforward agreement on the optimal hull but are dissimilar on the initial hull

Investigate the Drag Resistance of Antifouling Self-Adhesive Film

Fouling has always been a common issue for ships as fouling drastically increases the surface roughness and ship resistance. The microfiber self-adhesive antifouling film is claimed to be effective up to 5 years and is environmentally friendly. However, there is lack of information about the drag characteristics of the antifouling material. Thus, this project is conducted based on an experimental study to determine the drag characteristics of the surface installed with microfiber self-adhesive antifouling film. The rotor apparatus is used to study the coefficient of friction of the microfiber surface. From the experimental results, a flat plate simulation using ANSYS-Fluent is conducted to further estimate the coefficient of friction up to Reynolds number of 109 and to evaluate the total ship resistance for the Semi-SWATH (fast vessel) and KVLCC (slow trading ships). The results show that the percentage increase in total ship resistance for the KVLCC is about 80%, which is more than the Semi-SWATH of 30%, as frictional resistance has high significance for slow trading ships. The speed drop experienced by the ship model installed with the microfiber antifouling is 2 knots for the KVLCC and 1 knot for the Semi-SWATH if the power remained the same for both models.

Numerical Investigation of Hydrodynamic Behavior of Foil Shaped Zinc Anode for Reducing the Hull Appendages Effect

Appendages are parts of a ship that might increase viscous resistance. The geometric shapes of appendages should be made appropriately in order to generate designs capable of reducing the negative effects of appendages. Therefore, the zinc anodes as sacrificial cathodic protection of ship hull are designed to decrease the amount of drag force that might cause an increase of the total resistance of ship, and it should be installed aligned with the direction of local flow. Regarding the effort to minimize the appendage effect, the foil shaped zinc anode has been proposed in order to improve the performance of drag force on the conventional zinc anode. This research is focused on investigating the hydrodynamic behavior of the foil shaped zinc anode in reducing the effect of hull appendages on ship performance. In this paper, a numerical study has been carried out using the Computational Fluid Dynamics (CFD) method. A comparison of the performance for each variation of foil shaped and conventional zinc anode will be discussed. The results show that foil shaped zinc anodes have generated smaller drag force compared with the conventional ones.

Main engine calculation for ferry Ro-Ro 500 DWT ship using electric propulsion

The development of the current design of electrical system to protect the environment in the world. The purpose of this research is to obtain an electric propulsion system and engine power needed by the Ferry RoRo 500 DWT ship. The analysis begins by calculating the total ship resistance using the software. Next, the calculation of determining the generator power is calculated by a mathematical method. Resistance of 500 DWT RORO ferry at 12 knots 67.7 kN service speed. The increase in ship resistance is affected by the volume of the hull below the waterline. The greater the volume the greater the value resistance ship to get. The power play engine generator required to fight the value of ship resistance at the ferry RORO service speed of 984.49 kW.

An experimental investigation of the impact of retrofitting an underwater stern foil on the resistance and motion

Due to growing concerns about the environment and increasing prices in fuel, Energy Saving Device are becoming more and more important for ship. Hull Vane is an Energy Saving Device that can be retrofitted to the existing vessels or designed to new builds. This paper investigates the effect of retrofit to reduce the ship resistance and to improve the motion response in still water and sea states based on experimental tests. After the Hull Vane with Rhodes St. Gense 32 profile is designed and applied on a model DTMB 5415 hull in 1:51 scale with different attack angles and locations, the various experiments are conducted in the Kelvin Hydrodynamics Laboratory, University of Strathclyde. The model test shows Hull Vane can reduce and smoothen the stern wake markedly and significantly reduce the total resistance of ship. Pitch and heave motion of ship can be reduced by Hull Vane, because of which the comfort and operability of ship can be improved.