In this research, a commercial CFD code “Fluent” was applied to optimization of bulbous bow shape for a non ballast water ships (NBS). The ship was developed at the Laboratory of the authors in Osaka Prefecture University, Japan. At first, accuracy of the CFD code was validated by comparing the CFD results with experimental results at towing tank of Osaka Prefecture University. In the optimizing process, the resistances acting on ships in calm water and in regular head waves were defined as the object function. Following features of bulbous bow shapes were considered as design parameters: volume of bulbous bow, height of its volume center, angle of bow bottom, and length of bulbous bow. When referring to the computed results given by the CFD like resistance, pressure and wave pattern made by ships in calm water and in waves, an optimal bow shape for ships was discovered by comparing the results in the series of bow shapes. In the computation on waves, the ship is in fully captured condition because shorter waves, λ/Lpp<0.6, are assumed.

Nowadays, there are many studies conducted in the field of marine hydrodynamics which focus on two vessels traveling and floating in sufficiently close proximity to experience significant interactions. The hydrodynamic behavior of parallel moving ships in waves is an interesting and important topic of late. A numerical investigation has been carried out for the prediction of wave exciting forces and motion responses of parallel moving ships in regular waves. The numerical solution was based on 3D distribution technique and using the linear wave theory to determine the exciting forces and ship’s motion. The speed effects have been considered in the Green function for more realistic results. The numerical computations of wave exciting forces and motion responses were carried out for a Mariner and Series 60 for the purpose of discovering different Froude numbers and different separation distances in head sea conditions. Based on the numerical computations, it was revealed that the sway, roll and yaw have a significant effect due to hydrodynamic interaction.

The purpose of this research study was to examine the attitude response of a planing craft under the controllable hydrofoils. Firstly, a non-linear longitudinal attitude model was established. In the mathematical model, effects of wind loads were considered. Both the wetted length and windward area varied in different navigation conditions. Secondly, control strategies for hydrofoils were specified. Using the above strategies, the heave and trim of the planing craft was adjusted by controllable hydrofoils. Finally, a simulation program was developed to predict the longitudinal attitudes of the planing craft with wind loads. A series of simulations were performed and effects of control strategies on longitudinal attitudes were analyzed. The results show that under effects of wind loads, heave of fixed hydrofoils planing craft decreased by 6.3%, and pitch increased by 8.6% when the main engine power was constant. Heave decreased by less than 1% and trim angle decreased by 1.7% as a result of using variable attack angle hydrofoils; however, amplitude changes of heave and pitch were less than 1% under the control of changeable attack angle hydrofoils and longitudinal attitude.

In this paper a 3D numerical model was developed to study the complicated interaction between waves and a set of tandem fixed cylinders. The fluid was considered to be inviscid and irrotational. Therefore, the Helmholtz equation was used as a governing equation. The boundary element method (BEM) was adopted to discretize the relevant equations. Open boundaries were used in far fields of the study domain. Linear waves were generated and propagated towards tandem fixed cylinders to estimate the forces applied on them. Special attention was paid to consideration of the effect on varying non-dimensional cylinder radius and distance between cylinders, ka and kd on forces and trapped modes. The middle cylinder wave forces and trapped modes in a set of nine tandem cylinders were validated utilizing analytical data. The comparisons confirm the accuracy of the model. The results of the inline wave force estimation on n tandem cylinders show that the critical cylinder in the row is the middle one for odd numbers of cylinders. Furthermore the results show that the critical trapped mode effect occurs for normalized cylinder radiuses close to 0.5 and 1.0. Finally the force estimation for n tandem cylinders confirms that force amplitude of the middle cylinder versus normalized separation distance fluctuates about that of a single cylinder.

Small water-plane area twin-hull (SWATH) has drawn the attention of many researchers due to its good sea-keeping ability. In this paper, MMG’s idea of separation was used to perform SWATH movement modeling and simulation; respectively the forces and moment of SWATH were divided into bare hull, propeller, rudder at the fluid hydrodynamics, etc. Wake coefficient at the propellers which reduces thrust coefficient, and rudder mutual interference forces among the hull and propeller, for the calculation of SWATH, were all considered. The fourth-order Runge-Kutta method of integration was used by solving differential equations, in order to get SWATH’s movement states. As an example, a turning test at full speed and full starboard rudder of ‘Seagull’ craft is shown. The simulation results show the SWATH’s regular pattern and trend of motion. It verifies the correctness of the mathematical model of the turning movement. The SWATH’s mathematical model is applied to marine simulator in order to train the pilots or seamen, or safety assessment for ocean engineering project. Lastly, the full mission navigation simulating system (FMNSS) was determined to be a successful virtual reality technology application sample in the field of navigation simulation.

The application of multi-hull ship or trimaran vessel as a mode of transports in both river and sea environments have grown rapidly in recent years. Trimaran vessels are currently of interest for many new high speed ship projects due to the high levels of hydrodynamic efficiency that can be achieved, compared to the mono-hull and catamaran hull forms. The purpose of this study is to identify the possible effects of using an unsymmetrical trimaran ship model with configuration (S/L) 0.1–0.3 and R/L=0.1–0.2. Unsymmetrical trimaran ship model with main dimensions: L=2000mm, B=200 mm and T=45 mm. Experimental methods (towing tank) were performed in the study using speed variations at Froude number 0.1–0.6. The ship model was pulled by an electric motor whose speed could be varied and adjusted. The ship model resistance was measured precisely by using a load cell transducer. The comparison of ship resistance for each configuration with mono-hull was shown on the graph as a function of the total resistance coefficient and Froude number. The test results found that the effective drag reduction could be achieved up to 17% at Fr=0.35 with configuration S/L=0.1.

In this paper, various aspects of the 2D and 3D nonlinear liquid sloshing problems in vertically excited containers have been studied numerically along with the help of a modified -transformation. Based on this new numerical algorithm, a numerical study on a regularly and randomly excited container in vertical direction was conducted utilizing four different cases: The first case was performed utilizing a 2D container with regular excitations. The next case examined a regularly excited 3D container with two different initial conditions for the liquid free surface, and finally, 3D container with random excitation in the vertical direction. A grid independence study was performed along with a series of validation tests. An iteration error estimation method was used to stop the iterative solver (used for solving the discretized governing equations in the computational domain) upon reaching steady state of results at each time step. In the present case, this method was found to produce quite accurate results and to be more time efficient as compared to other conventional stopping procedures for iterative solvers. The results were validated with benchmark results. The wave elevation time history, phase plane diagram and surface plots represent the wave nonlinearity during its motion.

Two coaxial vertical cylinders one is a riding hollow cylinder and the other a solid cylinder of greater radius at some distance above an impermeable horizontal bottom, were considered. This problem of diffraction by these two cylinders, which were considered as idealization of a buoy and a circular plate, can be considered as a wave energy device. The wave energy that is created and transferred by this device can be appropriately used in many applications in lieu of conventional energy. Method of separation of variables was used to obtain the analytical expressions for the diffracted potentials in four clearly identified regions. By applying the appropriate matching conditions along the three virtual boundaries between the regions, a system of linear equations was obtained, which was solved for the unknown coefficients. The potentials allowed us to obtain the exciting forces acting on both cylinders. Sets of exciting forces were obtained for different radii of the cylinders and for different gaps between the cylinders. It was observed that changes in radius and the gap had significant effect on the forces. It was found that mostly the exciting forces were significant only at lower frequencies. The exciting forces almost vanished at higher frequencies. The problem was also investigated for the base case of no plate arrangement, i.e., the case having only the floating cylinder tethered to the sea-bed. Comparison of forces for both arrangements was carried out. In order to take care of the radiation of the cylinders due to surge motion, the corresponding added mass and the damping coefficients for both cylinders were also computed. All the results were depicted graphically and compared with available results.

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates, separated by a gap of finite width, floating horizontally on water of finite depth, are investigated in the present work for a two-dimensional time-harmonic case. Within the frame of linear water wave theory, the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions. Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem. In both the problems, the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates. Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations. The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration. The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.

A pipe model with a mass ratio (mass/displaced mass) of 4.30 was tested to investigate the vortex-induced vibrations of submarine pipeline spans near the seabed. The pipe model was designed as a bending stiffness-dominated beam. The gap ratios (gap to diameter ratio) at the pipe ends were 4.0, 6.0, and 8.0. The flow velocity was systematically varied in the 0–16.71 nondimensional velocity range based on the first natural frequency. The mode transition between the first and the second mode as the flow velocity increases was investigated. At various transition flow velocities, the research indicates that the peak frequencies with respect to displacement are not identical along the pipe, nor the frequencies associated with the peak of the amplitude spectra for the first four modes as well. The mode transition is associated with a continuous change in the amplitude, but there’s a jump in frequency, and a gradual process along the pipe length.

Secure storage yard is one of the optimal core goals of container transportation; thus, making the necessary storage arrangements has become the most crucial part of the container terminal management systems (CTMS). This paper investigates a random hybrid stacking algorithm (RHSA) for outbound containers that randomly enter the yard. In the first stage of RHSA, the distribution among blocks was analyzed with respect to the utilization ratio. In the second stage, the optimization of bay configuration was carried out by using the hybrid genetic algorithm. Moreover, an experiment was performed to test the RHSA. The results show that the explored algorithm is useful to increase the efficiency.

The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically studied. The simulation was carried out using computational fluid dynamics (CFD) and ACTRAN. The acoustic field was investigated with Lighthill’s acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale model. Firstly, the validation of mesh was well conducted, illustrating that two million elements were sufficient in this situation. Secondly, the treatment of the steam was deliberated, and conclusions indicate that when predicting the flow-induced noise of the stop-valve, the steam can be treated as incompressible gas at a low inlet velocity. Thirdly, the flow-induced noises under different inlet velocities were compared. The findings reveal it has remarkable influence on the flow-induced noises. Lastly, whether or not the heat preservation of the wall has influence on the noise was taken into account. The results show that heat preservation of the wall had little influence.

In this study, a 2 kHz Tonpilz projector was designed using a Terfenol-D and modeled in ATILA. For the purpose of modeling studies, it has been determined that a radiating head mass exhibits better transmitting current response (TCR) at 136 mm diameter, where the resonance occurs at 2.4 kHz and the peak value of 118 dB re 1 ?Pa/A at 1 m occurs at 12 kHz. Also bolt at a 46 mm distance from the center of the head mass offers resonance at 2.4 kHz, and the peak value of 115.3 dB re 1 ?Pa/A at 1m occurs at 11.5 kHz. This optimized design is fabricated and molded with polyurethane of 3 mm thickness. The prototype was tested at the Acoustic Test Facility (ATF) of National Institute of Ocean Technology (NIOT) for its underwater performances. Based on the result, the fundamental resonance was determined to be 2.18 kHz and the peak value of TCR of 182 dB re 1 ?Pa/A at 1m occurs at 14 kHz. The maximum value of the RS was found to be –190 dB re 1V/?Pa at 1m at a frequency of 2.1 kHz.

A simulation model of an electronically controlled two solenoid valve fuel injection system for a diesel engine is established in the AMESim environment. The accuracy of the model is validated through comparison with experimental data. The influence of pre-injection control parameters on main-injection quantity under different control modes is analyzed. In the spill control valve mode, main-injection fuel quantity decreases gradually and then reaches a stable level because of the increase in multi-injection dwell time. In the needle control valve mode, main-injection fuel quantity increases with rising multi-injection dwell time; this effect becomes more obvious at high-speed revolutions and large main-injection pulse widths. Pre-injection pulse width has no obvious influence on main-injection quantity under the two control modes; the variation in main-injection quantity is in the range of 1 mm3.

This paper mainly studies on the performance of high-speed diesel engines and emission reduction when the engine uses heavy oil mixed with nanometer-sized additives Ce0.9Cu0.1O2 and Ce0.9Zr0.1O2. During the test, Indiset 620 combustion analyzer made by AVL, was used to make a real-time survey on the cylinder pressure, the fuel ignition moment, and establish a relation between the change trend of temperature in cylinder and the crank angle. For the engine burning heavy oil and heavy oil mixed with additives, combustion analysis software Indicom and Concerto were used to analyze its combustion process and emission conditions. Experimental investigation shows that nano-sized complex oxide can improve the performance of diesel engine fueled with heavy oil, and reduce the emission of pollutants like NOx and CO, comparing it with the pure heavy oil. According to the consequences of this experiment, the additives improve the overall performance in the use of heavy oil.