Hull form optimization for reduced calm-water resistance and improved vertical motion performance in irregular head waves

2021 ◽  
Vol 233 ◽  
pp. 109208
Author(s):  
Le Zha ◽  
Renchuan Zhu ◽  
Liang Hong ◽  
Shan Huang
Keyword(s):  
Water Resistance ◽  
Vertical Motion ◽  
Hull Form ◽  
Head Waves ◽  
Calm Water ◽  
Motion Performance

Comparative Performance of Optimum High Speed SWATH and Semi-SWATH in Calm Water and in Waves

2015 ◽  
Author(s):  
S. Brizzolara ◽  
G. Vernengo ◽  
L. Bonfiglio ◽  
D. Bruzzone
Keyword(s):  
High Speed ◽  
Hydrodynamic Performance ◽  
Forward Speed ◽  
Comparative Performance ◽  
Hull Form ◽  
High Speeds ◽  
Head Waves ◽  
Calm Water ◽  
Minimization Algorithms ◽  
Ranse Solver

The hydrodynamic performance of unconventional SWATH and Semi-SWATH for high speed applications are analyzed and compared in this paper. Bare hull resistance in calm water is estimated by an inviscid boundary element method with viscous corrections and verified by a fully turbulent, multiphase unsteady RANSE solver. Motions response in head waves, calculated by a frequency domain 3D panel method with forward speed effects are also evaluated and compared. Both considered hulls are the best designs coming from full parametric hull form optimization procedures, based on CFD solvers for the estimation of their hydrodynamic performance and driven by evolutionary minimization algorithms. The SWATH has twin parabolic struts and an unconventional underwater shape, the semi-SWATH has a slender triangular waterline, a bulbous shape in the entrance body which gradually morph into a U-section with a shallow transom in the run body. In general, as expected, the Semi-SWATH hull shows a lower drag at high speeds while the single strut SWATH is superior at lower speeds. As regards seakeeping, the SWATH shows unbeatable lower pitch and heave motions in shorter waves, where the Semi-SWATH evidences a double peaked RAO. More detailed analysis and conclusion are drawn in the paper.

Experimental Analysis on Flow around Fin Assisted Semi SWATH

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
Arifah Ali ◽  
Adi Maimun ◽  
Yasser M. Ahmed ◽  
Rahimuddin Rahimuddin ◽  
Mohamad Pauzi A. Ghani
Keyword(s):  
Froude Number ◽  
High Speed ◽  
Water Resistance ◽  
Wave Pattern ◽  
Resistance Test ◽  
Hull Form ◽  
Wave Interference ◽  
Calm Water ◽  
Water Test ◽  
Zero Degree

Demand on High Speed Craft (HSC) is increasing due to development of inland transportation. Therefore, many analysis have been conducted to evaluate performance of this modern ship. One of the important analysis is calm water resistance test. Resistance component of the hull and wave pattern around the hull are obtained from the calm water test. These criteria are important in analyzing flow around hull, especially on wave interference between the hulls. In this paper, flow around hull has been studied for one model of Semi SWATH hull form with fin stabilizers installation by performing calm water resistance test in deep water. The fore fin angle is fixed to zero degree while the aft fin angle is varied to 0, 5 and 15 degree. The effects of fin angle to resistance criteria and flow around hull are investigated. Wave height has been recorded using longitudinal wave probe during resistance test. For each configuration, the investigation is conducted with range of Length Froude Number from 0.34 to 0.69. From the analysis, it is found that flow around the hull of Semi SWATH is affected by fin angle and the effect is various depend on the Froude number.

scholarly journals Study on Hull Optimization Process Considering Operational Efficiency in Waves

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 898
Author(s):  
Beom-Soo Kim ◽  
Min-Jae Oh ◽  
Jae-Hoon Lee ◽  
Yong-hwan Kim ◽  
Myung-Il Roh
Keyword(s):  
Water Resistance ◽  
Operational Efficiency ◽  
Free Form ◽  
Total Resistance ◽  
Added Resistance ◽  
Deformation Method ◽  
Cross Sectional ◽  
Hull Form ◽  
Strip Theory ◽  
Calm Water

This study investigates the optimization of the hull form of a tanker, considering the operational efficiency in waves, in accordance with the recent Energy Efficiency Design Index regulation. For this purpose, the total resistance and speed loss of the ship under representative sea conditions were minimized simultaneously. The total resistance was divided into three components: calm water resistance, added resistance due to wind, and to waves. The first two components were calculated using regression formulas, and the last component was estimated using the strip theory, far-field method, and the short-wave correction formula. Next, prismatic coefficient, waterline length, waterplane area, and flare angle were selected as design variables from the perspective of operational efficiency. The hull form was described as a combination of cross-sectional curves. A combination of the method shifting these sections in the longitudinal direction and the Free-Form Deformation method was used to deform the hull. As a result of applying the non-dominated sorting genetic algorithm to a tanker, the hull was deformed thinner and longer, and it was determined that the total resistance and speed loss were reduced by 3.58 and 10.2%, respectively. In particular, the added resistance due to waves decreased significantly compared to the calm water resistance, which implies that the present tendency differs from conventional ship design that optimizes only the calm water resistance.

Hull Form Optimization for Hydrodynamic Performance

2004 ◽  
Vol 41 (04) ◽  
pp. 167-182
Author(s):  
Gregory J. Grigoropoulos
Keyword(s):  
Water Resistance ◽  
Optimization Procedure ◽  
Hydrodynamic Performance ◽  
Hull Form ◽  
Principal Characteristics ◽  
Calm Water ◽  
Rough Water ◽  
Hull Forms ◽  
Scaled Models ◽  
Formal Optimization

A method for optimizing hull forms with respect to their hydrodynamic performance in calm and rough water is presented. The method is based on an initial optimization of a parent hull form for seakeeping and the improvement of the resulting optimum hull form for calm water resistance. In the first part of the method, variant hull forms differing from a parent in the main dimensions and/or in one or more hull form parameters, such as CWP, LCF, CB, LCB, KB, CP, are automatically generated and their seakeeping qualities evaluated. When appropriate ranges for the principal characteristics and parameters of the hull form under investigation are prescribed, a formal optimization procedure is used to obtain the variant with the best seakeeping behavior. The weighted sum of the resonant values of selected ship responses for a number of ship speeds and headings in regular waves forms the objective function. The Hooke and Jeeves algorithm is used to accomplish the optimization. The procedure results in a set of trends regarding the proposed variations of the selected hull form parameters, within the specified constraints. These trends are then applied on the parent hull to derive an optimized hull form with fair lines. Subsequently, this hull form can be locally modified to improve its calm water resistance or, as it should be done, its propulsion characteristics. The applicability of the method is demonstrated in two cases: a conventional reefer ship and a naval destroyer. Scaled models of the parent and the optimized hull forms have been tested for calm water resistance and seakeeping. In both cases the validity of the methodology is demonstrated.

An Optimization Study of TriSWACH Side-Hull Position for Minimum Resistance in Calm Water

2017 ◽  
Author(s):  
Yufei Ai ◽  
Yulin Zhao ◽  
Raju Datla
Keyword(s):  
Froude Number ◽  
Water Resistance ◽  
Hydrodynamic Characteristics ◽  
Hull Form ◽  
Optimization Study ◽  
Seakeeping Performance ◽  
Stevens Institute ◽  
Calm Water ◽  
Institute Of Technology ◽  
Minimum Resistance

TriSWACH is a promising novel hull form for its reduced resistance, larger deck area and good seakeeping performance. This paper aims to determine an optimal sidehull position for TriSWACH based on the minimum resistance in calm water. STAR-CCM+, a RANS-based commercial CFD tool and a potential flow code Michelet are compared in their calculations of resistance. Four different side-hull positions of the TriSWACH operated within Froude number from 0.1 to 0.5 with increment 0.05 are considered for the numerical simulations. The simulation results are further validated by the model tests performed in Stevens Institute of Technology Davidson Laboratory towing tank. The comparison shows that STAR-CCM+ RANS codes can predict TriSWACH’s hydrodynamic characteristics in calm water with high accuracy. Finally, TriSWACH's optimal side-hulls’ position was discussed based on calm water resistance within different Froude number ranges.

The Effect of Bow Steepness and Flare on the Resistance of Sailing Yachts in Calm Water and Waves

2001 ◽  
Author(s):  
J. A. Keuning ◽  
R. Onnink ◽  
A. Damman
Keyword(s):  
Water Resistance ◽  
Added Resistance ◽  
University Of Technology ◽  
Head Waves ◽  
Master Thesis ◽  
Calm Water ◽  
Added Resistance In Waves ◽  
Bow Flare ◽  
Sailing Yacht ◽  
Resistance Performance

In this paper some results are presented of two studies carried out at the Ship hydromechanics Department of the Delft University of Technology: one, on the influence of an increase of stem steepness of a sailing yacht, and another, which was largely carried out by T.J.E. Tincelin as part of his master thesis at Delft University of Technology, on the effect of above waterline bow flare are presented. To investigate the influence of bow steepness a model of the Delft Systematic Yacht Hull Series (DSYHS) has been used as a parent model of a new small subseries with two additional derivatives each with increased bow steepness. The influence on both the calm water resistance and the added resistance in head waves has been investigated. To investigate the influence of bow flare, two models of a typical "Open 60" design have been used: one "normal" and one with almost no flare in the bowsections. These have been tested in calm water and in both head- and following­waves to investigate the effects of this difference in bow shape on the calm water resistance, on added resistance in waves, and on the relative motions at the bow. The results are presented and some comparisons with calculations made. Also some general conclusions with respect to resistance, performance and safety are drawn.

scholarly journals An Approach to Determine Optimal Bow Configuration of Polar Ships under Combined Ice and Calm-Water Conditions

2021 ◽  
Vol 9 (6) ◽  
pp. 680
Author(s):  
Hui Li ◽  
Yan Feng ◽  
Muk Chen Ong ◽  
Xin Zhao ◽  
Li Zhou
Keyword(s):  
Numerical Simulation ◽  
Water Resistance ◽  
Numerical Technique ◽  
Experimental Studies ◽  
Resistance Index ◽  
Simulation Method ◽  
Present Approach ◽  
Calm Water ◽  
Level Ice ◽  
Ice Resistance

Selecting an optimal bow configuration is critical to the preliminary design of polar ships. This paper proposes an approach to determine the optimal bow of polar ships based on present numerical simulation and available published experimental studies. Unlike conventional methods, the present approach integrates both ice resistance and calm-water resistance with the navigating time. A numerical simulation method of an icebreaking vessel going straight ahead in level ice is developed using SPH (smoothed particle hydrodynamics) numerical technique of LS-DYNA. The present numerical results for the ice resistance in level ice are in satisfactory agreement with the available published experimental data. The bow configurations with superior icebreaking capability are obtained by analyzing the sensitivities due to the buttock angle γ, the frame angle β and the waterline angle α. The calm-water resistance is calculated using FVM (finite volume method). Finally, an overall resistance index devised from the ship resistance in ice/water weighted by their corresponding weighted navigation time is proposed. The present approach can be used for evaluating the integrated resistance performance of the polar ships operating in both a water route and ice route.

Calm-Water Resistance

2018 ◽  
pp. 139-210
Author(s):  
Liang Yun ◽  
Alan Bliault ◽  
Huan Zong Rong
Keyword(s):  
Water Resistance ◽  
Calm Water

scholarly journals Tank Tests with a Scaled Model of a BOC-50 Sailing Yacht Model in Calm Water and in Regular and Random Head Waves

2015 ◽  
Vol 5 (6) ◽  
Author(s):  
Dimitrios Liarokapis ◽  
Konstantina Sfakianaki ◽  
Giannis Papantonatos ◽  
Gregory Grigoropoulos
Keyword(s):  
Scaled Model ◽  
Head Waves ◽  
Calm Water ◽  
Sailing Yacht

The Flooding After Damage of a Warship with Complex Internal Compartments - Experiments on a Fully Constrained Model in Calm Water and Regular Beam Seas

2012 ◽  
Vol 154 (A2) ◽  
Keyword(s):  
Degrees Of Freedom ◽  
Numerical Code ◽  
Scale Model ◽  
Experimental Program ◽  
Hull Form ◽  
Video Footage ◽  
Unconstrained Model ◽  
Beam Seas ◽  
Calm Water ◽  
Constrained Model

In order to provide data to assist in developing and validating a numerical code to simulate the flooding immediately following damage scale model experiments were conducted on a fully constrained model to investigate the progressive flooding through a complex series of internal compartments within a generic destroyer type hull form. A 3.268 metre long model of a generic destroyer hull form with a simplified, typical internal arrangement was constructed to cover the configuration of greatest interest. A very rapid damage opening scenario was simulated by rupturing a taut membrane covering an opening. The model was instrumented to measure the levels of water and the air pressures in various compartments. In addition, video footage was obtained of the flooding process from both internally and externally of the model. Previous work presented by Macfarlane et al. (2010) showed the results for the unconstrained model. This paper reports on the outcomes from the experimental program where the model was fully constrained in all six degrees of freedom. Firstly, tests were conducted in calm water with damage opening extents ranging from 50% to 100%. When the damage opening was only 50% the rate of rise of water in each of the compartments was only marginally slower than for the 100% damage extent case. Secondly, the test results in calm water were compared against results from tests in regular beam seas. A ‘set-up’ of water inside each of the compartments on the 2nd Deck was found during the wave tests. The result of this is that the mean equilibrium water level in each compartment in the regular beam sea cases is noticeably higher than the equivalent calm water case, particularly for the two compartments on the port side, away from the damage. Finally, analysis of the data from further calm water and beam sea tests suggests that a similar result also occurs when the model is fixed at various non-zero heel angles.

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