Characteristics of a bubble jet near a vertical wall

A numerical model of a coupled bubble jet and wall was built on the assumption of potential flow and calculated by the boundary integral method. A three-dimensional computing program was then developed. Starting with the basic phenomenon of the interaction between a bubble and a wall, the dynamics of bubbles near rigid walls were studied systematically with the program. Calculated results agreed well with experimental results. The relationship between the Bjerknes effect of a wall and characteristic parameters was then studied and the calculated results of various cases were compared and discussed with the Blake criterion based on the Kelvin-impulse theory. Our analyses show that the angle of the jet＇s direction and the pressure on the rigid wall have a close relationship with collapse force and the bubble＇s characteristic parameters. From this, the application range of Blake criterion can be determined. This paper aims to provide a basis for future research on the dynamics of bubbles near a wall.     

Evaluating the impact of PSC inspectors’ professional profile: a case study of the Spanish Maritime Administration

Full-scale globalisation of trade has been accompanied by a progressive liberalisation of maritime transport. The proliferation of open registries has created a situation in which Port State Control (PSC) has become much more effective than the feeble or non-existent control exercised by those States. This study has been conducted on the influence of the professional profile of inspectors on inspection results. The objective of our paper was to evaluate the impact of PSC inspectors’ professional profile by conducting a case study of the Spanish Maritime Administration. The paper concludes with a discussion of the correlation between deficiencies detected and professional profiles.     

Numerical simulation of the anti-shock performance of a gear case

Both sea battles and testing of ship in underwater explosions reveal unacceptably poor anti-shock performance of important shipboard equipment. Anti-shock performance of shipboard equipment is a significant factor determining fighting strength and survivability. The anti-shock performance of a shipboard gear case based on BV043/85 was investigated using numerical simulation. A geometric model of the gear case was built using MDT software and meshed in HyperMesh software, and then the finite element model of the gear case was formed. Using ABAQUS software, the anti-shock performance of the gear case was simulated. First, shock response of typical regions of gear case was determined. Next, some generalizations were made about the anti-shock performance of the gear case by analyzing the Mises stress of typical regions varied with shock inputs. Third, weak regions were determined from simulation results. The threshold values of shock resistance of the gear case at different impulse widths were obtained through interpolating the numerical simulation results selected from the most dangerous spot. This research provides a basis for further optimization of the design of gear cases.     

Design optimization of a torpedo shell structure

An optimized methodology to design a more robust torpedo shell is proposed. The method has taken into account reliability requirements and controllable and uncontrollable factors such as geometry, load, material properties, manufacturing processes, installation, etc. as well as human and environmental factors. The result is a more realistic shell design. Our reliability optimization design model was developed based on sensitivity analysis. Details of the design model are given in this paper. An example of a torpedo shell design based on this model is given and demonstrates that the method produces designs that are more effective and reliable than traditional torpedo shell designs. This method can be used for other torpedo system designs.     

Analysis of a marine cargo insurance case

Background: In a marine cargo insurance case, many glass lens was loaded in one container and transported from USA to Shanghai At the time of discharging, all pallets were found in normal condition. When the end-user received the cargo, one pallet was found fresh-waterdamaged. The glass lens were very carefully packaged and the warehouse was found dry and clean at the time of survey. It was assumed in the preliminary survey report that the water might have entered into the container through     

An application of BBNs on the integrated energy efficiency of ship–port interface: a dry bulk shipping case

ABSTRACT

A considerable amount of energy is consumed with every completed ship voyage and each port operation performed. Recent regulative approaches by the IMO are to enforce the shipping industry to become more energy efficient and sustainable. There is a growing amount of literature on the energy efficiency management of ships and ports. However, there is still inadequate research effort on the ship–port interface in order to obtain an Integrated Energy Efficiency framework for marine transport operations. In this research, a theoretical concept is generated to measure holistic energy efficiency in shipping operations. The main purpose of this paper is to identify nodes of the integrated ship-port energy efficiency framework and develop a probabilistic approach, which can help to increase energy efficiency and reduce CO2 emissions for shipping companies. This research generates an application of BBNs on ship–port interface regarding the integrated operational energy efficiency interactions by aiming to optimise holistic operational energy efficiency and CO2 emissions. The outcomes suggest that it would be possible to increase the probability of a more energy efficient and sustainable marine transport operation by integrating the influences of port and ship operation performances and their elements on the related route planning and slow steaming decision-making.     

The interaction of oblique flexural gravity waves with a small bottom deformation on a porous ocean-bed: Green’s function approach

The interaction of oblique incident water waves with a small bottom deformation on a porous ocean-bed is examined analytically here within the framework of linear water wave theory. The upper surface of the ocean is assumed to be covered by an infinitely extended thin uniform elastic plate, while the lower surface is bounded by a porous bottom surface having a small deformation. By employing a simplified perturbation analysis, involving a small parameter δ(=1), which measures the smallness of the deformation, the governing Boundary Value Problem (BVP) is reduced to a simpler BVP for the first-order correction of the potential function. This BVP is solved using a method based on Green’s integral theorem with the introduction of suitable Green’s function to obtain the first-order potential, and this potential function is then utilized to calculate the first-order reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom deformation. Consideration of a patch of sinusoidal ripples shows that when the quotient of twice the component of the incident field wave number propagating just below the elastic plate and the ripple wave number approaches one, the theory predicts a resonant interaction between the bed and the surface below the elastic plate. Again, for small angles of incidence, the reflected wave energy is more as compared to the other angles of incidence. It is also observed that the reflected wave energy is somewhat sensitive to the changes in the flexural rigidity of the elastic plate, the porosity of the bed and the ripple wave numbers. The main advantage of the present study is that the results for the values of reflection and transmission coefficients obtained are found to satisfy the energy-balance relation almost accurately.     

Calculation of the Added Mass of a Liquid Tank＇s Bulkheads

The added mass coefficient and the water level indexformulas for the same-phase and anti-phase vibration of rectangularliquid tanks＇ bulkheads were derived based on dry mode theory.Three fluid-structure interaction numerical methods including FluidFEM and Fluid BEM were used in this case. The comparison ofnumerical and theoretical results by the present method shows thatANSYS/FluidS0 is more credible, the NASTRAN/Virtual MassMethod is more suitable for engineering calculations and results ofthe same-phase vibration by the present method is more accurate.     

Dynamic characteristics of a WPC-comparison of transfer matrix method and FE method

To find the difference in dynamic characteristics between conventional monohull ship and wave penetrating catamaran (WPC), a WPC was taken as an object; its dynamic characteristics were computed by transfer matrix method and finite element method respectively. According to the comparison of the nature frequency results and mode shape results, the fact that FEM method is more suitable to dynamic characteristics analysis of a WPC was pointed out, special features on dynamic characteristics of WPC were given, and some beneficial suggestions are proposed to optimize the strength of a WPC in design period.     

Time Domain Calculation of Connector Loads of a Very Large Floating Structure

Loads generated after an air crash, ship collision, and other accidents may destroy very large floating structures(VLFSs) and create additional connector loads. In this study, the combined effects of ship collision and wave loads are considered to establish motion differential equations for a multi-body VLFS. A time domain calculation method is proposed to calculate the connector load of the VLFS in waves. The Longuet–Higgins model is employed to simulate the stochastic wave load. Fluid force and hydrodynamic coefficient are obtained with DNV Sesam software. The motion differential equation is calculated by applying the time domain method when the frequency domain hydrodynamic coefficient is converted into the memory function of the motion differential equation of the time domain. As a result of the combined action of wave and impact loads, high-frequency oscillation is observed in the time history curve of the connector load. At wave directions of 0° and 75°, the regularities of the time history curves of the connector loads in different directions are similar and the connector loads of C1 and C2 in the X direction are the largest. The oscillation load is observed in the connector in the Y direction at a wave direction of 75° and not at 0°. This paper presents a time domain calculation method of connector load to provide a certain reference function for the future development of Chinese VLFS     

Freight market prospects: a Baltic perspective

The indices of shipping freight market activity published daily by the Baltic Exchange, provide a graphic illustration of the vicissitudes of the international shipping industry and a useful reminder (if it were needed) of the basic economic principles of supply and demand.     

Hydroelastic Analysis of a Flexible Floating Body for the Variation of Incident Wave

As for the hydroelastic response of a flexible floating body, various kinds of simplified analytical and numerical methods based on the different assumption have been developed, however, the most versatile and applicable approach is the three-dimensional hydroelasticity theory. Currently, most studies mainly focused on the wave condition of head seas without taking the differences for the variation of the incident wave angle into account. In this paper, based on the three-dimensional hydroelasticity theory, an investigation into the variation of the hydroelastic response for different incident wave angles is presented; also some comparisons are demonstrated and discussed.     

Numerical investigation of turbulence near a sheared air–water interface. Part 2: Interaction of turbulent shear flow with surface waves

Large-eddy simulations (LES) of the interactions between turbulent shear flow and surface waves are presented. The formation mechanism of Langmuir circulation and its contribution to the vertical momentum transport are investigated in detail. The effect of surface waves is modeled in two ways in the LES runs. One model includes only the phase-averaged effect of the waves as an added source term in the momentum equation, and the other model includes the full effect of the waves by use of the fully nonlinear conditions of the air-water interface. Langmuir circulations are clearly indicated in both cases, indicating that the phase-averaged effect is essential for the formation of this circulation. It is shown that the formation of Langmuir circulations enhances the vertical transport of momentum. As a result, the mean velocity gradient and the streamwise component of the turbulence intensity are decreased, while the spanwise and interface normal components are increased. Examination of the turbulence energy budget equations shows that production is due to the interaction between the vorticity and the Lagrangian drift as the phase-averaged effect of the wave becomes the dominant source of turbulence. Received: August 17, 2000 / Accepted: December 22, 2000     

Mathematical simulation of steep waves at a focus point

Mathematical models simulating steep waves at a focus point are presented in this paper. Simulations of extreme waves in a model basin were used to determine the loads on floating structures induced by the waves. Based on a new wave theory, numerical test results show that the simulation procedure is effective and the induced motion of water particles in the front of waves is an important factor influencing impact loads on floating bodies.     

Numerical Simulation of Liquid Sloshing——a Review

Liqui dsloshing is associated with various engineering problems．Many studies have been performed since 1950s．A comprehensive review on the study and advance of numerical simulation of liquid sloshing．with emphasis on free surface tracking techniques，has been presented in this paper．At present．several methods can be used to simulate liquid sloshing numerically．However，each method has its own advantages and disadvantages and it should be applied according tO characteristics of practical engineering problems．In the future．further work should be placed on developing more effective techniques for treating very large amplitude sloshing problems，namely，for simulating overturning，breaking and merging of free surface，for predicting transient impact loads pressure of sloshing．     

Dynamic Simulation of a Smart Crank and Slider Mechanism

In this paper, a smart crank and slider mechanism is analyzed mostly from a dynamic view. By means of dynamic explicit finite element method, 3D nonlinear structure is simulated. It is proved that the mechanism can effectively accomplish smart movement prescribed. And in order to ensure reciprocal movement with higher frequency, measures should be taken to avoid over heating of parts. Compared with internal energy, kinetic energy of total rigid body is dominating, and Y direction equivalent rigid velocity is much higher than X direction velocity. Equivalent rigid velocity of all parts is consistent with respective movement condition. For both energy and velocity, slider effect is dominating. Three direction equivalent inertia force oscillates. Force amplitude in Y -direction is comparitively the greatest.     

Reliability?Based Analysis of a Caisson Breakwater with the Application of Bayesian Inference

Caisson breakwaters are mainly constructed in deep waters to protect an area against waves. These breakwaters are con-ventionally designed based on the concept ...     

Numerical investigation of turbulence near a sheared air–water interface. Part 1: Turbulence statistics beneath a flat water surface sheared by wind

Direct numerical simulation (DNS) and large eddy simulation (LES) of turbulent shear flow beneath a flat water surface with imposed wind shear stress are presented. The results of DNS indicate that there are clear differences, and also similarities, between wind-driven flow and the flow near a solid wall. The qualitative structures of turbulence are similar in both types of flow. Low-speed streaks are also present in wind-driven flow. On the other hand, profiles of the mean velocity and turbulence intensities in wind-driven flow are significantly different from those in flow near a solid wall. The differences are attributed to the lack of a viscous sublayer, and to the boundary condition which allows fluctuations of the tangential velocity components at the boundary. LES of the same flow was also carried out to evaluate subgrid-scale models. It was shown that the features of the flow observed in DNS are well simulated by all models tested, and that the discrepancies between DNS and LES with the dynamic mixed model are very small. Received: August 17, 2000 / Accepted: December 22, 2000     

Italian ports: towards a new governance?

The adoption in 1994 of the law n. 84 introducing the landlord port model marked the starting point of a prime period for the Italian port industry. It contributed to the national port industry renaissance: Italian ports became again the leaders in the Mediterranean basin, both as gateway ports and as transhipment ports. Looking back to its 15 years of enforcement, critical aspects and weaknesses have been observed. The incentive to reflect on the governance structure of ports and on the changes affecting the whole logistics transport chain is driven by the relative and absolute loss of position of Italian ports with respect to their competitors of the North as well as of the South European range (and the ports of Northern Africa which are expected to compete fiercely in the coming future). Considering only the container traffic, from 2003 to 2008 the market share of Italian ports decreased from 20.7% to 15.7% in favor of its main European competitors. The loss of attractiveness of Italian harbors is a clear symptom of the several difficulties national ports face in dealing with the rapid changes affecting the port industry. This paper discusses the bill presented by the Italian Government concerning the ports governance reform.     

Structural-acoustic optimization of stiffened panels based on a genetic algorithm

For the structural-acoustic radiation optimization problem under external loading,acoustic radiation power was considered to be an objective function in the optimization method. The finite element method(FEM) and boundary element method(BEM) were adopted in numerical calculations,and structural response and the acoustic response were assumed to be de-coupled in the analysis. A genetic algorithm was used as the strategy in optimization. In order to build the relational expression of the pressure objective function and the power objective function,the enveloping surface model was used to evaluate pressure in the acoustic domain. By taking the stiffened panel structural-acoustic optimization problem as an example,the acoustic power and field pressure after optimized was compared. Optimization results prove that this method is reasonable and effective.