Analysis of Turbulent Flow Around Horizontal Axis Wind Turbines Using Algebraic Stress Model

2015 ◽  
Author(s):  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Turbulent Flow ◽  
Wind Turbine ◽  
Reynolds Stress ◽  
Wind Turbines ◽  
Cost Effective ◽  
Horizontal Axis ◽  
Stress Model ◽  
Reynolds Stresses ◽  
Algebraic Stress Model ◽  
Near Wall

Due to the problems associated with increase of greenhouse gases, and the limited supply of fossil fuels, switching to clean and renewable sources of energy seems necessary. Wind energy is a very suitable form of renewable energy which can be a good choice for those areas around the world with sufficient amount of wind annually. However, in order for the commercial wind turbines to be cost-effective, they need to operate at very high elevations, and therefore, blades with the length as high as 60–70 m are common. Because of the high manufacturing and transportation costs of the wind turbine components, it is necessary to evaluate and predict the performance of the turbine prior to shipping it to the installation site. Computational Fluid Dynamics (CFD) has proven to be a simple, cheap and yet relatively accurate tool for prediction of wind turbine performance, where suitability of different designs can be evaluated at a low cost. Total lift and drag forces can be calculated, from which one can estimate the torque, and ultimately the output power. Reynolds Stress Model (RSM) is a well-known Reynolds Averaged Navier-Stokes (RANS) turbulence model, which is typically more accurate than eddy viscosity models, but it comes with higher computational cost. In the present work, turbulent flow of air around a horizontal axis wind turbine blade is modeled computationally by using a modified version of RSM, known as Algebraic Stress Model (ASM) for the near-blade region. Because of the periodicity nature of the flow domain, only one of three blades is modeled by applying the periodic conditions on the sides of a 120 degree sector of the domain. While the flow is solved in the bulk fluid using the k-epsilon model, in order to better capture the near-wall effects and to make the computations cost effective, it is proposed to apply ASM only in the locations very close to the blade surface. A number of reasonable assumptions are made in ASM in order to convert the transport differential equations of the Reynolds stresses into an algebraic form. The highly coupled system of non-linear equations is then solved concurrently for six Reynolds stress components. Turbulent kinetic energy, turbulent dissipation rate, and mean velocity gradients are calculated from the k-epsilon model and used as initial values and iterated through the ASM computations. To the best of our knowledge, this is the first time that ASM is used for analysis of Reynolds stress for flow around rotating wind turbines blades. Reynolds stresses are obtained at several locations (heights) along the blade, and at different radial distances from the blade. Different variations of implicit and explicit ASM are examined and compared in terms of accuracy. Results indicate that the implicit ASM method using the full form of pressure-strain term tends to show predictions that are closer to the predictions of the fully-resolved RSM simulation, as compared to the other ASM models examined. Therefore, there seems to be a good potential for reducing computational costs for determination of near wall Reynolds stresses and ultimately calculating torque and power generated from wind turbines without sacrificing the accuracy.

Improved Prediction of Turbomachinery Flows Using Near-Wall Reynolds-Stress Model

2001 ◽  
Vol 124 (1) ◽  
pp. 86-99 ◽  
Author(s):  
G. A. Gerolymos ◽  
J. Neubauer ◽  
V. C. Sharma ◽  
I. Vallet
Keyword(s):  
Experimental Data ◽  
Turbulent Flows ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Equations ◽  
Near Wall

In this paper an assessment of the improvement in the prediction of complex turbomachinery flows using a new near-wall Reynolds-stress model is attempted. The turbulence closure used is a near-wall low-turbulence-Reynolds-number Reynolds-stress model, that is independent of the distance-from-the-wall and of the normal-to-the-wall direction. The model takes into account the Coriolis redistribution effect on the Reynolds-stresses. The five mean flow equations and the seven turbulence model equations are solved using an implicit coupled OΔx3 upwind-biased solver. Results are compared with experimental data for three turbomachinery configurations: the NTUA high subsonic annular cascade, the NASA_37 rotor, and the RWTH 1 1/2 stage turbine. A detailed analysis of the flowfield is given. It is seen that the new model that takes into account the Reynolds-stress anisotropy substantially improves the agreement with experimental data, particularily for flows with large separation, while being only 30 percent more expensive than the k−ε model (thanks to an efficient implicit implementation). It is believed that further work on advanced turbulence models will substantially enhance the predictive capability of complex turbulent flows in turbomachinery.

Application of the Reynolds Stress Model to Direct Modeling and Actuator Disk Simulations of a Small-Scale Horizontal-Axis Wind Turbine

2016 ◽  
Author(s):  
Randall Jackson ◽  
Ryoichi S. Amano
Keyword(s):  
Wind Turbine ◽  
Reynolds Stress ◽  
Reynolds Stress Model ◽  
Horizontal Axis ◽  
Tip Vortex ◽  
Small Scale ◽  
Stress Model ◽  
Closure Model ◽  
Horizontal Axis Wind Turbine ◽  
Turbulence Closure Model

Computational Fluid Dynamics (CFD) has become a staple in wind energy research and studies cover a broad range of topics including atmospheric wind profiles, airfoil design, wind turbine design, terrain effects, and wake dynamics. One of the most important aspects of applying CFD methods is the selection of a turbulence closure model when solving the Reynolds Averaged Navier-Stokes (RANS) equations. In this research, the Reynolds Stress Model (RSM) was applied to predict the wake turbulence and velocity profiles for a small scale, 3-bladed, horizontal-axis wind turbine (HAWT) using a commercial CFD software, Star CCM+. The wind turbine was modeled directly by discretizing the rotor and also using an actuator disc concept to simulate the rotor. Wind tunnel experiments were performed using hot-wire anemometry to measure the velocity deficit at various downstream locations. High speed images were also captured to examine qualitatively the wake and tip vortex dissipation created from an oil mist. The CFD results show the RSM turbulence closure model to be excellent in predicting the wake velocity and tip vortex structure when compared to experimental results.

Improved Prediction of Turbomachinery Flows Using Near-Wall Reynolds-Stress Model

2001 ◽  
Author(s):  
G. A. Gerolymos ◽  
J. Neubauer ◽  
V. C. Sharma ◽  
I. Vallet
Keyword(s):  
Experimental Data ◽  
Turbulent Flows ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Stress Model ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Flow Equations ◽  
Near Wall

In this paper an assessment of the improvement in the prediction of complex turbomachinery flows using a new near-wall Reynolds-stress model is attempted. The turbulence closure used is a near-wall low-turbulence-Reynolds-number Reynolds-stress model, that is independent of the distance-from-the-wall and of the normal-to-the-wall direction. The model takes into account the Coriolis redistribution effect on the Reynolds-stresses. The 5 mean flow equations and the 7 turbulence model equations are solved using an implicit coupled O(Δx3) upwind-biased solver. Results are compared with experimental data for 3 turbomachinery configurations: the ntua high subsonic annular cascade, the nasa_37 rotor, and the rwth 1½ stage turbine. A detailed analysis of the flowfield is given. It is seen that the new model that takes into account the Reynolds-stress anisotropy substantially improves the agreement with experimental data, particularly for flows with large separation, while being only 30% more expensive than the k – ε model (thanks to an efficient implicit implementation). It is believed that further work on advanced turbulence models will substantially enhance the predictive capability of complex turbulent flows in turbomachinery.

scholarly journals Aerodynamic performance simulation of three selected airfoils

2021 ◽  
Vol 25 (111) ◽  
pp. 201-211
Author(s):  
Mariana Montenegro Montero ◽  
Gustavo Richmond Navarro
Keyword(s):  
Renewable Energy ◽  
Turbulent Flow ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Aerodynamic Performance ◽  
Horizontal Axis ◽  
Wind Engineering ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Turbulence Effects

This work presents the lift and drag coefficient curves, as functions of the angle of attack, for the NACA0012, S809 and SG6043 airfoils in turbulent flow conditions. The objective is to identify the airfoil with the best aerodynamic performance under conditions that are descriptive of small scale wind turbine. With the use of OpenFOAM, an analysis was done by numerical simulation. In the case of the NACA0012 airfoil, it was found that the performance is insensitive to the changes in turbulence and the Reynold number. The aerodynamic response of the S809 airfoil is to increase both the drag and lift as the turbulence increases. The SG6043 airfoil responds the best out of the three in turbulent flow, given that the lift curves mostly increase with the turbulence. The curves reported in this work are new and not found in previous literature. Keywords: aerodynamics, lift, drag, turbulence References [1]R. Madriz-Vargas, A. Bruce, M. Watt, L. G. Mogollón and H. R. Álvarez, «Community renewable energy in Panama: a sustainability assessment of the “Bocade Lura” PV-Wind-Battery hybrid power system,» Renewable Energy and Environmental Sustainability, vol. 2, nº 18, pp. 1-7, 2017. https://doi.org/10.1051/rees/2017040. [2]S. Mertenes, «Wind Energy in the Built Environment, » Ph.D. dissertation. Multi-Science, Brentwood, 2006. [3]P. Giguere and M. S. Selig, «New airfoils for small horizontal axis wind turbines,» Journal of Solar Energy Engineering-transactions, vol. 120, pp. 108-114, 1988. https://doi.org/10.1115/1.2888052. [4]A. K. Wright and D. H. Wood, «The starting and low wind speed behaviour of a small horizontal axis wind turbine,» Journal of wind engineering and industrial aerodynamics, vol. 92, nº 14-15, pp. 1265-1279, 2004. https://doi.org/10.1016/j.jweia.2004.08.003. [5]G. Richmond-Navarro, M. Montenegro-Montero and C. Otárola, «Revisión de los perfiles aerodinámicos apropiados para turbinas eólicas de eje horizontal y de pequeña escala en zonas boscosas,» Revista Lasallista de Investigación, vol. 17, nº 1, pp. 233-251, 2020. https://doi.org/10.22507/rli.v17n1a22. [6]A. Tummala, R. K. Velamati, D. K. Sinha, V. Indraja and V. H. Krishna, «A review on small scale wind turbines, » Renewable and Sustainable Energy Reviews,vol. 56, pp. 1351-1371, 2016. https://doi.org/10.1016/j.rser.2015.12.027. [7]L. Pagnini, M. Burlando and M. Repetto, «Experimental power curve of small-size wind turbines in turbulent urban environment,» Applied Energy, vol. 154,pp. 112-121, 2015. https://doi.org/10.1016/j.apenergy. 2015.04.117. [8]W. D. Lubitz, «Impact of ambient turbulence on performance of a small wind turbine,» Renewable Energy, vol. 61, pp. 69-73, 2014. https://doi.org/10.1016/j.renene.2012.08.015. [9]P. Devinant, T. Laverne and J. Hureau, «Experimental study of wind-turbine airfoil aerodynamics in high turbulence, » Journal of Wind Engineering and Industrial Aerodynamics, vol. 90, nº 6, pp. 689-707, 2002. https://doi.org/10.1016/S0167-6105(02)00162-9. [10]C. Sicot, P. Devinant, S. Loyer and J. Hureau, «Rotational and turbulence effects on a wind turbine blade. Investigation of the stall mechanisms,» Journal ofwind engineering and industrial aerodynamics, vol. 96, nº 8-9, pp. 1320-1331, 2008. https://doi.org/10.1016/j.jweia.2008.01.013. [11]C. R. Chu and P. H. Chiang, «Turbulence effects on the wake flow and power production of a horizontal-axis wind turbine,» Journal of Wind Engineering and Industrial Aerodynamics, vol. 124, pp. 82-89, 2014. https://doi.org/10.1016/j.jweia.2013.11.001. [12]Y. Kamada, T. Maeda, J. Murata and Y. Nishida, «Visualization of the flow field and aerodynamic force on a Horizontal Axis Wind Turbine in turbulent inflows,» Energy, vol. 111, pp. 57-67, 2016. https://doi.org/10.1016/j.energy.2016.05.098. [13]Q. A. Li, J. Murata, M. Endo, T. Maeda and Y. Kamada, «Experimental and numerical investigation of the effect of turbulent inflow on a Horizontal Axis WindTurbine (Part I: Power performance),» Energy, vol.113, pp. 713-722, 2016. https://doi.org/10.1016/j.energy.2016.06.138. [14]S. W. Li, S. Wang, J. P. Wang and J. Mi, «Effect of turbulence intensity on airfoil flow: Numerical simulations and experimental measurements,» Applied Mathematics and Mechanics, vol. 32, nº 8, pp. 1029-1038, 2011. https://doi.org/10.1007/s10483-011-1478-8. [15]S. Wang, Y. Zhou, M. M. Alam and H. Yang, «Turbulent intensity and Reynolds number effects on an airfoil at low Reynolds numbers,» Physics of Fluids, vol. 26, nº11, p. 115107, 2014. https://doi.org/10.1063/1.4901969. [16]M. Lin and H. Sarlak, «A comparative study on the flow over an airfoil using transitional turbulence models, » AIP Conference Proceedings, vol. 1738, p.030050, 2016. https://doi.org/10.1063/1.4951806. [17]Langley Research Center, «Turbulence Modelling Resource,» NASA, [Online]. Available: https://turbmodels.larc.nasa.gov/langtrymenter_4eqn.html. [Last access: 08 03 2021].

Development and Field Testing of an Inclined Flanged Compact Diffuser for a Micro Wind Turbine

2014 ◽  
Author(s):  
Sandip Kale ◽  
S. N. Sapali
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Wind Turbines ◽  
Energy Production ◽  
Cost Effective ◽  
Field Testing ◽  
International Electrotechnical Commission ◽  
Average Wind Speed ◽  
Average Wind ◽  
Power Curves

Micro wind turbines installed in various applications, experience average wind speed for most of the time during operations. Power produced by the wind turbine is proportional to the cubic power of the wind velocity and a small increase in wind velocity results increases power output significantly. The approach wind velocity can be increased by covering traditional wind turbine with a diffuser. Researchers are continuously working to develop a compact, lightweight, cost effective and feasible diffuser for wind turbines. The present work carried out to develop a diffuser with these stated objectives. A compact, lightweight inclined flanged diffuser developed for a micro wind turbine. Bare micro wind turbine and wind turbine covered with developed efficient inclined flanged diffuser tested in the field as per International Electrotechnical Commission (IEC) standards and results presented in the form of power curves. The prediction of annual energy production for both wind turbines determined as per IEC standards.

Fast CFD Simulation of Horizontal Axis Wind Turbines

2010 ◽  
Author(s):  
Fabio De Bellis ◽  
Luciano A. Catalano ◽  
Andrea Dadone
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Horizontal Axis ◽  
Wall Functions ◽  
Mesh Topology ◽  
Numerical Predictions ◽  
Horizontal Axis Wind Turbines ◽  
Time Required

The numerical simulation of horizontal axis wind turbines (HAWT) has been analysed using computational fluid dynamics (CFD) with the aim of obtaining reliable but at the same time affordable wind turbine simulations, while significantly reducing required overall resources (time, computational power, user skills), for example in an optimization perspective. Starting from mesh generation, time required to extract preliminary aerodynamic predictions of a wind turbine blade has been shortened by means of some simplifications, i.e.: fully unstructured mesh topology, reduced grid size, incompressible flow assumption, use of wall functions, commercial available CFD package employment. Ansys Fluent software package has been employed to solve Reynolds Averaged Navier Stokes (RANS) equations, and results obtained have been compared against NREL Phase VI campaign data. The whole CFD process (pre-processing, processing, postprocessing) has been analysed and the chosen final settings are the result of a trade-off between numerical accuracy and required resources. Besides the introduced simplifications, numerical predictions of shaft torque, forces and flow distribution are in good agreement with experimental data and as accurate as those calcuted by other more sophisticated works.

scholarly journals Modeling and simulation of forces applied to the horizontal axis wind turbine rotors by the vortex method coupled with the method of the blade element

2021 ◽  
Vol 12 (1) ◽  
pp. 413
Author(s):  
Ibtissem Barkat ◽  
Abdelouahab Benretem ◽  
Fawaz Massouh ◽  
Issam Meghlaoui ◽  
Ahlem Chebel
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Vortex Method ◽  
Operating Conditions ◽  
Horizontal Axis ◽  
Rotor Blades ◽  
Good Representation ◽  
Horizontal Axis Wind Turbine ◽  
Blade Element

This article aims to study the forces applied to the rotors of horizontal axis wind turbines. The aerodynamics of a turbine are controlled by the flow around the rotor, or estimate of air charges on the rotor blades under various operating conditions and their relation to the structural dynamics of the rotor are critical for design. One of the major challenges in wind turbine aerodynamics is to predict the forces on the blade as various methods, including blade element moment theory (BEM), the approach that is naturally adapted to the simulation of the aerodynamics of wind turbines and the dynamic and models (CFD) that describes with fidelity the flow around the rotor. In our article we proposed a modeling method and a simulation of the forces applied to the horizontal axis wind rotors turbines using the application of the blade elements method to model the rotor and the vortex method of free wake modeling in order to develop a rotor model, which can be used to study wind farms. This model is intended to speed up the calculation, guaranteeing a good representation of the aerodynamic loads exerted by the wind.

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