In this paper, full-scale data for two ships have been used for the comparison of five different added resistance methods. The effect of using separate wave spectra for wind waves and swell on performance prediction has been explored. The importance of the peak enhancement factor(γ) in the JONSWAP spectrum for added resistance computation has been studied. Simulation model including calm water resistance, added resistance and wind resistance has been used. Ships have been simulated in the same weather conditions and propeller speed as in the case of full-scale ships using different methods for added resistance. The performance of these methods has been quantified by comparing speed and power predictions with the full-scale data. The paper also discusses the challenges involved in using full-scale data for such a comparison because of difficulty in isolating the effect of added resistance in full-scale data. It was observed that three out of five methods were able to predict added resistance even in high waveheights. Even though these methods showed significantly different RAOs, its effect on speed and power prediction was minor. Simulation results were not sensitive to the choice of peak enhancement factor(γ) in the JONSWAP spectrum. There was minor improvement in results by using separate wave spectra for wind waves and swell instead of single wave spectrum for combined wind waves and swell.
In the present study, conjugate heat transfer (CHT) calculations are applied in a computational fluid dynamics (CFD) simulation to simultaneously solve the in-cylinder gas phase dynamics and the temperature field within the liner of the engine. The effects of different initial temperatures with linear profiles across the liner are investigated on the wall heat transfer as well as on the sulfuric acid formation and condensation. The temporal and spatial behavior of sulfuric acid condensation on the liner suggests the importance of CHT calculations under large two-stroke marine engine relevant conditions. Comparing the mean value of the heat transfer through the inner and outer sides of the liner, an initial temperature difference of 15 K with a linear profile is an appropriate initial condition to initiate the temperature within the liner. Moreover, the effect of the amount of water vapor in the air on the sulfuric acid formation and condensation is studied. The current results show that the sulfuric acid vapor formation is more sensitive to the variation of the water vapor amount than the sulfuric acid condensation.
With the blue economic sectors growing, marine macroalgae cultivation plays an important role in securing food and energy supplies, as well as better water quality in sustainable ways, whether alone or as part of a cluster solution to mitigate the effects of fish farming. While macroalgae cultivation exists in Europe, it is not that widely distributed yet; with increasing marine activities at sea, Maritime Spatial Planning (MSP) needs to ensure social recognition as well as social and spatial representation for such a new marine activity. This comparative case study analysis of MSPs of three eastern Baltic Sea countries explores the levels of support for the development of macroalgae cultivation in MSP and the degree of co-location options for this new and increasingly important sector. It presents new analytical ways of incorporating co-location considerations into the concept of social sustainability. The results of this study support the harmonisation of views on co-location, propose ways of using space to benefit multiple users as well as marine ecosystems, and highlight some of the key social challenges and enablers for this sector.
This study presents a novel approach to forecast freight rates in container shipping by integrating soft facts in the form of measures originating from surveys among practitioners asked about their sentiment, confidence or perception about present and future market development. As a base case, an autoregressive integrated moving average (ARIMA) model was used and compared the results with multivariate modelling frameworks that could integrate exogenous variables, that is, ARIMAX and Vector Autoregressive (VAR). We find that incorporating the Logistics Confidence Index (LCI) provided by Transport Intelligence into the ARIMAX model improves forecast performance greatly. Hence, a sampling of sentiments, perceptions and/or confidence from a panel of practitioners active in the maritime shipping market contributes to an improved predictive power, even when compared to models that integrate hard facts in the sense of factual data collected by official statistical sources. While investigating the Far East to Northern Europe trade route only, we believe that the proposed approach of integrating such judgements by practitioners can improve forecast performance for other trade routes and shipping markets, too, and probably allows detection of market changes and/or economic development notably earlier than factual data available at that time.
Rotor dynamic force coefficients of gas seals strongly depend on the machine operational conditions. These force coefficients influence the overall dynamical response and modal properties of machines, consequently defining the machine vibration levels. Accurate estimations of the rotor dynamic coefficients are required for designing machines with low vibration amplifications and well-defined stability margins throughout the operational range. Experimental methods applied to test benches are used to validate such force coefficients and they normally rely on (i) the quality of the measurements and (ii) the assumption that the mathematical model is able to capture the whole system dynamics. If relevant dynamical contributions in a system are neglected by the mathematical model, the contribution will erroneously be concluded to originate from the seal being tested. The theoretical and experimental investigation in this paper focuses on quantifying and qualifying the effect of neglected system dynamics modelling on the estimation of seals force coefficients and stability margins. The in-situ identification of seal forces shows that the direct stiffness, cross-coupling stiffness, and direct damping coefficient estimations for a gas seal with high preswirl are statistically significantly affected by the baseline model. Nevertheless, the baseline model leads to small deviations of the seal force coefficient estimations. The prediction accuracy of stability margins is found to be more influenced by the baseline model describing the system dynamics than by the deviations between the seal force coefficient estimations.
Due to the harsh weather conditions, severe spatial limitations and extremely high safety requirements, the indoor climate control for offshore oil & gas production platforms is much more challenging than any on-shore situations. For instance, the indoor pressure of man-board quarters should be kept all the way above the ambient pressure according to safety regulations. Meanwhile, the indoor air needs to be regularly changed in order to guarantee the indoor air quality. Both requirements could be possibly achieved by automatically manipulating either the throttle valve located at the terminal of the inlet channel in the considered Heating Ventilation and Air-Condition (HVAC) system, or the pressurization system located inside the inlet channel, or both of them in a coordinated way. A Model-Predictive Control (MPC) solution to control the inlet throttle has been proposed in our previous work. This paper proposes a set of control solutions to regulate the variable speed pressurization fan system such that the energy efficiency of the considered HVAC system can be explicitly considered. A combined feed-forward with a PI-based feedback control solution, and an MPC solution are proposed based on derived simple system models. Some preliminary simulation results show that both control solutions can keep the indoor pressure and the air circulation in a very satisfactory and robust manner, even subject to the presence of severe disturbances.
Piracy has unfortunately become a health and safety risk for seafarers in the maritime industry today. However, little do we know about the impact of a pirate hijacking situation and how seafarers cope. Focusing on negotiation communication, the analysis debouches in a discussion of the dynamics of coping strategies, by investigating 173 authentic audio recordings of communication sequences recorded during a pirate hijacking situation that were donated voluntarily by a shipping company. The Captain assessed and reflected on the course of events in the situation, to which the negotiator responded appropriately, with acknowledging brief responses or psychological aid. This is similar to other highly dynamic decision-making settings, where decision-makers tend to continuously reflect and revise their view of the situation (Eraut 2000). The data is also consistent with the “reflection-in-action” concept by Schön (1983) used by van den Heuvel et al. (Cogn Technol Work 16: 25–45, 2014) in their investigation of communication of police officers in hostage situations. However, the coping dynamics changed when the negotiator’s responses became too minimal. This shows how the context and the individual’s cognitive appraisal of the encounter co-shapes the coping dynamics in the situation. It is urged that pre-piracy care and seafarer training involves practical examples and information about roles and coping dynamics in negotiation communication as part of an orchestrated approach to the scourge of piracy.
This article analyzes the competitive strategies of Odense Steel Shipyard between 1918 and 2012 and challenges existing scholarship on competition in global industries. Until the 1980s, the yard adopted typical strategies in shipbuilding, starting with cost leadership and subsequently adopting global segmentation and differentiation strategies. From the mid-1980s, however, it successfully followed a unique national responsiveness strategy, which scholars including Dong Sung Cho and Michael E. Porter had ruled out in shipbuilding. The article shows how shipyard owners shaped strategies and influenced competitiveness.
This paper is framed in the context of the EU Interreg IVB North Sea Region project Food Port. In line with this project, this paper aims to define mathematically cost and time models able to provide realistic information about the performances of road haulage and of intermodal chains using short sea shipping (SSS) in the North Sea Region (NSR). The models integrate the necessary variables to establish the impact of different fleets and SSS features on the competitiveness of intermodal chains for the movement of food related goods. The models were applied to evaluate the opportunities for the success of intermodal chains using the Rosyth-Zeebrugge route. The results obtained validate the utility of the models and they suggest possible changes to the current operation of this SSS service in order to increase the marked potential possibilities for the intermodal chains through Rosyth-Zeebrugge.