Model Studies of Mobile Breakwaters Progress Report for July-November, 1949

This report covers further work on the refraction of waves by opposing currents, and is essentially an elaboration of earlier results. Two types of currents have been considered, a horizontal flow of substantially constant velocity from surface to bottom, and a horizontally stratified flow characterized by high velocities near the surface and relatively low velocities in the opposite direction across the rest of the vertical section. For the first type of current, a revised theoretical treatment is presented, together with experimental results which are in good agreement with the theory. For the second type of current, experimental results have been obtained for a range of current intensities much higher than would be practical in a prototype installation. The results of these experiments do not change the earlier conclusion that the refraction of waves by opposing currents, and hence the pneumatic breakwater, is not a practical means for materially reducing wave disturbances. These experiments do extend the experimental investigation to cover the complete range of wave types, from deep-water to shallow-water and of current values to well over any conceivable prototype range.