Variation of transmission coefficient and mooring forces with wave steepness on horizontal interlaced multilayered moored floating pipe breakwater with three layers

Abstract

The paper presents the results of a series of physical model scale experiments conducted for the study of the transmission characteristics and mooring forces of horizontal interlaced, multi-layer, moored floating pipe breakwater, part of which have been presented in conferences. The studies are conducted on physical breakwater models having three layers of PVC pipes, wave steepness, H<inf>i</inf>/L (H<inf>i</inf> is incident wave height and L is incident wave length) varying from 0.01384 to 0.0661, relative width, W/L (W is width of breakwater) varying from 0.4 to 2.65 and relative spacing, S/D = 3 (S is horizontal spacing of pipes and D is diameter of pipe). The transmitted wave height is measured and data gathered is analyzed by plotting non-dimensional graphs depicting the variation of K<inf>t</inf> (transmission coefficient) with H<inf>i</inf>/L for values of d/W (d is depth of water) varying between 0.082 to 0.276 and K<inf>t</inf> with W/L for values of d/W varying between 0.082 to 0.221. It is observed that Kt marginally decreases as H<inf>i</inf>/L increases for the range of d/W between 0.082 and 0.221, considered in the present study. The maximum wave attenuation achieved with present breakwater configuration is 68%. The variation of measured mooring forces are analyzed by plotting non-dimensional graphs depicting fs/?w2 and fl/?W2 (f<inf>s</inf> and f<inf>l</inf> are the forces in the seaside and leeside moorings per unit length of the breakwater, ? is the unit weight of sea water) as a function H<inf>i</inf>/L for various values of d/W. The mooring force parameter (f<inf>s</inf> /?W2) increases with an increase in wave steepness (H<inf>i</inf>/L) for a range of d/W values studied. It is observed that for d/W = 0.082, maximum force parameter attained was 2.11E-04, and for d/W = 0.276 maximum force parameter was 6.88E-04. A similar trend is observed for leeside side force parameter. Hence, it clearly indicates the influence of d/W on f/?W2. © 2011 CAFET-INNOVA technical society. All right reserved.