Deltares has supported Jan De Nul in investigating hydrodynamic loads on its gravity-based foundations (GBFs) for the high voltage substations for the Kriegers Flak offshore wind farm in the Baltic Sea.
Tom Vermeersch, design manager of the Kriegers Flak project from Jan De Nul said, “Computing slamming loads using simple methods such as phase-focused waves does not capture the right physics and leads to unrealistic designs. We therefore asked Deltares to use advanced CFD methods to investigate the local hydrodynamics and to understand what a realistic breaking wave looks like at the site. In this way, we managed to achieve a safe, yet economical design. Their approach was a huge improvement compared to conventional methods.”
The advanced CFD models applied by Deltares consist of a two-step approach. In step one, more than 10.000 storm waves are analysed using a fully nonlinear wave model. This provides sufficient information for understanding the site-specific waves and for determining what a realistic breaking wave looks like.
In the second step, the identified extreme waves are used as boundary conditions for a detailed CFD model, where loads on the structure are computed, the company explained.
“The advantage of this methodology is that the slamming waves have a size and shape that are realistic and representative of the specific site. By staying close to the physics, we get the most accurate results,“ said Dr. Niels Jacobsen, expert at Deltares.
The two gravity-based structures will support two substations, which will serving both the future Krieger Flaks offshore wind farm and an interconnector between the Danish and German power net.