Numerical modelling of a multi-chambered low-reflective caisson

Abstract

[Abstract:] The efficiency of a low-reflective caisson built at the Outer Port of Punta Langosteira (A Coruña, Spain), with a front-wall porosity of ≈ 5%, has been numerically investigated by means of OpenFOAM® for different chamber configurations and different sea states. The numerical model is validated with data coming from experimental tests performed on a scaled prototype. First, two different water levels, low and mean tide levels, are analysed. Results show that the caisson is inefficient when the water level inside the chamber is low, and suggest its proper installation taking into account the tidal regime of the area. For mean tide level inside the chamber, the efficiency of the caisson shows to be strongly dependent on the wave period and height. However, it is shown to be more sensitive to the period for low wave heights than for the high ones. Overall, the reflection coefficient ranged from 0.365 (B/Lc=0.14 s, H=0.02 m) to 0.660 (B/Lc=0.26 s, H=0.02 m). Alternative configurations with one and two chambers are also examined instead of three. Overall, the reflection coefficient is very high ( > 0.95) for the configuration with only one chamber. For the two and three-chambered caissons the mean reflection coefficient is similar ( ≈ 0.5) but the dispersion of the values is much higher for the two-chambered caisson, with values ranging from 0.176 to 0.794.