Abstract
The reflection coefficient of Jarlan-type perforated caissons can be well estimated using linear potential theory. But the resistance coefficient of perforated front wall must be known a priori. This study gives a new empirical formula in terms of Keulegan-Carpenter (KC) number for calculating the resistance coefficients of perforated walls. Then, the effects of wave height and period on the resistance coefficient are both involved. The calculated reflection coefficients using the new formula agree well with experimental data.
Highlights
Jarlan-type perforated caissons (See Figs. 1 and 2) Caisson front walls are punched Merits of low reflection coefficients and small wave forces Often used for building breakwaters and quaywallsEstimating reflection coefficient CR The reflection coefficient can be generally well estimated by linear potential theory The effect of perforated wall must be known a priorAn often used perforated wall condition (Yu, 1995) Horizontal fluid velocity passing through the perforated wall is proportional to the pressure difference between two sides of the wall z x o φ1 φ2 ∂φ1 ∂x = ∂φ2 ∂x = ik0G(φ1 − φ2 )Porosity of perforated wall G k0δ ε (f − is)
Resistance coefficient formula based on large scale model tests (Bergmann, 2000) For each incident wave: two data of single-chamber caissons; two data of three-chamber caissons Fitting the four data gives a value of the resistance coefficient for one incident wave condition Develop a resistance coefficient formula based on large scale model tests (See Fig. 10) Estimate CR using the resistance coefficient formula of large scale tests (See Fig. 11)
Scale effect on the resistance coefficient f (See Fig. 12) The resistance coefficient formula obtained by large scale model tests gives lower results f = 0.9821( KC )0.7509
Summary
Wave number Resistance coefficient of perforated wall Objective of present study Develop new method to estimate resistance coefficient (including wave parameter effects) Two-chamber perforated caissons Compare calculated CR with experimental data of two-chamber perforated caissons (See Fig. 8)
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