Air flow over the R.R.S. Charles Darwin: the disturbance of the flow at the anemometer sites used during cruises CD43 and CD98

The Computational Fluid Dynamics (Crn) package "Vectis" was used to model the effect of air flow distortion, caused by the hull and superstructure of the ship, on wind speed measurements made from two RRS Charles Darwin cruises. Wind speed errors are calculated for the positions of the anemometers on CD43, which was instrumented with four fast sampling instruments used to measure the wind stress. This report describes the errors predicted by the model results: the comparison between model and cruise results is discussed in Yelland et a!. (1996). Errors are also calculated for the anemometer positions on CD98 and CD98a, cruises where the ship carried an array of eleven anemometers for the purpose of evaluating the CFD package. The Vectis model considered in this report simulates a surface layer wind profile, directly over the bows of the ship, with a IOm wind speed of 13,8 m/s.