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4 TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

4 2014

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The Mooring Pattern Study for Q-Flex Type LNG Carriers Scheduled for Berthing at Ege Gaz Aliaga LNG Terminal

Nas S., Zorba Y., Ucan E.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2014

Vol. 8 no. 4

543--548

Ever growing energy industry requires larger quantities of LNG to be transported by bigger ships between terminals. Every day, new kind of large vessels created by new technologies, and these are used to trade around the globe. This is the dynamic change in shipping industry. But on the other hand these new vessels need to safely berth to existing terminals which we may accept as more static part of the trade. Thus this study born by the request of Ege Gaz Aliaga LNG Terminal management to determine if it is safe to berth to the terminal by a new breed of large LNG carrier type named as Q-Flex and Q-Max. Transas Bridge Simulator NTPRO 5000 series was used in this study for extensive experiments which had been simulated by the use of hook function. During the study, every force applied to mooring hooks and dolphins by the ship lines were divided into 3 dimensions and then measured by simulation experiments. With analysis of the data, required hook and dolphins strengths were determined for the safe mooring arrangements. Upon the completion of the study Ege Gaz Aliaga LNG Terminal became the first safe berth for Q-Flex type vessels in the Mediterranean and the Black Sea. And finally all experiments were confirmed with real life experience when the first Q-Flex type LNG carrier berthed to the Ege Gaz Aliaga LNG Terminal.

Steady-state Manoeuvring of a Generic ASD Tug in Escort Pull and Bow-rope Aided Push Operation

Artyszuk J.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2014

Vol. 8, no. 3

449--457

This paper is devoted to expand the very promising research undertaken in the author's previous work, basically done on simplified modelling the escort push operation. Now, the other two modes of a tug's employment, as stated in the title, are covered. The special focus is again set on the indirect towing in that the towline force is much higher than the thruster force. The ratio of these two forces, referred to as the relative towing force (or amplification ratio) is evaluated together with the hull drift angle and the thruster(-s) angle for a given escort speed. This mutual relationship is known as the tug performance diagram. Although rather generic (container-type) formulas are derived, they are supplied for exemplification purposes with simple, analytically given hull hydrodynamic forces. The aim is also here to provide a basis for further sensitivity analysis of the model and possible improvement/optimisation to the tug design. The obtained charts also could serve as rough and clear guidance for towmasters while escorting.

Drag and Torque on Locked Screw Propeller

Tabaczek T., Bugalski T.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2014

Vol. 8, no. 3

441--447

Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades). The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

Approximate Method of Calculating Forces on Rudder During Ship Sailing on a Shipping Route

Żelazny K.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

2014

Vol. 8, no. 3

459--464

Service speed of a ship in real weather conditions is a basic design parameter. Forecasting of this speed at preliminary design stage is made difficult by the lack of simple but at the same accurate models of forces acting upon a ship sailing on a preset shipping route. The article presents a model for calculating forces and moment on plane rudder, useful for forecasting of ship service speed at preliminary stages of ship design.