Water surface fluctuations around a vertical cylinder encircled by a perforated square caisson

The water surface fluctuations around a sea water intake structure consisting of a vertical circular cylinder encircled by a perforated square caisson (Figure1) were experimentally investigated. The porosity, p of the outer square caisson was varied from 4.24% to 14.58%. The variations of the water surface fluctuations are not insignificantly influenced by the porosity of the outer square caisson in this range. The wave height ratio (ratio of wave height at a point in the vicinity of the structure to the incident wave height) is also less sensitive for the varying input wave height and period combinations. Simple predictive equations for the water surface fluctuations are proposed, which are applicable for 4.24% < p < 14.58%, 0.114 < H/d < 0.429 and 0.013 < D/L < 0.048, where `H' is the incident wave height, 'd' is the water depth, 'D' is the inner cylinder diameter and 'L' is the wave length.