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 Numerical Study on Correlation Between the Bow Design Parameters and Added Resistance Using the Design of Experiments

2016 ◽  
Author(s):  
Gwan Hoon Kim ◽  
Hyun Joon Shin ◽  
Jeonghwa Seo ◽  
Shin Hyung Rhee
Keyword(s):  
Design Of Experiments ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Design Parameters ◽  
Added Resistance ◽  
Hull Form ◽  
Entrance Angle ◽  
Wave Condition ◽  
Added Resistance In Waves ◽  
Bulbous Bow

In this study, numerical computation was carried out for evaluating the effects of the design parameter variations on the added resistance of Aframax tanker in head seas. The design of experiments (DOE) was used to efficiently conduct the numerical simulations with the hull form variations and save computational resources. A computational fluid dynamics (CFD) code based on the continuity and Reynolds averaged Navier-Stokes (RANS) equation was used for the numerical simulation. The simulation was performed in a short wave condition where the wave length was half of the ship length, which is expected to be most frequent in the vessel operation. Five design parameters of fore-body hull form were selected for the variations: design waterline length (DWL), bulbous bow height (BBH), bulbous bow volume (BBV), bow flare angle (BFA) and bow entrance angle (BEA). Each parameter had two levels in the variations, thus total 32 cases were designed initially. The results of the numerical simulations were analyzed statistically to determine the main effects and correlations in the five design parameters variations. Among them, the most significant parameter that influences on the added resistance in waves was DWL, followed by BBV and BEA. The other parameters had little effects on the added resistance in waves. By the computations, it was revealed that Extending DWL and decreasing BEA promoted the reflection of waves more toward the side than forward. In addition, there existed two-way interactions for the following two-factor combinations: DWL-BFA, DWL-BEA, DWL-BBV, BBH-BBV.

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.

Numerical and experimental study on hydrodynamic bulbous bow hull-form optimization for various service conditions due to slow steaming of container vessel

2018 ◽  
Vol 233 (4) ◽  
pp. 1103-1122
Author(s):  
Xun-bin Yin ◽  
Yu Lu ◽  
Jin Zou ◽  
Lei Wan
Keyword(s):  
Optimization Design ◽  
Optimization Technique ◽  
Experimental Studies ◽  
Design Stage ◽  
Probability Density Distribution ◽  
Hull Form ◽  
Slow Steaming ◽  
Service Conditions ◽  
Bulbous Bow ◽  
Hydrodynamic Optimization

In this article, an innovative hydrodynamic optimization design of bulbous bow hull-form under various service conditions resulting from the slow steaming of container vessel is presented, improving the overall performances for the real multi-variant usage situations more practical than the single specification of design, which includes both numerical computation and experimental validation. Effects of slow steaming–based statistical analysis of the actual operative occurrence during the lifetime is conducted, obtaining a combined probability density distribution of speed and displacement ushering in the evaluation of objective function. Three main component elements of the hydrodynamic optimization procedure that comprises parametric design of bulbous bow hull-form variation part, hydrodynamic numerical solver part, and optimization technique part are established and integrated. The proposed optimization process is subsequently applied to find the optimal bulbous bow of a container carrier for the hipping demand of different speeds and displacement distributed utilization, reducing significantly total conditions resistance of the hull, on a higher level decreasing the operative cost as well as gas emissions of the ship. Finally, there is an experimental campaign carried out between the optimal and original models to validate the numerical optimization computations. The compared investigation has provided a good agreement from the perspective of both numerical and experimental studies, as a result confirming the success of the present optimization framework and the utility value of the proposed optimization consideration on various service conditions during ship design stage.

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.

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.

New Promising Generation of Twin-Gondola LNG Carriers Optimized with the Aid of CFD Calculations

2005 ◽  
Author(s):  
Henk V. Valkhof ◽  
Eduardo Minguito ◽  
Klaas Kooiker
Keyword(s):  
Viscous Flow ◽  
Far East ◽  
Point Of View ◽  
Maximum Efficiency ◽  
Hull Form ◽  
Overall Design ◽  
Computational Fluid Dynamics Cfd ◽  
New Generation ◽  
Hydrodynamic Optimization ◽  
Adequate Design

As natural gas is becoming an important energy source, a large fleet is needed to transport it in liquefied form across the oceans in specially designed LNG carriers from mainly the Middle East towards the Far East. During the overall design process of such a vessel the shape of the hull form and its propulsors play an important role from a hydrodynamic point of view. This paper describes the design of a twin-gondola LNG carrier for Navantia. The twingondola aft body has proven to be an adequate design concept, but due to the complexity of the flow around the aft body the design should be carried out with great care. Computational Fluid Dynamics (CFD) tools are extremely valuable in the hydrodynamic optimization process of the hull. In this design both potential flow codes and viscous flow codes have been used to obtain the optimum hull form. With the results of the PARNASSOS viscous flow calculations it was possible to make decisions with regard to the horizontal angle and the inclination of the gondolas, and the slope of the buttocks in the area between the gondolas. Special attention has been paid to avoid flow separation around the aft body. The gondolas have been oriented in such a way that maximum efficiency is achieved. The performance of the resulting design has been verified by model tests in MARIN’s Deep Water Towing Tank. Given the very promising results of this new generation of LNG carriers, achieving besides the excellent propulsive properties also a higher payload target, the yard became more competitive and is expecting quite some orders for this particular ship type.

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.

Geometrical Variation and Distortion of Ship Hull Forms

2003 ◽  
Vol 40 (04) ◽  
pp. 239-248
Author(s):  
Ebru Narh ◽  
Kadir Sariöz
Keyword(s):  
Computer Aided Design ◽  
Ship Hull ◽  
Hydrodynamic Performance ◽  
Hull Form ◽  
Nonlinear Distortions ◽  
Form Design ◽  
Hull Form Design ◽  
Geometrical Variation ◽  
Hull Forms ◽  
Aided Design

Because of the risk involved with starting the hull form design from scratch, the designer most frequently initiates the hull form design process with a parent form that has satisfactory hydrodynamic performance. Hence, linear and nonlinear variation and distortion techniques have found wide applications in the hull form design studies. Some of these methods are simple and easy to apply by practicing naval architects, whereas others may be considered too complicated and difficult to use without simplifications. Existing and emerging techniques to distort a parent ship hull form are discussed and applied to a typical ship form. These techniques range from a simple one minus prismatic method to complex nonlinear distortions and include emerging computer-aided design (CAD) methods, such as shape averaging. The applications indicate that the techniques presented can be safely applied to conventional ship hull forms. The advantages and drawbacks of these methods are discussed, and numerical results are presented.

A Comparison of Alternative Bow Configurations

1995 ◽  
Vol 32 (03) ◽  
pp. 224-230
Author(s):  
Chel Stromgren
Keyword(s):  
State Of The Art ◽  
Computer Software ◽  
Hydrodynamic Performance ◽  
Construction Costs ◽  
Hull Form ◽  
Newport News ◽  
Standard Product ◽  
Computational Fluid Dynamics Cfd ◽  
Hydrodynamic Effects ◽  
Ship Speed

Newport News Shipbuilding (NNS) has been preparing for a reentry into the commercial shipbuilding market for several years. Those preparations resulted in the signing of a contract in October of 1994 with Eletson Corporation for the construction of two (with an option for an additional two)46500 dwt product carriers. This is the first contract for a U.S. shipyard to build commercial ships for a foreign owner in 37 years. In developing the hull form for the standard product carrier Double Eagle, NNS performed studies to determine the economic and hydrodynamic effects of alternative bow configurations on a representative modern, high-block tanker. The objectives of the study were to update the NNS commercial ship speed-power database, investigate the application of state of the art computer software, and create a bow design which strikes a balance between hydrodynamic performance and producibility. To achieve these goals, NNS worked with SAIC to use the computational fluid dynamics (CFD) SLAW software to mathematically analyze several candidate bows. These designs were then model tested at the Swedish State Model Basin in Gothenburg to validate the results of the CFD codes. Construction costs were then estimated for each design and finally, the bow forms were compared on an overall economic basis.

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