Fig 4 - uploaded by James Donegan
Content may be subject to copyright.
Torque convergence of a cross-flow turbine at a tip-speed ratio of 2.50. The top and bottom plots show the same curve with different scaling in the y-axis for legibility.
Source publication
Cross-flow turbine technology is an interesting alternative to the more common horizontal axis turbine design for tidal or river flow environments. One important feature of marine hydrokinetic turbines operating in shallow water is the interaction with the free surface. Blockage can increase power output dramatically and must be accounted for accur...
Similar publications
This study aimed to analyze and examine the precision of a middle-fidelity simulation tool by performing load analysis using CFD and middle-fidelity analysis tools. The analysis was performed on a fully coupled system including turbine, platform, and mooring system under the severe operating state. Grid sensitivity tests were performed on the turbi...
Citations
... With the OpenFOAM CFD solver, Feinberg et al., (2019) study the crossflow on a VATT and the free surface effects which are generated. Lift, drag and power coefficients are computed for different water depth and two different boundary conditions on the upper surface, no slip condition or free surface. ...
Committee Mandate
Concern for load analysis and structural design of offshore renewable energy devices. Attention shall be given to the interaction between the load and structural response of fixed and floating installations taking due consideration of the stochastic and extreme nature of the ocean environment. Aspects related to design, prototype testing, certification, marine operations, levelized cost of energy and life cycle management shall be considered.
Introduction
This is the sixth time that ISSC has included the Specialist Committee V.4 Offshore Renewable Energy, which started in 2006. Two members of the committee for this term (2018-2022) were involved in the work for the previous term (2016-2018), which formulates a good base for the cooperative work in the last three years.
The mandate of the committee was discussed at the beginning of the work, and it was slightly modified to include extreme environmental conditions and interaction of structures to the seabed, reliability-based design, safety and integrated design, topics which have been central to the discussion for developing offshore renewable energy, and hence should be discussed in the committee report. Another variation of this committee’s report has been the consideration of floating wind developments in a separate chapter as deployments are currently moving further offshore and in deeper waters, as well as the explicit reference to hybrid solutions.
Offshore wind energy still dominates offshore renewable energy technologies with extensive installed capacity and ambitious targets which constitute this technology as a key contributor towards the ambitious 2050 net zero emissions targets. For these targets to be achieved, it is imperative to innovate and further develop not only wind energy but also other offshore, marine and hybrid energy technologies, harvesting as much as possible the energy potential. Challenges related to wind energy include, among others, the upscaling at both a unit as well as a farm level, development of foundations relevant to deep waters, serial production of floating foundations and effective mooring systems, and investigation of support systems to inform end-of-life scenarios including service life extension, repowering or decommissioning. Marine renewables on the other hand, still need to overcome challenges related to structural response in extreme phenomena and reliability of mechanical components which sharply escalate the levelized cost of energy.
Within this report we have considered peer reviewed academic articles, selected conference proceedings and some reference industry reports. Overall, more than 500 sources have been reviewed and 350 have eventually qualified to be included in this state-of-the-art review. The time span of the review includes contributions from August 2017 to August 2021. The term of this committee has been extended due to the COVID-19 pandemic.
The report has been organized into 9 subsections. Following this short introduction, a session on bottom fixed wind turbines is included, following the structure of the previous committee’s report, with the addition of design provisions for extreme phenomena which are particularly relevant in South-East Asia and a subsection on advanced structural analysis. Next, a dedicated section on floating wind turbines is included, following a similar structure, with the addition of moorings and dynamic cables which is relevant to this class of foundations. Next three subsections present developments on wave energy converters, tidal and ocean current turbines, and other offshore renewable energy technologies and hybrid solutions. Following this, a subsection on life-cycle cost and operational management of offshore renewable energy is presented, identifying key cost elements that attract attention for research and development. Section 8 summarizes the efforts of the committee members to investigate a benchmarking study on the comparison of the existing design guidelines with respect to design of mooring systems. Finally, the last section of the report lists some conclusions which stem out of the review and key challenges that research should try to address in the next few years.
... The requirement of a much lower Co number seems to negate expected efficiency gains. However, in many applications the time step is not limited by wave propagation but motion solvers (Feinberg 2019;Schmitt and Elsäer 2015). ...
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 the entire set of possible hydrodynamic phenomena are not of interest and the reduced complexity could allow the use of simpler, more computationally efficient solvers. One barrier for the application of such alternative solvers is the lack of suitable wavemaking and absorption capabilities, which this paper aims to address. A wavemaking and absorption methodology is presented, which can be applied to different solvers using the same fundamental concept. The implementation is presented for interFoam and interIsoFoam, as well as two other solvers whose use as numerical wave tanks has not previously been reported in the literature, shallowWaterFoam and potentialFreeSurfaceFoam. Parameter studies are performed to guide the user in the use of the methods. Example applications for two industrially relevant test cases are demonstrated; a multi-frequency wave packet focused at one position over flat bottom and regular waves propagating over a submerged shoal. All solvers yielded useful results, but some complex wave transformations in the shoal case were only resolved by the VoF methods. Alternative methods beyond the already well established VoF methods seem worth considering because potential for significant reductions in computational effort exist.
