A Combined Breakwaters System

A Combined Breakwaters System: A Wave Attenuation Study on the Combination of Submerged and Floating Breakwaters using REEF3D

Damdam, Khaled (TU Delft Civil Engineering & Geosciences)

Bihs, Hans (mentor)
Kamath, Arun (graduation committee)

Delft University of Technology
Norwegian University of Science and Technology (NTNU)

Coastal and Marine Engineering and Management (CoMEM)

2019-08-11

Coastal zones have been a dynamic area and most favoured locations utilized for living, leisure, recreational activities, tourism, commerce and many other human activities. Submerged and floating breakwaters have been used as effective systems to protect these zones from wave attack. However, they are only effectively functional if the incident wave height is relatively low. Under such condition, these systems can reduce the wave transmission with significant wave dissipation and hence achieving a desirable tranquillity in designated areas. Therefore, the focus of this research is mainly to investigate the possibility of using a combination of a submerged porous breakwater (SBW) with a floating breakwater (FBW) as an innovative coastal protection system that can provide adequate calm conditions in the coastal zones with minimum visual impact. This study utilizes the open-source CFD model, REEF3D to simulate such wave-structure interaction. This CFD model is based on the RANS equations coupled with the level set method and the k − ω turbulence model. In the present study, the first section deals with the simulation of irregular wave breaking over an irregular bed profile with the use of wave reconstruction method to generate irregular waves. An excellent agreement between the computed results and the experimental data is obtained showing that REEF3D model is capable of capturing the dominant features of the evolution of the wave breaking process, both in the shoaling region and the surf zone. The second section deals with the simulation of regular wave interaction with the SBW. The simulation is conducted using the VRANS method to resolve the porous flow. The wave interaction with the SBW is validated by comparison with experimental data. An impressive agreement between the numerical results and the experimental data is achieved with very small RMSE values. Finally, the validated model is then used to simulate the combination of the SBW and the FBW. Three different cases are investigated with three different spacing between these structures. For each case, five different configurations related to the geometry of the FBW are simulated. It is found out that an effective reduction of more than 90%, on average, of the incident wave height, can be achieved for this combined breakwaters system. This means that a transmission coefficient (Kt) of less than 10% is calculated across this combination. Besides, it is found out that 1.75 FBW length to wavelength (L/λ) ratio produces a very low transmission coefficient (Kt). Further, an effective distance of 1-2 wavelength between the SBW and the FBW subsystems can also result in lower transmission coefficients (Kt).

CoMEM
REEF3D
Wave-structure interaction
Wave Attenuation
Submerged Breakwater
Floating Breakwater

http://resolver.tudelft.nl/uuid:7b1912f0-bde6-4953-b8ae-ad4a37419817

2019-09-30

Student theses

master thesis

© 2019 Khaled Damdam