Aerodynamics of Vehicles and Airplanes, and Hydrodynamics of Ships - Decreasing Fuel Consumption and Exhaust Gas Emissions in Transportation - page 113

0.9

1000

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0 1000 2000 3000 4000 5000

DWT [t]

Fig. 7.5 Wave output in relation to DWT on river

7.3.2 Inland Shipping

On inland water ways, construction requirements for stability and rescue equip-
ment are adjusted to the characteristics of where the ships are going to be oper-
ating. Inland ships are smaller than sea-going ships and the resistance in shallow
water plays a decisive role in engine performance, fuel consumption and exhaust
gas emissions [ 20 ].
Inland ships have been constructed with an increasing load capacity over the
last decades. Similar to sea-going ships, this increase in size has led to higher
efficiency and to the reduction of the Specific Fuel Consumption (SCF) per DWT
capacity [ 21 ].
However, there are strict limits in inland shipping. The main limiting factors are
the resistance to the ground and to the river bank. Enlargement of inland container
ships over 3,000 DWT usually leads to a volume of more than 5,000 m 3 (176,553
ft 3 ). In special cases the flow can be optimized through the installation of an
additional propeller in the ship's centre. Optimal flow reduces fuel consumption,
especially in the mid-speed range. Shipping up river and against the wind with
high waves at wide rivers or large lakes can increase fuel consumption by up to
10% [ 22 ].
Different rotation speeds of the propeller cause turbulence between the ship's
hull and the banks of the water way [ 23 ]. If the distance is too small, an increasing
blocking of the feed stream to the propeller requires an increasing wave output
from the engine; see Fig. 7.5 [ 24 ].
In inland freight transportation, tug boats highly efficiently push or tow a
number of barges [ 25 , 26 ]. The bow of a single ship should be as streamlined as
possible. If a tug pushes a pre-coupled barge, the bow of the tug must be rounded
by artificial designed flow plates in order to keep the turbulence at the coupling
point as small as possible; see Fig. 7.6 [ 27 ].