Research

17 pages, 6976 KiB

Open AccessArticle

Application of the IMO Second Generation Intact Stability Criteria to a Ballast-Free Containership

by Nicola Petacco, Danilo Pitardi, Carlo Podenzana Bonvino and Paola Gualeni

J. Mar. Sci. Eng. 2021, 9(12), 1416; https://doi.org/10.3390/jmse9121416 - 11 Dec 2021

Cited by 12 | Viewed by 2394

A methodology is presented to systematically modify the hull shape of a ballast-free container ship, in order to manage the issue of righting lever variation in waves. The IMO second generation intact stability criteria have been identified as a stability performance assessment tool, [...] Read more.

A methodology is presented to systematically modify the hull shape of a ballast-free container ship, in order to manage the issue of righting lever variation in waves. The IMO second generation intact stability criteria have been identified as a stability performance assessment tool, while the vertical prismatic coefficient has been selected as the leading parameter of hull modifications to carry out the sensitivity analysis. A revised Lackenby procedure has been chosen to make systematic changes at the hull form. The outcomes of this investigation point out that the proposed procedure is suitable to enable the ship to be fully compliant with the IMO vulnerability levels with minor design adjustment. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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17 pages, 14155 KiB

Open AccessArticle

An Effective Mesh Deformation Approach for Hull Shape Design by Optimization

by Diego Villa, Francesco Furcas, Jan Oscar Pralits, Giuliano Vernengo and Stefano Gaggero

J. Mar. Sci. Eng. 2021, 9(10), 1107; https://doi.org/10.3390/jmse9101107 - 12 Oct 2021

Cited by 6 | Viewed by 2489

Abstract

A method for the morphing of surface/volume meshes suitable to be used in hydrodynamic shape optimization is proposed. Built in the OpenFOAM environment, it relies on a Laplace equation that propagates the modifications of the surface boundaries, realized by applying a free-form deformation [...] Read more.

A method for the morphing of surface/volume meshes suitable to be used in hydrodynamic shape optimization is proposed. Built in the OpenFOAM environment, it relies on a Laplace equation that propagates the modifications of the surface boundaries, realized by applying a free-form deformation to a subdivision surface description of the geometry, into the computational volume mesh initially built through a combination of BlockMesh with cfMesh. The feasibility and robustness of this mesh morphing technique, used as a computationally efficient pre-processing tool, is demonstrated in the case of the resistance minimization of the DTC hull. All the hull variations generated within a relatively large design space are efficiently and successfully realized, i.e., without mesh inconsistencies and quality issues, only by deforming the initial mesh of the reference geometry. Coupled with a surrogate model approach, a significant reduction in the calm water resistance, in the extent of 10%, has been achieved in a reasonable computational time. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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22 pages, 6415 KiB

Open AccessArticle

Application of Basis Functions for Hull Form Surface Modification

by Baiwei Feng, Chengsheng Zhan, Zuyuan Liu, Xide Cheng and Haichao Chang

J. Mar. Sci. Eng. 2021, 9(9), 1005; https://doi.org/10.3390/jmse9091005 - 14 Sep 2021

Cited by 3 | Viewed by 1616

Abstract

Basis functions are key in constructing interpolation equations in hull surface modification based on radial basis functions (RBF) interpolation. However, few have studied the selection of basis functions in depth. By comparing several typical basis functions through a theoretical analysis and two-dimensional modification [...] Read more.

Basis functions are key in constructing interpolation equations in hull surface modification based on radial basis functions (RBF) interpolation. However, few have studied the selection of basis functions in depth. By comparing several typical basis functions through a theoretical analysis and two-dimensional modification examples, the Wendland ψ3,1 (W) function is selected. The advantages of hull form surface modification based on W function interpolation are further validated through a case study. Finally, the modification method is used to optimize a trimaran model. An optimal hull form with fair lines is obtained, and its wave-making resistance coefficient and total resistance are reduced by 8.3% and 3.8%, respectively, compared to those of the original model. These findings not only further illustrate that the W function is relatively suitable for hull form surface modification, but also validate the feasibility and value of the RBF interpolation-based surface modification method in engineering practice. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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17 pages, 5735 KiB

Open AccessArticle

Information Matrix-Based Adaptive Sampling in Hull Form Optimisation

by Xuyu Ouyang, Haichao Chang, Baiwei Feng, Zuyuan Liu, Chengsheng Zhan and Xide Cheng

J. Mar. Sci. Eng. 2021, 9(9), 973; https://doi.org/10.3390/jmse9090973 - 07 Sep 2021

Cited by 1 | Viewed by 1540

Abstract

Hull form optimisation involves challenges such as large design spaces, numerous design variables, and high nonlinearity. Therefore, optimisation that only use global approximate models alone cannot yield desirable results. An information matrix-based method is proposed for dynamically embedded local approximate models (IM-DEAM) in [...] Read more.

Hull form optimisation involves challenges such as large design spaces, numerous design variables, and high nonlinearity. Therefore, optimisation that only use global approximate models alone cannot yield desirable results. An information matrix-based method is proposed for dynamically embedded local approximate models (IM-DEAM) in this paper, which uses the Gaussian-function information matrix to extract one or more subspaces for additional sampling and a Latin hypercube design (LHD) for adaptive sampling. In addition, to prevent overfitting by global approximate models in some spaces because of the uneven distribution of the samples, local approximate models are embedded in the subspaces identified for additional sampling to enable accurate description of subspaces. The effectiveness and robustness of the method are validated and analysed by applying the proposed method to optimise mathematical functions and the hull form of the DTMB 5415. The results demonstrate that the proposed method is effective for improving the accuracies and can produce reliable optimisation results. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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20 pages, 4886 KiB

Open AccessArticle

Application of Improved Particle Swarm Optimisation Algorithm in Hull form Optimisation

by Qiang Zheng, Bai-Wei Feng, Zu-Yuan Liu and Hai-Chao Chang

J. Mar. Sci. Eng. 2021, 9(9), 955; https://doi.org/10.3390/jmse9090955 - 02 Sep 2021

Cited by 11 | Viewed by 2357

Abstract

The particle swarm optimisation (PSO) algorithm has been widely used in hull form optimisation owing to its feasibility and fast convergence. However, similar to other intelligent algorithms, PSO also has the disadvantages of local premature convergence and low convergence performance. Moreover, optimization data [...] Read more.

The particle swarm optimisation (PSO) algorithm has been widely used in hull form optimisation owing to its feasibility and fast convergence. However, similar to other intelligent algorithms, PSO also has the disadvantages of local premature convergence and low convergence performance. Moreover, optimization data are not used to analyse and reduce the range of values for relevant design variables. Our study aimed to solve these existing problems in the PSO algorithm and improve PSO from four aspects, namely data processing of particle swarm population initialisation, data processing of iterative optimisation, particle velocity adjustment, and particle cross-boundary configuration, in combination with space reduction technology. The improved PSO algorithm was used to optimise the hull form of an engineering vessel at Fn = 0.24 to reduce the wave-making resistance coefficient under static constraints. The results showed that the improved PSO algorithm could effectively improve the optimisation efficiency and reliability of PSO and effectively overcome the drawbacks of the PSO algorithm. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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22 pages, 1650 KiB

Open AccessFeature PaperArticle

Increase in Stability of an X-Configured AUV through Hydrodynamic Design Iterations with the Definition of a New Stability Index to Include Effect of Gravity

by Lakshmi Miller, Stefano Brizzolara and Daniel J. Stilwell

J. Mar. Sci. Eng. 2021, 9(9), 942; https://doi.org/10.3390/jmse9090942 - 30 Aug 2021

Cited by 10 | Viewed by 2559

Abstract

A study about the effect of different configurations of stationary and movable appendages on the dynamic stability of an autonomous underwater vehicle (AUV) is presented. A new stability index that can be used to assess dynamic stability in the vertical plane is derived. [...] Read more.

A study about the effect of different configurations of stationary and movable appendages on the dynamic stability of an autonomous underwater vehicle (AUV) is presented. A new stability index that can be used to assess dynamic stability in the vertical plane is derived. It improves upon the vertical plane stability index by accurately accounting for the contribution of hydrostatic forces to dynamic stability, even at low speeds. The use of the new stability index is illustrated by applying it to a set of AUV configurations based on an AUV initially designed at Virginia Tech and built by Dive Technologies. The applicability of this index depends on the speed of the craft. The range of applicability in terms of speed is presented for the DIVE craft as an example. The baseline design of the DIVE craft has asymmetry in the vertical plane and symmetry in the horizontal plane. A virtual planar motion mechanism (VPMM) is used to obtain the hydrodynamic coefficients of the hull. Design iterations are performed on the baseline design by varying the appendages in shape and size, adding appendages and adding features on appendages. The best and the baseline design from this effort are incorporated in a 6 DOF lumped-parameter model (LPM) to compare results of a straight line maneuver. A computational fluid dynamic (CFD) tool is used to obtain the trajectory comparison of turn-circle maneuver for these two designs. A principal conclusion is the important contribution of a hydrostatic restoring force at low-moderate speeds by using

G_{V g r a v}

and the influence of design of control surfaces, both stationary and non-stationary, in the achievement of control-fixed course stability. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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22 pages, 3888 KiB

Open AccessArticle

Hull Shape Design Optimization with Parameter Space and Model Reductions, and Self-Learning Mesh Morphing

by Nicola Demo, Marco Tezzele, Andrea Mola and Gianluigi Rozza

J. Mar. Sci. Eng. 2021, 9(2), 185; https://doi.org/10.3390/jmse9020185 - 11 Feb 2021

Cited by 22 | Viewed by 3762

Abstract

In the field of parametric partial differential equations, shape optimization represents a challenging problem due to the required computational resources. In this contribution, a data-driven framework involving multiple reduction techniques is proposed to reduce such computational burden. Proper orthogonal decomposition (POD) and active [...] Read more.

In the field of parametric partial differential equations, shape optimization represents a challenging problem due to the required computational resources. In this contribution, a data-driven framework involving multiple reduction techniques is proposed to reduce such computational burden. Proper orthogonal decomposition (POD) and active subspace genetic algorithm (ASGA) are applied for a dimensional reduction of the original (high fidelity) model and for an efficient genetic optimization based on active subspace property. The parameterization of the shape is applied directly to the computational mesh, propagating the generic deformation map applied to the surface (of the object to optimize) to the mesh nodes using a radial basis function (RBF) interpolation. Thus, topology and quality of the original mesh are preserved, enabling application of POD-based reduced order modeling techniques, and avoiding the necessity of additional meshing steps. Model order reduction is performed coupling POD and Gaussian process regression (GPR) in a data-driven fashion. The framework is validated on a benchmark ship. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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17 pages, 6442 KiB

Open AccessArticle

Influence of Impeller Gap Drainage Width on the Performance of Low Specific Speed Centrifugal Pump

by Yangyang Wei, Yang Yang, Ling Zhou, Lei Jiang, Weidong Shi and Gaoyang Huang

J. Mar. Sci. Eng. 2021, 9(2), 106; https://doi.org/10.3390/jmse9020106 - 20 Jan 2021

Cited by 9 | Viewed by 3219

Abstract

The centrifugal pump is one of the most important pieces of energy-consuming equipment in various hydraulic engineering applications. This paper takes a low specific speed centrifugal pump as the research object. Based on the research method combining numerical calculation and experimental verification, the [...] Read more.

The centrifugal pump is one of the most important pieces of energy-consuming equipment in various hydraulic engineering applications. This paper takes a low specific speed centrifugal pump as the research object. Based on the research method combining numerical calculation and experimental verification, the influence of the gap drainage structure on the performance of the low specific speed centrifugal pump and its internal flow field distribution were investigated. The flow field inside the low specific speed centrifugal pump impeller under different gap widths was studied. The comparison between the numerical calculation results and the experimental results confirms that the numerical calculations in this paper have high accuracy. It was found that the gap drainage will reduce the head of the low specific speed centrifugal pump, but increase its hydraulic efficiency. Using a smaller gap width could greatly improve the performance of the low specific speed centrifugal pump on the basis of a slight reduction in the head. The high-pressure leakage flow at the gap flows from the blade pressure surface to the suction surface can effectively suppress the low-pressure area at the impeller inlet. The flow rate of the high-pressure leakage flow increases with the gap width. Excessive gap width may cause a low-pressure zone at the inlet of the previous flow passage. These results could serve as a reference for the subsequent gap design to further improve the operating stability of the low specific speed centrifugal pump. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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20 pages, 5479 KiB

Open AccessArticle

Near-Trapping on a Four-Column Structure and the Reduction of Wave Drift Forces Using Optimized Method

by Guanghua He, Zhigang Zhang, Wei Wang, Zhengke Wang and Penglin Jing

J. Mar. Sci. Eng. 2020, 8(3), 174; https://doi.org/10.3390/jmse8030174 - 05 Mar 2020

Cited by 5 | Viewed by 1837

Abstract

The near-trapping phenomenon, which can lead to high wave elevations and large wave drift forces, is investigated by a floating four-column structure. To solve this wave-structure interaction problem, a numerical model is established by combining the wave interaction theory with a higher-order boundary [...] Read more.

The near-trapping phenomenon, which can lead to high wave elevations and large wave drift forces, is investigated by a floating four-column structure. To solve this wave-structure interaction problem, a numerical model is established by combining the wave interaction theory with a higher-order boundary element method. Based on this numerical model, behaviors of scattered waves at near-trapping conditions are studied; and the superposition principle of free-surface waves is introduced to understand this near-trapping phenomenon. To avoid the near-trapping phenomenon and protect the structure, a way for rotating the structure to change the wave-approach angle is adopted, and improvements of the wave elevations around the structure and the wave drift forces acting on each column are found. Moreover, a genetic-algorithm-based optimization method is adopted in order to minimize the total wave drift force acting on the whole structure at various wavenumbers by controlling the draft of floating bodies, the wave-approach angle and the separation distance between adjacent floating bodies. With the final optimized parameters, the wave drift forces both on each column and on the whole structure can be significantly reduced. The optimized arrangement obtained from a certain wavenumber can work not only at this target wavenumber but also at a range of wavenumbers. Full article

(This article belongs to the Special Issue Shape Optimization of Engineering Systems for Superior Hydrodynamic Performance)

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