Examination of drag coefficient with special reference to the windsea Reynolds number: Conditions with counter and mixed swell

The effect of swell on the drag coefficient, C D , observed at the Hiratsuka Tower Station, presented by Suzuki et al. (1998, 2002), has been investigated. C D increases sharply with the windsea Reynolds number, R B , when there is a counter swell against the windsea direction, and only gradually when the swell comes from a mixture of directions. In cases where 2-D wave spectra were unavailable (1998, and others), swells showed a scattering effect compared with the pure windsea case on the C D - R B Diagram. R B is a useful parameter for investigating the effect of swells and further systematic accumulation of appropriate data is needed.