• Energy Research

The present article presents results of a laboratory study on the assessment of erosion patterns around a hydrodynamic transparent offshore foundation exposed to combined waves and currents. The model tests were conducted under irregular, long-crested waves in a scale of 1:30 in a wave-current basin. A terrestrial 3D laser scanner was used to acquire data of the sediment surface around the foundation structure. Tests have been conducted systematically varying from wave- to current-dominated conditions. Different volume analyzing methods are introduced, which can be related for any offshore or coastal structure to disclose physical processes in complex erosion patterns. Empirical formulations are proposed for the quantification of spatially eroded sediment volumes and scour depths in the near-field and vicinity of the structure. Findings from the present study agree well with in-situ data stemming from the field. Contrasting spatial erosion development between experimental and in-situ data determines a stable maximum of erosion intensity at a distance of 1.25 A, 1.25 times the structure’s footprint A, as well as a global scour extent of 2.1–2.7 A within the present study and about 2.7–2.8 A from the field. By this means, a structure-induced environmental footprint as a measure for erosion of sediment affecting marine habitat is quantified.

The present article presents results of a laboratory study on the assessment of erosion patterns around a hydrodynamic transparent offshore foundation exposed to combined waves and currents. The model tests were conducted under irregular, long-crested waves in a scale of 1:30 in a wave-current basin. A terrestrial 3D laser scanner was used to acquire data of the sediment surface around the foundation structure. Tests have been conducted systematically varying from wave- to current-dominated conditions. Different volume analyzing methods are introduced, which can be related for any offshore or coastal structure to disclose physical processes in complex erosion patterns. Empirical formulations are proposed for the quantification of spatially eroded sediment volumes and scour depths in the near-field and vicinity of the structure. Findings from the present study agree well with in-situ data stemming from the field. Contrasting spatial erosion development between experimental and in-situ data determines a stable maximum of erosion intensity at a distance of 1.25 A, 1.25 times the structure’s footprint A, as well as a global scour extent of 2.1–2.7 A within the present study and about 2.7–2.8 A from the field. By this means, a structure-induced environmental footprint as a measure for erosion of sediment affecting marine habitat is quantified.

The early stages of wave farm design require many parametric studies, e.g., regarding geometrical optimization of the array layout. Hence, mid-fidelity numerical models are employed due to their computational efficiency. In this study, the accuracy of these models and the necessary quality of input data (e.g., from Boundary Element Method simulations) is investigated using different calibration approaches. A heaving point absorber array comprising 24 devices, which are connected using a rigid frame, is used as the example wave farm. Three different approaches of model calibration are compared: (i) a low-effort approach without any calibration of the input data; (ii) an approach with medium-effort calibration based on experimental data of a single point absorber; and (iii) an approach with high-effort calibration based on experimental data of a whole wave farm. After a comparison with experimental data, the wave farm's power output using the three approaches is calculated and the accuracy as well as the implications for further design stages are discussed. The mid-fidelity hydrodynamic model can reproduce the mechanical interactions in the wave farm accurately, while the medium effort calibration shows high applicability due to the strong influence of the single point absorber calibration on the wave farm's power output.

The early stages of wave farm design require many parametric studies, e.g., regarding geometrical optimization of the array layout. Hence, mid-fidelity numerical models are employed due to their computational efficiency. In this study, the accuracy of these models and the necessary quality of input data (e.g., from Boundary Element Method simulations) is investigated using different calibration approaches. A heaving point absorber array comprising 24 devices, which are connected using a rigid frame, is used as the example wave farm. Three different approaches of model calibration are compared: (i) a low-effort approach without any calibration of the input data; (ii) an approach with medium-effort calibration based on experimental data of a single point absorber; and (iii) an approach with high-effort calibration based on experimental data of a whole wave farm. After a comparison with experimental data, the wave farm's power output using the three approaches is calculated and the accuracy as well as the implications for further design stages are discussed. The mid-fidelity hydrodynamic model can reproduce the mechanical interactions in the wave farm accurately, while the medium effort calibration shows high applicability due to the strong influence of the single point absorber calibration on the wave farm's power output.