Dynamic Characteristics of Lifting Pipe on a Retrofitted Mining Vessel

Lifting pipe used in deep ocean mining is the tool to transport mineral from seabed to vessel. In this study, a vessel was retrofitted as an experimental ship for deep ocean mining with a U-type lifting pipe installed on the right side of vessel. Assuming pipe as a rigid structure, the impact of pipe on movements of vessel were discussed based on frequency domain method for hydrodynamic analysis.

A REVIEW OF METHODS FOR HYDRO-ACOUSTIC ANALYSIS OF NON-CAVITATING MARINE PROPELLERS

Underwater Radiated Noise (URN) emanating from surface and underwater marine platforms has become a significant concern for all the Nations in view of the global requirement to minimise the increasing adverse impact on marine mammals and fishes and maintain ecological balance in the ‘Silent’ ocean environment. Ambient noise level in the sea, in 10 to 300 Hz frequency band, has increased by 20 to 30 dB due to shipping (Wittekind, 2009). Marine propeller (in non- cavitating and cavitating regime) is a potential contributor to the ships noise and a lot of scientific research has been undertaken and considerable progress has been achieved in estimating the hydro-acoustic performance of marine propellers. In light of this, the scope of this paper is to review and critically examine the various methods used for estimating the hydro-acoustic performance of marine propellers, particularly in the non-cavitating regime, over the past many years. This review paper brings out the details, applicability, merits and demerits of various methods, extrapolation laws to obtain full scale results, scientific conclusion of all the know-how on this subject and the scope of further research as perceived by the authors. This paper also presents a numerical methodology to estimate the noise radiated by a DTMB 4119 model propeller in the non-cavitating regime in open water condition. The hydrodynamic analysis of the propeller was performed using commercial CFD software STARCCM+, closure was achieved using standard k-ε turbulence model and hydro-acoustic predictions have been performed using FWH acoustic analogy. The results compare very well with the published literature.

VERTICAL AND SLOPED BANK EFFECTS ON DIFFERENT SHIP TYPES

This study employed computer design software to completely draft 3D ship models; then, computational fluid dynamics were used to establish numeric navigation channels and simulate fluid hydrodynamic analysis of ships navigating along shore banks. The parameters considered comprised bank type (vertical and sloped), ship model (two types), velocity, ship-to-bank distance, and navigation time. Figures and tables were used to present the distribution of ship stern eddy current, flow field pressure, and velocity, and the comparison of center of mass deviation, sway force, and yaw moment. Results showed that ships navigating along embankments and channels produced asymmetric flows, which draw the bow away from the shore. Larger ships are substantially more influenced by bank effects than smaller ships. Large sway forces and yaw moments are produced in large ships, drifting the bow away from the bank and the stern towards the bank, increasing the risk of collision with the embankment. From the study results, the characteristics of bank effects are understood and can be used for assisting the safe navigation of ships in restricted waters.

CFD-BASED HYDRODYNAMIC ANALYSIS FOR A SHIP SAILING ALONG A BANK IN RESTRICTED WATERS

The paper is interesting, good structured and deals with an important problem concerning ship behaviour in restricted water. The use of a CFD method as FLUENT (code also used at Ghent University) shows the possibilities of numerical methods for the calculation of ship-bank interaction. The content could still be improved as some topics in the paper miss some depth.

CFD-BASED HYDRODYNAMIC ANALYSIS FOR A SHIP SAILING ALONG A BANK IN RESTRICTED WATERS

For a ship navigating along a bank in restricted waters, it is usually accompanied by obvious bank effect which may cause ship-bank collision. In order to avoid collision, it is necessary to provide control force and moment by using control devices such as a rudder. In this paper, CFD method is applied to numerically simulate the viscous flow around a ship appended with a rudder sailing along a bank. Systematical simulations are carried out for the hull-rudder system with different rudder angles at different ship-bank distances and water depths. The flow field features and the hydrodynamic forces of the hull-rudder system are obtained and analysed. This study is of significance for revealing the physical mechanism behind the bank effect and providing guidance for ship steering and control in restricted waters.