Arboleda Chavez, C.E.

Stratigaki, V.

Troch, P.

Wu, W.

Open Marine Archive

 66 
Development of a numerical wave flume for the study of scour 
protection around offshore monopile foundations under waves and 
currents 
Arboleda Chavez Carlos Emilio, Wu Minghao, Stratigaki Vasiliki and Troch Peter 
Coastal Engineering Research Group, Department of Civil Engineering, Ghent University, 
Technologiepark 904, 9000 Ghent, Belgium 
E-mail: carlosemilio.arboledachavez@ugent.be  
 
So far, the majority of the offshore wind turbines are supported by monopile structures. As any 
structure embedded in the seabed, erosion/scour may occur around the monopile foundations. In 
order to counter erosion, a scour protection is placed around the monopile’s foundation on the sea 
bed. In this study, the behavior of the scour protection will be modeled using numerical tools. 
 
De Vos et al. (2012) [1] give an overview of key experimental research carried out in the large wave 
flume of the Coastal Engineering Research Group - CERG - of Ghent University – UGent -, Belgium, 
regarding scour protection. Tests were carried out with a scale model (1:50) under the combined 
action of waves and currents. Three main failure modes have been distinguished: (i) damage of the 
scour protection by the flow, (ii) failure due to scour at the edge of the protection, and (iii) sinking of 
the scour protection. 
 
The latter failure mode was studied by Nielsen et al. (2013) [2] and a numerical model for currents 
based on the Flow 3D software is proposed. This study concludes that a porous medium approach of 
scour protection can be used to determine the bed shear stresses underneath the scour protection, 
although calibration is needed. 
 
Numerical models able to model the sinking failure of the scour protection around monopiles under 
the action of waves and currents using the porous medium approach are currently not available. The 
objective of this study is to cover this literature gap. 
 
The toolbox selected for the development of the numerical model is OpenFOAM, Jasak (1996) [3], 
while the wave generation/absorption is performed using the module IHFOAM, Higuera (2015) [4]. In 
the latter module, the incompressible Volume Averaged Reynolds Averaged Naviers Stokes - VARANS 
- equations are solved in a finite volume discretization. In order to deal with the multi fluid (air, water) 
nature of the problem, the Volume of Fluid - VOF - method is used, which allows using the same set 
of equations to solve the momentum balance in both phases, thus, speeding up the calculations. The 
turbulence is modeled following the approach of Devolder et al. (2017) [5] as it has shown to reduce 
the turbulent kinetic energy production at the interface between the two fluids. Finally, the scour 
protection is considered as a porous medium as performed in Nielsen et al. (2013) [2]. 
 
The numerical model will be validated using experimental data. Physical model tests will be carried 
out in an upcoming European Hydralab+ project (spring 2018) which focuses on experimental 
modeling of scour protection around offshore wind turbine monopiles and is coordinated by CERG 
from UGent. The tests will be performed in the Fast Flow Facility in HR Wallingford with a scale of 
1:8.33 and aim to extend and complement the 1:50 experiments performed by CERG (De Vos et al. 
(2012) [1]). 
 
Acknowledgement 
 
The work described in this publication was supported by the European Community’s Horizon 2020 
Research and Innovation Programme through the grant to HYDRALAB-PLUS, Contract no. 654110. The 
first author would like to acknowledge his PhD funding through a Special Research Fund of UGent, 
(BOF). 
 
References  
 
[1] De Vos, L., De Rouck, J., Troch, P., Frigaard P. 2012. Empirical design of scour protections around 
monopile foundations. Part 2: Dynamic approach. Coastal Engineering 60:286-298. 
[2] Nielsen A. W., Liu X, Sumer B. M., Fredsoe J. 2013, Flow and bed shear stresses in scour 
protections around a pile in a current, Coastal Engineering 72:20-38 
 67 
[3] Jasak H. 1996, Error Analysis and Estimation for the Finite Volume Method with Applications to 
Fluid Flows, PhD. Thesis, Imperial College, University of London 
[4] Higuera P. 2015, Application of Computational Fluid Dynamics to Wave Action on Structures, 
PhD. thesis, Universidad de Cantabria 
[5] Devolder B., Rauwoens P., Troch P. 2017, Application of a buoyancy-modified k-ω SST turbulence 
model to simulate wave run-up around a monopile subjected to regular waves using OpenFOAM, 
Coastal Engineering 125:81-94 
 
Keywords: scour protection; offshore wind turbines; numerical modelling; porous flow; waves; 
currents  


Development of a numerical wave flume for the study of scour protection around offshore monopile foundations under waves and currents

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Development of a numerical wave flume for the study of scour protection around offshore monopile foundations under waves and currents

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