International Shipbuilding Progress, Marine Technology, ISP, Volume 62, 2015

Internalional Shipbuilding Progress 62 (2015) 1-15 DOI 10.3233/1SP-140114

lOS Press

1

Genetic algorithm-based counter-flooding decision

model for damaged warship

Li-fen Hu *, Zliongmin Tian, Zhongyu Sun, Quanziiong Zhang and

Baofu Feng

Deparhnent of Naval Architecture and Ocean Engineering, Ludong University, Yantai, China

Received 14 June 2012 Revised 4 October 2014 Accepted 15 December 2014

A good counter-flooding strategy is vital to the decision maker in case of emergency, but how to eval-uate the scheme is still lack of a definite function. To estabhsh a definite evaluation standard, this paper presents a counter-flooding decision model for scheme evaluation and decision support in shipboard flood-ing emergency, ft adopts genetic algorithm to solve the proposed optimization model, whicli involves the combination of counter-flooding tanks that should be filled or evacuation in order to achieve an optimal re-sponse to a flooding accident. The genetic algorithm is developed with roulette wheel selection, one-point crossover, mutation, and iterative process continues until terminating condition is encountered. The stop-ping criterion proposed in this paper is the tilt angle, also the heeling angle is another terminate rule. The computational results validate the effectiveness of proposed optimization model and genetic algorithm. Keywords: Counter-flooding, decision model, genetic algorithm, evolutionary strategy

1. Introduction

Safety is one of tlie main concerns in maritime activity. Although the safety of

a ship may be determined by many uncontrollable factors (such as weather or

hu-man error), efficient and continuous monitoring of shipboard systems and the current

safety status is crucial to avoid or at least minimize the effects. Most modern ships

have a damage control center onboard where the crew monitors ship systems and

structures and coordinates emergency teams. With the increasing complexity of ships

and equipment and the numerous systems to support activities onboard, a substantial

amount of data can be received and processed in the damage control center. This

'Corresponding author: Li-fen Hu, Department of Naval Architecture and Ocean Engineering, Ludong University, Hongqi Middle Road 186, Zhifu District, Yantai, China. Tel.: -1-86 535 669 6123; Fax: -1-86 535 668 1468; E-mail: hlfgffff2008@aliyun.com.

Inlernalional Shipbuilding Progress 62 (2015) 1 7 ^ 2 DOI 10.3233/ISP-150115

IOS Press

17

A contribution to curves network based ship hull form

reverse engineering

Desta Milkessa Edessa * and Robert Bronsart

Department of Mechanical Engineering and Marine Technology, University of Rostock, Rostock, Germany

Received 30 September 2014 Revised 4 Marcli 2015 Accepted 26 March 2015

In reverse engineering (RE) there are several strategies, technologies and mathematical numerics in-volved from data acquisition system to surface fitting. This makes the reverse engineering methods always computationally expensive, time taking and more over error prone. Therefore, developing application spe-cific RE method can offer the required quality with reasonable associated time and then cost. This paper presents a practical and efficient ship hull form reconstruction strategy which align the reverse engineer-ing results into traditional hull form design procedures. The developed approach reads points from a set of unorganized noisy 3D point cloud and fits to cross-sectional curves network (transversal and water-line sections). It consists of several point cloud pre-processing functions, the curves fitting (interpolation and approximation) and presents different Non-Uniform Rational B-Spline (NURBS) surface fitting ap-proaches from curves network. The point cloud pre-processing removes outliers and extracts transversal and waterline sections. It is also equipped with different functions to successfully filter and smooth point cloud so that it can be fitted to curves by interpolation or approximation. The suitability of different ex-isting surface generations (lofting, patching and surface from curves network) are experimented based on cross-sectional curves. The developed approach is tested against two hull forms (scanned and manually generated) point cloud. The tests reveals that, the developed approach is time saving and suitable for hull form reconstruction.

Keywords: Reverse engineering, hull form, point cloud, curves network, surface fitting

1. Introduction

Reverse engineering (RE) in tlie context of Computer Aided Design (CAD) is an

activity which deals with digitization of a real objects in order to create a

numeri-cal or virtual model [33], RE in CAD systems with regard to product development

CoiTesponding author: Desta Milkessa Edessa, Mechanical Engineering and Maritime Technology Faculty, University of Rostock, Albert-Einstein-StraBe 2, 18059 Rostock, Germany Tel.: -1-49 381 498 9274; Fax: -1-49 381 498 9272; E-mail: desta.edessa2@uni-rostock.de.

Inlernalional Sliipbuilding Progress 62 (2015) 43-56 DOI 10.3233/ISP-I50I16

IOS Press

43

Retrofitting of offshore cyHndrical structures with

different geometrical configuration of perforated

outer cover

Srinivasan Ctiandrasekaran * and N . Madliavi

Depanment of Ocean Engineering. Indian In.ililnle ofTechnology Madras, Chennai, India

Received 28 May 2014 Revised 6 March 2015 Accepted 1 May 2015

Presence of perforated members in ocean structures reduces the wave force on the damaged member because of the wave structure interaction; breakwaters with perforated members are classical examples of such kind. While retrofitting and rehabilitation is usuaUy related to strengthening of members, the presented concept is a novel attempt as it addresses decrease in the encountered forces on the members. The present study is attempted numerically to quantify the force reduction on ocean structures encom-passed by perforated outer covers with different geometric configuration of outer cylinder. Present study highlights the reduction of hydrodynamic response of perforated members under regular waves using nu-merical simulation. Hydrodynamic responses of cylinders with and without perforated cover are estimated for different sea states which are categorized as low, medium and steep wave steepness index. Based on the studies carried out, it is shown that there is average force reduction of about 60% is seen for the cho-sen geometric configuration. For this study the orientation of the structure under regular waves are also considered.

Keywords: Force reduction, hydrodynamic response, perforated members, ocean structures, orientation of structure

1. General

Tlie presented rehabilitation technique on structures is one of the stress relieving

concept which is used to taking the advantages of reducing the external forces on

the over stressed member Encompassing perforated outer cover around the existing

member is a novel attempt as it does not demand any replacement of the member;

it suggests encompassing the inner existing cylinder with outer perforated member

The recommended technique of encompassing the inner cyUnder with outer

perfo-rated cover is a very practical retrofitting and feasible method. The recommended

Con esponding author: Srinivasan Chandrasekaran, Department of Ocean Engineering, Indian Institute ofTechnology Madras, Chennai, India. Fax: +91 044 22574802; E-mail: drsek:aran@iitm.ac.in.

Inlernalional Shipbuilding Progress 62 (2015) 57-111 DOI 10.3233/1SP-150117

lOS Press

57

Uncertainty assessment for ship maneuvering

mathematical model

A n i l Kumar Dasli, Vishwanatli Nagarajan * and Om Prakasli Slia

Received 15 March 2013 Revised 2 March 2015 Accepted 1 May 2015

An 8 DoF ship maneuvering motion model for a twin-propeller twin-rudder high-speed hull form is developed from captive model experiment data available from literatures. The degrees of freedom con-sidered are surge, sway, yaw, roll, rudder rate and propeller rate. Besides maneuvering motion model, variation of port/starboard propeller thrust and torque and port/starboard rudder normal force and rudder torque are also included in the model. An uncertainty analysis computation for the mathematical model is carried out. Uncertainties in the experimental data and the polynomial curve fitting during modeling are included in the computation. It is shown that the mathematical model uncertainty is higher than the experimental uncertainty. Uncertainty is propagated to full-scale zigzag maneuver using the conventional Monte Carlo simulation (MCS) method. The uncertainty analysis results will be useful for further im-provement of mathematical inodel, validation of CFD simulation results of appended hull maneuvering tests, etc. We have also shown the utility of asymmetric operations of the twin-propeller and twin-rudder by carrying out full-scale simulation a zigzag maneuver and showing the variation of the rudder normal force and torque.

Keywords: Maneuvering inodel, twin-propeller asymmetry, twin-rudder asymmetry, uncertainty assess-ment, MCS

1. Introduction

Mathematical modeling of ship maneuvering motion involves developing a set

of non-linear, cross-coupled ordinary differential equations. The motion equations

are usually developed in the body-fixed non-inertial coordinate system. Therefore,

non-linear inertial force corrections come to the motion equation. To trace out the

ship trajectory in space, Euler's angle transformation of the body-fixed dynamics to

Earth-fixed coordinate system is required. Besides the motion equation, the

expres-* Corresponding author: Vishwanath Nagarajan, Department of Ocean Engineering & Naval Architecture, IIT Kharagpur, Kharagpur, West Bengal, 721 302, India. Tel.: +91 3222 283782; Fax: +91 3222 255303; E-mail: vishwanath_n@naval.iitkgp.ernet.in.

International Shipbuilding Progress 62 (2015) 113-138 DOI I0.3233/ISP-I50il8

IOS Press

113

Estimation of hydrodynamic forces and motion of ships

with steady forward speed

Amitava Guha * and Jeffrey Falzarano

Marine Dynamics Laijoratory, Department of Civil Engineering, Texas A&M University, College Station, TX, USA

Received 18 February 2014 Revised 8 May 2015 Accepted 2 July 2015

The growing number of large ships demands predicting their optimum performance with respect to travel time, fuel efficiency and the safety of cargo and personnel in specified shipping routes. This can be achieved using efficient and easy to use numerical tools capable of predicting hydrodynamic loads on floating vessels with steady forward speed and solving their motion response in various wave con-ditions. A three-dimensional potential theory based code using the Green function method is developed with consideration of forward speed effects. The generalized coordinate system is used to allow motion response calculations with respect to any desired body coordinate system and a common quadrilateral meshing format. The formulation and calculafion of added mass and damping coefficients at zero and infinite frequency in forward speed case has been also provided.

A number of shuctures including simple geometries and full ship huU forms have been analyzed and validated against published theoretical, numerical and experimental results. The comparison results are found to be in excellent agreement. The theoretical formulation, numerical implementation and result comparisons are presented here.

Keywords: Forward speed, potential theory, 3D panel method. Green funcfion

Nomenclature

U

ship forward speed

fi wave heading

A wave amplitude

k wave number

o)/ incident wave frequency

We encounter wave frequency

'CoiTesponding author: Amitava Guha, Marine Dynamics Laboratory, Department of Civil Engineering, Texas A & M University, College Station, T X 77843-3136, USA. Tel.: -l-l 979 739 9555; E-maü: tava.amitava@email.tamu.edu.

Inlernalional Shipbuilding Progress 62 (2015) 139-160 DOI 10.3233/ISP-150119

IOS Press

13')

Performance aspects of podded propulsor in dynamic

operating conditions

M . Islam'•>•*, A . Akinturk'' and B . Veitch"

^ Ocean, Coastal and River Engineering, National Reseaich Council, Ottawa, ON, Canada Faculty of Engineeiing •& Applied Science, Memorial University of Newfoundland, St. John's, NL, Canada

Received 28 February 2014 Revised 6 July 2015 Accepted 16 October 2015

This paper presents various aspects of propulsive performance of a dynamic azimuthing puller podded propulsor in open water condition derived from an experimental research. A model podded propulsor was instrumented to measure thrust, torque and rotational speed of the propeller, three orthogonal forces and moments, azimuthing angle and azimuthing rate of the unit. Experiments were carried out in which the azimuthing angle was varied dynamically at multiple azimuthing rates and propeller rotational speeds for different advance speeds. The model podded propulsor was capable of azimuthing or yawing continuously in the range of - 1 8 0 ° to +180°, 0° (straight-ahead) being the design operating condhion and positive azimuthing means a counter-clockwise rotation. The performance coefficients of the propeller and the pod unit showed a strong dependence on the propeller loading and azimuthing angle. The open water characteristics were mostly irregular for the astern thrust conditions in the azimuthing angle beyond the normal inflow condition and the fluctuation of the magnitude of the performance coefficients showed a considerable range. The azimuthing rate showed little or no effect on the performance coefficients in the range of azimuthing angles examined. Both at high and moderate propeller loading conditions, an increase in the shaft speed resulted in slight change in the performance coefficients and the change was more obvious as the azimuthing angle was increased. The increase in the performance coefficients due to the increase of propeller shaft speed was not noficeably affected by the change of azimuthing rate. Keywords: Podded propulsor, dynamic azimuthing, azimuthing rate, propulsive performance, unit forces and moments

1. Introduction

One of the attractive features of podded propulsor is that the entire unit can be

ro-tated 360° in the horizon so as to direct the thrust vector in any direction. In dynamic

* Corresponding author: Mohammed F. Islam, PhD, PEng., Director of Technical Solutions, Oceanic ConsiiUing Coiporation, 95 Bonaventure Avenue, Suite 401, St. John's, NL, A1B2X5, Canada. Tel.: -l-l 709 722 9060, Ex. 13; Fax: +1 709 722 9064; E-mail: islain.mohainmed@oceaniccorp.com.

Intemational Shipbuilding Progress 62 (2015) 161-187 DOI 10.3233/ISP-160120

IOS Press

1 6 1

Time domain prediction of seakeeping behaviour

of catamarans

Fuat Kara

School of Energy, Environmem and Agrifood, Cranfield University, Building 40, Bedfordshire, England, UK

Tel.: +44 0 1234 754118; E-maU: f.kara@cranfield.ac.uk

Received 9 December 2015 Revised 17 February 2016 Accepted 23 March 2016

The numerical predictions of the seakeeping characteristics of catamarans with and without fonvard speed are presented using a direct time domain approximation. Boundary-Integral Equation Method (BIEM) with three-dimensional transient free surface Green function and Neumman-Kelvin linearization is used for the solution of the hydrodynamic interactions in the gap between catamaran hulls and solved as impulsive velocity potential. The numerical results have shown that the response of the fluid between multi-hulls can affect seakeeping performance and influence the hydrodynamic forces and the motion am-plitude operators of the floating multi-bodies. It is also shown numerically if the critical reduced frequency is smaller than the ratio of vessel length to hull separation, the wave interactions between hulls are very significant due to trapped waves in the gap of twin-hull. A hemi-spheroid catamaran, Wigley catamaran, and DUT high speed catamaran hull forms are used for the numerical analyses and the comparisons of the present ITU-WAVE numerical results for added-mass, damping coefficients, exciting force, and response amplitude operators show satisfactory agreeinent with existing numerical and experimental results. Keywords: Seakeeping, multi-hull vessels, catamaran, rime domain, transient free-surface wave Green function, boundary integral equation method, Neumman-Kelvin linearization

1. Introduction

Tlie accurate predictions of wave loads and motion charactenstics are of critically

important for the design of multi-hull floating structures which are in sufficiently

close proximity to experience significant hydrodynamic interactions. The oscillation

of each body radiates waves assuming that other bodies are not present. Some of

these radiated waves interact with other bodies which can be considered as incident

waves and wave diffraction occurs as the consequences while some others radiate to

infinity. The response of the fluid between multi-hulls can affect both manoeuvring

and seakeeping performance as well as influence the hydrodynamic forces and the

motions of the floating multi-bodies.