The propagation of wind-generated waves onto and in ocean currents 

 such as the Gulf Stream is then discussed in a quantitative manner 

 making use of the above results. The reflection and trapping of waves 

 are particularly noted. 



The effect of the circumpolar Antarctic Current on waves propagat- 

 ing from the Indian Ocean to the Pacific Ocean is estimated and found to 

 be of the order of magnitude necessary to explain observations by Munk, 

 et al. (1963) and Snodgrass, et al. (1966). These observations indi- 

 cated that swell in the Pacific Ocean had traveled greater distances 

 than were possible on the basis of great-circle propagation. The 

 refraction of the ocean currents is adequate to curve the propagation 

 path of the swell into the geometric "shadow" of landmasses for these 

 examples . 



Coastal Engineering Significance . This paper is important since it 

 deals with the refraction of waves by ocean currents in a quantitative 

 manner. The estimates of wave behavior are based on measured currents 

 and waves. It also provides interesting, accurate diagrams showing how 

 rays differ from curves parallel to the wave number vector on a shearing 

 current . 



32. KRUIJT, J.A., and VAN OORSCHOT, J.R., "Interaction Between Wave and 

 Current Forces on the Concrete Piers of the Eastern Scheldt Storm 

 Surge Barrier," Mechanics of Wave-Induced Forces on Cylinders, T. 

 L. Shaw, ed., Pitman Publishing Ltd., London, England, 1979, pp. 

 684-703. 



Keywords. Experiment; Forces on Structures. 



Discussion. A relatively full report is given of force and moment 

 measurements on a model caisson. The study was made in connection with 

 the Delta Plan (established in 1953 by the Rijkswaterstaat) , and the 

 caisson was one of a group of four closely spaced piers (three in a 

 preliminary investigation). Currents and waves were directed at the 

 structure. Various angles of incidence and angles between waves and 

 currents were used. Some experiments were with periodic waves, others 

 with wave spectra. 



Conclusions drawn from the experiments are that the wave-current 

 interaction is especially important for the transverse force component, 

 while less so for the longitudinal force component provided the 

 appropriate Doppler correction to frequency is made. The average force 

 component is always increased over that due to the current alone, 

 whatever the wave direction relative to the current. There are 

 indications from the torsion measurements that there is appreciable 

 interaction between the waves and the flow due to the presence of the 

 cylinder. 



39 



