-
The local effects of hull roughness on skin friction. Calculations based on floating element data and three dimensional boundary layer theory
AuthorsL E Johansson
Date published1985
AbstractA mathematical study correlates ship hull roughness with boundary layer flow and viscous resistance and leads to the development of an experimental technique for evaluating roughness effects by direct measurement of skin friction and velocity profile. Calculations are presented for a tanker a container ship and a flat plate. Results on resistance for various degrees of roughness are presented local effects are also studied. Economics of hull surface treatment are discussed.
AuthorsL E Johansson
Date published1985
-
MFV Rotche ON FR965 and MFV Stroma II ON FR156 Report of Court No S500 - The Merchant Shipping Act 1894 Formal Investigation
AuthorsHMSO
PublisherHMSO
AbstractReport into the circumstances surrounding the collision of MFV Rotche and MFV Stroma II on or about 8 July 1977 of Mallaig.
AuthorsHMSO
PublisherHMSO
-
A study on the accuracy of the recent prediction technique of ship's manoeuvrability at early design stage
AuthorsT Ishiguro ; S Tanaka ; Y Yoshimura et al.
Shelf Location213c
AbstractA validation of the current prediction tool of ship's manoeuvrability at the early design stage has been conducted on three hull forms with differing course stability and on hulls which have the same principal particulars but different stern frame lines. Kijima's mathematical model now used widely by shipbuilders is chosen for the predictions. The prediction method is described. The validation study on the prediction model is looked at. A sensitivity study on simulation parameters is performed and discussed. An attempt is made to improve the prediction accuracy based on the sensitivity study.
AuthorsDate publishedT Ishiguro ; S Tanaka ; Y Yoshimura et al.
1996
Shelf Location213c
-
Analysis of pressure distribution coefficient on steps under hydraulic jump conditions in sloping stilling basins
AuthorsA M Negm
Date published1998
AbstractThe results of a theoretical and experimental investigation on the coefficient of pressure distribution on steps under hydraulic jump conditions in sloping basins are presented. The results show the coefficient is a function of the initial Froude number the step height ratio the slope of the channel bed and the type of jump. The developed equations are used to study the effect of various parameters on the coefficient. It is concluded that negative pressure may occur on a negative step. Consequently dynamic pressure fluctuations on the faces of the steps should be measured to locate any negative zones and to verify the occurrence of cavitation.
AuthorsA M Negm
Date published1998
-
Effect of non-plastic fines on liquefaction characteristics of sandy soils under cyclic loading
AuthorsY Nabeshima ; M A El Mesmary ; T Matsui
Date published2002
AbstractIn recent decades many liquefaction phenomena have been reported which are due to earthquakes in reclaimed deposits that contain fines. When the deposits liquefy structures built on these deposits are seriously damaged. A full understanding of the effect of fines on the liquefaction characteristics is necessary for selecting the most suitable and reliable remediation. A series of undrained cyclic torsional shear loading tests was carried out on sandy soils with non-plastic fines to investigate the effect of fines properties on the liquefaction characteristics. The features of the cyclic failure modes of sandy soils with non-plastic fines at different initial densities are presented and the effects of both fines properties and initial relative density of the soil on the liquefaction strength and the development rates of both pore water pressure and shear strain during cyclic loading are discussed. The liquefaction strength is shown to decrease slightly with increasing non-plastic fines content in sandy soils and the rates of development of both pore water pressure and shear strain during cyclic loading increase with increasing non-plastic fines content and initial relative density of the soil.
AuthorsY Nabeshima ; M A El Mesmary ; T Matsui
Date published2002
-
Green Water on Ship-Type Offshore Structures
AuthorsBas Buchner
Shelf Location231d
AbstractIn heavy storms, the waves and ship motions can become so large that water flows onto the deck of the ship. This is generally known as 'green water loading'. On ship-type offshore structures green water loading can result in risk for the ship, its crew and its sensitive equipment. Therefore, it should be taken into account in the design of such structures. The main objective of this study was to develop methods for the evaluation of green water on ship-type offshore structures based on a clear description of the green water physics. Contents cover the physics of green water on the bow, systematic model testing, non-linear relative wave motions at the bow, water flow onto and on the bow deck, green water impact loading, green water from the side and stern, review and application of the method, numerical prediction of green water, and conclusions and recommendations of the study.
AuthorsPublisherBas Buchner
Wageningen : Grafisch Bedrijf Ponsen & Looijen bv
ISBN number904646883
Shelf LocationDate published231d
2002
-
Implication of Inspection Updating on System Fatigue Reliability of Offshore Structures
AuthorsT Moan ; R Song
Date published1998
AbstractIn this paper the effect of inspection updating on fatigue reliability of offshore structures is investigated. In particular the effect of inspection on the reliability of both inspected and un-inspected joints is assessed dependent upon the correlation of properties of different joints. The effect of repeated inspections and inspection sample size on fatigue reliability is also investigated. The influence of inspection of certain joints on the reliability of a series system is studied and the effect of system-based updating policy on fatigue reliability is investigated. It is found that the system reliability is significantly affected by the inspection updating policy.
AuthorsT Moan ; R Song
Date published1998
-
Marine Accident Investigation Branch (MAIB) Report of the investigation into fire on board ro-ro passenger vessel Sally Star on 25 August 1994
AuthorsMAIB
PublisherDepartment of Transport (DOT)
AbstractOn 25 August 1994 fire broke out in the main engine room of MV Sally Star a ro-ro passenger ferry. The fire was caused by the failure of a bolted lange joint on the low pressure fuel system of No 4 main engine allowing flammable fuel oil vapour to come into contact with part of the engine exhaust system. Recommendations include matters concerning the early warning of oil fuel vapour leakage in machinery spaces and more stringent requirements for low pressure fuel systems of medium speed diesel engines
AuthorsDate publishedMAIB
1995
PublisherDepartment of Transport (DOT)
-
Mean Wave Drift Loads on Connected Multiple Semisubmersible Modules
AuthorsX Liu ; R C Ertekin ; H R Riggs et al.
Date published1998
AbstractThe second-order mean wave drift loads on multiply-connected semi-submersibles are studied in this paper. The calculations are done on three Very Large Floating Structures (VLFS) which are formed by connecting three five and seven identical semi-submersible modules. For the 5 module VLFS the first-order responses are also compared with the published results. To reduce the computational effort the symmetry properties of the modules are utilized. The mean wave drift loads are obtained for a number of incoming wave directions. Different types of connectors are used to understand the effect of connector stiffness on the drift loads. It is shown that the mean wave drift loads on connected multiple semisubmersible modules are generally small compared with box- or mat-type very large floating structures. It is also found that due to the small water plane surface of the semisubmersible-type VLFS the effect of the interaction of the neighboring modules on the drift loads is small.
AuthorsX Liu ; R C Ertekin ; H R Riggs et al.
Date published1998
-
On the contribution of swell to sea surface phenomena (2)
AuthorsHisashi Mitsuyasu ; Yuichi Maeda
Date published2002
AbstractThe effect of swell on air-sea interaction phenomena is controversial. The problem is important not only as dynamical processes at air-sea boundary but also for practical application such as wave forecasting. On the basis of recent studies contributions of swell to sea surface phenomena are discussed. It is shown that the attenuation of wind waves by swell depends not only on swell steepness but also on the ratio of the frequency of the swell to the spectral peak frequency of wind waves. It is also shown that the measured growth rate of swell in a wind area agrees well with the empirical formula of Hsiao and Shemdin (1983) in a region of small inverse wave age while it approaches the empirical formula of Mitsuyasu and Honda (1982) in a region of large inverse wave age. Finally the increase of surface drift current by opposing swell using the result of recent study on Langmuir circulation (Mizuno 2002) is briefly discussed.
AuthorsHisashi Mitsuyasu ; Yuichi Maeda
Date published2002
-
On the effect of narrow and long corrosion defects on the collapse pressure of pipelines
AuthorsT A Netto
Date published2007
AbstractAs offshore activities move to deeper scenarios pipelines and risers used to connect sea-floor wells to platforms can also be susceptible to collapse due to the ambient external pressure. Internal corrosion in pipelines is often caused by water sediment or chemical contaminants present in the multi-phase flow. This normally occurs at the bottom of the pipe and at low points in the pipeline where sediment and water can settle out of the product being transported therefore creating narrow and long defects. The effect of corrosion defects on the collapse pressure of offshore pipelines was studied through combined small-scale experiments and nonlinear numerical analyses based on the finite element method. After calibrated in view of the experimental results the model was used to determine the collapse pressure as a function of material and geometric parameters of different pipes and defects. An extensive parametric study using 2D and 3D numerical models was carried out encompassing different defect geometries and their interaction with pipe ovalisation. These results are reported. They are subsequently used to develop a simple procedure for estimating the collapse pressure of pipes with narrow defects.
AuthorsT A Netto
Date published2007
-
On the hydrodynamic design of podded propulsors for fast commercial vessels
AuthorsAntonio Sanchez-Caja ; Jaakko V Pylkkanen
Date published2004
AbstractThe application of the RANS solver FINFLO to the hydrodynamic design of podded propulsors for high-speed operation is described. In particular a Ropax and a cargo ship are used as candidates for speeds of 35-38 knots. For such high speeds the hydrodynamic design of the propeller with its housing is critical due to the danger of cavitation on both propeller blades and supporting strut. The optimisation process of the propeller housing is dealt with using RANS solver FINFLO. Even though RANS solvers are analysis tools as opposed to design ones they can be used iteratively for design purposes. The right choice of the computational grid together with the computational model make it possible to test alternative geometries in a relatively short time. A non-symmetric strut is designed to delay cavitation inception keeping at the same time low drag and low lateral forces on the strut. A remarkable reduction of low-pressure areas is observed on the strut surfaces for a tailor-made design as compared to a conventional symmetric strut. Several pod configurations have also been analysed. Their hydrodynamic merit is evaluated on the basis on RANS results.
AuthorsAntonio Sanchez-Caja ; Jaakko V Pylkkanen
Date published2004
-
Reduction of wave pressures on vertical seawall/caissons due to an offshore breakwater
AuthorsMuthukuru G MuniReddy ; Subramanian Neelamani
Date published2003
AbstractEstimation of wave pressures on vertical impermeable caissons and seawall is needed to determine the dimensions and appropriate material selection of the structure. Reduction of extreme wave loadings (pressures) by constructing an offshore breakwater on seaward side of these structures is investigated. A series of physical model tests were carried out in a wave flume to examine the performance of the defence structure (offshore breakwater) in reducing the wave pressures on the seawall/caisson. Quasi-static nature of the wave pressures was observed due to piling-up of fluid mass behind the breakwater. The influence of the pool length on reduction of pressures on seawall/caisson is also investigated for regular waves.
AuthorsMuthukuru G MuniReddy ; Subramanian Neelamani
Date published2003
-
Research on characteristics of responses on floating structures due to various tsunami wave profiles
AuthorsKoichi Masuda ; Tomoki Ikoma ; Maki Uchida et al.
Date published2003
AbstractThe aim of this research is to develop practical estimation methodologies for responses of and the mooring force on a floating structure in shallow seas and to clarify the characteristics of responses induced by various tsunami wave profiles. In this paper the estimation methodology is introduced. In the paper some tools of parts of system are verified. The analysis method for the Tsunami exciting forces based on the 2-D BEM simulation program code is verified by comparing with the experimental results and other simulation results. The characteristics of responses due to the difference of Tsunami wave profile are discussed.
AuthorsKoichi Masuda ; Tomoki Ikoma ; Maki Uchida et al.
Date published2003
-
The resistance of ships in level ice
AuthorsPetri Valanto
Date published2006
AbstractThe research on the numerical prediction of ice-breaking loads and resistance has reached a point at which practical problems related to ship design and construction can be solved. A 3D numerical model of the ice-breaking process on the waterline of a ship advancing in level ice was developed for investigating ice loads and resistance forces on ship hulls. For the purposes of validation ice forces on the waterline of the Swedish Coast Guard Ship KBV-181 were computed for several ship speeds and values of level ice thickness and compared to measurements with a load panel installed on the sister ship MS Uisko. The correlation between the computed results and the measured short-term ice loads proved to be very satisfactory. The processes on the underwater hull causing resistance to ship motion in level ice were identified but their modelling is not complete. Therefore the ship resistance is evaluated by computing the resistance forces on the DWL with the theoretical model and the underwater components of resistance with the semi-empirical method of Lindqvist. The sum of these components makes out the total resistance in level ice which in turn was compared to measurements on several ships. A very satisfactory correlation was reached.
AuthorsPetri Valanto
Date published2006
-
Wave drifting forces on multiple connected floating structures
AuthorsM Takaki ; Y Tango ; O Faltinsen et al.
Date published1994
AbstractThe wave drifting forces acting on a very large floating structure consisting of multiple barge type modules is studied theoretically and experimentally. The wave drifting forces are estimated with two module connectors. The effects of connector conditions and the number of bodies on the wave drifting forces are discussed. It is verified that the coefficient of the wave drifting force on the multiple connected structure with hinge connectors can exceed the value of 3. The forces on the structure with hinge connectors are smaller than those on the structure with rigid connectors in long wave length range. The effect of the hydrodynamic interaction is strongly affected by the connecting conditions. It cannot be neglected for calculations of seakeeping performance for the huge floating structure.
AuthorsM Takaki ; Y Tango ; O Faltinsen et al.
Date published1994
-
Wave spectral evolution on the coastlines of southern Italy
AuthorsG Benassai ; E Chianese ; E Sansone
Date published2004
AbstractA method is proposed to obtain the wave spectral evolution in waters of different depth. The method is based on the transfer of the measured spectra on deep water and on the saturation of the spectra on finite depth. The offshore wave spectra were transferred from the measurement station offshore Ponza to the sites of interest located offshore the Gulf of Naples and offshore the Gulf of Salerno respectively. The inshore wave spectra were obtained from the offshore ones with a mathematical model which takes into account the saturation process. The numerical results in terms of offshore wave spectra were compared with those recorded offshore the Gulf of Naples by a wave-rider buoy. The inshore results in terms of significant wave heights were compared with those recorded by a meteo-oceanographic station on the Salerno coastline of Salerno at a depth of 9 m.
AuthorsG Benassai ; E Chianese ; E Sansone
Date published2004
-
Bureau of Maritime Affairs Republic of Liberia Decision of the Commissioner of Maritime Affairs R.L and Report of the Investigation into the Matter of the Loss by Grounding of the Motor Tanker Braer ON 7703 on the South Coast of Shetland Island 5 January
AuthorsBureau of Maritime Affairs
PublisherBureau of Maritime Affairs
AbstractItems include - Interviews Findings of Fact Recommendation on Fuel Tank Venting and Conclusions.
AuthorsDate publishedBureau of Maritime Affairs
1994
PublisherBureau of Maritime Affairs
-
Comprehensive study on two-stage combustion for the reduction of soot and NOx emissions from DI diesel engines
AuthorsT Chikahisa
Date published2000
AbstractResults are presented of a series of works on two-stage combustion. The effect of turbulent jet on smoke reduction is investigated - it is found that turbulence induced during the main combustion reduces smoke without increasing NOx. Next experimental results are discussed of several trials with two-stage combustion for NOx reduction. Then to see the NOx reduction potential of the two-stage combustion and to identify the effective control-factors for the reduction NOx formation kinetics are analysed together with the jet momentum on smoke reduction. Finally jet impingement on flame is observed to find out the condition that will give the maximum mixing with the same energy of CCD jets. Results are listed as a conclusion.
AuthorsT Chikahisa
Date published2000
-
Effects of slip-stick on top tensioned riser fatigue
AuthorsJohn J Murray ; Djoni E Sidarta ; Xiaohua Lu et al.
Date published2002
AbstractThis paper compares and discusses the results of coupled and uncoupled models to compute the damage in the risers due to slip-stick. The two models are based on identical finite-element models of the riser system. The main difference is how the motion input to each model is computed. In the coupled model the effects of the riser on the motions are integrated in to the time-domain solution of the motion. In the uncoupled model motions that are computed assuming only horizontal restoring forces from the risers are imposed on the contacts between the riser and the hull. In general the coupling effects showed that the risers dampen motion in surge sway roll pitch and yaw but have an insignificant effect on the natural periods. The heave comparison showed a reduction in heave due to damping from the risers sliding as well as from the constraints of the risers while they are stuck. Results of the coupled analysis showed lower fatigue damage than those predicted by the uncoupled model and these results are used to show the level of conservatism introduced by the uncoupled model.
AuthorsJohn J Murray ; Djoni E Sidarta ; Xiaohua Lu et al.
Date published2002