Our recent experimental investigations of flexible side-by-side blades under both steady and unsteady flows have observed flutter in both scenarios. Flutter significantly impacts blade kinematics and the hydrodynamic drag experienced by the blades. Our numerical approach [1], utilizing the reactive force model, successfully reproduces flutter phenomena. In contrast, the traditional Morison’s equation fails to trigger flutter. In the static regime where flutter does not occur, the bulk drag coefficients calibrated from experiments in steady and unsteady flows can be unified through an effective Cauchy number, allowing for the use of analytical models developed for steady flows in unsteady flows. In the flutter regime, using the bulk drag coefficient from steady flows underestimates the drag load in oscillatory flow.
Harbour vessel emissions are growing concerns in the maritime industry regarding environmental sustainability. Accurate emissions prediction can stand in monitoring and addressing the issue. This study proposes a machine-learning approach using Artificial Neural Network (ANN) for predicting harbour vessel emissions. The approach shows superiority over the bottom-up method introduced by the 4th IMO GHG Study regarding prediction accuracy. Actual emissions data from onboard measurements are used for training ANN models and as references for evaluating the methods. Compared to the bottom-up method, the improvement in error reduction can be up to 30% for predicting nitrogen oxides and 54% for carbon monoxide when only using ship-related factors as input variables. By adding selected meteorological factors in the experiments, the prediction accuracy enhancement can achieve up to 48% for nitrogen oxides and 62% for carbon monoxide. The proposed ANN approach could assist relevant stakeholders in improving emissions prediction and operations optimisation.
This work is part of the ongoing implementation of hydroelastic solution for ships inside the OceanWave3D-seakeeping code. This solver has been developed by the Maritime Group at DTU- Department of Civil and Mechanical Engineering based on linearized potential flow theory. The numerical implementation has been conducted on overlapping grids using a high-order finite difference method. A Fast Fourier Transform (FFT) has been employed to transform the time-domain hydrodynamic solutions to frequency-domain solutions. A pseudo-impulse tailored to the desired frequency range is used as the forcing for the time-domain solution. In previous work, a preliminary implementation of hydroelastic solutions was implemented in OceanWave3D-seakeeping with an Euler-Bernoulli beam model to represent the eigenmodes of the flexible ship hull. However, shear effects are ignored by this beam theory, even though the shear effect is very important to acurately predict the structural deformation especially for a thick beam model. In this work, ship hulls have been treated using the Timoshenko beam model includ- ing shear effects. The influence of shear effects are also discussed through a couple of numerical test cases. Good agreement with reference solutions illustrates the effectiveness of the numerical implementation. The current work focuses on zero speed, and work is also in progress to validate the implementation at forward speeds
This work is part of the ongoing implementation of generalized modes for ship hydroe- lasticity inside the OceanWave3D-seakeeping solver. The solver has been developed by the Mar- itime Group at DTU- Civil & Mechanical Engineering based on solving the linearized potential flow problem using a high-order finite difference method on overlapping grids. The focus of this paper is a comparison between the hydroelastic solutions obtained using two different implementations of the hydrostatic restoring force coefficients. The first hydrostatic model is according to Newman, and the second model is based on Malenica and Bigot. These two hydrostatic models agree for the rigid modes, but are slightly different for the flexible modes. The results are validated using both numerical and experimental solutions for two different ship geometries at zero forward speed.
Cold ironing is the process of providing shorepower to cover the energy demands of ships calling at ports. This technological solution can eliminate the emissions of auxiliary engines at berth, resulting in a global reduction of emissions if the grid powering the ships is an environmentally friendly energy source. This paper conducts a literature review of recent academic work in the field and presents the status of this technology worldwide and the current barriers for its further implementation. The use of cold ironing is mandatory in Californian ports for ship operators and as a result terminal and ship operators were required to invest in this technology. In Europe, all ports will be required to have cold ironing provision by the end of 2025. Other regulations that target local emissions such as Emission Control Areas can have a significant impact on whether cold ironing is used in the future as a potential compliance solution. This paper constructs a quantitative framework for the examination of the technology considering all stakeholders. The role of regulation is shown to be critical for the further adoption of this technology. Illustrative case studies are presented that consider the perspective of ship operators of various ship types, and terminal operators that opt to invest in shorepower facilities. The results of the case studies show that for medium and high fuel price scenarios there is economic motivation for ship operators to use cold ironing. For the port, the cost per abated ton of pollutants is much lower than current estimates of the external costs of pollutants. Therefore, shorepower may be a viable emissions reduction option for the maritime sector, provided that regulatory bodies assist the further adoption of the technology from ship operators and ports. The methodology can be useful to port and ship operators in examining the benefits of using cold ironing as an emissions reduction action.
As of January 2015, the new maximum limit of fuel sulfur content for ships sailing within emission control areas has been reduced to 0.1%. A critical decision for ship owners in advance of the new limits was the selection of an abatement method that complies with the regulations. Two main options exist: investing in scrubber systems that remove sulfur dioxide emissions from the exhaust and switching to low-sulfur fuel when sailing in regulated waters. The first option would involve significant capital costs, while the latter would lead to operating cost increases because of the higher price of the fuel used. This paper presents a literature review of emissions abatement options and relevant research in the field. A cost–benefit methodology to assess emission reduction investments from ship owners is also presented. A study examined the effects of recent drops in bunker fuel price to the payback period of a potential scrubber investment. The results show that lower prices would significantly delay the payback period of such investments, up to two times in some cases. The case studies present the emissions generation through each option for representative short sea shipping routes. The repercussions of low-sulfur policies on large emission reduction investments including cold ironing are examined, along with implications of slow steaming for their respective payback periods. Recommendations are made for research in anticipation of future regulations and technological improvements.
Maritime shipping is regarded as the most efficient mode of transport; however, its contribution to climate change through greenhouse gas emissions and the health issues related to shipping activity near residential centers cannot be neglected. In recent years, the efforts of regulators, ship operators, and port authorities have led to actions for ship emissions reduction to improve shipping's environmental performance. This work builds on an activity-based methodology that allows the estimation of emissions and examines environmental effects of slow steaming, fuel regulations, near-port speed-reduction schemes, and cold ironing. Pollutant emissions of carbon dioxide, sulfur dioxide, nitrogen oxides, and black carbon are modeled. A linear programming model minimizes fuel consumption through speed differentiation on a shipping line's routes based on fuel costs and binding regulations in each segment of the journey. Although the examined emissions-reduction actions may have a positive regional environmental effect by cutting emissions, it is possible that additional emissions are generated elsewhere because of increased sailing speeds beyond regulated areas. Trade-offs between pollutants are observed for reduction actions that may have a positive effect on some emission species but at the same time result in additional particulate matter and black carbon emissions. The presented framework allows key actors to conduct comprehensive studies and design improved emissions reduction actions with fewer negative impacts in other areas.
Different port operating policies have the potential to reduce emissions from shipping; however, their efficacy varies for different ports. This article extends existing literature to present a consistent and transferable methodology that examines emissions reduction port policies based on ship-call data. Carbon dioxide (CO2); sulphur dioxide (SO2); nitrogen oxides (NOx); and black carbon (BC) emissions from near-port containership activities are estimated. Two emissions reduction policies are considered for typical container terminals. Participation of all calling vessels with a speed reduction scheme can lead to reductions of 8–20 per cent, 9–40 per cent and 9–17 per cent for CO2, SO2 and NOx, respectively. However, speed reduction policies may increase BC emissions by up to 10 per cent. Provision of Alternative Marine Power (AMP) for all berthing vessels can reduce in-port emissions by 48–70 per cent, 3–60 per cent, 40–60 per cent and 57–70 per cent for CO2, SO2, NOx and BC, respectively. The analysis shows that emissions depend on visiting fleet, berthing durations, baseline operating pattern of calling ships, sulphur reduction policies in force and the emissions intensity of electricity supply. The potential of emissions reduction policies varies considerably across ports making imperative the evaluation and prioritization of such policies based on the unique characteristics of each port and each vessel.
The 0.1% sulphur limit within Sulphur Emission Control Areas (SECA) has made compulsory the use of either pricier ultra-low sulphur fuel, or the installation of abatement technologies that require significant capital investments. Due to the unexpectedly low fuel prices, Ro-Ro operators have been able to cope with the new sulphur limits, but recent research has shown that if fuel prices increase some Ro-Ro services may face the risk of closure. This paper proposes three key performance indicators (KPIs) to enable the asssessment of the impact of SECAs on Ro-Ro shipping. The KPIs are used on a set of case studies for services of a leading European Ro-Ro operator, and allow benchmarking of a series of operational and policy measures that aim to reverse the negative impacts of SECAs. The operational measures consider speed reduction, new sailing frequency, fleet reconfiguration, as well as investments in abatement technologies. Policy measures include the options of either subsidizing shippers or ship operators, or alternatively introducing new taxes on landbased options. The KPIs can be useful to ship operators seeking to improve the resilience of their network, as well as to regulatory bodies designing new environmental policies and understanding any negative implications these may have on ship operators.
In an effort to reduce the environmental impacts of maritime transportation, the International Maritime Organization (IMO) designated special Sulphur Emission Control Areas (SECAs) where ships are required to use low-sulphur fuel. In January 2015, the sulphur limit within SECAs was lowered to 0.1%, which can only be achieved if vessels are using pricier ultra-low sulphur fuel, or invest in abatement technologies. The increased operating costs borne by Ro-Ro operators in SECAs due to the stricter limits can result in the shutting down of some routes and a redistribution of cargo flows with land-based alternatives. The exact repercussions of the new sulphur limits are difficult to identify in the wake of significant recent reductions of the fuel prices for both low-sulphur and heavy fuel oil. This paper presents a modal split model that estimates modal shifts vis-a-vis competing maritime and land-based modes available to shippers. This allows examining the implications of the recent low prices to modal choice, and the influence a potential increase in fuel prices may have. The model is applied to seven routes affected by the regulation based on data from a leading European Ro-Ro operator. Sensitivity analyses on market share data, cargo values, freight rates, and haulers rates are conducted. Emissions inventories are constructed to assess the environmental efficacy of the SECA regulation. The novelty of the proposed model lies in the examination of the ex-post implications of shutting down a service and the redistribution of transport. Recommendations to mitigate and reverse the negative side-effects of such environmental legislation are proposed.