Optimization of Resistance Performance for Inland Twin-Skeg Ship Based on CFD and Surrogate Modeling

2021 ◽  
Author(s):  
Helei Yan ◽  
Baiwei Feng ◽  
Qiang Zheng ◽  
Heng Li
Keyword(s):  
Surface Deformation ◽  
Rapid Development ◽  
Hydrodynamic Performance ◽  
Deformation Method ◽  
Hull Form ◽  
Reduction Methods ◽  
Energy Efficiency Design Index ◽  
Bulbous Bow ◽  
Longitudinal Position ◽  
Resistance Performance

Abstract With the increasingly serious energy problems in the world and the introduction of Energy Efficiency Design Index (EEDI) by International Maritime Organization (IMO), the application of energy conservation and emission reduction methods in ships has been paid more and more attention. With the rapid development of computational fluid dynamics (CFD), ship hull form optimization based on CFD has become a hot topic, Inland twin-skeg ship has a relatively complicated hull form, and it has strong theoretical significance and engineering practical value to carry out hull form optimization research on this type of ship. Based on the multidisciplinary comprehensive optimization platform for ship hydrodynamic performance (SHIPMDO-WUT) self-developed by Wuhan University of Technology research institute of multidisciplinary design optimization of ship performance, this paper using the hull surface deformation method based on the radial basis function interpolation to change the hull form and skeg shape of a 3000t inland twin-skeg oil tanker with invisible bulbous bow. And the high-precision CFD calculation software SHIPFLOW was used to predict the resistance of this ship. Finally, combined with CFD surrogate model and optimization algorithm, the ship with excellent resistance performance is obtained and ensuring the ship displacement and the longitudinal position of the buoyancy center are within the range of certain constraints. At last, the optimization results were verified numerically.

Hydrodynamic Optimization of a Wedge Hull

2015 ◽  
Author(s):  
Lijue Wang ◽  
Fuxin Huang ◽  
Chi Yang ◽  
Raju Datla
Keyword(s):  
Hydrodynamic Performance ◽  
Surface Mesh ◽  
Nurbs Surface ◽  
Bottom Edge ◽  
Hull Form ◽  
Entrance Angle ◽  
Total Drag ◽  
Rounded Corner ◽  
Bulbous Bow ◽  
Hydrodynamic Optimization

A novel wedge-shaped hull form is optimized for reduced drag using a further developed practical hydrodynamic optimization tool. The hull features a sharp entrance angle, rectilinear sides, sharp bottom edges, a triangular waterplane and a linear aftward taper from a deep bow to a shallow transom. The optimization involves two modifications of the hull form, one is to smooth out the sharp bottom edge with a rounded corner and the other is to generate a bulbous bow. In order to perform the hydrodynamic optimization of the hull, a Non-Uniform Rational BSpline (NURBS)-based hull surface modification tool, a NURBS surface mesh generator, a surrogate model and an evolutionary optimization solver are developed and integrated into the practical hydrodynamic optimization tool. The hydrodynamic performances, i.e., the total drag and the flow field near the obtained hull bodies are assessed and compared with the original wedge hull using numerical simulations. Results showed that rounding the sharp edge of the wedge hull can reduce the total drag by alleviating the flow separations around the hull body. The wedge hull with rounded bottom edge and optimized bulbous bow can achieve larger drag reduction and the flow separations are almost eliminated. The total drag of the optimal hull is compared with an earlier-optimized wedge hull that has a different type of bulbous bow, whose hydrodynamic performance has been validated by model tests.

A Study on Resistance Performance for Various Trim Conditions and Bulb Shapes on a Container Ship Under Slow Steaming

2015 ◽  
Author(s):  
Hyun-Suk Park ◽  
Dae-Won Seo ◽  
Ki-Min Han ◽  
Dae-Heon Kim ◽  
Tae-Bum Ha
Keyword(s):  
Form Factor ◽  
Prediction Method ◽  
Experimental Result ◽  
Operating Efficiency ◽  
Container Ship ◽  
Power Prediction ◽  
Hull Form ◽  
Slow Steaming ◽  
Bulbous Bow ◽  
Resistance Performance

Hull form had been unavoidably optimized for a single speed condition, normally a contract speed at design draft in the past many years due to various reasons such as limited design period, less advanced data processing capacity of a computer and so on. For this reason, for maximizing present ship’s operating efficiency, additional analysis relevant to resistance performance for slow steaming condition is newly required since the original hull form for this study also was developed about 10 years ago. In this paper, the resistance performances corresponding to various trim conditions are investigated not only for ship’s original contract speed (Fn: 0.255) but for slow speed (Fn: 0.163∼0.183) by slow steaming. Through this study, it can be accomplished to identify the optimum trim condition meeting the objectives of ship operator. Further to the trim optimization, bulbous bow shape renovation was carried out for off design condition (Fn:0.173) and both of CFD results, one is from an original bulbous bow shape, the other is from a reformed bulbous bow shape by us, are compared each other to identify the concrete reason for the improvement of resistance performance. Commercial CFD code of the STAR-CCM+ was utilized to evaluate the ship’s resistance performance on a 6,800 TEU container ship. To validate of the effectiveness of Starccm+, the experimental result of the subject hull form is referred and compared with the result from STAR-CCM+. Form factor prediction method by CFD that is based on extracting form pressure resistance component from difference of two different computational domains is presented. In this study, it is investigated to compare the form factor calculated by CFD with the model test result. This approach allows hull form designer to calculate a form factor corresponding ship’s trim variation by CFD in order to separate total resistance into wave making resistance and viscous resistance for more accurate effective power prediction.

scholarly journals OPTIMISATION OF HULL FORM OF OCEAN-GOING TRAWLER

Brodogradnja ◽  
2021 ◽  
Vol 72 (4) ◽  
pp. 33-46
Author(s):  
Cheng Zhao ◽  
◽  
Wei Wang ◽  
Panpan Jia ◽  
Yonghe Xie ◽  
...  
Keyword(s):  
Computer Aided Design ◽  
Free Form ◽  
Deformation Method ◽  
Nsga Ii ◽  
Hull Form ◽  
Free Form Deformation ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd ◽  
Bulbous Bow ◽  
Aided Design

This paper proposes a method for optimising the hull form of ocean-going trawlers to decrease resistance and consequently reduce the energy consumption. The entire optimisation process was managed by the integration of computer-aided design and computational fluid dynamics (CFD) in the CAESES software. Resistance was simulated using the CFD solver and STAR-CCM+. The ocean-going trawler was investigated under two main navigation conditions: trawling and design. Under the trawling condition, the main hull of the trawler was modified using the Lackenby method and optimised by NSGA-II algorithm and Sobol + Tsearch algorithm. Under the design condition, the bulbous bow was changed using the free-form deformation method, and the trawler was optimised by NSGA-Ⅱ. The best hull form is obtained by comparing the ship resistance under various design schemes. Towing experiments were conducted to measure the navigation resistance of trawlers before and after optimisation, thus verifying the reliability of the optimisation results. The results show that the proposed optimisation method can effectively reduce the resistance of trawlers under the two navigation conditions.

scholarly journals Hydrodynamic study of the influence of bulbous bow design for an Offshore Patrol Vessel using Computational Fluid Dynamics

2018 ◽  
Vol 11 (22) ◽  
pp. 29
Author(s):  
Luis Leal ◽  
Edison Flores ◽  
David Fuentes ◽  
Bharat Verma
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Hydrodynamic Performance ◽  
Design Stage ◽  
Hull Form ◽  
Preliminary Design Stage ◽  
Hydrodynamic Study ◽  
Resistance Curves ◽  
Design Speed ◽  
Bulbous Bow

The resistance of a ship is of vital importance in giving greater viability to the development of a design project, since at lower ship resistance, the power demand to achieve a desired design speed will be lower which will reduce the amount of power to be installed in the ship resulting in lower fuel consumption. The use of computational fluid dynamics to analyze and optimize hull form and its appendages permits the hydrodynamic performance of the ship to be improved from the early design stages, allowing improvements to the hull shape and appendages. This paper shows a qualitative analysis which was performed to reduce the resistance of the OPVMKII (Second Generation Offshore Patrol Vessel) in its preliminary design stage by means of designing and integrating three types of bulbous bow with the ship´s hull and analyzing the resistance curves obtained using computational fluid dynamics.

scholarly journals Test research on the resistance performance of high-speed trimaran planing hull

2013 ◽  
Vol 20 (4) ◽  
pp. 45-51 ◽  
Author(s):  
Weijia Ma ◽  
Huawei Sun ◽  
Jin Zou ◽  
Heng Yang
Keyword(s):  
High Speed ◽  
Model Tests ◽  
Hydrodynamic Performance ◽  
Test Results ◽  
Longitudinal Stability ◽  
Hull Form ◽  
Ship Model ◽  
Resistance Performance ◽  
Resistance Peak ◽  
Aerodynamic Lift

ABSTRACT In order to identify high-speed navigation ability of trimaran planing hull, as well as investigate the characteristics of its resistance and hull form, ship model tests were conducted to measure resistance, trim and heaving under different displacements and gravity centre locations. The test results were then used to study the influence of spray strips on resistance and sea-keeping qualities. Moreover, different planing surfaces were compared in the model tests which helped to look into influence of steps on hull resistance and its moving position. Also, the resistance features of monohull and trimaran planing hulls, both with and without steps, were compared to each other. From the tests it can be concluded that: the two auxiliary side hulls increase aerodynamic lift at high-speed motion, which improves the hydrodynamic performance; the trimaran planing hull has also excellent longitudinal stability and low wave-making action; when Fr∇ > 8, its motion is still stable and two distinct resistance peaks and two changes of sailing state (the second change is smaller) appear; spray strips are favourable for sea-keeping qualities at high speed. The change trends before the second resistance peak as to the resistance and sailing behaviour of trimaran planing hull without steps are the same as for monohull planing hull without steps. but when steps in both hulls exist the change trends are different; more specifically: trimaran planing hull with steps has only one resistance peak and its resistance increases along with its speed increasing, and the resistance is improved at the increasing speed as the number of steps increases.

Construction and Reduction Methods of Web Spam Identification Index System

2019 ◽  
Vol 12 (3) ◽  
pp. 202-211
Author(s):  
Yuancheng Li ◽  
Rong Huang ◽  
Xiangqian Nie
Keyword(s):  
Index System ◽  
Rapid Development ◽  
Recognition Rate ◽  
Computing Power ◽  
Detection Model ◽  
Web Spam ◽  
Reduction Methods ◽  
Massive Scale ◽  
The Index System ◽  
The Web

Background: With the rapid development of the Internet, the number of web spam has increased dramatically in recent years, which has wasted search engine storage and computing power on a massive scale. To identify the web spam effectively, the content features, link features, hidden features and quality features of web page are integrated to establish the corresponding web spam identification index system. However, the index system is highly correlation dimension. Methods: An improved method of autoencoder named stacked autoencoder neural network (SAE) is used to realize the reduction of the web spam identification index system. Results: The experiment results show that our method could reduce effectively the index of web spam and significantly improves the recognition rate in the following work. Conclusion: An autoencoder based web spam indexes reduction method is proposed in this paper. The experimental results show that it greatly reduces the temporal and spatial complexity of the future web spam detection model.

An Integrated Ship Re-Design/Modification Strategy

2019 ◽  
Vol 161 (A1) ◽  
Keyword(s):  
Computer Aided Design ◽  
Modular Design ◽  
Ship Hull ◽  
Cfd Model ◽  
Hull Form ◽  
Design Modification ◽  
Technical Parameters ◽  
Computational Fluid Dynamics Cfd ◽  
Bulbous Bow ◽  
Aided Design

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.

Sample Selection Method for Ship Resistance Performance Optimization Based on Approximated Model

2016 ◽  
Vol 60 (01) ◽  
pp. 1-13
Author(s):  
Haichao Chang ◽  
Xide Cheng ◽  
Zuyuan Liu ◽  
Baiwei Feng ◽  
Chengsheng Zhan
Keyword(s):  
Performance Optimization ◽  
Model Building ◽  
Interpolation Method ◽  
Uniform Design ◽  
Sample Selection ◽  
Selection Method ◽  
Ocean Engineering ◽  
Hull Form ◽  
Ship Resistance ◽  
Resistance Performance

Approximated model instead of computational fluid dynamics tool is utilized for performance analysis in hull form optimization process, which can save time significantly. Sample selection is the central issue of approximated model building. This article focuses on the sample selection method and the application of approximated model in hull form optimization. Latin hypercube sampling and uniform design are compared. The uniform design based on genetic algorithm approach is proposed. The radial basis function interpolation method is used for hull surface automatic modification. An approximated model using a neural network for ship resistance performance is established. The stem profile's optimization for the Korea Research Institute of Ships and Ocean Engineering (KRISO) container ship is completed. The results show that hull form optimization based on the approximated model can significantly improve optimization efficiency and is practical for engineering design.

Multiple-Points Constraints Based Deformation for Free-Form Surfaces

1999 ◽  
Author(s):  
J. M. Zheng ◽  
K. W. Chan ◽  
I. Gibson
Keyword(s):  
Surface Deformation ◽  
Single Point ◽  
Displacement Function ◽  
Surface Shape ◽  
Free Form ◽  
Surface Model ◽  
Deformation Method ◽  
Multiple Points ◽  
Free Form Surface ◽  
Free Form Surfaces

Abstract There is an increasing demand in the conceptual design for more intuitive methods for creating and modifying free-form curves and surfaces in CAD modeling systems. The methods should be based not only on the change of the mathematical parameters but also on the user’s specified constraints and shapes. This paper presents a new surface representation model for free-form surface deformation representation. The model is a combination of two functions: a displacement function and a function for representing an existing NURBS surface called parent surface. Based on the surface model, the authors develop two deformation methods which are named SingleDef (Single-point constraint based deformation method), and MultiDef (Multiple-points constraints based deformation method). The techniques for free-form surface deformation allow conceptual designer to modify a parent surface by directly applying point constraints to the parent surface. The deformation methods are implemented and taken in an experimental CAD system. The results show that the designer can easily and intuitively control the surface shape.

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