3.3 Wind tests

 The wind speed should comply with the following:

• .1 The minimum wind speed to perform tests should be over the critical Reynolds’ number, after which C_D is constant.

• .2 The wind speed profile should be as uniform as reasonably possible. Except for the boundary layer in the vicinity of the end plate (figure 3.3.1), spatial deviation^footnote of the wind speed should be less than 1%.

• .3 The effects of end plate (due to its shape, size, roughness, etc.) and of the gap between end plate and model should be minimized.

Figure 3.3.1 Example of an arrangement for tests in wind

 The lateral horizontal force F_wind (and corresponding drag coefficient C_D ) and the heeling moment due to wind M_wind with respect to O are obtained by a wind tunnel test or in wind from a blower. In calculating C_D according to equation (3.1.4), the actual value of air density during tests should be used. An example of model test arrangement is shown in figure 3.3.1. Model tests should be carried out in compliance with the following:

• .1 Before tests are carried out, the vertical and horizontal distribution of the wind speed at the model position should be verified.

• .2 Tests should be carried out in upright condition and at some heeling angles with appropriate increment to lee and wind side covering a sufficient range of heeling angles to the satisfaction of the Administration.

• .3 In heeled conditions the model shape exposed to wind should be the same as the above-water shape when the ship is floating freely. The change of trim due to heel can be neglected.

 As an alternative simplified procedure, the lateral horizontal force F_wind (and corresponding drag coefficient C_D ) and the heeling moment due to wind M_wind with respect to O can be obtained for the upright condition only and considered as constants (not depending by heeling angle).