390
J. Murawski and J. Woge Nielsen
such a structure is that ship engines reach maximum efficiency under certain constant conditions and that ship construction typically makes course changes fuelconsuming.
In this section we continue the analysis of drift patterns from the viewpoint of
the design of optimum fairways and evaluation of the potential gain from their use.
Along with the continuing practice of path optimization in shipping operations with
respect to a steady ocean and atmosphere, we make an attempt to incorporate into the
fairway design the aggregated information about the transport of pollutants under
realistic metocean conditions. The basic fairway designs are derived by Monte Carlo
techniques accounting for both the increase in oil combating time (expressed via the
residence time of oil at sea) and the decrease in the probability of oil landing. Such
a design of the favourable fairway makes use of both the derived distributions and
especially of the location of low probabilities and long residence times.
The constraint of travel distance reduction is imposed by a path length optimization routine. The efforts result in separate fairway designs for seasonal and combined drift patterns. The ‘winning’ design is identified by using of a ship routing
analysis software and a comparison of the economical performance of various fairways in terms of travel time and fuel consumption. The basic designs represent
indicators on which the specific design process could be based. Ship routing evaluations might serve as a tool for further investigation. To the authors’ knowledge there
has been no attempt yet to explore the possibility of route evaluations during the
planning process of fairways. Neither environmental viewpoints, in terms of pollutant impact reduction, nor economical viewpoints, in terms of fuel and travel time
reduction due to ocean circulation have been taken into consideration.
11.5.1 The Design Method
In its essence the problem of deriving optimum fairways from model results is an
inverse one. The available information about the oil residence time in open waters
and of the probability of coastal hits for individual runs is related to global distributions of risk parameters and cost functions φ(x, t) for the optimization procedures.
The output are pathways of low aggregated risk specified by path integrals of φ(x, t)
over certain curves that are identified as optimum fairways. While the cost functions
are specified by statistical ensembles of model results and derived risk measures, the
fairways not only follow the local risk minima (which may lead to extensive and unjustified detours, see Soomere et al. 2011b; Lu et al. 2012) but also optimize the path
length to some extent. Longer ship tracks are not only fuel and cost intensive, but
also less preferable environmentally, because of, e.g., a larger amount of emissions.
Furthermore, longer pathways represent a larger risk per se, as the time spent at sea
and potential accident risks increase.
Optimum routes thus combine minimums of the path length and risk values integrated over these paths. This sort of problem is typically addressed by Monte Carlo
techniques. Its straightforward use together with combined risk and path length
J. Murawski and J. Woge Nielsen
such a structure is that ship engines reach maximum efficiency under certain constant conditions and that ship construction typically makes course changes fuelconsuming.
In this section we continue the analysis of drift patterns from the viewpoint of
the design of optimum fairways and evaluation of the potential gain from their use.
Along with the continuing practice of path optimization in shipping operations with
respect to a steady ocean and atmosphere, we make an attempt to incorporate into the
fairway design the aggregated information about the transport of pollutants under
realistic metocean conditions. The basic fairway designs are derived by Monte Carlo
techniques accounting for both the increase in oil combating time (expressed via the
residence time of oil at sea) and the decrease in the probability of oil landing. Such
a design of the favourable fairway makes use of both the derived distributions and
especially of the location of low probabilities and long residence times.
The constraint of travel distance reduction is imposed by a path length optimization routine. The efforts result in separate fairway designs for seasonal and combined drift patterns. The ‘winning’ design is identified by using of a ship routing
analysis software and a comparison of the economical performance of various fairways in terms of travel time and fuel consumption. The basic designs represent
indicators on which the specific design process could be based. Ship routing evaluations might serve as a tool for further investigation. To the authors’ knowledge there
has been no attempt yet to explore the possibility of route evaluations during the
planning process of fairways. Neither environmental viewpoints, in terms of pollutant impact reduction, nor economical viewpoints, in terms of fuel and travel time
reduction due to ocean circulation have been taken into consideration.
11.5.1 The Design Method
In its essence the problem of deriving optimum fairways from model results is an
inverse one. The available information about the oil residence time in open waters
and of the probability of coastal hits for individual runs is related to global distributions of risk parameters and cost functions φ(x, t) for the optimization procedures.
The output are pathways of low aggregated risk specified by path integrals of φ(x, t)
over certain curves that are identified as optimum fairways. While the cost functions
are specified by statistical ensembles of model results and derived risk measures, the
fairways not only follow the local risk minima (which may lead to extensive and unjustified detours, see Soomere et al. 2011b; Lu et al. 2012) but also optimize the path
length to some extent. Longer ship tracks are not only fuel and cost intensive, but
also less preferable environmentally, because of, e.g., a larger amount of emissions.
Furthermore, longer pathways represent a larger risk per se, as the time spent at sea
and potential accident risks increase.
Optimum routes thus combine minimums of the path length and risk values integrated over these paths. This sort of problem is typically addressed by Monte Carlo
techniques. Its straightforward use together with combined risk and path length