Interactions of flow, tidal stream turbines and local sediment bed under combined waves and tidal conditions (INSTRON)
Lead Research Organisation:
University of Dundee
Department Name: Civil Engineering
Abstract
The increased political recognition in recent years of the economic and societal benefits of renewable energy systems has led to an increased pace of technological advances in such systems and an increased urgency to deploy renewable energy devices on land and in coastal waters. At the same time, there has been a realisation that, in order to exploit fully the opportunities for renewable power generation, it is necessary to be aware of (and to adjust to) a wide range of environmental disturbances in the vicinity of the power generation installations themselves. The present project examines this potential conflict for the case of a tidal stream turbine (TST) - a device installed in tidal waters to generate power by the rotation of a set of rotor blades driven by the tidal current. It is known that flow passing TST support structure combined with the rotation of the turbine rotors produces a turbulent downstream wake that can be sufficiently energetic to disturb the stability of the sediments on the sea bed on which the turbine is constructed and affect the sediment suspension. This may have significant impact on the sea floor topography and adverse consequences for the indigenous marine flora and fauna displaced by the geomorphologiocal changes and changes of suspended sediment in water. As a result, large-scale implementation of TST devices is often viewed with serious concern by environmental and ecological agencies, the fisheries authorities and local communities dependent economically on the affected zones.
Thus far, little is known about the nature of the pressure distributions within the turbulent wakes of the rotors and the mechanisms by which these wake flows perturb the sediments in water and on the seabed. For cases in which several tidal stream turbines are constructed in an array, the configuration of the sea bed sediments is subjected to complex pressure distributions arising from from each of the constituent installations and the prediction of sea floor sediment response is even more uncertain. Because of these knowledge gaps in predicting the sea bed response, developers of TST projects have presently to carry out costly environmental monitoring programs in order to obtain environmental permission for installation of devices.
The marine environment, especially in those areas that are subject to strong tidal currents, is usually subject to complex sediment transport dynamics. The main aim of the proposed research is, therefore, to develop advanced computational tools to overcome the above knowledge gaps, in order to predict the consequences of complex interactions between tidal flow, tidal stream turbines and the sea floor sediment bed under combined waves and tidal conditions. The research will build upon results from previous research programmes such as Supergen I and II.
To tackle the above uncertainties, computational and laboratory modelling studies will be carried out (i) to investigate the fundamental processes controlling the complex flow-TST-sediment interactions and (ii) to improve practical prediction methods that can be used not only by engineers in full-scale TST planning and design but also by regulatory authorities monitoring environmental and ecological consequences of installing TST arrays. The research will take a systematic, multidisciplinary, evidence-based approach involving analysis, physical model experiments and numerical modelling components to address and delineate the key processes affecting the sea bed response to TST placements in coastal waters
Thus far, little is known about the nature of the pressure distributions within the turbulent wakes of the rotors and the mechanisms by which these wake flows perturb the sediments in water and on the seabed. For cases in which several tidal stream turbines are constructed in an array, the configuration of the sea bed sediments is subjected to complex pressure distributions arising from from each of the constituent installations and the prediction of sea floor sediment response is even more uncertain. Because of these knowledge gaps in predicting the sea bed response, developers of TST projects have presently to carry out costly environmental monitoring programs in order to obtain environmental permission for installation of devices.
The marine environment, especially in those areas that are subject to strong tidal currents, is usually subject to complex sediment transport dynamics. The main aim of the proposed research is, therefore, to develop advanced computational tools to overcome the above knowledge gaps, in order to predict the consequences of complex interactions between tidal flow, tidal stream turbines and the sea floor sediment bed under combined waves and tidal conditions. The research will build upon results from previous research programmes such as Supergen I and II.
To tackle the above uncertainties, computational and laboratory modelling studies will be carried out (i) to investigate the fundamental processes controlling the complex flow-TST-sediment interactions and (ii) to improve practical prediction methods that can be used not only by engineers in full-scale TST planning and design but also by regulatory authorities monitoring environmental and ecological consequences of installing TST arrays. The research will take a systematic, multidisciplinary, evidence-based approach involving analysis, physical model experiments and numerical modelling components to address and delineate the key processes affecting the sea bed response to TST placements in coastal waters
Planned Impact
The non-academic beneficiaries of the research will be drawn from (i) the private commercial sector (principally civil engineering consulting companies), (ii) national (and eventually international) policy makers concerned with low carbon (i.e renewable) energy production, (iii) environmental monitoring agencies, (iv) nature protection agencies and (iv) local communities, conservation groups/societies and local businesses (fishing, tourism etc) affected by new coastal developments of tidal stream turbines.
The prediction of the consequences of installing arrays of tidal stream turbines is of relevance to all of the above groups, not least because one of the most threatening consequences of such developments, namely the disturbance produced to the sea bed on which the turbines are constructed, has wide commercial, environmental and societal repercussions. The private sector has a direct commercial interest in being supplied with predictions on the stability and erodibility of the sea bed sediments around the construction. This affects primarily civil engineering consultancies concerned with (i) the design, stability and integrity of the structures and (ii) the prediction of the resulting sediment erosion and deposition patterns that can affect navigability, trapping of contaminants from anthropogenic discharges into coastal waters and sea bed infrastructure (pipes, cables) close to shore. The other commercial sector affected by uncertainties in knowledge of the effects of TST installations and the risk to the stability of such structures on an erodible sea bed (e.g scour and downstream erosion) is the insurance industry charged with substantial investment in such structures and a need for awareness of the risks of structural and environmental costs of inadequate predictions of TST installation consequences.
The environmental consequences of the TST installations generating significant sediment transport and geomorphological changes to the original site are potentially very serious; the disturbances to the local ecology and the potentially-disruptive redistribution of indigenous benthic species can affect in a complex way the survival of communities of sea bed plants and animals (and the birds and higher forms of marine life that predate these species). It is with the research- and evidence-based studies typified by this proposed project that the environmental constituency derives benefits, initially via the environmental regulatory and monitoring agencies charged with understanding and incorporating into regulation new research on this relatively-unknown set of problems and then via local and national opinion formers and vested interests (politicians, marine protection groups and special interest lobbies such as those depending upon shellfish and fin fish harvesting). The impact of the research is far reaching, even on a local scale; the wider consequences of deleterious effects of TST construction are of international significance with so many tidal stream devices being developed and deployed overseas. The benefits of evidence-based, additional predictive tools to UK civil engineering consultancies (and insurance companies) who operate globally in this specialised area are clear.
The prediction of the consequences of installing arrays of tidal stream turbines is of relevance to all of the above groups, not least because one of the most threatening consequences of such developments, namely the disturbance produced to the sea bed on which the turbines are constructed, has wide commercial, environmental and societal repercussions. The private sector has a direct commercial interest in being supplied with predictions on the stability and erodibility of the sea bed sediments around the construction. This affects primarily civil engineering consultancies concerned with (i) the design, stability and integrity of the structures and (ii) the prediction of the resulting sediment erosion and deposition patterns that can affect navigability, trapping of contaminants from anthropogenic discharges into coastal waters and sea bed infrastructure (pipes, cables) close to shore. The other commercial sector affected by uncertainties in knowledge of the effects of TST installations and the risk to the stability of such structures on an erodible sea bed (e.g scour and downstream erosion) is the insurance industry charged with substantial investment in such structures and a need for awareness of the risks of structural and environmental costs of inadequate predictions of TST installation consequences.
The environmental consequences of the TST installations generating significant sediment transport and geomorphological changes to the original site are potentially very serious; the disturbances to the local ecology and the potentially-disruptive redistribution of indigenous benthic species can affect in a complex way the survival of communities of sea bed plants and animals (and the birds and higher forms of marine life that predate these species). It is with the research- and evidence-based studies typified by this proposed project that the environmental constituency derives benefits, initially via the environmental regulatory and monitoring agencies charged with understanding and incorporating into regulation new research on this relatively-unknown set of problems and then via local and national opinion formers and vested interests (politicians, marine protection groups and special interest lobbies such as those depending upon shellfish and fin fish harvesting). The impact of the research is far reaching, even on a local scale; the wider consequences of deleterious effects of TST construction are of international significance with so many tidal stream devices being developed and deployed overseas. The benefits of evidence-based, additional predictive tools to UK civil engineering consultancies (and insurance companies) who operate globally in this specialised area are clear.
Publications
Ahmadi M
(2019)
Influence of upstream turbulence on the wake characteristics of a tidal stream turbine
in Renewable Energy
Ahmadi M
(2020)
The evolution of turbulence characteristics in the wake of a horizontal axis tidal stream turbine
in Renewable Energy
Baba-Ahmadi M
(2017)
Validation of the actuator line method for simulating flow through a horizontal axis tidal stream turbine by comparison with measurements
in Renewable Energy
Baba-Ahmadi M
(2017)
Numerical simulations of wake characteristics of a horizontal axis tidal stream turbine using actuator line model
in Renewable Energy
Gui Q
(2014)
Numerical study of PPE source term errors in the incompressible SPH models
in International Journal for Numerical Methods in Fluids
Gui Q
(2014)
Wave Impact Simulations by an Improved ISPH Model
in Journal of Waterway, Port, Coastal, and Ocean Engineering
Li X
(2017)
Modelling tidal stream turbines in a three-dimensional wave-current fully coupled oceanographic model
in Renewable Energy
Li X
(2019)
Modelling impacts of tidal stream turbines on surface waves
in Renewable Energy
Li X
(2014)
3D NUMERICAL MODELLING OF LARGE SCALE IMPACTS OF TIDAL TURBINE ARRAYS USING AN OCEANOGRAPHIC MODEL
in Coastal Engineering Proceedings
Li X
(2020)
Three-dimensional modelling of suspended sediment transport in the far wake of tidal stream turbines
in Renewable Energy
Ramírez-Mendoza R
(2020)
Asymmetric effects of a modelled tidal turbine on the flow and seabed
in Renewable Energy
Ramírez-Mendoza R
(2018)
Laboratory study on the effects of hydro kinetic turbines on hydrodynamics and sediment dynamics
in Renewable Energy
Ren B
(2015)
Nonlinear simulations of wave-induced motions of a freely floating body using WCSPH method
in Applied Ocean Research
Ren B
(2016)
Improved SPH simulation of wave motions and turbulent flows through porous media
in Coastal Engineering
Sufian S
(2014)
3D-CFD NUMERICAL MODELING OF IMPACTS FROM HORIZONTAL AXIS TIDAL TURBINES IN THE NEAR REGION
in Coastal Engineering Proceedings
Sufian S
(2017)
3D modelling of impacts from waves on tidal turbine wake characteristics and energy output
in Renewable Energy
Description | The tidal turbine has significant influence on near-field flow and adequate prediction can only be achieved using the combination of LES and ALM models. Sediment motions in the turbine wake area are complicated and the current formula for sediment initiation and transport are inadequate in capturing the effects of large turbulent eddies on sediments. |
Exploitation Route | Working closely with tidal turbine developers. |
Sectors | Aerospace Defence and Marine Environment |
Description | The numerical results have provided the theoretical basis for achieving more accurate prediction of turbine wake and for designing cost effective turbine groups. |
First Year Of Impact | 2017 |
Sector | Energy,Environment |
Impact Types | Economic |
Description | H R Wallingford Ltd |
Organisation | HR Wallingford Ltd |
Country | United Kingdom |
Sector | Private |
PI Contribution | Report research outcome and plans. |
Collaborator Contribution | Participate in project meetings and provide advise on research directions. |
Impact | None |
Start Year | 2006 |
Description | Halcrow Group |
Organisation | Halcrow Group |
Country | United Kingdom |
Sector | Private |
PI Contribution | inform the new analysis methods developed. |
Collaborator Contribution | Comment on the research and outcomes |
Impact | None |
Start Year | 2006 |
Description | New Forest District Council |
Organisation | New Forest District Council |
Country | United Kingdom |
Sector | Public |
PI Contribution | Inform the research results including new methods developed. |
Collaborator Contribution | Provide data for model validation and participate in project meetings |
Impact | None |
Start Year | 2006 |