Christian Windt

Christian Windt
Technische Universität Braunschweig · Faculty of Architecture, Civil Engineering, and Environmental Sciences

PhD

About

56
Publications
25,494
Reads
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600
Citations
Additional affiliations
October 2015 - June 2016
University of California, Berkeley
Position
  • Visiting Researcher
January 2014 - August 2014
Queen's University Belfast
Position
  • Visiting Researcher

Publications

Publications (56)
Preprint
Full-text available
The modelling of wave-structure interaction (WSI) has significant applications in understanding natural processes as well as securing the safety and efficiency of marine engineering. Based on the technique of Computational Fluid Dynamics (CFD) and the open-source simulation framework - OpenFOAM, this paper provides a state-of-the-art review of WSI...
Article
Full-text available
Knowledge of the interaction between free surface waves and the seabed is required for the reliable design of marine structures, preventing severe structural failures. To that end, this paper presents the numerical modelling of wave-induced residual liquefaction of seabed soil. An OpenFOAM® finite volume solver is developed to simulate the behaviou...
Article
Full-text available
The Mocean wave energy converter consists of two sections, hinged at a central location, allowing the device to convert energy from the relative pitching motion of the sections. In a simplified form, the scattering problem for the device can be modelled as monochromatic waves incident upon a thin, inclined, surface-piercing plate of length $$L'$$ L...
Conference Paper
Full-text available
Recent developments in wave energy converter (WEC) control include robust control strategies , which admit a level of uncertainty in the model description. Then, for the application of such control methods, some knowledge of the uncertainty bounds is initially required. As recently shown in the literature, some approaches for uncertainty quantifica...
Conference Paper
Full-text available
Wave energy converter (WEC) modelling attracts significant uncertainty, often due to the need to develop compact parametric models for simulation, op-timisation and control design. For linear models, which form the basis of many WEC control philosophies, this uncertainty can be as a result of real system nonlinear-ity, particularly as a result of c...
Conference Paper
Full-text available
Due to the amount of iterative computation involved, researchers involved in geometric optimisation of wave energy devices typically employ linear hydrodynamic models. However, the exaggerated motion of wave energy devices, aided by energy maximising control action, challenges the assumptions upon which linear hydrodynamic modelling relies. Further...
Article
Full-text available
Wave energy converters (WECs) need to be optimally controlled to be commercially viable. These controllers often require an estimate of the (unmeasurable) wave excitation force. To date, observers for WECs are often based upon ‘complex’ techniques, which are counter-intuitive in their design, additionally requiring an explicit model to describe the...
Article
Full-text available
Scaled model tests are an important step during the research and development of wave energy converters (WECs). While such scaled model tests in physical wave tanks are prone to undesired scaling effects due to e.g. mechanical artefacts and/or fluid effects, numerical wave tanks (NWTs) provide excellent tools for the analysis of WECs across a range...
Conference Paper
Exploiting the offshore wind resources using floating offshore wind systems at sites with deep water depths requires advanced knowledge of the system behaviour, including the hydro-, areo-, and mooring dynamics. To that end, high-fidelity numerical modelling tools, based on Computational Fluid Dynamics, can support the research and development of f...
Article
Full-text available
The implementation of energy maximising control systems (EMCSs) in wave energy converter (WEC) devices is an important step towards commercially viable operation of WECs. During the design stage of such EMCSs, linear hy-drodynamic models are commonly used and are, in fact, the most viable option due to the real-time computational requirements of op...
Chapter
Full-text available
This document aims to disseminate the results of the 3rd UCL OpenFOAM Workshop, which was held during 24-26 February 2021. It gives a summary of the event and presents links to all recorded videos. The author list is organisers and then speakers in the order of presenting. Keynote Speeches: (1) Bayesian Optimisation with OpenFOAM (2) The finite vo...
Article
Full-text available
This study addresses the experimental validation of a linear time-invariant (LTI) energy-maximizing control strategy for wave energy converters (WECs), applied to a 1/20 scale Wavestar WEC. To fulfill this objective, system identification routines are utilized to compute a mathematical (parametric) model of the input-output dynamics of the device,...
Article
Full-text available
Reviewing the literature of CFD-based numerical wave tanks for wave energy applications, it can be observed that different flow conditions and different turbulence models are applied during numerical wave energy converter (WEC) experiments. No single turbulence model can be identified as an `industry standard’ for WEC modeling. The complexity of th...
Preprint
Full-text available
The modelling of ocean waves is an integral part of coastal and offshore engineering. Both theoretical and experimental modelling methods are available and are commonly used in support of each other. In particular, due to the difficulty in measuring the velocity throughout the water column, the wave kinematics are often derived, by means of wave th...
Article
The paper presents results from the Collaborative Computational Project in Wave Structure Interaction (CCP-WSI) Blind Test Series 2. Without prior access to the physical data, participants, with numerical methods ranging from low-fidelity linear models to fully nonlinear Navier-Stokes (NS) solvers, simulate the interaction between focused wave even...
Article
Full-text available
The vast majority of numerical wave tank applications are solved using finite volume-based, volume of fluid methods. One popular numerical modelling framework is OpenFOAM and its two phase solvers, interFoam and interIsoFoam, enabling the simulation of a broad range of marine hydrodynamic phenomena. However, in many applications, certain aspects of...
Article
Full-text available
Numerical wave tanks (NWTs) provide efficient test beds for the numerical analysis at various stages during the development of wave energy converters (WECs). To ensure the acquisition of accurate, high-fidelity data sets, validation of NWTs is a crucial step. However, using experimental data as reference during model validation, exact knowledge of...
Conference Paper
Full-text available
Considering the Wave Star wave energy converter (WEC), which is a standard point absorber prototype, this study addresses the complete energy maximising control design procedure. The WEC model is obtained using system identification routines. Then, using the identified model, a LTI energy maximising control strategy, recently presented in the liter...
Article
Full-text available
Measurement uncertainties are inevitable during physical wave tank tests. Therefore, when validating a numerical wave tank against experiments, knowledge of the uncertainties in the physical experiments, and the sensitivity of the body dynamics to such uncertainties, is crucial. Specifically, the inertial properties, as well as the location of the...
Article
Results from the CCP-WSI Blind Test Series 3 are presented. Participants, with numerical methods, ranging from low-fidelity linear models to high-fidelity Navier–Stokes (NS) solvers, simulate the interaction between focused waves and floating structures without prior access to the physical data. The waves are crest-focused New Waves with various cr...
Article
Full-text available
Computational fluid dynamics (CFD)-based numerical wave tanks are valuable tools for the development and evaluation of energy maximising control systems for wave energy converters (WECs). However, the exaggerated body motion amplitude, which can be induced by the energy maximising control system, challenges the commonly applied mesh morphing method...
Preprint
Full-text available
During the development and optimisation of wave energy converters, numerical wave tanks are useful tools, providing detailed insight into the hydrodynamic performance of devices. Specifically, computational fluid dynamics (CFD)-based numerical wave tanks (CNWTs) can deliver high-fidelity, high-resolution results for a wide range of test conditions....
Article
Full-text available
Considering the Wave Star wave energy converter (WEC), which is a standard point absorber prototype, this study addresses the complete energy maximising control design procedure. The WEC model is obtained using system identification routines. Then, using the identified model, a LTI energy maximising control strategy, recently presented in the liter...
Preprint
Full-text available
Computational fluid dynamics (CFD)-based numerical wave tanks are valuable tools for the development and evaluation of energy maximising control systems for wave energy converters (WECs). However, the exaggerated body motion amplitude, which can be induced by the energy maximising control system, challenges the commonly applied mesh morphing method...
Poster
Full-text available
Free Surface Effects Turbines like the ORPC RivGen cross-flow turbine, but also conventional horizontal axis turbines deployed in surface proximity, will be affected by the deformation of the free surface. For industrial design and development , those effects must be taken into account. Fully non-linear volume of fluid methods increase the computat...
Article
Full-text available
The implementation of energy-maximizing control systems (EMCSs) can significantly increase the efficiency and economic viability of resonant wave-energy converters (WECs). To achieve optimal control and drive the WEC into resonance with the incoming wave field, knowledge of the wave excitation force is required. In operational conditions, this quan...
Conference Paper
Full-text available
Cummins' equation is commonly used to describe the motion of Wave Energy Converters (WECs), where the radiation force is characterised by a convolution operation. The computational effort associated with the solution of the convo-lution term, often represents a drawback for e.g. optimisation or exhaustive-search studies. To overcome this disadvanta...
Conference Paper
Full-text available
Computational fluid dynamics (CFD) based numerical wave tanks (NWTs) can provide valuable insight into the hydrodynamic performance of wave energy converters (WECs). Being able to capture hydro-dynamic non-linearities, CFD-based NWTs (CNWTs) allow the analysis of WECs over a wide range of test conditions, such as sea states, power takeoff control s...
Conference Paper
Full-text available
During the development and optimisation of wave energy converters, numerical wave tanks are useful tools, providing detailed insight into the hydrodynamic performance of devices. Specifically, computational fluid dynamics based numerical wave tanks can deliver high-fidelity, high resolution, results for a wide range of test conditions. However, CFD...
Conference Paper
Full-text available
Numerical wave tanks (NWTs) provide a cost efficient and accurate tool to assess the complex fluid dynamic field around wave energy converters (WECs). In recent years, high fidelity methods based on the Reynolds-averaged Navier-Stokes (RANS) equations are increasingly applied for this type of analysis. However, the computational cost for a RANS-bas...
Presentation
Full-text available
For the economical operation of wave energy converts (WECs), energy maximising control systems (EMCSs) are included in the device design, introducing large structural motions. During the numerical modelling of WECs in CFD-based numerical wave tanks (NWTs), the structural motions must be explicitly accommodated in the finite volume domain. Using wel...
Article
CFD-based numerical wave tank (CNWT) models, are a useful tool for the analysis of wave energy converters (WECs). During the development of a CNWT, model validation is vital, to prove the accuracy of the numerical solution. This paper presents an extensive validation study of a CNWT model for the 1:5 scale Wavestar point-absorber device. The previo...
Conference Paper
Full-text available
During the design process and evaluation of energy maximising control systems (EMCSs) for wave energy converters (WECs), control techniques rely heavily on numerical modelling. For fast computation, these numerical models are mostly based on low-fidelity boundary element method (BEM) codes and linear hydrodynamic models. However, to ensure optimal...
Conference Paper
Full-text available
Numerical wave tanks (NWTs) are an essential tool for wave energy converter (WEC) development. Due to it's opensource nature and wide user base, OpenFOAM is proving to be an eective software platform for implementing NWTs for WEC experiments. Indeed, in a recent review of Computational Fluid Dynamics based NWTs (CNWTs) for WECs, OpenFOAM was the mo...
Article
Full-text available
Computational Fluid Dynamics (CFD) simulations, based on Reynolds-Averaged Navier-Stokes (RANS) models, are a useful tool for a wide range of coastal and offshore applications, providing a high fidelity representation of the underlying hydrodynamic processes. Generating input waves in the CFD simulation is performed by a Numerical Wavemaker (NWM),...
Code
Cummins' equation is commonly used to describe the motion of Wave Energy Converters (WECs), where the radiation force is characterised by a convolution operation. The computational effort associated with the solution of the convolution term often represents a drawback for e.g. optimisation or exhaustive-search studies. To overcome this disadvantage...
Article
Full-text available
A fully non-linear numerical wave tank (NWT), based on Computational Fluid Dynamics (CFD), provides a useful tool for the analysis of coastal and offshore engineering problems. To generate and absorb free surface waves within a NWT, a variety of numerical wave maker (NWM) methodologies have been suggested in the literature. Therefore, when setting...
Preprint
Full-text available
Computational Fluid Dynamics (CFD) simulations, based on Reynolds Averaged Navier Stokes (RANS) models, are a useful tool for a wide range of coastal and offshore applications, providing a high fidelity representation of the underlying hydrodynamic processes. Generating input waves in the CFD simulation is performed by a numerical wavemaker (NWM),...
Chapter
Full-text available
Wave energy conversion is an active field of research, aiming to harness the vast amounts of energy present in ocean waves. An essential development trajectory towards an economically competitive wave energy converter (WEC) requires early device experimentation and refinement using numerical tools. OpenFOAM\(^{\textregistered }\) is proving to be a...
Preprint
Full-text available
CFD-based numerical wave tank (CNWT) models, are a useful tool for the analysis of wave energy converters (WECs). During the development of a CNWT, model validation is important, to prove the accuracy of the numerical solution. This paper presents a validation study of a CNWT model for the 1:10 scale Wavestar point-absorber device. The previous stu...
Article
Performing rigorous technical and commercial assessment of wave energy converters (WECs) numerically, before engaging in expensive wave tank and open ocean tests, is vital for the economically successful development of prototypes. To that end, this paper presents a high-fidelity wave-to-wire simulation platform (the HiFiWEC), where a Computational...
Article
For the research and development (R&D) of wave energy converters (WECs), numerical wave tanks (NWTs) provide an excellent numerical tool, enabling a cost-effective testbed for WEC experimentation, analysis and optimisation. Different methods for simulating the fluid dynamics and fluid structure interaction (FSI) within the NWT have been developed o...
Conference Paper
To maximise the energy output of wave energy converters (WECs), large structural motions are desired. When simulating WEC performance in Computational Fluid Dynamics (CFD) based numerical wave tanks, these motions must be explicitly accommodated in the computational domain. Using well established mesh morphing (MM) methods, this explicit accommodat...
Conference Paper
Full-text available
The analysis of wave-current interaction (WCI) in numerical wave tanks (NWTs) requires the simultaneous generation of a current velocity profile and free surface waves. This paper presents a novel approach to simulate the WCI using an impulse-source-based methodology together with a numerical beach implementation. Three additional terms are added t...
Chapter
Full-text available
Wave energy conversion is an active field of research, aiming to harness the vast amounts of energy present in ocean waves. An essential development tra-jectory towards an economically competitive wave energy converter (WEC) requires early device experimentation and refinement using numerical tools. OpenFOAM is proving to be a useful numerical tool...
Conference Paper
Full-text available
A numerical wave tank (NWT) based on Computational Fluid Dynamics (CFD) provides a useful tool for the analysis of offshore renewable energy (ORE) systems, such as wave energy converters (WECs). NWT experiments, of WEC operation, rely on accurate wave generation and absorption at the NWT boundaries. To tackle this problem, different method-ologies,...
Presentation
Full-text available
Turbulence Modelling for Ocean Wave Energy Systems
Conference Paper
Full-text available
We investigate here the influence of three dimensional features on the determination of the wave excitation force on a submerged rigid board. Our results are obtained by Direct Numerical Simulations (using ANSYS Fluent) of linear and weakly non-linear Stokes waves in a numerical wave tank, and validated with results from an independent frequency-do...
Article
Full-text available
Abstract During extreme sea states so called impact events can be observed on the wave energy converter Oyster. In small scale experimental tests these impact events cause high frequency signals in the measured load which decrease confidence in the data obtained. These loads depend on the structural dynamics of the model. Amplification of the loads...
Conference Paper
Full-text available
The term fatigue loads on the Oyster Oscillating Wave Surge Converter (OWSC) is used to describe hydrostatic loads due to water surface elevation with quasi-static changes of state. Therefore a procedure to implement hydrostatic pressure distributions into finite element analysis of the structure is desired. Currently available experimental methods...