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 ultra large container ship. 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 computational fluid dynamics (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.
wind coefficients, ULCS, wind profile, reference pressure, CFD
 SEA Europe, 2017 Market Forecast Report. 2017.
 B lendermann, W., Estimation of wind loads on ships in wind with a strong gradient. 14th International Conference on offshore mechanics and arctic engineering (OMAE), pp. 271–7, 1995.
 ITTC , ITTC Symbols and Terminology List Version 2017. 2017.
 RINA , Significant ships of 2015. 2016.
 Andersen, IMV., Wind loads on post-panamax container ship. Ocean Engineering, 58, pp. 115–34, 2013.
 Coelingh, JP., Wijk, AJM. & Holtslag, AAM., Analysis of wind speed observations over the North Sea. Journal of Wind Engineering and Industrial Aerodynamics, 61, pp. 51–69,1996.
 Garatt, JR., Review of drag coefficients over oceans and continents. Monthly Weather Review. 1977.
 Simiu, E. & Scanlan, RH., Wind effects on structures : Fundamentals and applications to design. 1996.
 Charnock, Wind stress on a water surface. Journal of the Royal Meteorological Society, 81, pp. 639–40, 1955.
 Janssen, WD, Blocken, B & van Wijhe, HJ., CFD simulations of wind loads on a container ship : Validation and impact of geometrical simplifications. Journal of Wind Engineering and Industrial Aerodynamics, 166, pp. 106–16, 2017.
 MariKom, HPA., Determination of aerodynamic drag ceofficients of ship models with different air draughts and loading conditions. 2015.
 Fujiwara, T. & Nimura, T., New Estimation Method of Wind Forces Acting on Ships on the Basis of Mathematical Model. The International Society of Offshore and Polar Engineers (ISOPE), editor. Proceedings of the 15th International Offsohre and Polar Engineering Conference. 2005, Seoul, Korea.
 Fujiwara, T., Tsukada, Y. & Kitamura, F., Experimental Investigation and Estimation on Wind Forces for a Container Ship. Nineteenth (2009) International Offshore and Polar Engineering Conference, 1, pp. 555–62, 2009.