Sail–sail and sail–hull interaction effects of hybrid-sail assisted bulk carrier

In a previously reported study, wind tunnel experiments were undertaken to investigate the aerodynamic characteristics of hybrid-sails in isolation. Such sails are seen as providing a worthwhile reduction in the delivered power to the propeller and hence the engine generated thrust, with a corresponding reduction in the CO₂ production of diesel engine exhaust. In this paper, wind tunnel testing is used to investigate sail–sail interaction effects for two sets of four identical hybrid-sails, and the sail–hull interaction effects for the same two sets of four identical sails in the presence of a bulk carrier hullform. The analysis presented suggests that to build a sail-assisted ship requires an appreciation of the sail–sail and sail–hull interaction effects.     

A GPS-based system for precise shipping guidance and control

This paper discusses the general concept of an automatic berthing system. The research considered the automatic berthing of a large merchant ship. A global positioning system (GPS)-based system, which provides the necessary information on position, velocity, attitude (roll, pitch, and heading), angular velocity, and time, was the principal sensor used. Field tests were conducted on board a hydrographic sounding ship to assess the quality of information obtained from a GPS-based system. The data were processed using the software with which the algorithms developed in this research were implemented. This paper also discusses various aspects concerning a real-time GPS-based system in relation to an automatic berthing system, such as integration of sensors, mathematical models, port infrastructure, and training of crews. Received: October 22, 1999 / Accepted: June 30, 2000     

Case study on health assessments related to a modal shift in transportation

Historically, the emphasis on environmental problems has been on visible pollution. However, as a result of the reduction in visible pollution in recent years, many people have become anxious about invisible dangers. The method for objectively evaluating these invisible dangers is risk assessment. Therefore, in the present study we propose and discuss a method for evaluating the influence of a modal shift in transportation on cancer risk using the technique of risk assessment. First, two representative transportation routes were selected for analysis. Subsequently, the level of airborne carcinogens from the exhaust of ships and trucks was determined. Next, the concentration of each carcinogen in locations across Japan was calculated. Finally, the number of people in Japan who will suffer from cancer related to these emissions was derived and the effects of the modal shift on health are discussed.     

Steady sailing performance of a hybrid-sail assisted bulk carrier

The steady sailing performance of a sail-assisted bulk carrier is investigated utilising towing-tank derived hydrodynamic derivatives and wind tunnel measured aerodynamic properties of the sails and the ship. The aerodynamic characteristics investigated include the ship hull at the fully-loaded draught, the sail–sail interaction effects for two sets of four identical hybrid-sails, and the sail–hull interaction effects for the same two sets of identical sails in the presence of the selected bulk carrier hull-form. This is in addition to lift–drag measurements of single isolated sails of each shape. The form of the two sets of soft sails was rectangular and triangular. This paper is concerned with assessing the benefits of a sail-assisted ship operation, and hence a steady-state rather than complete time-domain integrations of the governing equations are reported. The results of the completed analysis suggest that the benefits of the derived sail generated driving force are greater than the overhead of equipping the ship with a selected system of hybrid-sails. Sail-assisted ships could represent an important contribution to an improving global environment by reducing the demands for a driving force through the propeller.     

Estimation and prediction of effective inflow velocity to propeller in waves

A free running test using a container ship model clarified properties of effective inflow velocity to propellers in waves. The analysis assumes that thrust and torque vary keeping their relation to the effective inflow velocity as represented by open-water characteristics of a propeller in a steady calm water condition. Measurement in regular waves confirmed the variation of average values of the effective wake coefficient and ship speed depending on wavelength and wave encounter angle. Comparison with the longitudinal flow velocity measured at the sides of the propeller using an onboard vane-wheel current meters confirmed that one can estimate the effective inflow velocity based on thrust or torque data. Theoretical estimates in regular waves based on a strip method are provided and compared with the experimental data. A prediction model of the future inflow velocity is proposed to cope with a time delay of a propeller pitch controller for higher propeller efficiency in waves.     

Circular motion tests and uncertainty analysis for ship maneuverability

Circular motion test data and uncertainty analysis results of investigations of the hydrodynamic characteristics of ship maneuvering are presented. The model ships used were a container ship and two tankers, and the measured items were the surge and sway forces, yaw moment, propeller thrust, rudder normal and tangential forces, pitch and roll angles, and heave. The test parameters were the oblique angle and yaw rate for the conditions of a hull with a rudder and propeller in which the rudder angle was set to zero and the propeller speed was set to the model self-propulsion conditions. Carriage data showing the accuracy of the towing conditions in the circular motion test are also presented. It was confirmed that the uncertainties in the hydrodynamic forces such as the surge and sway forces, yaw moment, rudder tangential and normal forces, and propeller thrust were fairly small. The reported uncertainty analysis results of the circular motion test data may be beneficial in validating data quality and in discussing reliability for simulation of ship maneuvering performance.     

Model experiment reproducing an incident of fast ferry

A model scale experiment at a new basin reproduced a phenomenon occurring for a fast ferry; large roll motion and subsequent cargo shift in a quartering sea. Wave generators surrounding the whole periphery of the basin realized a designated directional sea. A carriage system tracked a free-running model ship and a movable weight simulated the cargo shift. Measuring the directional wave field in the basin confirmed the all-around wave generator successfully reproduced the intended wave field that was estimated for the location and the time of the incident. The encounter wave spectrum analyzed using measured data agree well with the theoretically predicted one. The reproduced ship motion, triggered by a small concentrating wave, tells how the ship responded in the successive large quartering waves and the validity of the procedure to reproduce the incident. Repeated measurements of the model ship’s extreme motion confirm a high repeatability of the experiment.