# Simulation of Irregular Waves and Wave Induced Loads on Wind Power Plants in Shallow Water Licentiate thesis, 2003

The essay gives a short introduction to waves and discusses the problem with non-linear waves in shallow water and how they effect an offshore wind energy converter. The focus is on the realisation of non-linear waves in the time domain from short-term statistics in the form of a variance density spectrum of the wave elevation. For this purpose the wave transformation from deep water to the near to shore site of a wind energy farm at Bockstigen has been calculated with the use of SWAN (Simulating WAves Near Shore). The result is a wave spectrum, which can be used as input to the realisation. The realisation of waves is done by perturbation theory to the first and second-order. The properties calculated are the wave elevation, water particle velocity and acceleration. The wave heights from the second order perturbation equations are higher than those from the first order perturbation equations. This is also the case for the water particle kinematics. The increase of variance is significant between the first order and the second order realisation. The calculated wave elevation exhibits non-linear features as the peaks become sharper and the troughs flatter. The resulting forces are calculated using Morisons equation. For second order force and base moment there is an increase in the maximum values. The force and base moment are largest approximately at the zero up and down crossing of the wave elevation. This indicates an inertia dominated wave load. So far the flexibility and the response of the structure have not been taken into account. They are, however, of vital importance. For verification of the wave model the results will later on be compared with measurements at Bockstigen off the coast of Gotland in the Baltic Sea.

wave load

Non-linear wave models

ocean engineering

wind energy converter

perturbation theory

shallow water

## Author

### Jenny Trumars

Chalmers, Department of Water Environment Transport, Waves and Hydraulics

1650-4143 (ISSN)

### Extreme non-linear wave forces on a monopile in shallow water

OMAE Offshore Mechanics and Arctic Engineering,; Vol. 22(2003)

Paper in proceedings

### The effect of wave non-linerarity on the forces on a wind turbine foundation in shallow water

Proceedings of the European Wind Energy Conference and Exhibition, 16 - 19 June, 2003, Madrid, Spain,; (2003)

Conference contribution

### Subject Categories

Civil Engineering

Doktorsavhandlingar och licentiatuppsatser på Vatten Miljö Transport: 7

10/7/2017