Numerical simulation of viscous liquid sloshing by moving-particle semi-implicit method

A meshless numerical simulation method, the moving-particle semi-implicit method （MPS） is presented in this paper to study the sloshing phenomenon in ocean and naval engineering. As a meshless method, MPS uses particles to replace the mesh in traditional methods, the governing equations are discretized by virtue of the relationship of particles, and the Poisson equation of pressure is solved by incomplete Cholesky conjugate gradient method （ICCG）, the free surface is tracked by the change of numerical density. A numerical experiment of viscous liquid sloshing tank was presented and compared with the result got by the difference method with the VOF, and an additional modification step was added to make the simulation more stable. The results show that the MPS method is suitable for the simulation of viscous liquid sloshing, with the advantage in arranging the particles easily, especially on some complex curved surface.     

Confidence bounds on structural reliability estimations for offshore platforms

Second-order estimates to measure platform reliability are generated and used to provide an additional space to select safety margins appropriate to the owner's perception or for risk-averse managers. The aleatory and epistemic uncertainties in the parameters of an offshore platform are explicitly considered in the reliability analysis and the platform structural reliability becomes a random variable, assessing then the beneficial effects of a reduction on these uncertainties. One of these benefits is for risk-aversive managers who often demand additional room to make conservative decisions regarding reliability estimations. Proposed here is a procedure to generate the frequency diagram of platform reliability with the use of confidence bounds to support reliability and cost decisions based on percentiles instead of mean values. The concepts are illustrated through a typical offshore platform in Mexico. The frequency diagram of the platform reliability index is built for several alternative designs and three levels of epistemic uncertainty. The results may be applied for decision making on new designs and also on the assessment and optimal inspection, retrofit, and decommissioning of existing platforms.     

Trace element levels in some commercially valuable fish species from coastal waters of Mediterranean Sea, Egypt

Concentrations of 5 trace elements (Cd, Pb, Cu, Cr, Zn) were determined in muscle of fishes collected from two coastal areas of the Egyptian coast of the Mediterranean Sea west of Alexandria (El-Mex Bay and Eastern Harbour). Sardinella aurita, Alepes djedaba, Siganus luridus, Siganus rivulatus, Sphyraena chrysotoenia, and Scomberomorus commerson were collected from El-Mex Bay. While Boops boops, Lithognathus mormyrus, Sparisoma cretense, Serranus cabrilla and Synodus saurus were collected from the E.H. In all fishes zinc was highest (up to 57 mg/kg) followed by Cr, Cu, Pb and Cd. The concentrations of several metals in fishes were significantly different among the species in each area. For all trace element examined, the concentrations decreased significantly with body weight of some fishes. In contrast, a positive correlation with body weight was found especially for Zn and Cu concentrations in 5 fish species and for Pb in 4 fish species. The concentrations of Cd, Pb and Zn were higher in fishes from El-Mex Bay (3.76, 6.49 and 57.21 mg/kg) than those from Eastern Harbour, whereas the opposite trend was observed for Cu and Cr, revealing the direct sources of trace metal pollution present in El-Mex coastal area. Levels of Cr surpassed the Maximum Permissible Concentration in most fish tissues, followed by Pb and Cd in some species. Cu and Zn presented concentrations below the maximum permissible levels in fish tissues.     

Experimental and numerical investigations of the flow around an oar blade

This article aims at verifying the capabilities of a Reynolds-Averaged Navier-Stokes Equations (RANSE) solver (ISIS-CFD, developed at the Fluid Mechanics Laboratory of Ecole Centrale de Nantes [LMF]) to accurately compute the flow around an oar blade and to deduce the forces on it and other quantities such as efficiency. This solver is structurally capable of computing the flow around any blade shape for any movement in six degrees of freedom, both when the blade pierces the free surface of the water and when it does not. To attempt a first validation, a computation was performed for a simplified case chosen among those for which experimental results are available at LMF. If results prove satisfactory for a simplified blade shape and for a movement that respects the main characteristics of blade kinematics, then the solver could be used for real oars and more realistic kinematics. First, the experimental setup is considered, and the objectives, methodologies, and procedures are elucidated. The choice of the test case for numerical validation is explained, i.e., a plane rectangular blade with a constant immersion and a specified movement deduced from analogy with tests on propellers. Next, the numerical framework is presented and the Navier-Stokes solver and methods for handling multifluid flows and moving bodies are described. Lastly, numerical results are compared with experimental data, highlighting an encouraging agreement and proving the relevance and the complementarity of both approaches.     

Critical success conditions of collaborative methods: a comparative evaluation of transport planning projects

This paper explores critical success conditions of collaborative planning projects in the area of urban transport, evaluating the impact of new collaborative methods, instruments and processes on project performance. Hypothesis building is based on a comparative, empirical research design, rather than on deductive theory construction. Potential critical success conditions are derived from literature. Based on five urban transport planning projects in Gothenburg (Sweden), London (United Kingdom), Milwaukee (United States), Tokyo (Japan) and Mexico City (Mexico), a rough set analysis of the five cases reveals validated success conditions, which can be used for formulating hypotheses for further research or for policy and process improvement. The results suggest that a dedicated management of the multi-actor network, a high diversity of actors, as well as an extensive use of knowledge integration methods in combination with a high network density are critical success conditions of these planning processes. Surprisingly, the extensive use of unilateral methods also showed to be an important success condition. The traditional role of the planner will have to be complemented with the expertise of network and methodology management. The authors conclude that rough set analysis can be a valuable addition to narrative, single-case analysis of collaborative urban transport planning processes.     

Incorporated probability that a fleet meets a given permissible value for the hull girder section modulus loss

The paper presents a study on the incorporated probability that a tanker fleet meets a given permissible value of hull girder strength loss. The analysis was based on a database of hull girder section modulus (HGSM) for as-gauged girth belts of tankers. It was found that its mean value is below 5% over the entire life span of the analyzed tanker fleet. The Weibull probabilistic distribution was found to best represent the time-varying HGSM loss. A method was developed for calculating the incorporated safety of a fleet. As an example, the IMO requirement for a maximum HGSM reduction of 10% relative to its required value was analyzed, accounting for time-variant HGSM loss and including a probabilistic model for coating longevity. The views expressed in the paper are those of the authors and not necessary those of ABS.     

ISS-based robust adaptive fuzzy algorithm for maintaining a ship＇s track

This paper focuses on the problem of linear track keeping for marine surface vessels. The influence exerted by sea currents on the kinematic equation of ships is considered first. The input-to-state stability （ISS） theory used to verify the system is input-to-state stable. Combining the Nussbaum gain with backstepping techniques, a robust adaptive fuzzy algorithm is presented by employing fuzzy systems as an approximator for unknown nonlinearities in the system. It is proved that the proposed algorithm that guarantees all signals in the closed-loop system are ultimately bounded. Consequently, a ship＇s linear track-keeping control can be implemented. Simulation results using Dalian Maritime University＇s ocean-going training ship ＇YULONG＇ are presented to validate the effectiveness of the proposed algorithm.     

Monitoring long-term environmental change: Some lessons from Sullom Voe,Shetland Islands

The impact on the marine environment of the operation of the Sullom Voe Oil Terminal and its major port facility in the Shetland Islands has been monitored continuously for more than twenty-five years. The site of this very large terminal straddles a peninsula and the separation of the impact of the port on the sheltered west side (Sullom Voe) and the aqueous discharge from the terminal to the east, into the strong tidal current of Yell Sound, has proven to be advantageous. There are two types of monitoring, statutory (to comply with relevant legislation) and voluntary (to establish good practice and to examine a wider range of impacts e.g. island-wide ornithology). The latter function is undertaken by an independent advisory committee (SOTEAG). Over time, the nature and amount of voluntary monitoring has decreased in response to the long term evidence that both terminal and port operations are having little or no impact on a wide range of habitats and species. Voluntary monitoring also acts as an independent check on both compliance and other forms of environmental assessment. Although the terminal is now operating at less than half its peak capacity, this does not mean that there has been apro-rata decrease in monitoring activity.     

Flow resistance characteristics of water in narrow annulus during heat exchange

Considering the special resistance characteristics of fluids flowing through ducts with small gaps, experiments are per-formed to investigate the resistance characteristics of single-phase water, which is forced to flow through vertical annuli. The gap sizes are 0.9, 1,4 and 2.4ram, respectively. The experiments are conducted under condition of 1 atm. The water in the annuli is heated by high temperature water reversely flowing through the inner tube and the outer annulus. The results show that the flow pattern begin to change from laminar to turbulent before Reynolds number approaches 2000, the flow resistance in annulus has llttie relations with the temperature difference and ways of being heated, but mainly depends on the ratio of mass flux to the width of annulus.