ABSTRACT
The presented work is part of the research project HyConCast, which contributes to the development of a novel support structure for offshore wind turbines. The concept is based on the advantages of combined ductile iron casting knots and precast concrete pipes, while the design is based on a typical jacket structure foundation type. Up to now, few systematic studies address the scour development of jacket structures under combined wave and current conditions (i.e. Chen 2014). The understanding of intrinsic drivers and effects of scouring processes for different types of jacket foundations is limited due to for example the complex interaction of the ground clearance of the nodes, the angles of the braces and the diameter of the structure’s elements along with the metocean loads stemming from waves and current; and a lack of appropriate laboratory facilities to simulate the environmental conditions.
Physical model tests with a scale of 1:30 are performed in the wave-current basin of the Ludwig-Fran-zius-Institute. The test model is printed in 3D and is installed in the middle of the wave basin in a sediment pit.
This work is related to jacket-type platform induced local and near-field erosion processes for different wave and current conditions. The measurement of the scour development over time is achieved by small echo sounding devices in a similar way as shown in McGovern (2014). The final topography of the sediment is measured with a high-resolution 3D laser scanner. Figure 1 shows the bed topography of test 03 after ~6500 waves under combined waves and current for a more current dominated flow condition (Ucw = 0.76; velocity ratio of waves and current, Ucw = 1.0 corresponds to current only).
Nondimensional areal erosion volumes are computed, which help to understand the sediment entrain-ment and redistribution potential around the structure. Volume differences of two different spacings of the structural nodes near to the sea bed are compared for the same hydrodynamic conditions. The equilibrium scour depth of different wave and current conditions is compared to each other including typical monopile scour developments for reference and comparison.
