Underwater Sound Characteristics of a Ship with Controllable Pitch Propeller

The time-dependent spectral characteristics of underwater sound radiated by an oceanic vessel have complex dependencies on ship machinery, propeller dynamics, and the hydrodynamics of the ship exhaust and motion, as well as onboard activities. Here, the underwater sound radiated by a ship equipped with a controllable pitch propeller (CPP) is analyzed and quantified via its (i) power spectral density for signal energetics, (ii) temporal coherence for machinery tonal sound, and (iii) spectral coherence for propeller amplitude-modulated cavitation noise. Frequency-modulated (FM) tonal signals are also characterized in terms of their frequency variations. These characteristics are compared for different propeller pitch ratios, ranging from 20% to 82% at a fixed number of propeller revolutions per minute (RPM). The efficacy and robustness of ship parameter estimation at different pitches are discussed. Finally, an analysis of one special measurement is provided: propeller pitch and RPM over the duration of the measurement when the ship changes speed. The 50% pitch was found to be a crucial point for this ship, around which the tonal characteristics of its underwater radiated sound attain their peak values while broadband sound and associated spectral coherences are at a minimum. The findings here elucidate the effects of pitch variation on underwater sound radiated by ships with controllable pitch propellers and has applications in ship design and underwater noise mitigation

On the survivorship and historical growth of the South African cape rock lobster

Natural survivorship parameters for male and female Cape rock lobsters Jasus lalandii are estimated using size-structure information from pristine sections of the population, such as animals in sanctuaries. It is assumedthat these pristine subpopulations are at steady states, i.e. that annual juvenile settlement is constant, and that migration into and from these populations is negligible. The natural survivorship parameters are calculated in terms of parameters for somatic growth rate, which are obtained by fitting the Ford-Walford growth model to male and female tag data. The results indicate that female natural survivorship is consistently higher than that ofmales, and that the somatic growth rate of J. lalandii was considerably higher at the beginning of the century than during the past 25 years

Retention and application of Skylab experiences to future programs

The problems encountered and special techniques and procedures developed on the Skylab program are described along with the experiences and practical benefits obtained for dissemination and use on future programs. Three major topics are discussed: electrical problems, mechanical problems, and special techniques. Special techniques and procedures are identified that were either developed or refined during the Skylab program. These techniques and procedures came from all manufacturing and test phases of the Skylab program and include both flight and GSE items from component level to sophisticated spaceflight systems

Hydrodynamic Characteristics of 30 GT Fishing Ship Hull Form in Sulawesi Waters

This study aims to determine the hydrodynamic characteristics of the 30 GT fishing ship hull form, operating around Sulawesi waters. The hydrodynamic study includes determinations of; i) ship main dimensions, ii) ship resistance and power, iii) ship stability and maneuvering. The main dimensions identifications were based on a several fishing ship. Ship resistance and power aproximination used Holtrop method. The investigation of ship stability and maneuvering was based on the IMO criteria. Three samples of the fishing ship were investigated. The results of the hydrodynamic analysis showed that the influences of B/T ratio is significant. Properly selecting the B/T ratio on fishing ships can be improved in power reduction and possible increase in safety of shi

River Rhine – hydraulic and ship dynamic modelling

River engineeringNavigation waterways and dredgin

Fluid Dynamic Simulation of Sail Design Performance on Sail-Assisted Ship; A Preliminary Study

Ships are a reliable means of transportation in an archipelagic country like Indonesia. The high use of fossil fuels in sea transportation is one of the contributors to emissions that needs attention apart from their dwindling availability. Efforts to use sails as an additional propulsion force on ships are one of the green technology issues in shipping for reducing the use of fossil fuels. It is about how the design affects the thrust on the ship. Tests were carried out on models M1, M2, and M3 in variations 0°, 30°, and 45° wind angles in computational fluid dynamic simulation at 12 knots constant speed. Through this article, there will be a discourse related to optimizing the design of the sail to produce energy efficiency and reduce the use of fossil fuels on ships. The shaped M3 makes greater thrust on the ships than the other two models. The tendency of a decrease in the thrust of the sails with an increase in the wind direction angle, the distribution of force in two directions, namely as normal and parallel to the sails, is suspected as the cause.Ships are a reliable means of transportation in an archipelagic country like Indonesia. The high use of fossil fuels in sea transportation is one of the contributors to emissions that needs attention apart from their dwindling availability. Efforts to use sails as an additional propulsion force on ships are one of the green technology issues in shipping for reducing the use of fossil fuels. It is about how the design affects the thrust on the ship. Tests were carried out on models M1, M2, and M3 in variations 0°, 30°, and 45° wind angles in computational fluid dynamic simulation at 12 knots constant speed. Through this article, there will be a discourse related to optimizing the design of the sail to produce energy efficiency and reduce the use of fossil fuels on ships. The shaped M3 makes greater thrust on the ships than the other two models. The tendency of a decrease in the thrust of the sails with an increase in the wind direction angle, the distribution of force in two directions, namely as normal and parallel to the sails, is suspected as the cause

Improvement of the energy efficiency of vessels as a measure for the reduction of greenhouses gases emission froem sea shipping

As all we know, pollution is a serious actual problem that affects our society. Maritime transport is responsible of part of that pollution and with this purpose; measure to be taken in the logistical and maritime transport field is to reduce ships emissions. Air pollution is not the only problem, but greenhouse gas emissions too, mainly in the case of maritime transport pollutants as NOx and SOx gasses. This article tries to do a quick view on the last measures took by the International Maritime Organization (IMO) in order to reduce greenhouse gas emissions of shipping. An energy efficiency index for ships was created by the Marine Environment Protection Committee (MEPC) to improve their energy efficiency and then reduce fuel consumption. This index was developed in voluntary interim guidelines established in last sessions of the MEPC among 2009 and 2010, and can be applied to both new designs and ships in operation. Nowadays is just a voluntary measure that whatever ship-owner could take and verify, but until its approval there is for the moment no sanction if the results are not the expected ones by the guidelines. A description of the above mentioned guidelines will be exposed.Postprint (published version

THE RESISTANCE ASPECT OF FISHING BOAT SKIPJACK POLE AND LINE

The operation of fishing vessels skipjack pole and line contributes in catching tuna and skipjack fishes particularly in Indonesian waters. A previous study conducted by the authors found that there was no suitable method provided for the resistance computation atearly ship design phase. Besides, there was aninitial trim existed on the vessel during the operation which contributes for the resistance. The purpose of the study is to find the difference of resistance between the model test and the existing methods. The study was executed also to find the effect of initial trim of the vessel. The study began with collecting the database of a parent ship then to develop and transform into a model-scale for testing purpose in the towing tank. The results of model test were converted to the full-scale vessel. The resistance of full-scale vessel was computed based on the Holtrop and Guldhammer methods. The result of full-of resistance obtained from the model test and the methods were collected, evaluated and compared. The results showed the difference of the resistance for all methods. The result of model test is greater 21 % than that of Holtrop method at the service speed of 10 knots. Meanwhile, the result of model test is lower 14 % than that of Gulhammer method at the same speed. In addition, at the speed of 10 knots the initial trim of 0.5O increase 5 % ofthe resistance, the initial trim of 1O increase 10 % of resistance and the initial trim of 2O increase 16 % of resistance compared to the vesselwithout initial trim. In conclusion, the existing resistance methods are not suitable to be applied for skipjack pole and line fishing vessels. In addition, the initial trim contributes to increase the resistance and should be avoided during the vessel operation