Wind modeling for large container vessels: A critical review of the calculation proce dure
2019
With the increasing size of container ships, accurate methods to model manoeuvring and mooring
conditions are indispensable. Especially in confined waters, where the ship speed is low or even zero,
wind forces add a significant contribution to the force balance. The calculation of wind forces is
typically done using wind coefficients based on wind tunnel tests. In these computations, a reference
wind pressure must be used which is often based on the wind speed at 10 m height. When the wind
blows over a rough surface however, the wind profiles become non-uniform, resulting in much higher
wind speeds near the top of the ship, for the same wind speed at 10 m height. In case of differences
between the wind profile used in the wind tunnel and the one expected in the reality, an appropriate
reference pressure should be used. A method proposed by Blendermann to calculate such reference
pressure is applied in this paper to a wind force calculation for an ULCS. It is shown that, depending
on the roughness of the surface, the reference pressure can be a factor 2 to 3 higher than the one
corresponding to 10 m height. This means that wind forces are potentially highly underestimated. The
results of the method are compared with CFD simulations with a uniform and non-uniform inlet profile.
The comparison shows a good agreement between Blendermann’s method and CFD results for the
surge force and roll moment. On the other hand, Blendermann’s method seems to overestimate the sway
force, but more simulations are needed before a firm conclusion can be drawn
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