Analysis and Modifications of Turbulence Models for Wind Turbine Wake Simulations in Atmospheric Boundary Layers

2016 ◽  
Author(s):  
Enrico G. A. Antonini ◽  
David A. Romero ◽  
Cristina H. Amon
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Cfd Simulations ◽  
Rans Equations ◽  
Stress Models ◽  
Turbine Wake ◽  
Wind Turbine Wake

Computational Fluid Dynamics (CFD) simulations of wind turbine wakes are strongly influenced by the choice of the turbulence model used to close the Reynolds-averaged Navier-Stokes (RANS) equations. A wrong choice can lead to incorrect predictions of the velocity field characterizing the wind turbine wake, and consequently to an incorrect power estimation for wind turbines operating downstream. This study aims to investigate the influence of different turbulence models on the results of CFD wind turbine simulations. In particular, the k–ε, k–ω, SSTk–ω, and Reynolds stress models are used to close the RANS equations and their influence on the CFD simulations is evaluated from the flow field generated downstream a stand-alone wind turbine. The assessment of the turbulence models was conducted by comparing the CFD results with publicly available experimental measurements of the flow field from the Sexbierum wind farm. Consistent turbulence model constants were proposed for atmospheric boundary layer and wake flows according to previous literature and appropriate experimental observations. Modifications of the derived turbulence model constants were also investigated in order to improve agreement with experimental data. The results showed that the simulations using the k–ε and k–ω turbulence models consistently overestimated the velocity in the wind turbine wakes. On the other hand, the simulations using the SSTk–ω and Reynolds stress models could accurately capture the velocity in the wake of the wind turbine. Results also showed that the predictions from the k–ε and k–ω turbulence models could be improved by using the modified set of turbulence coefficients.

Analysis and Modifications of Turbulence Models for Wind Turbine Wake Simulations in Atmospheric Boundary Layers

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Enrico G. A. Antonini ◽  
David A. Romero ◽  
Cristina H. Amon
Keyword(s):  
Experimental Data ◽  
Velocity Field ◽  
Wind Turbine ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Wind Farms ◽  
Navier Stokes ◽  
Stress Models ◽  
Turbine Wake ◽  
Wind Turbine Wake

Computational fluid dynamics (CFD) simulations of wind turbine wakes are strongly influenced by the choice of the turbulence model used to close the Reynolds-averaged Navier-Stokes (RANS) equations. A wrong choice can lead to incorrect predictions of the velocity field characterizing the wind turbine wake and, consequently, to an incorrect power estimation for wind turbines operating downstream. This study aims to investigate the influence of different turbulence models, namely the k–ε, k–ω, SSTk–ω, and Reynolds stress models (RSM), on the results of CFD wind turbine simulations. Their influence was evaluated by comparing the CFD results with the publicly available experimental measurements of the velocity field and turbulence quantities from the Sexbierum and Nibe wind farms. Consistent turbulence model constants were proposed for atmospheric boundary layer (ABL) and wake flows according to previous literature and appropriate experimental observations, and modifications of the derived turbulence model constants were also investigated in order to improve agreement with experimental data. The results showed that the simulations using the k–ε and k–ω turbulence models consistently overestimated the velocity and turbulence quantities in the wind turbine wakes, whereas the simulations using the shear-stress transport (SST) k–ω and RSMs could accurately match the experimental data. Results also showed that the predictions from the k–ε and k–ω turbulence models could be improved by using the modified set of turbulence coefficients.

A comparative numerical study of four turbulence models for the prediction of horizontal axis wind turbine flow

2010 ◽  
Vol 224 (9) ◽  
pp. 1973-1979 ◽  
Author(s):  
N S Tachos ◽  
A E Filios ◽  
D P Margaris
Keyword(s):  
Wind Turbine ◽  
Turbulence Model ◽  
Numerical Study ◽  
Free Field ◽  
Turbulence Models ◽  
Horizontal Axis ◽  
Wind Condition ◽  
Computational Domain ◽  
Horizontal Axis Wind Turbine ◽  
Rans Equations

The analysis of the near and far flow fields of an experimental National Renewable Energy Laboratory (NREL) rotor, which has been used as the reference rotor for the Viscous and Aeroelastic Effects on Wind Turbine Blades (VISCEL) research program of the European Union, is described. The horizontal axis wind turbine (HAWT) flow is obtained by solving the steady-state Reynolds-averaged Navier—Stokes (RANS) equations, which are combined with one of four turbulence models (Spalart—Allmaras, k—∊, k—∊ renormalization group, and k—ω shear stress transport (SST)) aiming at validation of these models through a comparison of the predictions and the free field experimental measurements for the selected rotor. The computational domain is composed of 4.2×106 cells merged in a structured way, taking care of refinement of the grid near the rotor blade in order to enclose the boundary layer approach. The constant wind condition 7.2 m/s, which is the velocity of the selected experimental data, is considered in all calculations, and only the turbulence model is altered. It is confirmed that it is possible to analyse a HAWT rotor flow field with the RANS equations and that there is good agreement with experimental results, especially when they are combined with the k—ω SST turbulence model.

Investigation and Validation of Wind Turbine Wake Models

2008 ◽  
Vol 32 (5) ◽  
pp. 459-475 ◽  
Author(s):  
A. Duckworth ◽  
R.J. Barthelmie
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
State Of The Art ◽  
Turbulence Models ◽  
Measured Data ◽  
Subsequent Work ◽  
Velocity Deficit ◽  
The Individual ◽  
Turbine Wake ◽  
Wind Turbine Wake

This article discusses the application of widely used, state of the art, wake models, focusing on the Ainslie [1], Katic [2] and Larsen [3] models, breaking these down and explaining the individual, integral components. Models used to predict the turbulence intensity within the wake are also explained. Measured data are subsequently used to validate these wake and turbulence models, showing acceptable results for the prediction of velocity deficit within the wake, wake width and wake shape. Results also highlight the validity of the analysed turbulence models. The paper describes the problems encountered when using measured data to validate wake models and concludes by outlining subsequent work which could be carried out to further validate these models.

Adaptive neuro-fuzzy generalization of wind turbine wake added turbulence models

2014 ◽  
Vol 36 ◽  
pp. 270-276 ◽  
Author(s):  
Shahaboddin Shamshirband ◽  
Dalibor Petković ◽  
Nor Badrul Anuar ◽  
Abdullah Gani
Keyword(s):  
Wind Turbine ◽  
Turbulence Models ◽  
Neuro Fuzzy ◽  
Turbine Wake ◽  
Wind Turbine Wake

Numerical analysis for wake flow field of Ahmed model based on a nonlinear-LRN/DES turbulence model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Le Dian Zheng ◽  
Yi Yang ◽  
Guang Lin Qiang ◽  
Zhengqi Gu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Wake Flow ◽  
Field Analysis ◽  
Content Type ◽  
Des Model

Purpose This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately. Design/methodology/approach As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases. Findings Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately. Research limitations/implications The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model. Practical implications This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles. Originality/value Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

Experimental and Numerical Investigation of Turbulent High Reynolds Number Flows in a Square Duct With 90-Degree Streamwise Curvature: Part 1 — Experiment

2003 ◽  
Author(s):  
Faustin Ondore
Keyword(s):  
Turbulent Flows ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Flow Visualisation ◽  
Square Duct ◽  
Plane Flow ◽  
Convex Wall ◽  
The Mean ◽  
Stress Models

This study was aimed at obtaining a better understanding of turbulent flows in a square duct with a 90° bend, using both experimental and numerical techniques. Turbulent flows that are subjected to streamwise curvature occur in numerical engineering applications. These flows are known to experience extra rates of strain in the plane of mean shear in comparison to plane flows. Hence the gross parameters, such as the mean flow velocities, turbulence intensities and Reynolds stresses are altered dramatically from the plane flow characteristics. The flows examined are specified by the free-stream entry velocities of 12.3 m/s and 20.4 m/s measured at 1.01 duct height upstream of the bend entry plane. These velocities correspond to Reynolds numbers 3.56 × 105 and 6.43 × 105 respectively. The duct has a cross-section of 0.457 × 0.457 m 2 and the mean radius of curvature to duct height ratio is 1:21. Airflow from a wind tunnel passes through an upstream tangent of 1.31 duct height before entering the bend. The flow then exits the bend into a 7.0 duct height downstream tangent before discharging into the atmosphere. The experimental part involved hot-wire measurements. Flow visualisation was performed by smoke in a region close to the convex wall at the bend exit to confirm the numerical prediction of recirculating flow in that area. The numerical part of the investigation was based on the solution of the governing differential equations for turbulent flows in conjunction with a number of turbulence models. The discretisation of the equations was achieved using a finite-volume technique and different discretisation schemes. The main turbulence model used for the study was the Reynolds Stress Model, but the comparisons of the results were also made with those from the standard κ-ε and the RNG-κ-ε turbulence models. The boundary conditions for these simulations were obtained as part of the experimental investigations. Numerical calculations with the Reynolds stress models show a separated flow near the convex wall starting at the bend exit, which was confirmed by experiment using flow visualisation by smoke. The Reynolds stress models are observed to be superior in comparison with the standard κ-ε and the RNG-κ-ε turbulence models in terms of accuracy. Further conclusions from this work can be summarised as: 1. The proper numerical resolution of this type of flow is dependent on the turbulence model formulations as well as numerical procedures. The results highlight the limitations of the generality of turbulence models when used to model more intricate features of complex flows. 2. The need for more accurate experimental techniques in support of improvement of turbulence models is thus underlined.

Further Developments in Numerical Simulations of Wind Turbine Flows Using the Actuator Line Method

2016 ◽  
Author(s):  
Murphy Leo O’Dea ◽  
Laila Guessous
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Turbulence Model ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Cfd Modeling ◽  
Time Step ◽  
Grid Points ◽  
Turbine Wake

Current large-scale wind turbine installations are sited using layouts based on site topology, real estate costs and restrictions, and turbine power output. Existing optimization programs attempt to site multiple turbines based on simple geometric turbine wake models, which typically overestimate individual turbine output. In addition, advanced Computational Fluid Dynamics (CFD) modeling of individual turbine wake fields have revealed complex flow patterns and “wake meandering” which have not been taken into account in current optimization and flow field models. CFD models of entire turbine fields have had limited application because of the enormous compute resources required; limitations of the simplified turbine models used which do not provide high resolution results in the wake field; and the lack of efforts to adapt the results of complex CFD output to analytical models which can be incorporated into wind turbine siting optimization routines. In this paper, we report on our efforts to simulate flow past wind turbines using a new adaptation of the Actuator Line (AL) method for turbine blade modeling. This method creates a geometric representation of each rotating turbine blade. Grid points in the CFD flow field are selected within the outline of the blades and near downstream planes, and the aerodynamic forces are calculated using traditional blade element equations. The forces are distributed using an automated routine which dynamically determines the application area based on the number of applied grid points at each time step. Turbine blades are rotated in time with progressing CFD field calculations. This method distributes blade forces without using a geometric distribution function used in other recent research. Blade forces are then input as body forces into the Navier Stokes equations in the host CFD program. A Smagorisnky LES turbulence model is employed to model turbulent effects. To improve accuracy and reduce computing power requirements, the advanced parallel CFD code, NEK5000, is used in this study. FORTRAN subroutines are written to generate the actuator line and blade geometry, and to calculate the blade lift and drag forces. These subroutines are then linked to the solver source code and compiled. Details of the actuator line setup and calculations, LES turbulence model, CFD flow simulation setup, and results from current turbine runs will be presented. Current results are consistent with published research. A roadmap to ongoing development will also be discussed.

scholarly journals A Modified Reynolds-Averaged Navier–Stokes-Based Wind Turbine Wake Model Considering Correction Modules

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4430
Author(s):  
Yuan Li ◽  
Zengjin Xu ◽  
Zuoxia Xing ◽  
Bowen Zhou ◽  
Haoqian Cui ◽  
...  
Keyword(s):  
Power Generation ◽  
Power Systems ◽  
Wind Turbine ◽  
Turbulence Model ◽  
Wind Turbines ◽  
Navier Stokes ◽  
Aerodynamic Model ◽  
Wake Model ◽  
Turbine Wake ◽  
Wind Turbine Wake

Increasing wind power generation has been introduced into power systems to meet the renewable energy targets in power generation. The output efficiency and output power stability are of great importance for wind turbines to be integrated into power systems. The wake effect influences the power generation efficiency and stability of wind turbines. However, few studies consider comprehensive corrections in an aerodynamic model and a turbulence model, which challenges the calculation accuracy of the velocity field and turbulence field in the wind turbine wake model, thus affecting wind power integration into power systems. To tackle this challenge, this paper proposes a modified Reynolds-averaged Navier–Stokes (MRANS)-based wind turbine wake model to simulate the wake effects. Our main aim is to add correction modules in a 3D aerodynamic model and a shear-stress transport (SST) k-ω turbulence model, which are converted into a volume source term and a Reynolds stress term for the MRANS-based wake model, respectively. A correction module including blade tip loss, hub loss, and attack angle deviation is considered in the 3D aerodynamic model, which is established by blade element momentum aerodynamic theory and an improved Cauchy fuzzy distribution. Meanwhile, another correction module, including a hold source term, regulating parameters and reducing the dissipation term, is added into the SST k-ω turbulence model. Furthermore, a structured hexahedron mesh with variable size is developed to significantly improve computational efficiency and make results smoother. Simulation results of the velocity field and turbulent field with the proposed approach are consistent with the data of real wind turbines, which verifies the effectiveness of the proposed approach. The variation law of the expansion effect and the double-hump effect are also given.

Modeling Separation-Induced Transition Using a Non-Linear Three Equation Turbulence Model and a Reynolds Stress Turbulence Model

2010 ◽  
Author(s):  
Zinon Vlahostergios ◽  
Kyros Yakinthos
Keyword(s):  
Transport Equation ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Transitional Flows ◽  
Eddy Viscosity Model ◽  
Non Linear ◽  
Stress Models

This paper presents an effort to model separation-induced transition on a flat plate with a semi-circular leading edge, by using two advanced turbulence models, the three equation non-linear model k-ε-A2 of Craft et al. [16] and the Reynolds-stress model of Craft [13]. The mechanism of the transition is governed by the different inlet velocity and turbulence intensity conditions, which lead to different recirculation bubbles and different transition onset points for each case. The use of advanced turbulence models in predicting the development of transitional flows has shown, in past studies, good perspectives. The k-ε-A2 model uses an additional transport equation for the A2 Reynolds stress invariant and it is an improvement of Craft et al. [12] non-linear eddy viscosity model. The use of the third transport equation gives improved results in the prediction of the longitudinal Reynolds stress distributions and especially, in flows where transitional phenomena may occur. Although this model is a pure eddy-viscosity model, it borrows many aspects from the more complex Reynolds-stress models. On the other hand, the use of an advanced Reynolds-stress turbulence model, such as the one of Craft [13], can predict many complex flows and there are indications that it can be applied to transitional flows also, since the crucial terms of Reynolds stress generation are computed exactly and normal stress anisotropy is resolved. The model of Craft [13], overcomes the drawbacks of the common used Reynolds-stress models regarding the computation of wall-normal distances and vectors in order to account for wall proximity effects. Instead of these quantities, it employs “normalized turbulence lengthscale gradients” which give the ability to identify the presence of strong inhomogeneity in a flow development, in an easier way. The final results of both turbulence models showed acceptable agreement with the experimental data. In this work it is shown that there is a good potential to model separation-induced transitional flows, with advanced turbulence modeling without any additional use of ad-hoc modifications or additional equations, based on various transition models.

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