3.2.1
The arrangement for the wind
tunnel tests is shown in figure 3.1.
The connection between the model and load cell had a rotating device
for testing the model in heeled conditions. In heeled conditions the
height of the model was adjusted by the adjusting plate to keep the
displacement constant when floating freely. The change of trim due
to heel was neglected.
3.2.2
In order to keep the blockage
ratio less than 5%, the floor plate was set to the same level of the
floor of the tunnel. The gap between the model and the floor plate
was kept within approximately 3 mm and covered by soft sheets for
avoiding the effect of downflow through the gapfootnote.
Arrangement for wind tunnel tests
3.2.3
The vertical distribution of
wind speed is shown in figure 3.2.
For the test arrangement (figure 3.1),
the height of the ship model from the floor was approximately 19 cm
in upright condition. This means that the lower half of the model
is placed in the boundary layer. The distributions of wind speed in
the lateral and longitudinal directions were almost uniform (deviation
less than 1%) around the model.
Vertifical distribution of wind speed
3.2.4
The wind speed was varied from
5 m/s to 15 m/s in upright condition and confirmed that the drag coefficient
is almost constant in this speed range. For the full tests a wind
speed of 10 m/s was used, corresponding to a Reynolds' number of 1.52×
105, as defined by the following equation:
where U is the uniform wind speed outside
the boundary layer, B is the breadth of the model and ν is the kinematic viscosity coefficient of air.
3.2.5
The horizontal force Fwind
, the heeling moment M and the lift force L were measured by the load cell. The heeling moment M was
converted to the one with respect to point O, defined
as Mwind
, by the following equation:
where l is the distance from the centre
of the load cell to point O. The point O is
defined as the cross point of the centreline of the ship and waterline
in upright condition.