Stopping manoeuvre of high speed vessels fitted with screw and waterjet propulsion

Concern about the increase in high-speed vessel traffic necessitates steps to bring out safety guidelines in order to regulate and improve their manoeuvrability. The stopping abilities of vessels ranging from medium speed containerships to high-speed vessels have been estimated. Assuming a straight contour track, the stopping distances have been checked against the known stopping criteria of IM

An experimental investigation into the constant velocity water entry of wedge-shaped sections

Constant velocity water entry is important in understanding planing and slamming of marine vessels. A test rig has been developed that drives a wedge section with end plates down guides to enter the water vertically at near constant velocity. Entry force and velocity are measured. Analysis of the test data shows that the wetting factor is about 1.6 at low deadrise angles and reduces nearly linearly to 1.3 at 451 deadrise angle. The added mass increases quadratically with immersed depth until the chines become wetted. It then continues to increase at a reducing rate, reaching a maximum value between 20% and 80% greater than at chine immersion. The flow momentum drag coefficient is estimated from the results to be 0.78 at 51 deadrise angle reducing to 0.41 at 451 deadrise angles. Constant velocity exit tests show that the momentum of the added mass is expended in driving the water above the surface level and that exit forces are low and equivalent to a drag coefficient of about 1.0-1.3. Considerable dynamic noise limits the accuracy of the results, particularly after chine immersion

Drag and inertia coefficients for horizontally submerged rectangular cylinders in waves and currents

The results of an experimental investigation carried out to measure combined wave and current loads on horizontally submerged square and rectangular cylinders are reported in this paper. The wave and current induced forces on a section of the cylinders with breadth-depth (aspect) ratios equal to 1, 0.5, and 0.75 are measured in a wave tank. The maximum value of Keulegan-Carpenter (KC) number obtained in waves alone is about 5 and Reynolds (Re) number ranged from 6.3976103 to 1.186105. The drag (CD) and inertia (CM) coefficients for each cylinder are evaluated using measured sectional wave forces and particle kinematics calculated from linear wave theory. The values of CD and CM obtained for waves alone have already been reported (Venugopal, V., Varyani, K. S., and Barltrop, N. D. P. Wave force coefficients for horizontally submerged rectangular cylinders. Ocean Engineering, 2006, 33, 11-12, 1669-1704) and the coefficients derived in combined waves and currents are presented here. The results indicate that both drag and inertia coefficients are strongly affected by the presenceof the current and show different trends for different cylinders. The values of the vertical component inertia coefficients (CMY) in waves and currents are generally smaller than the inertia coefficients obtained in waves alone, irrespective of the current's magnitude and direction. The results also illustrate the effect of a cylinder's aspect ratio on force coefficients. This study will be useful in the design of offshore structures whose columns and caissons are rectangular sections

Whaleback forecastle for reducing green water loading on high-speed container vessels

This paper investigates the employment of whaleback forecastle tackling the problem of green water. Green water experimental set-up is briefly described, and the hydrodynamic model of green water is introduced. Generic designs of whaleback forecastle are also described, and the development of the model for computational fluid dynamics simulation is explained. Two green water conditions (categorised by its severity) are considered for analysis, and the simulation results are analysed to understand the changes in the green water loading. Conclusions are finally drawn on the effectiveness and adequacy of the whaleback forecastle as an option to reduce green water loading on high-speed container vessels

New generic equation for interaction effects on a moored containership due to passing tanker

In order to improve the formulation of moored-passing ship interaction forces and moments in the mathematical model of a ship maneuvering simulator, a comprehensive captive model test program was carried out and a theoretical calculation method was developed. At present, semiempirical approaches, resulting in an estimation of forces and moments in the horizontal plane caused by hydrodynamic interaction on a moored ship due to a passing ship, are not available in literature. The present research intends to enhance the theoretical approach by validating the calculated peak forces and moments with experimental data. The numerical method is subsequently applied to generate a systematic database for the development of a new set of generic formulae for estimating the effect of passing vessels on moored ships in the equations of motion for surge, sway, and yaw applied in maneuvering and mooring simulators

Green water investigation for a container ship

Presents a green water investigation for a container ship

Effective and efficient breakwater design for trading vessels and FPSOS

Breakwaters obviously need to fulfill their function (protecting sensitive structures or cargo) while at the same time remaining intact and imposing manageable loads onto supporting structure. It goes without saying that such breakwaters should be cost effective, so that complex designs with extensive welding may not be preferable. In this paper the authors discuss green water loading on breakwaters for trading vessels like container ships which have forward speed and FPSOs which have zero speed. Different generic designs of V shape, vane type, double skin with and without holes, and forward sloping forecastle (whaleback deck) breakwaters applied to trading vessels are discussed. Guidelines for modeling green water horizontal loading on breakwaters of FPSOs and trading vessels using computational fluid dynamics (CFD) techniques are provided. The paper will also include a review of breakwater design criteria in rules and regulations