11 Applications of an Oil Drift and Fate Model for Fairway Design
401
and 0.75 mt more fuel consumption. The distance is again the major performance
defining factor. SPO optimal fairways follow the southern coast closely, but stay out
of shallow waters.
The data presented in Table 11.3 vividly demonstrates that the effects of shallow
water resistance greatly reduced the performance of near-coastal designs and that the
distance is the main performance factor for the considered harbours, some of which
are better accessed over the northern route (Vyborg), some others over the southern
route (Sillamäe, Ust-Luga), whereas the optimum to Saint Petersburg probably goes
along an axial route. The presence of a heterogenous circulation pattern has a strong
effect on the performance of fairways, mostly in the northern part of the Gulf of
Finland where the impact of the River Neva outflow is significant.
The result is a spatial separation of the eastern and western going optimal fairways, which either try to make use of or to avoid the predominant circulation. This is
most apparent for Saint Petersburg where the optimum routes (SPO north) are either
passing by Gogland in the north, turning gradually to the south as they approach the
entrance to the Baltic Proper, or they are coming from the west and move gradually
northwards as they pass by Gogland in the deep South. Therefore, economically
optimized solutions may be provided by specially tailored fairways for individual
harbours and transport directions.
The fairways stemming from the combined design (CMB) seem to be closer to
the performance of economically optimized designs than any of the seasonal designs. For the southern harbours Sillamäe and Ust-Luga, they perform far better
than the fairways from the route atlas, and for northern and eastern harbours their
performance is comparable.
11.6 Wave-Induced Oil Propagation
Waves mix the upper ocean and have tremendous effects on surface oil slicks. The
additional layer of oil is efficiently damping the waves, by reducing the wind energy uptake and by extracting energy for downwards mixing of buoyant oil droplets
and for intermixing of water with oil. Emulsions are formed which increase the viscosity enormously, intensifying the damping effect. The Braer accident in January
1993 which happened off the coast of the Shetland Islands provides a good example
for this (Edgell 1994). The accident was followed by a storm and heavy seas which
mixed down the oil completely, so that it vanished from the view of the observers.
Later on, when winds and waves subsided, the oil re-emerged as emulsified patches.
Contemporary oil drift and fate models include efficient parameterizations for mixing and emulsification. However, wave-induced oil propagation has been largely
neglected because of the intense computational efforts and the widespread belief
that the wave-induced drift is relatively small compared to the drift caused by ocean
circulation and wind. The estimates given below demonstrate that wave-induced
(Stokes) drift can locally reach the magnitude of the wind- and current-induced
drift.
401
and 0.75 mt more fuel consumption. The distance is again the major performance
defining factor. SPO optimal fairways follow the southern coast closely, but stay out
of shallow waters.
The data presented in Table 11.3 vividly demonstrates that the effects of shallow
water resistance greatly reduced the performance of near-coastal designs and that the
distance is the main performance factor for the considered harbours, some of which
are better accessed over the northern route (Vyborg), some others over the southern
route (Sillamäe, Ust-Luga), whereas the optimum to Saint Petersburg probably goes
along an axial route. The presence of a heterogenous circulation pattern has a strong
effect on the performance of fairways, mostly in the northern part of the Gulf of
Finland where the impact of the River Neva outflow is significant.
The result is a spatial separation of the eastern and western going optimal fairways, which either try to make use of or to avoid the predominant circulation. This is
most apparent for Saint Petersburg where the optimum routes (SPO north) are either
passing by Gogland in the north, turning gradually to the south as they approach the
entrance to the Baltic Proper, or they are coming from the west and move gradually
northwards as they pass by Gogland in the deep South. Therefore, economically
optimized solutions may be provided by specially tailored fairways for individual
harbours and transport directions.
The fairways stemming from the combined design (CMB) seem to be closer to
the performance of economically optimized designs than any of the seasonal designs. For the southern harbours Sillamäe and Ust-Luga, they perform far better
than the fairways from the route atlas, and for northern and eastern harbours their
performance is comparable.
11.6 Wave-Induced Oil Propagation
Waves mix the upper ocean and have tremendous effects on surface oil slicks. The
additional layer of oil is efficiently damping the waves, by reducing the wind energy uptake and by extracting energy for downwards mixing of buoyant oil droplets
and for intermixing of water with oil. Emulsions are formed which increase the viscosity enormously, intensifying the damping effect. The Braer accident in January
1993 which happened off the coast of the Shetland Islands provides a good example
for this (Edgell 1994). The accident was followed by a storm and heavy seas which
mixed down the oil completely, so that it vanished from the view of the observers.
Later on, when winds and waves subsided, the oil re-emerged as emulsified patches.
Contemporary oil drift and fate models include efficient parameterizations for mixing and emulsification. However, wave-induced oil propagation has been largely
neglected because of the intense computational efforts and the widespread belief
that the wave-induced drift is relatively small compared to the drift caused by ocean
circulation and wind. The estimates given below demonstrate that wave-induced
(Stokes) drift can locally reach the magnitude of the wind- and current-induced
drift.