Equilibrium range spectra of wind waves on currents

It is well known that water waves tend to be higher or lower as they propagate onto an opposing or following current, respectively. This is also true for wind waves generated on currents. In the equilibrium range of wind waves, however, the spectral densities of the waves generated on a following or opposing current are larger and smaller, respectively, than those for the waves generated on quiescent water. To see this, a series of laboratory experiments was carried out in a wind-wave and current flume for various conditions of water depth, current and wind. The experimental results qualitatively confirm the theoretical equations proposed by Gadzhiyev et al. in 1978 and Suh et al. in 1994 with the former performing marginally better for following currents.