Effects of Trailing Edge Alterations on the Performance of a Small-Scale, Low-Solidity Tidal Turbine Blade Designed for Less Energetic Flows

2019 ◽  
Author(s):  
Job Immanuel Encarnacion ◽  
Gavin Lavery ◽  
Stephanie Ordoñez-Sanchez ◽  
Cameron Johnstone
Keyword(s):  
Turbine Rotor ◽  
Small Scale ◽  
Minimum Thickness ◽  
Ansys Fluent ◽  
The Best Approximation ◽  
Simulated Performance ◽  
Physical Testing ◽  
Tidal Turbine ◽  
Lift And Drag ◽  
The Ideal

Abstract Computer simulations aid in the design of any device. However, physical testing is still needed to validate these simulations and problems may arise if fabrication limits are not incorporated. This study was undertaken to quantify the losses in a low-solidity turbine rotor designed for less energetic flow. The blade was tested at a scale of 1m resulting in a blade length of 219mm. A 0.5mm minimum thickness fabrication limit was worked with by shifting all the points of the upper surface of the blade sections by 0.5mm at the 219mm scale introducing a huge distortion in each of the blade sections. Lift and drag characteristics of the distorted aerofoil are obtained via ANSYS Fluent and served as the corrected inputs for the BEM characterisation. It was found that the BEM predicts a reduced performance similar to the physical testing although it still over predicts the performance of the turbine. However, there is an agreement on the trend of the simulated performance and the physical testing in addition to the reduction of the variation between the two. Additional aerofoil alterations are studied to inform on future experimental designs. It was then found that out of the altered cases, shifting the upper surface by the required minimum thickness resulted in the best approximation of the simulated performance. This is far from acceptable as the variation between the ideal computer simulated case is too large to just incorporate corrections. Thus, an analysis is carried out using a 400mm scaled blade, thereby decreasing the distortion on each blade section. The results of the analysis show good agreement with the ideal section and minimal reduction in performance at about 5% less than the ideal.

scholarly journals A Hybrid BEM-CFD Virtual Blade Model to Predict Interactions between Tidal Stream Turbines under Wave Conditions

2020 ◽  
Vol 8 (12) ◽  
pp. 969
Author(s):  
Nicolo’ Lombardi ◽  
Stephanie Ordonez-Sanchez ◽  
Stefania Zanforlin ◽  
Cameron Johnstone
Keyword(s):  
Numerical Study ◽  
Experimental Tests ◽  
Full Scale ◽  
Small Scale ◽  
Ansys Fluent ◽  
Narrow Channels ◽  
Tidal Turbine ◽  
Performance Deterioration ◽  
Set Up ◽  
Blade Model

Tidal turbine array optimization is crucial for the further development of the marine sector. It has already been observed that tidal turbines within an array can be heavily affected by excessive aerodynamic interference, thus leading to performance deterioration. Small-scale experimental tests aimed at understanding the physical mechanisms of interaction and identifying optimal distances between machines can be found in the literature. However, often, the relatively narrow channels of laboratories imply high blockage ratios, which could affect the results, making them unreliable if extrapolated to full-scale cases. The main aim of this numerical study was to analyze the effects of the blockage caused by the laboratory channel walls in cases of current and also current surface waves. For this purpose, the performance predictions achieved for two turbines arranged in line for different lateral offsets in case of a typical laboratory scale were compared to the predictions obtained for a full scale, unconfined environment. The methodology consisted in the adoption a hybrid Blade Element Momentum–Computational Fluid Dynamics (BEM-CFD) approach, which was based on the Virtual Blade Model of ANSYS-Fluent. The results indicate that (1) the performance of a downstream turbine can increase up to 5% when this has a lateral separation of 1.5D from an upstream device in a full-scale environment compared to a misleading 15% calculated for the laboratory set-up, and (2) the relative fluctuations of power and thrust generated by waves are not significantly affected by the domain dimensions.

Rapid distortion of turbulence into an open turbine rotor

2017 ◽  
Vol 825 ◽  
pp. 764-794 ◽  
Author(s):  
J. M. R. Graham
Keyword(s):  
Isotropic Turbulence ◽  
Strain Analysis ◽  
Turbine Rotor ◽  
Small Scale ◽  
Mean Flow ◽  
Mean Velocity ◽  
Actuator Disc ◽  
Tidal Turbine ◽  
Tidal Stream ◽  
The Mean

Rapid distortion of turbulence (RDT) theory is applied to homogeneous, isotropic turbulence incident on a horizontal axis turbine rotor such as a wind turbine or tidal-stream turbine. The mean flow field of the rotor which distorts the turbulence is represented by the commonly used axisymmetric actuator disc model due to Betz and Joukowski. The fluctuating streamwise component of the turbulence distorted by this field is calculated at the actuator disc plane. Turbulence velocity intensities and spectra are evaluated for general ratios of turbulence integral length scale to the rotor diameter, including the small-scale limit for which the original homogeneous strain analysis of Batchelor and Proudman may be applied. The distortion of the mean velocity profile of an incident rotor wake which may be considered a zero frequency disturbance relevant to wind and tidal turbine operation in large arrays is also analysed by the same method, treating it as a deterministic disturbance in the incident flow.

Turbulence velocity spectra and intensities in the inflow of a turbine rotor

2019 ◽  
Vol 870 ◽  
Author(s):  
I. A. Milne ◽  
J. M. R. Graham
Keyword(s):  
Flow Field ◽  
Direct Interaction ◽  
Turbine Rotor ◽  
Small Scale ◽  
Length Scale ◽  
Velocity Measurements ◽  
Tidal Turbine ◽  
Turbulence Velocity ◽  
Scale Turbulence ◽  
Velocity Spectra

The changes in spectra and intensities of the streamwise component of turbulent velocity are calculated in the inflow of a turbine rotor. The flow is initially calculated in the limit when the turbulence is of small scale compared with the rotor diameter. Rapid distortion theory (RDT), Batchelor & Proudman (Q. J. Mech. Appl. Maths, vol. 7 (1), 1954, pp. 83–103) (BP), for small-scale turbulence is combined with the effect of the fluctuating potential flow field on the turbulence caused by the direct interaction of the incident turbulence with the rotor as a sheet of resistance. A second computation is then carried out for turbulence of larger length scale. The results of the calculations are compared with velocity measurements in the inflow of both a commercial wind turbine and a tidal turbine rotor.

DEVELOPMENT OF MATHEMATICS LEARNING PACKAGE WITH GEOGEBRA-ASSISTED SCIENTIFIC APPROACH FOR THE EIGHT GRADERS

2019 ◽  
Vol 1 (1) ◽  
pp. 79-87
Author(s):  
Sugian Nurwijaya
Keyword(s):  
Learning Outcomes ◽  
Mathematics Learning ◽  
Average Score ◽  
Small Scale ◽  
Student Activity ◽  
Development Procedure ◽  
Scientific Approach ◽  
Distribution Phase ◽  
Implementation Plans ◽  
The Ideal

This is a research and developmentstudy with limited trials which aims to develop the Mathematics Learning Package by using a geogebra-assisted scientific approach in the eight grade of MTs Al-Junaidiyah Biru, Bone Regency. Such learning package includes student books, student activity sheets, learning implementation plans and learning outcomes test. The subjects of this study were twenty two students of class VIIIC MTs Al-Junaidiyah Biru Bone Regency. The development procedure used in this study is the Thiagarajan model or 4D model (Define, Design, Develop, and Disseminate) which includes four phases, namely the limitation, the design, the development, and the small scale distribution phase. Learning packagewith geogebra-assisted scientific approach that had been developed have been validated by experts and have been revised so that results are feasible to use. The results of limited trials show that the learning package produced has been practical and effective. (4) skor rata-rata yang diperoleh siswa pada tes hasil belajar adalah 78,40 dari skor ideal 100 dengan standar deviasi 11,89. Dimana 19 dari 22 siswa atau 86,36% memenuhi ketuntasan individu yang menunjukkan bahwa ketuntasan klasikal tercapai.The results of data analysis are as follows: (1) teacher activities can guide groups to work and learneffectively; (2) students generally give the positive responses to the developed learning package; (3) mathematics learning package with geogebra-assisted scientific approach make students more active in the learning process; (4) the average score obtained by students on the learning outcomes test is 78.40 from the ideal score of 100 with a standard deviation of 11.89. Then, 19 of 22 students or 86.36% fulfilled individual completeness which shows that classical completeness was achieved

Formalization as a tool for environmental peacebuilding? Artisanal and small-scale mining in Liberia and Sierra Leone

2021 ◽  
Vol 97 (1) ◽  
pp. 35-55
Author(s):  
Christina Ankenbrand ◽  
Abrina Welter ◽  
Nina Engwicht
Keyword(s):  
Sierra Leone ◽  
Well Being ◽  
Small Scale ◽  
Transformative Change ◽  
Community Based ◽  
Community Benefits ◽  
Sustainable Peace ◽  
Underlying Causes ◽  
Ethical Sourcing ◽  
The Ideal

Abstract Artisanal and small-scale mining (ASM) has long been a vital source of livelihoods for rural populations in the global South. Yet, it has also been linked to a host of social, political and environmental adversities, including violent conflict. As environmental peacebuilding increasingly stresses the importance of livelihood improvement as a means of fostering peace in conflict-affected extractive societies, ASM formalization has been identified as a solution to mitigate the sector's challenges, thereby addressing underlying causes of conflict. This article critically investigates the contribution of ASM formalization to sustainable peace by focusing on its impact on the livelihood dimension of peacebuilding. It analyses the livelihood impact of three formalization interventions in the diamond sectors of two countries: cooperatives in Liberia, and, in Sierra Leone, ethical sourcing schemes and a community-based natural resource management initiative. In line with calls for a paradigm shift from a narrow legalization-centred understanding of formalization to a broader approach that accounts for livelihood quality, the analysis presented here focuses on interventions that were informed by the ideal of improving the well-being of ASM workers and communities. We propose three pathways through which ASM formalization could potentially contribute to livelihood enhancement: income security, working conditions and community benefits. Based on fieldwork, this article highlights the challenges of generating livelihood improvements through formalization. Even when specifically designed to address the needs of ASM communities, during implementation, they risk prioritizing a narrow conceptualization of formalization and thus failing to become a conductor of transformative change.

Arriving at the Optimum Overlap Ratio for an Elliptical-Bladed Savonius Rotor

2017 ◽  
Author(s):  
Nur Alom ◽  
Ujjwal K. Saha
Keyword(s):  
Numerical Study ◽  
Superior Performance ◽  
Navier Stokes ◽  
Speed Ratio ◽  
Small Scale ◽  
Efficient Manner ◽  
Ansys Fluent ◽  
Savonius Rotor ◽  
Velocity Magnitude ◽  
Overlap Ratio

The Savonius rotor appears to be particularly promising for the small-scale applications because of its design simplicity, good starting ability, and insensitivity to wind directions. There has been a growing interest in recent times to harness wind energy in an efficient manner by developing newer blade profiles of Savonius rotor. The overlap ratio (OR), one of the important geometric parameters, plays a crucial role in the turbine performance. In a recent study, an elliptical blade profile with a sectional cut angle (θ) of 47.5° has demonstrated its superior performance when set at an OR = 0.20. However, this value of OR is ideal for a semicircular profile, and therefore, requires further investigation to arrive at the optimum overlap ratio for the elliptical profile. In view of this, the present study attempts to make a systemic numerical study to arrive at the optimum OR of the elliptical profile having sectional cut angle, θ = 47.5°. The 2D unsteady simulation is carried out around the elliptical profile considering various overlap ratios in the range of 0.0 to 0.30. The continuity, unsteady Reynolds Averaged Navier-Stokes (URANS) equations and two equation eddy viscosity SST (Shear Stress transport) k-ω model are solved by using the commercial finite volume method (FVM) based solver ANSYS Fluent. The torque and power coefficients are calculated as a function of tip speed ratio (TSR) and at rotating conditions. The total pressure, velocity magnitude and turbulence intensity contours are obtained and analyzed to arrive at the intended objective. The numerical simulation demonstrates an improved performance of the elliptical profile at an OR = 0.15.

scholarly journals Estimation of wind turbine blade aerodynamic performances computed using different numerical approaches

2018 ◽  
Vol 45 (1) ◽  
pp. 53-65 ◽  
Author(s):  
Jelena Svorcan ◽  
Ognjen Pekovic ◽  
Toni Ivanov
Keyword(s):  
Wind Turbine ◽  
Thrust Force ◽  
Turbulence Models ◽  
Turbine Rotor ◽  
Momentum Balance ◽  
Horizontal Axis Wind Turbine ◽  
Ansys Fluent ◽  
Force Coefficients ◽  
Aerodynamic Performances ◽  
Numerical Approaches

Although much employed, wind energy systems still present an open, contemporary topic of many research studies. Special attention is given to precise aerodynamic modeling performed in the beginning since overall wind turbine performances directly depend on blade aerodynamic performances. Several models different in complexity and computational requirements are still widely used. Most common numerical approaches include: i) momentum balance models, ii) potential flow methods and iii) full computational fluid dynamics solutions. Short explanations, reviews and comparison of the existing computational concepts are presented in the paper. Simpler models are described and implemented while numerous numerical investigations of isolated horizontal-axis wind turbine rotor consisting of three blades have also been performed in ANSYS FLUENT 16.2. Flow field is modeled by Reynolds Averaged Navier-Stokes (RANS) equations closed by two different turbulence models. Results including global parameters such as thrust and power coefficients as well as local distributions along the blade obtained by different models are compared to available experimental data. Presented results include fluid flow visualizations in the form of velocity contours, sectional pressure distributions and values of power and thrust force coefficients for a range of operational regimes. Although obtained numerical results vary in accuracy, all presented numerical settings seem to slightly under- or over-estimate the global wind turbine parameters (power and thrust force coefficients). Turbulence can greatly affect the wind turbine aerodynamics and should be modeled with care.

Computer Analysis of S822 Aerofoil Section for Blades of Small Wind Turbines at Low Wind Speed

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Prachi R. Prabhukhot ◽  
Aditya R. Prabhukhot
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Maximum Velocity ◽  
Small Scale ◽  
Blade Profile ◽  
Ansys Fluent ◽  
Low Wind Speed ◽  
Upward Direction ◽  
Computational Fluid Dynamics Cfd

The power generated in wind turbine depends on wind speed and parameters of blade geometry like aerofoil shape, blade radius, chord length, pitch angle, solidity, etc. Aerofoil selection is the crucial factor in establishing the efficient wind turbine. More than one aerofoil in a blade can increase the efficiency further. Previous studies of different aerofoils have shown that efficiency of small scale wind turbine increases when NREL S822 aerofoil is used for wind speed on and above 10 m/s. This paper introduces a study on effect of low wind speed (V = 5 m/s) on performance of blade profile. Aerofoils NREL S822/S823 are used for microwind turbine with S823 near root and S822 near tip. Blade of 3 m radius with spherical tubercles over entire span is analyzed considering 5 deg angle of attack. The computational fluid dynamics (CFD) simulation was carried out using ANSYS fluent to study the behavior of blade profile at various contours. The study shows that blade experiences maximum turbulence and minimum pressure near trailing edge of the tip of blade. The region also experiences maximum velocity of the flow. These factors result in pushing the aerofoil in upward direction for starting the wind turbine to rotate at the speed as low as 5 m/s.

Modeling of unsteady structure of sheet/cloud cavitation around a two-dimensional stationary hydrofoil

2015 ◽  
Vol 231 (3) ◽  
pp. 455-469 ◽  
Author(s):  
Feng Hong ◽  
Jianping Yuan ◽  
Banglun Zhou ◽  
Zhong Li
Keyword(s):  
Volume Fraction ◽  
Cavitating Flow ◽  
Wake Flow ◽  
Two Dimensional ◽  
Cavitating Flows ◽  
Cavitation Model ◽  
Ansys Fluent ◽  
Cloud Cavitation ◽  
Lift And Drag ◽  
Multi Phase

Compared to non-cavitating flow, cavitating flow is much complex owing to the numerical difficulties caused by cavity generation and collapse. In the present work, cavitating flow around a two-dimensional Clark-Y hydrofoil is studied numerically with particular emphasis on understanding the cavitation structures and the shedding dynamics. A cavitation model, coupled with the mixture multi-phase approach, and the modified shear stress transport k-ω turbulence model has been developed and implemented in this study to calculate the pressure, velocity, and vapor volume fraction of the hydrofoil. The cavitation model has been implemented in ANSYS FLUENT platform. The hydrofoil has a fixed angle of attack of α = 8° with a Reynolds number of Re = 7.5 × 105. Simulations have been carried out for various cavitation numbers ranging from non-cavitating flows to the cloud cavitation regime. In particular, we compared the lift and drag coefficients, the cavitation dynamics, and the time-averaged velocity with available experimental data. The comparisons between the numerical and experimental results show that the present numerical method is capable to predict the formation, breakup, shedding, and collapse of the sheet/cloud cavity. The periodical formation, shedding, and collapse of sheet/cloud cavity lead to substantial increase in turbulent velocity fluctuations in the cavitation regimes around the hydrofoil and in the wake flow.

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