EXPERIMENTAL RESEARCHES AND COMPARATIVE STUDIES ON SEAKEEPING FOR A LARGE CONTAINER SHIP

Experiment was carried out to investigate the effects of wave direction and rolling motion on deck wetness and relative motion for a large fast container ship. The experimental results of the regular and irregular waves were presented. It is concluded that the wave directions and rolling motion have a considerable influence on the relative motion at mid-ship.

IMPROVEMENT OF FATIGUE STRENGTH OF TUBULAR T-JOINT IN OFFSHORE PLATFORMS DUE TO POSTWELD TREATMENT

Improvement of the fatigue life of welded tubular T-joints in offshore platforms due to weld toe grinding and TIG dressing is studied physically and experimentally. It is shown that the two methods of treatment can improve the fatigue strength of welded tubular joints not only in the environment of air but even in the envirnment of seawater accordingly.

HYDROELASTIC FATIGUE ANALYSIS AND LONG-TERM STRESS PREDICTION OF SALS RISER

In this paper the stress transfer function of a riser is obtained by using the theory of hydroelasticity. The two-parameter wave spectrum group is formed through the joint distribution of wave height and period. The wave spectrum group is transformed into the stress spectrum group by virtue of the stress tranfer function. The fatigue life and extreme stress are predicted by applying the random fatigue analysis technique and long-term prediction theory. The design scheme of a SALS riser in the South China Sea is analysed.

NUMERICAL SIMULATION OF SCALE EFFECT ON SHIP STERN FLOW AND HYDRODYNAMIC PERFORMANCE

The variations of ship stern flow field structure and its corresponding hydrodnamic performance under full scale Reynolds numbal (5 109) and model scale Reynolds numbal(5 106) are investigated numerically in this paper. The governing equations for 3-D incompressible turbulent flow which consist of RANS equation and K-ε two equation turbulence model are solved by finite difference scheme. Derailed computational results are presented graphically. The comparisons between present calculation, existing measurement and other calculation are made.

NUMERICAL SIMULATION OF REYNOLDS NUMBER EFFECT ON EFFETIVE WAKE FIELD AND HYDRODYNAMIC PERFORMANCE OF PROPELLER BEHIND SHIP

The Reynolds number effect of the interaction between the three-dimen-sional ship stern with multi-propellers and its corresponding hydrodynamic performance under four different orders of the Reynolds number (including the full scale Reynolds number 1. 67×109 and the model scale Reynolds number 1. 67×106) are numerically investigated in this paper. This approach to propeller-hull interaction is based on three-di-mensional unsteady RANS equations coupled with a propeller performance program in an interactive and iterative manner to predict the combined flow field and hydrodynamic per- formance of propeller. By comparing the computed effective wake distribution and fraction under four different orders of the Reynolds number, the scale effect of nominal and effec-tive wake distribution is examined and discussed.

VISCOUS FLOWS AROUND BODY-WING JUNCTURES

When an incoming boundary layer flow encounters the large pressure gradient in front of a protruded bluff body such as that of a wing/flat-plate juncture, a horseshoe vortex or a system of horseshoe vortices is generated. These horseshoe vortices travel downstream and form streamwise vortices in the wake. Such a flow phenomenon occurs in many practical applications such as the flow around wing/fuselage juncture of an aircraft, around appendage/hull junctures of a ships, around high-rise building, around bridge piers in rivers, and around blade passages in turbomachines. Due to the vortex flow generated at the juncture, the drag is in general increased and the heat transfer capacity is also degraded. For marine applications, there is an additional and perhaps more significant undesirable feature. That is the streamwise vortices in the wake cause the inflow to the propulsor system to become highly non-uniform. As a consequence, significant unsteady forces may result as the propeller is in operation. The purpose of this paper is to develop an integrated approach of experimentation, numerical evaluation and computer flow simulation for studying and control of the complex three-dimensional vortex flow in this matter.

THEORETICAL AND EXPERIMENTAL STUDY OF THE WAVE FORCES ACTING ON THE BASE WITHOUT GAP IN SHALLOW SEA

Wave forces acting on the offshore structure are of importance for the structure design point of view. There is a so called 'Two Tension Leg Buoy Mooring System' designed to open up the oil field in South China Sea. Two bases of the system are sitting on the sea floor of 30 - 40 meters depth of water. In order to confirm the safety of this system, wave forces are investigated experimentally and numerically. Nowadays, the measured materials on this subject are scarce. In the model test of Dr. Chakrabarti, the test set-up necessitated a small uniform gap between the model and tank floor, and the correct results must be come from an adjustment. The authors have solved the problem. In the paper, two numerical methods are adopted: 3-D boundary integral equation method; eigen-function expression and matching method. The former consists of distribution of Haskind Green' function on the body surface. The latter, however, by dividing the whole fluid domain into subregions, the velocity potential for each subregions can be determined uniquely by matching the velocity potential on their common boundaries, which was expressed formally by its eigen function expansion. As an example, experimental and numerical results were given for a circular base in shallow sea. They agree quite well. Although both methods are effective, the matching method has more efficiency.

ADDED MASS OF UNDERWATER PLATES AND BEAM STIFFENED PLATES IN VIBRATION

In this paper, the added mass of plates and beam stiffened plates vibrating in water are summarized for the purpose of convenience in engineering design. The analytical formulae, calculated data tables, calculated curves and some experimental results are presented.

HYDRODYNAMIC DESIGN METHOD FOR HIGHLY SKEWED PROPELLER AND ITS VALIDATION

In this paper a propeller design method based on acceleration potential without the linearization was described briefly. Six skewed propellers have been designed and tested for 4 different type ships. Experimental results show that developed program has satisfactory accuracy. Meanwhile, designed skewed propellers reach the same high speed as conventional MAU propellers and induced fluctuating pressure are 30% lower than conventional one.

NUMERICAL SIMULATION OF VISCOUS FLOW AROUND AN APPENDED SUBMARINE MODEL

A multizone/multiblock coupled RANS equation solver is presented to numerically simulate the viscous flow around an appended submarine model at Reynolds number 1. E7. k-ε two equation turbulenc model together with wall function are used. The resulting finite difference equations are solved by SIMPLEC, ADI. The technique of rising up the bottom surface is presented to overcome radial contraction problem in Cartesian coordinate system. Benchmark numerical calculations have been compared with experimental data, the radial distribution of axial velocity on the propeller disk plane is 4. 63%.