Hydrodynamic Engineering

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Within Emerald Energy we have intrinsic knowledge in the field of hydrodynamics and a thorough understanding of environmental dynamics. Our team members have a solid background in the marine energy sector, ranging from the realization of renewable energy concepts to the dynamics of large offshore operations. We can readily analyse the influence of wind, wave and current on a floating or submerged structure or resolve its dynamic interaction with wave energy converters, tidal turbines, FPSO’s, ships and semi subs.

Out team can help design a novel renewable marine energy concept from feasibility to detailed design. Complete hydrodynamic analysis can provide the loads and motions of a floating or moored structure during installation and operation and from our experience we understand what impact the environment has on performance and know how to mitigate extreme events. Using state of the art software packages and the newest techniques, we can employ frequency and time domain analysis for high level or detailed studies to the dynamic behavior of an offshore floating or submerged structure.

Due to our inherent theoretical and practical knowledge we can develop custom made analysis tools based on first principles to assist you in the development of your marine energy concept or the realization of a safe and cost effective offshore operation.

LIST OF SERVICES OFFERED

Design Support

Conceptual studies
Within Emerald Energy there is thorough experience in analysing the hydrodynamic interaction of a device with the environment. Multiple concepts of wave energy converters or tidal turbines can readily be analysed or reviewed.
Concept studies will among others focus on maximizing performance and power to weight ratio, whilst minimizing operating loads, mooring loads, extreme loads and fatigue. Sizing studies can be performed. In parallel small scale devices can be analysed for proof of technology and subsequently up scaled for commercial development.

Feasibility studies
Emerald Energy has the capability to assess the feasibility of a wave energy converter or tidal turbine in an energetic wave or tidal site. High level assessments on the structural loading and hydrodynamic performance quickly and accurately determine the feasibility of a concept.
Hydrodynamic feasibility studies can be augmented by a dynamic analysis of the installation and maintenance methodology.

Detailed design
During the design phase a detailed study can be undertaken to the structural loading and hydrodynamic performance of a device. Emerald Energy is experienced in developing numerical dynamic models in Matlab/Simulink involving realistic wind wave end current conditions. Furthermore wave tank test campaigns can be developed and executed for new or existing devices.

Model verification
Emerald Energy has the capability to review and verify computer models written in the Matlab/Simulink environment. Starting from the principle equations models involving hydrodynamic, multi body dynamics, moorings and electrical or hydraulic power take-off systems can be validated and optimized where necessary.

Operation and Installation

Weather windows & environmental optimisation
Emerald Energy is capable of reviewing and optimizing offshore installation methods. By analysing the installation methodology combined with the environmental conditions and vessel response characteristics, installation time and cost can be reduced. By adapting the installation process to present and past wind, wave and current (persistence) data a safer and more cost effective installation method can be developed.

Vessel motion and installation loads
During installation and operation, knowledge of the motions and loads of a floating offshore structure are a necessity. Using the correct environmental conditions and the floating structure response to these conditions, Emerald Energy can determine the dynamic behaviour of any floating offshore structure during installation and operation.
At local positions such as the crane tip, helideck and stinger tip, the motion, velocity, acceleration and loads can be determined.

Extreme event loading and motions
For offshore floating structure design the extreme wave loading is of trivial importance. Using response analysis and statistical methods extremes can be determined. Emerald Energy can perform both frequency and time domain analysis to determine the loads and motions during extreme events.
For moored vessel, FPSO’s, installation barges, the normal and extreme loads can be analysed during operation and installation. Mooring spreads and mooring line compositions can be optimised in adherence to proper classification codes.

Vessel-vessel interaction
Installation scenarios often involve multiple vessels moored together. Emerald Energy is experienced in performing dynamic analysis involving vessel-vessel interaction. The analysis of hydrodynamic interaction between vessels provides vessel motions, mooring loads and fender loads. This will allow optimisation of mooring sequences, mooring line selection, fenders sizing and sea fastening analysis.

Compliance with classification codes
Installation and operation analysis will comply with a classification code that suits the client needs. DNV, AS, API codes are among the most frequently used

Frequency domain studies

Frequency response analysis
Using the diffraction package WAMIT the frequency response characteristics of an offshore structure can be analysed. This allows Emerald Energy to determine the mean, significant and maximum response of a vessel or wave energy converter.
In combination with measured or theoretical wave spectra, the linear motion and loading response of a floating or submerged structure can be determined.

Significant and maximum response in given sea states
Based on a vessels response characteristics statistical analysis can be applied to determine the significant and maximum motions and loads in a given sea state.

Time domain studies

Vessel and WEC behaviour in regular and irregular waves
Accurate time domain calculations can be developed to mimic real time motions and loads of vessel, wave energy converters and tidal turbines in regular and irregular waves.
Emerald Energy has experience with developing numerical models from scratch and based on first principles. Model detail will suit the client’s need and can be expanded where necessary. Hydrodynamic time domain models include the potential of solving non-linear dynamics creating the capability to perform non-linear structural, mooring or riser analysis
Time domain data can be analysed statistically to find extreme loading or fatigue properties, where results can serve as input for subsequent structural analysis.

Frequency domain comparison
Time domain results can be compared to results from frequency domain analysis. This will allow the linearity of the system to be assessed and reveal non-linear behaviour of any vessel or wave energy converter.

Measurement data comparison and validation
Live (test) data can be compared to time domain models. Emerald Energy has experience with live in-water tests of wave energy converters and tidal turbines. By analysing test data using in house developed graphical interfaces, computer models can be tuned and augmented where necessary. This results in increased model accuracy for improved vessel, wave energy converter and tidal turbine behavioural analysis.

Wave tank testing
Wave tank tests provide realistic insight in the performance and behaviour of a vessel, floating offshore structure or wave energy converter. At Emerald Energy we are experienced in developing test plans, scaling studies, sourcing test facilities, supervising tests and analysing results. Test reports are written to suit the client’s needs.

Environmental

Interpreting wind, wave and current data
For any offshore operation, knowledge of the environment is essential. At Emerald Energy we have in depth knowledge on wave, wind and current behavioural analysis. Using wave buoy’s, ADCP’s and anemometers live environmental data can be obtained and combined with theoretical models. Results are summarized using scatter plots, spectral plots, current profiles, etc. In additional studies the impact of the environment conditions on any offshore floating or submerged structure can be analysed.

Wind, wave current heading sensitivity
The behaviour of offshore floating structures depends on the heading of the wind, wave and current with respect to the structure. Emerald Energy has experience in heading sensitivity analysis in order to optimize workability, increase installation weather windows and reduce floating structure motion and loads.

Virtual prototyping

Modelling complete dynamic systems
Wave energy converts, tidal turbines and other offshore floating structures are all dynamic systems influenced and excited by the environment. Using Matlab and or Matlab/Simulink combined with WAMIT, Emerald Energy is capable of writing custom made virtual prototypes of dynamic systems to suit the client’s needs.
Virtual prototypes can be used to quickly analyse different concepts of wave energy converters and tidal turbines, to analyse the response of moored vessel or chart the dynamic behaviour of vessel-vessel interactions. 3D irregular wave field can be implemented to achieve realistic results.
A virtual prototype gives the possibility to design for reduced loading and limited, reduce unwanted system vibrations and oscillations and perform fundamental frequency analysis.
Written in Matlab, hence there are no model limitations. Any component can be modelled into the system to assess their advantage and influence on the behaviour and performance. This results in durable construction whilst keep the cost low.

GUI development
To represent measured and modelled results Emerald Energy is capable of writing dedicated graphical user interfaces (GUI’s). Written in Matlab any GUI is custom made to suit the client’s needs
GUI’s can be developed to automate processes and quickly analyse different concepts of a custom made dynamic system. Interactive visualisation of graphs, data and measurements can be implemented to obtain a readily overview of results.

Visualisation
Emerald Energy has experience in visualizing the behaviour of vessels, wave energy converters and floating or submerged structure. Based on the results from a virtual prototype, full dynamic motions in regular and irregular 3D wave fields can be animated.

Animations
Based on the results from virtual prototypes and its visualizations, Emerald Energy is capable of creating animations showing wave energy converters, tidal turbines and offshore floating structure in regular and irregular waves. Animations can be developed into movie format, such as *.avi and *.mpeg and used for technical and commercial purposes.

Software

WAMIT
WAMIT is the most advanced package to analyse the wave interactions with offshore floating structures, wave energy converters and tidal turbines. The panel based 3D diffraction program is able to analyse the first order motions and loads combined with the mean drift forces. In addition, complete second-order nonlinear quantities can be determined.

MATLAB
Matlab is a numerical computing environment and fourth-generation programming language. MATLAB allows matrix manipulations, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs written in other languages, including C, C++, Java, and Fortran.
Matlab is used to develop time and frequency domain models used for offshore dynamic analysis. Tailor made GUI’s and visualisations are developed to assist analysis and understand dynamic behaviour.