J. van der Zanden1, F. Spaargaren1, W. Otto1, B. Walles2, T. Ysebaert2
The attenuation of waves is essential to secure maritime operations and to protect coastal regions against erosion. Wave-attenuating breakwaters, which can be either fixed or floating, attenuate incident wave energy by means of wave reflection and/or wave dissipation through friction and wave breaking. Compared to fixed breakwaters, advantages of floating breakwaters include their applicability in more challenging environments (deep water, poor foundation), their reduced environmental impacts (minimum interference with water circulation and fish migration, minimum bottom disturbance, minimum visual intrusion), and their flexibility (can relatively easily be re-arranged) . The added value of a floating breakwater can be increased when it supports additional functions such as food production or a new ecological habitat.
The aim of the present project is to develop a novel multifunctional floating breakwater. Cost-efficiency will be realised by optimizing the floater and mooring system such that the design has optimum attenuation characteristics for minimum mooring loads. The concept should aim for synergy between its primary objective (wave attenuation) and other economic (e.g., food production) or ecological objectives (i.e., positive environmental impact). Although the new design should be applicable at varying locations, the shallow lake Grevelingen (SW Netherlands) is used as a case study throughout the project.
The breakwater design will be optimized through Computational Fluid Dynamics (CFD) simulations in COMFLOW , focusing firstly on the optimization of the floater and at later stage on the mooring lay-out. As a starting point, it is anticipated that the wave attenuation is improved when breaking of incident waves is promoted. Therefore, the initial shape of the floater is a parabolic shaped floating beach that promotes wave shoaling and breaking (see Figure 1). The concept may be developed into a bird refuge or a shellfish reef; these and other potential side-functions will be further developed in parallel to the design optimization. The final design will be validated through physical wave basin tests.
Results of the CFD simulations will be presented at the conference.
Figure 1 COMFLOW simulation of waves breaking over a parabolic floating reef.
 B. L. McCartney, "Floating breakwater design", J. Waterw. Port, Coastal, Ocean Eng., vol. 111, no. 2, pp. 304–318, 1985
 A. E. P. Veldman, R. Luppes, H. J. L. van der Heiden, P. van der Plas, B. Duz, and R. H. M. Huijsmans, "Turbulence modeling, local grid refinement and absorbing boundary conditions for free-surface flow simulations in offshore applications", Proc. OMAE 2014.