Waves and Tidal Streams

Abstract

IT has been shown¹ that the steepness of secondary waves riding on primary ones ranges from s(1-πS)^-2 to s(1+πS)^-2, at crest and trough of primary, S and s being primary and secondary steepness. The special case in which the tidal wave is the primary, and the larger wind-formed waves are the secondaries, is of some interest. As S is then almost nil, s does not vary. This means that the steepness of wind-formed waves is unaffected by the mere turn or making of the tidal stream. So some further explanation must be sought for the great change in the state of the sea when the stream turns to the weather, a change too great to be accounted for by the increase in speed of wind over water, and one which ordinarily takes place even after the wind has dropped, as will be assumed here.