الفهرس 
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Abstract
The subjected ship area under water surface level, which is mainly called the
draught, can be considered as the most effective factor for ship stability against the
transverse velocity components from any field of cross water currents. These cross
currents can be encountered at river crossings, stream bends, outlet structures of
water plants, and in the approach zones to navigation locks. This instability in ship
navigation while passing through these previously mentioned fields is because of the
generated hydrodynamic forces due to acting transverse flow velocity components.
Such velocity components could affect ship navigation by complete lateral drift
across its course which may reach two times the ship width and/or rotation around
the vertical ship axis, (Ross, 1984). As a result of this shift in the ship course,
collision hazards may take place to other passing nearby ships.
To study the effect of cross water currents on navigational ships, a
representative design ship was worked out based on statistical analysis of the
available data for ship units along River Nile within Egypt. Such statistical analysis
concerned ship dimensions, types, modes, and main purposes of working ships. The
design ship applied in the current study was considered as the representative
navigation unit for which the waterway channel is designed.
In this study, a distorted scale model of 1:80 in horizontal direction and 1:20
in vertical direction was designed. A wooden ship of 14.62 kg weight, 0.94 m
length, and 0.19 m width, which specified as the geometrical model of the
representative prototype ship, was tested in rectangular flume inside the north
experimental hall of the Hydraulics Research Institute (HRI). The flume is 0.7 m
deep, 2.73 m wide, and 18.5 m long.
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A total of 135 experimental tests were carried out to develop a set of
dimension-less curves. These curves involved representative ship parameters (width,
draught and speed), fairway specifications (depth and width), field of cross water
currents conditions such as; the field width, the magnitude of the transverse flow
velocity component, and its inclination to the flow direction. The ship modeling was
carried out provided that two conditions; the ship was moved with the stream and
the rudder angle of the ship hadn’t any effect. The main output parameter is the
transverse movement of the ship which could be measured over a perspective grid
mesh of cell dimension; 0.5m length and 0.2m width, along the model at its water
level. The complete path of the ship model was digitally video recorded, afterwards,
this video film was divided into several images covering the whole path of the ship
model. Subsequently, these images were processed by developing software program
which was used to sign a suitable mark at the side of the ship model for each image.
Later on, a line was drawn connecting all image marks representing the ship model
path that influenced by cross water currents. Finally, the transverse movement was
obtained by subtracting the extremities of the plotted ship path line.
Analysis of the attainable results revealed that the ratio of ship transverse
movement to its width increases with the increase of the following dimension-less
parameters:
- Ratio of the cross water current field width to the distance between the ship and
the field of that current until this ratio reaches one and half.
- The ratio of the cross water current velocity to the relative ship unit speed.
- The horizontal angle between the cross water current field and the stream
direction.
- The ratio of water depth to ship draught.
Furthermore, also these results indicated that the ratio of the ship transverse
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movement to its width was inversely proportional with the ratio of the cross water
current field width to the distance between the ship unit and that field, while this
ratio was in the range of one and half to twice and half.
Application of the previously generated equations on the same data and there
results showed in agreement with these measured data. Each equation from these
equations neglects more than one parameter which may have a great effect on the
ratio of ship transverse movement to its width.
The results were represented by curves, as shown in Appendix (B), which
could be simply employed to work out the corresponding transverse movement of
the representative ship. This transverse movement should be utilized to check that
the navigational ship doesn’t move out from its permitted maneuvering path,
according to the specifications given by PIANC and IAPH (1997). Hence, this result
can be used to accomplish suitable designs of outfall structures, the proper design of
guide pier downstream barrage components, or to verify the safe navigable path
through bends.