Christiaan Adika Adenya

Experimental and Numerical Analysis of Hull Girder Vibrations and Bow Impact of a Large Ship Sailing in Waves

It is of great importance to evaluate the hull structural vibrations response of large ships in extreme seas. Studies of hydroelastic response of an ultra large ship have been conducted with comparative verification between experimental and numerical methods in order to estimate the wave loads response considering hull vibration and water impact. A segmented self-propelling model with steel backbone system was elaborately designed and the experiments were performed in a tank. Time domain numerical simulations of the ship were carried out by using three-dimensional nonlinear hydroelasticity theory. The results from the computational analyses have been correlated with those from model tests.

Experimental Investigation of Wave-Induced Ship Hydroelastic Vibrations by Large-Scale Model Measurement in Coastal Waves

Ship hydroelastic vibration is an issue involving mutual interactions among inertial, hydrodynamic, and elastic forces. The conventional laboratory tests for wave-induced hydroelastic vibrations of ships are performed in tank conditions. An alternative approach to the conventional laboratory basin measurement, proposed in this paper, is to perform tests by large-scale model measurement in real sea waves. In order to perform this kind of novel experimental measurement, a large-scale free running model and the experiment scheme are proposed and introduced. The proposed testing methodology is quite general and applicable to a wide range of ship hydrodynamic experimental research. The testing procedure is presented by illustrating a 5-hour voyage trial of the large-scale model carried out at Huludao harbor of China in August 2015. Hammer tests were performed to identify the natural frequencies of the ship model at the beginning of the tests. Then a series of tests under different sailing conditions were carried out to investigate the vibrational characteristics of the model. As a postvoyage analysis, load, pressure, acceleration, and motion responses of the model are studied with respect to different time durations based on the measured data.

Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model’s Motions and Loads Measurement in Realistic Sea Waves

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship’s navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign.

Experimental Investigation of the Behaviour of a Large Ship in Irregular Waves

A towing tank experimental investigation was carried out using a segmented scaled model of a large ship prototype to study its behaviour when sailing in irregular head waves. The tests were carried out for typical sailing speeds and wave conditions that would be encountered by the large ship at sea. The vertical plane motion of heave, pitch, and the accelerations at bow and stern, and the vertical bending moment load responses of the ship were measured and analyzed. The significant amplitude values of motion and load response of the ship for the investigated wave conditions and speeds were determined by using spectral analysis. Slamming induced whipping loads were also investigated for the studied sailing conditions. In addition, the load response characteristics were evaluated in both time-domain and frequency-domain. Increasing the sea state had a greater effect on the motion and load responses of the large ship than increasing the sailing speed.

Numerical analysis of the motion and load responses of a 400,000 DWT ore carrier in waves

The need to benefit from economy of scale has driven the design of larger and larger ships with increasing tonnage. The hull structures of large ships are more flexible and the natural frequencies of the hull girder can even fall within the range of wave encounter frequencies resulting in the resonance phenomenon termed springing. A numerical linear hydroelastic investigation of the wave induced motion and load responses of a 400,000 dead weight tonnage (DWT) ore carrier is carried out in this work using an in-house program: Linear Elastic Compass Wave Loads Calculation System (WALCS-LE). The full load condition at different ship speeds, wave lengths and incident wave headings in regular waves is investigated. Long term predictions are also made. It is imperative to account for springing loads and the probable extreme motions and loads at the design stage of large ships to ensure their endurance and safety at sea.