| Few experimental and numerical results have been found so far in the literature to study the effects of wave obliquity and multi-directionality on the wave forces acting on semicircular breakwaters.Based on 2-d and 3-d random wave physical model tests, the hydraulic characteristics of the semicircular breakwater are studied in this paper. The variations of wave forces on unit length of semicircular breakwater with the main effective factors including wave steepness H/L (π1), relative wave height H/ d (π2), relative water depth above the crown of semicircular breakwater d1/d (π3') , the angle of incidence θ0( π4 ) and spreading parameters s (π5) are studied. A simplified formula for calculating crests values and troughs values of the total horizontal wave forces on the submerged, alternately submerged, and emerged semicircular breakwater is suggested.The π3' is the most important factor for the pressure distribution on the semicircular breakwater, besides π1 and π2 The characteristics of the pressure distribution have no significant difference when the semicircular breakwater is subjected to regular waves, irregular waves and multi-directional waves.The analysis was made with the forces normalized. The crests values of the dimensionless total horizontal wave force Ph+ the total vertical wave force Pv and the uplift force applied to the bottom slab Pu increase obviously with decreasing π1 with π2 and π3' fixed. The troughs values of the dimensionless total horizontal wave forces Ph+ are not vary much with the π1; Ph+, Pv and Pu increase with increasing π2 when π2 and π3' were kept constant and decrease with increasing π3' when π2 and π2 fixed. The conditions for trough values of the total horizontal wave forces are larger than crest values are discussed.The regularity of oblique and multi-directional wave force on the semicircular breakwater with the main effecting factors are not vary much from the head-on wave forces. But short-crest waves will be produce in the water field just in front of the semicircular breakwater, and lead to the variety of the wave forces. Within the experimental consideration in this study, the angle of incidence of oblique wave varies in a range of 15° 45°. Ph+ does not decrease with increasing angle of attack θ0 as the modified Goda's formulae related. It is clear that oblique incident waves often impose larger forces than head-on waves do. In general, the Ph- under oblique waves is less... |
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