Hydrodynamic modelling for structural analysis of tidal stream turbine blades

The predictable nature of the tides offers a regular, reliable source of renewable energy that can be harnessed using tidal stream turbines (TSTs). The UK's practically extractable tidal stream energy resource has the potential to supply around 7% of the country's annual electricity demand. As of 2016, the world's first commercial scale arrays have been deployed around the UK and France. The harsh nature of the marine operating environment poses a number of engineering challenges, where the optimal turbine design solution remains under investigation. In this thesis, a numerical model is developed to assess the power production and hydrodynamic behaviour of horizontal axis tidal turbines. The developed model builds upon well established and computationally efficient Blade Element Momentum Theory (BEMT) method for modern three-bladed wind turbines. The main novel contribution of this thesis is extending the application to an alternative design of a ducted, high solidity and open centre TST. A validation study using measurements from multiple different scale model experimental tank tests has proven the applicability of the model and suitability of the imposed correction factors. The analytical modifications to account for ducted flow were subsequently indirectly verified, where predictions of turbine power and axial thrust forces under optimal operating speeds were within 2% of those using more advanced computational fluid dynamics (CFD) methods. This thesis presents a commercial application case of two turbines designed by OpenHydro, examining the BEMT performance with a sophisticated blade resolved CFD study. A comparison of results finds that the model is capable of predicting the average peak power to within 12%, however it under predicts thrust levels by an average of 35%. This study concludes that the model is applicable to ducted turbine configurations, but is limited in capturing the complex flow interactions towards the open centre, which requires further investigation. The computational effciency of the newly developed model allowed a structural analysis of the composite blades, thus demonstrating it is suitable to effectively evaluate engineering applications. Stresses are seen to be dominated by flap-wise bending moments, which peak at the mid-length of the blade. This tool will further enable EDF to perform third party assessments of the different turbine designs, to aid decision making for future projects

Blade-explicit fluid structure interaction of a ducted high-solidity tidal turbine

This work elaborates a computational fluid dynamic (CFD) model utilised in the investigation of the structural performance concerning a ducted high-solidity tidal turbine in aligned and yawed inlet flows. Analysing the hydrodynamic performance at aligned flows portrayed the distinctive power curve at which energy is transferred via the fluid-structure interaction. At distinct bearing angles with the axis of the turbine, variations in the blade-interaction due to the presence of the duct was acknowledged within a limited angular range at distinct tip-speed ratio values. As a result of the hydrodynamic analysis, a structural investigation of the blades was discretely evaluated in an effort to acknowledge fluid-structure phenomena

A validated BEM model to analyse hydrodynamic loading on tidal stream turbines blades

This is the author accepted manuscript. The final version is available from the link in this record.AWTEC 2016: 3rd Asian Wave and Tidal Energy Conference, 24-28 October 2016, SingaporeThis paper details a Blade Element Momentum (BEM) model for a 3 bladed, horizontal axis Tidal Stream Turbine (TST). The code capabilities are tested and validated by applying a range of different turbine parameters and operating conditions, where results are compared to numerous datasets. The model shows excellent agreement to performance and thrust measurements for 3 of the 4 datasets. Compared to other BEM models improved correlations are seen at higher rotational speeds. The fourth case shows over predictions of up to 30% in power at peak operating speed. In this case, CFD studies show better correlation due to the ability to capture detailed flow features around the blade as well as free surface effects, however require 3 to 4 orders of magnitude greater computational cost. Steady, non-uniform inflow functionality is incorporated into the model, where distributions of thrust and torque along the blade as well as cyclic loads are determined. These show the potential of the model to be used in combination with tools such as stress and fatigue analyses to improve the blade design process.This research is carried out as part of the Industrial Doctoral Centre for Offshore Renewable Energy (IDCORE) programme, funded by the Energy Technology partnership and the RCUK Energy programme (Grant number EP/J500847/1), in collaboration with EDF R&D

Investigation of Alcohol-Related Social Norms Among Youth Aged 14-17 Years in Perth, Western Australia: Protocol for a Respondent-Driven Sampling Study

Introduction: Alcohol use among young people is a major public health concern in Australia and internationally. Research elucidating social norms influencing alcohol use supports the desire to conform to peers. However, there is a lack of evidence on how social norms are transmitted from the community to young people and between family members and peers, as previous studies are limited to mainly school and university environments. This article describes the proposed process to investigate common alcohol-related norms held by 14-year-olds to 17-year-olds in Perth, Western Australia, and to clarify the process and pathways through which proalcohol norms are transmitted to adolescents.Methods and analysis: This cross-sectional quantitative study will use respondent-driven sampling (RDS) to recruit a sample of 672 adolescents from sporting groups, youth programmes and the community in Perth. Data will be collected with a previously developed and validated multidimensional online survey instrument. A variety of strategies will be explored to aid participation including face-to-face recruitment and survey administration, web-based RDS and a ‘mature minor’ consent assessment protocol. Data analysis will include descriptive statistics of demographic characteristics, as well as social network and dyadic analyses, to explore the connections between shared understanding of norms and behaviours among individuals and how these translate into reported practices.Ethics and dissemination: This research is expected to extend our understanding of normative development pathways to inform future interventions, and will be widely disseminated through conference presentations, peer-reviewed papers, media channels and community seminars. A study reference group of key health industry stakeholders will be established to encourage integration of study findings into policy and practice, and results will guide the development of community interventions. The Curtin University Human Research Ethics Committee has granted approval for this research

Analysing fibre composite designs for high-solidity ducted tidal turbine blades

This study elaborates a one-way fluid-structure interaction numerical model utilised in investigating the structural mechanics concerning the rotor blades comprising a ducted high-solidity tidal turbine. Coupling hydrodynamic outcomes as structural inputs in effort of acknowledging the most applicable setup, distinct designs are investigated, solid blades and cored blades, implementing fibre-reinforced composite materials, analysed within criteria related to blade axial deformation, induced radial strains, and rotor specific mass

A Validated BEM Model to Analyse Hydrodynamic Loading on Tidal Stream Turbine Blades

This paper details a Blade Element Momentum (BEM) model for a 3 bladed, horizontal axis Tidal Stream Turbine (TST). The code capabilities are rigorously tested by applying a range of different turbine parameters and operating conditions, where results are compared to numerous validation datasets. The model shows excellent agreement to performance and thrust measurements from 3 of the 4 datasets, where improved correlations are seen at high rotational speeds to other BEM models. The exception case shows over predictions of up to 30% in power at peak operating speed. In this case, CFD studies show better correlation due to the ability to capture detailed flow features around the blade as well as free surface effects, however require 3 to 4 orders of magnitude greater computational cost. Steady, non-uniform inflow functionality is incorporated into the model, where distributions of thrust and torque along the blade as well as cyclic loads are determined. These show the potential of the model to be used in combination with tools such as stress and fatigue analyses to improve the blade design process. This paper details the validation of an efficient BEM model through experimental results and additional CFD analysis, as well as demonstrating its application for detailed analysis of hydrodynamic loading to be used in blade designs. Keywords— Tidal Stream Turbine (TST), Blade Element Momentum (BEM), performance modelling, non-uniform inflow, blade cyclic loading, hydrodynamic loadin

A numerical performance analysis of a ducted high-solidity tidal turbine

This study puts forward an investigation into the hydrodynamic performance concerning a ducted, high-solidity tidal turbine utilising blade-resolved computational fluid dynamics. The model achieves similarity values of over 0.96 with experimentation data regarding a three-bladed horizontal-axis tidal turbine in validation of three distinct parameters: power & torque coefficient, thrust coefficient, and wake velocity profiles. Accordingly, the model was employed for the analysis of a ducted, high-solidity turbine in axially-aligned flows at distinct free-stream velocities. The resultant hydrodynamic performance characteristics portrayed a peak power coefficient of 0.34, with a thrust coefficient of 0.97, at a nominal tip-speed ratio of 1.75. Coefficient trend agreement was attained between the numerical model and experimentation data established in literature and blade-element momentum theory; the model furthers the analysis by elaborating the temporal hydrodynamic features induced by the fluid-structure interaction in specification to the wake formation velocity profiles, pressure distribution along the blades and duct, mass flow rate, and vortex shedding effects to establish the characteristic flow physics of the tidal turbine

A numerical structural analysis of ducted, high-solidity, fibre-composite tidal turbine rotor configurations in real flow conditions

Establishing a design and material evaluation of unique tidal turbine rotors in true hydrodynamic conditions by means of a numerical structural analysis has presented inadequacies in implementing spatial and temporal loading along the blade surfaces. This study puts forward a structural performance investigation of true-scale, ducted, high-solidity, fibre-composite tidal turbine rotor configurations in aligned and yawed flows by utilising outputs from unsteady blade-resolved computational fluid dynamic models as boundary condition loads within a finite-element numerical model. In implementation of the partitioned-approach fluid–structure interaction procedure, three distinct internal blade designs were analysed. Investigating criteria related to structural deformation and induced strains, hydrostatic & hydrodynamic analyses are put forward in representation of the rotor within the flow conditions at the installation depth. The resultant axial deflections for the proposed designs describe a maximum deflection-to-bladespan ratio of 0.04, inducing a maximum strain of 0.9%. A fatigue response analysis is undertaken to acknowledge the blade material properties required to prevent temporal failure

Hydrodynamic analysis of a ducted, open centre tidal stream turbine using blade element momentum theory

This paper analyses two different configurations of horizontal axis Tidal Stream Turbines (TST) using a Blade Element Momentum Theory (BEMT) model. Initially, a 'conventional' 3 bladed and bare turbine is assessed, comparing predictions of turbine power and thrust forces against experimental measurements and existing literature. Excellent agreement is seen, increasing confidence in both the implementation of the theory into the code and the applicability of the method to represent the turbine physical behaviour. The focus of the paper lies on the analysis of a ducted and open centre turbine, where the BEMT model is adapted to take into account the increased mass flow through a duct (or augmenter). This is based on an analytical framework, where empirical expressions are devised based on Computational Fluid Dynamics (CFD) studies to approximate the inlet efficiency, diffuser efficiency and base pressure. This is applied to a bi-directional ducted case, where calibration of certain duct parameters is performed through modelling the OpenHydro device and comparing results with blade resolved CFD studies. The results are validated with a comparison of this ducted BEMT model to a coupled CFD blade element model (RANS BEM). Both models align very closely for most Tip Speed Ratios, capturing the peak power at optimal conditions. Slight over predictions for thrust and power are seen at higher TSRs, where higher velocities are seen at localised elements around the hub. This is due to the model limitations in fully replicating the complex flow interactions in and around the hub and open centre. The presented approach has the benefit of significantly lower computational requirements, in the order of CPU-minutes, rather than CPU-days required for RANS BEM, allowing practicable engineering assessments of turbine performance and reliability

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification