A5046499575- Ocean Waves and Remote Sensing
- Wave and Wind Energy Systems
- Coastal and Marine Dynamics
- Fluid Dynamics Simulations and Interactions
- Tropical and Extratropical Cyclones Research
- Wind and Air Flow Studies
- Wind Energy Research and Development
- Vibration and Dynamic Analysis
- Numerical methods in engineering
- Structural Health Monitoring Techniques
- Hydraulic and Pneumatic Systems
- Underwater Acoustics Research
- Geotechnical Engineering and Underground Structures
- Earthquake and Tsunami Effects
- Fluid Dynamics and Vibration Analysis
- Metallurgy and Material Forming
- Fluid Dynamics and Heat Transfer
- Icing and De-icing Technologies
Technical University of Denmark
2014-2023
Loads from extreme waves can be dimensioning for the substructures of offshore wind turbines. The DeRisk project (2015-2019) aims at an improved load evaluation procedure through application advanced wave models, laboratory tests effects, development hydrodynamic aero-elastic response calculations and statistical analysis. This first paper outlines content philosophy behind DeRisk. Next, results with irregular are presented, including 2D 3D focused groups. group a 6-hour (full scale...
A pressure impulse model is presented for wave impact on vertical circular cylinders. Pressure the time integral of during an short scale. The derived a simplistic geometry and has relative height, crest length cylinder radius as effective variables. last parameter, maximum angle impact, free can be calibrated to yield right force impulse. progression simpler models are in terms three-dimensional box generalization two-dimensional wall axisymmetric dependence parameters investigated linked...
The design methods for highly nonlinear wave loads on monopile structures has over the past years been extended with based pre-computed fully kinematics. Yet, slamming events of strong sea states cannot currently be predicted these methods. We here present a simple recipe application recent pressure impulse load model in combination kinematics and validate results against lab measurements uni- multi-directional storm states. experimental are extracted from equivalent to 954 full scale hours....
The perturbations existing on a breaking wavefront can be potential explanation for the slamming pressure variability in wave impacts. Here, we investigate effect of these by forced vertical two-dimensional circular cylinder with constant downward velocity standing waves. Through experimental modelling and numerical simulation, force is measured several amplitudes wavelengths. phase tuned such that impact occurs symmetrically at instant maximum crest or trough. Our observations show...
The current method for calculating extreme wave loads on offshore wind turbine structures is based engineering models non-breaking regular waves. present article has the aim of validating previously developed at DTU, namely OceanWave3D potential flow model and a coupled OceanWave3D-OpenFOAM solver, against measurements focused group impacts monopile. 2D 3D groups are reproduced free surface elevation in-line forces compared to experimental results. In addition, pressure distribution monopile...
Experiments with a stiff pile subjected to extreme wave forces typical of offshore wind farm storm conditions are considered. The exceedance probability curves the nondimensional force peaks and crest heights analysed. average time history normalised their peak values compared across sea states. It is found that shapes show clear similarity when grouped after force, F/(ρghR2), depth h/(gT2p) presented in scale t/Ta. For largest events, slamming can be seen as distinct 'hat' on top smoother...
Experiments with both uni- and multidirectional wave realizations a stiff pile subjected to extreme forces are considered. Differences in crest heights force peaks resulting from directional spread waves analysed. The reproduced numerically the fully nonlinear model OceanWave3D. numerical reproductions compare well experiments. Only for largest significant differences seen, which is due very simple breaking filter applied In spectra, higher harmonics occur smaller frequencies than straight...
In design of substructures for offshore wind turbines, the extreme wave loads which are interest in Ultimate Limit States often estimated by choosing events from linear random sea states and replacing them either stream function theory or NewWave a certain height. As these theories super limitations such as symmetry around crest, other methods to estimate needed. present paper, First Order Reliability Method, FORM, is used systematically most likely shapes. Two parameters maximum crest...
Abstract This paper investigates the flow field in rotor plane of a full‐scale operating wind turbine using light detection and ranging (LiDAR) measurements for first time. Comparison measured with results from large eddy simulations (LES) combined an actuator line approach is also presented in‐depth study induction plane. The include data two synchronized LiDAR systems—one scanning undisturbed upstream inflow one measuring standard deviation mean velocity time series are as measure...
Abstract Monopiles are nowadays the preferred substructure type for bottom-fixed offshore wind turbines at shallow to intermediate water depths. At these locations, large waves that contribute extreme loads strongly nonlinear. Therefore they not easily reproduced via simple engineering models who commonly used in industry. In current approach, we develop a design pattern which improves this standard methodology. To retain nonlinearity force computations, have precomputed number of wave...
Abstract Empirical investigations have consistently demonstrated the multi-directional nature of actual ocean waves, a phenomenon that has been paid relatively limited attention in research field floating wind turbines. The present study seeks to reduce this knowledge gap by experimentally investigating response novel 15 MW turbine design when subjected wave conditions. experimental work was carried out deep water basin at DHI A/S (DHI), scale 1:40. In investigation, rotor simplistically...
Abstract As part of the ongoing development Stiesdal Offshore A/S TetraSub floating offshore wind turbine generator (WTG) platform, this study investigates wave run-up acting on front cylindrical ballast tanks. Using experimental results from a recent test campaign variant 1:50 scale model, work aims to review existing semi-empirical methods for predicting run-up. Moreover, defined eight regular cases, predicted theoretical values are compared measured recorded during tank experiments. The...
Two different numerical models, OceanWave3D and a coupled solver, OceanWave3D-OpenFOAM (Waves2Foam), are used to reproduce extreme events in one sea state. The chosen as, the measured event that generates largest peak moment (exceedance probability of 0.05%) with slightly smaller 0.3%). Time series free surface elevation, depth integrated forces, bending at bed pressure time 5 heights on cylinder compared for two between measurements models. field monopile impact is analyzed stagnation...
Abstract In this work, we compare the wave and loads statistics for two different sea states with a TP = 15.0[s] on h 33.0[m] depth, one 10-year return period (HS 7.5[m]) 100-year 9.5[m]). For each state, unidirectional multi-directional realization was measured experimentally then reproduced numerically via fully-nonlinear potential solver. The computed kinematics were used to calculate stiff cylinder diameter of D 7.0[m], compared experiments. To perform quantitative analysis, extracted...