scholarly journals A 2–D Mathematical Model of Vortex Induced Vibration Driven Bladeless Wind Turbine

2019 ◽  
Vol 291 ◽  
pp. 02007
Author(s):  
Sirada Saengsaen ◽  
Chawin Chantharasenawong ◽  
Tsung-Liang Wu
Keyword(s):  
Shear Stress ◽  
Flow Field ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Structural Vibration ◽  
Detached Eddy Simulation ◽  
Vortex Induced Vibration ◽  
Cylindrical Structures ◽  
Shear Stress Transport

Bladeless wind turbine (BWT) is a flexible cylindrical structure that extracts energy from wind by utilising vortex-induced vibration (VIV) - aerodynamic forces and the resulting structural vibration. This work focuses on taking possible advantage of the increase in lift forces in the similar fashion to birds flying in a V-formation. The purposes of the present study are 1) to study the flow pattern and characteristic around two BWTs which are cylindrical structures in the same flow field and 2) to study the extra lift force generation of the system. 2–D CFD models are used to simulate flow of stationary cylinder of BWTs at Re = 105. The two different turbulent models, Reynolds Averaged Navier-Stokes shear-stress transport k(RANS–SST k) and Detached Eddy Simulation shear-stress transport k(DES–SST k) are investigated. The results show that only DES–SST kgives converged results, therefore, DES–SST kis selected for the additional studies of two cylindrical structures. From 2–D CFD simulation, the one BWT in flow field case produces lift coefficient 0.851. In the case of two BTWs in same flow field (BWT no.2 is located at x = 3D, y = 0D, directly downstream of two cylinders), BTW no.1 and BWT no.2 show greater lift coefficients of 0.893 and 1.841, respectively. This result indicates that the kinetic energy generation of the downstream BWT in the two BWTs system in this study is greater than the baseline BWT with an increase of 116% of lift. Further work is needed to determine the optimum location of the behind wind turbine for greater lift and result to increasing of energy produce of the system.

Comparisons of Shear Stress Transport and Detached Eddy Simulations of the Flow Around Trains

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Tian Li ◽  
Hassan Hemida ◽  
Jiye Zhang ◽  
Mohammad Rashidi ◽  
Dominic Flynn
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Flow Field ◽  
Surface Pressure ◽  
Experimental Uncertainty ◽  
Detached Eddy Simulation ◽  
Aerodynamic Forces ◽  
Force Coefficients ◽  
Eddy Simulation ◽  
Shear Stress Transport

Shear stress transport (SST) k–ω model and detached eddy simulation (DES) have been widely applied in crosswind stability simulations for trains in the literature. In the previous research, the influence of the SST and DES approaches on the flow field around trains, which affects the surface pressure and consequently the aerodynamic forces of the train, was not properly investigated in terms of their influence flow field. The SST and improved delayed detached eddy simulation (IDDES) turbulence models have been tested in this study for their ability to predict the flow field around, surface pressure, and aerodynamic forces on a 1/25th scale Class 390 train subjected to crosswinds. Numerical simulation results were validated with experimental data. Results show that both SST and IDDES predict similar trends in the mean flow field around the train. However, there were some slight differences observed in the size of vortices, the position of separation points, and consequently, the separation and attachment lines. The SST results compared more closely to the experimental data than IDDES for pressure coefficient on the leeward surface and roof at certain loops. Slight differences were observed in force coefficients for SST and DES. The side force coefficients calculated using computational fluid dynamics (CFD) sit within the experimental uncertainty, whereas the lift force coefficients deviated greatly due to the omission of some underbody geometrical features. Both SST and IDDES approaches used the linear-upwind stabilized transport (LUST) scheme and were able to predict accurately the time-averaged surface pressure within the margin of the experimental uncertainty.

scholarly journals Numerical investigation of stall characteristics for winglet blade of a horizontal axis wind turbine

2021 ◽  
Vol 321 ◽  
pp. 03004
Author(s):  
Shalini Verma ◽  
Akshoy Ranjan Paul ◽  
Anuj Jain ◽  
Firoz Alam
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Numerical Investigation ◽  
Turbulence Intensity ◽  
Geometric Modeling ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Horizontal Axis ◽  
Renewable Energy Resources ◽  
Horizontal Axis Wind Turbine

Wind energy is one of the renewable energy resources which is clean and sustainable energy and the wind turbine is used for harnessing energy from the wind. The blades are the key components of a wind turbine to convert wind energy into rotational energy. Recently, wingtip devices are used in the blades of horizontal axis wind turbine (HAWT), which decreases the vortex and drag, while increases the lift and thereby improve the performance of the turbine. In the present study, a winglet is used at the tip of an NREL phase VI wind turbine blade. Solidworks, Pointwise, and Ansys-Fluent are used for geometric modeling, computational grid generation, and CFD simulation, respectively. The computational result obtained using SST k-ω turbulence modeling is well validated with the experimental data of NREL at 5 and 7 m/s of wind speeds. Numerical investigation of stall characteristics is carried out for wingleted blade at higher turbulence intensity (21% and 25%) and angle of attack (00 to 300 at 50 intervals) at 7 m/s wind speed. The result found that wingletd blade delay stall to 150 for both the cases of turbulence intensity. Increasing the turbulence intensity increases the lift coefficient at stall angle but drag coefficient also increases and thus a lower aerodynamic performance (CL/CD ratio = 13) is obtained. Wingleted blade improves the performance as the intensity of vortices is smaller compared to baseline blade

Influence of the Curvature Correction on Turbulence Models for the Prediction of the Aerodynamic Coefficients of the S809 Airfoil

2021 ◽  
Vol 43 ◽  
pp. 45-57
Author(s):  
Mohammed Nebbache ◽  
Abdelkader Youcefi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Lift Coefficient ◽  
Turbulence Models ◽  
Aerodynamic Coefficients ◽  
Ansys Fluent ◽  
Curvature Correction ◽  
Shear Stress Transport ◽  
Sst Model

Using the appropriate procedure, Computational Fluid Dynamics allows predicting many things in several fields, and especially in the field of renewable energies, which has become a promising research axis. The present study aims at highlighting the influence of the curvature correction on turbulence models for the prediction of the aerodynamic coefficients of the S809 airfoil using the Computational Fluid Dynamics code ANSYS Fluent 17.2. Three turbulence models are used: Spalart-Allmaras, Shear Stress Transport k-ω and Transition SST. Experimental results of the 1.8 m × 1.25 m low-turbulence wind tunnel at the Delft University of Technology are used in this work for comparison with the numerical results for a Reynolds number of 106. The results show that the use of the curvature correction improves the prediction of the aerodynamic coefficients for all the turbulence models used. A comparison of the three models is also made using curvature correction since it gave better results. The Transition SST model is the one that gives the best results for the lift coefficient, followed by the Shear Stress Transport kω model, and finally the Spalart-Allmaras model. For the drag coefficient, Transition SST model is the best, followed by the Spalart-Allmaras model, and finally the Shear Stress Transport kω model.

scholarly journals Adaptability of Turbulence Models for Pantograph Aerodynamic Noise Simulation

2019 ◽  
Vol 2019 ◽  
pp. 1-20 ◽  
Author(s):  
Xiao-ming Tan ◽  
Peng-peng Xie ◽  
Zhi-gang Yang ◽  
Jian-yong Gao
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
High Speed ◽  
Aerodynamic Noise ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Shear Stress Transport ◽  
Delayed Detached Eddy Simulation ◽  
Relative Errors ◽  
Les Model

This study was targeted at CX-PG-type Faiveley pantograph of high-speed train and cylinders and analysed the fluctuating flow field around these objects by using the large eddy simulation (LES) model, the scale adaptive simulation (SAS) model, the improved delayed detached eddy simulation with shear-stress transport-kω (IDDES sst-kω) model, the delayed detached eddy simulation with shear-stress transport-kω (DDES sst-kω) model, and the delayed detached eddy simulation with realizable-kε (DDES R-kε) model. The space distributions of velocity, vorticity, and vortex structures were compared to investigate their performances on simulating fluctuating flow fields and computing aeroacoustic sources through Fourier transformation based on the surface fluctuating pressures. Furthermore, the far-field radiated noise was calculated based on the Ffowcs Williams–Hawkings equation. Based on the computation precision of the five models, a feasible turbulent model was selected for simulating aerodynamic noise. The relative errors to the results from wind-tunnel experiments of the sound pressure level (SPL) were obtained as 0.7%, 1.6%, 7.8%, 3.8%, and 12.1%, respectively, and the peak Strouhal numbers were obtained as 2.0%, 8.5%, 5.5%, 11.5%, and 51.0% for cylinder simulation. Moreover, the relative errors of SAS, IDDES sst-kω, DDES sst-kω, and DDES R-kε models to the result from LES of SPL were respectively obtained as 2.3%, 4.5%, 5.6%, and 10.8% for pantograph. Thus, it is conclusive that none of the aforementioned models are comparable with the LES model with respect to the precision in the aeroacoustic simulation. However, SAS, IDDES sst-kω, and DDES sst-kω are practically competent with the LES model considering the numerical simulations with respect to the engineering computation precision. The numerical computation model was verified using the wind-tunnel test results.

Numerical Analysis of Fluid-Structure Interaction of Frame Structure Considering the Impact of Turbulent Wind Load

2011 ◽  
Vol 94-96 ◽  
pp. 2130-2133
Author(s):  
Wen Bin Sun
Keyword(s):  
Flow Field ◽  
Cfd Simulation ◽  
Coupling Effect ◽  
Frame Structure ◽  
Vortex Induced Vibration ◽  
Vibration Effect ◽  
Control Principle ◽  
And Control ◽  
Wind Induced Vibration ◽  
The Impact

According to the basic principle of CFD simulation and methods, a framework structure was studied for its vortex-induced vibration and control principle of around the flow field, it revealed the characteristics of vortex-induced vibration and rules, systematically studied frame structure fluid-solid coupling effect and the flow field active control methods and mechanism. Results provide the theory basis for the frame structure around the flow field and the wind induced vibration effect.

scholarly journals Effects of turbulence models and grid densities on computational accuracy of flows over a vertical axis wind turbine

2018 ◽  
Vol 7 (3) ◽  
pp. 213-222
Author(s):  
Jaruwan Chaiyanupong ◽  
Tawit Chitsomboon
Keyword(s):  
Shear Stress ◽  
Wind Turbine ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Vertical Axis ◽  
Operating Conditions ◽  
Speed Ratio ◽  
Vertical Axis Wind Turbine ◽  
Computational Accuracy ◽  
Shear Stress Transport

Flows through a vertical axis wind turbine (VAWT) are very complex due to their inherent unsteadiness caused by large variations of the angle of attacks as the turbine is rotating and changing its azimuth angles simultaneously. In addition, a turbine must go through a wide range of operating conditions especially the change in blade speed ratio (BSR). Accurate prediction of flows over VAWT using Reynolds-Averaged Navier-Stokes (RANS) model needs a well-tested turbulence model as well as a careful grid control around the airfoil. This paper aimed to compare various turbulence models and seek the most accurate one. Furthermore, grid convergence was studied using the Roache method to determine the sufficient number of grid elements around the blade section. The three-dimensional grid was generated by extrution from the two-dimensional grid along with the appropriate y+ controlling. Comparisons were made among the three turbulence models that are widely used namely: the RNG model, the shear stress transport k-ω model (SST) and the Menter’s shear stress transport k-ω model (transition SST). Results obtained clearly showed that turbulence models significantly affected computational accuracy. The SST turbulence model showed best agreement with reported experimental data at BSR lower than 2.35, while the transition SST model showed better results when BSR is higher than 2.35. In addition, grid extruding technique with y+ control could reduce total grid requirement while maintaining acceptable prediction accuracy.Article History: Received April 15th 2018; Received in revised form June 16th 2018; Accepted September 17th 2018; Available onlineHow to Cite This Article: Chaiyanupong,J and Chitsomboon, T. (2018) Effects of Turbulence Models and Grid Densities on Computational Accuracy of Flows Over a Vertical Axis Wind Turbine. Int. Journal of Renewable Energy Development, 7(3), 213-222.http://dx.doi.org/10.14710/ijred.7.3.213-222

k–ω SST (shear stress transport) turbulence model calibration: A case study on a small scale horizontal axis wind turbine

Energy ◽  
2014 ◽  
Vol 65 ◽  
pp. 412-418 ◽  
Author(s):  
P.A. Costa Rocha ◽  
H.H. Barbosa Rocha ◽  
F.O. Moura Carneiro ◽  
M.E. Vieira da Silva ◽  
A. Valente Bueno
Keyword(s):  
Shear Stress ◽  
Wind Turbine ◽  
Turbulence Model ◽  
Model Calibration ◽  
Horizontal Axis ◽  
Small Scale ◽  
Horizontal Axis Wind Turbine ◽  
Shear Stress Transport

Numeric Investigation of Fluid Solid Interaction and Performance Analysis of Pre-Bent Wind Turbine Blade

2014 ◽  
Author(s):  
Mohammad A. Hossain ◽  
Shakerur Ridwan ◽  
Mohammad Ikthair Hossain Soiket ◽  
Sarzina Hossain
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Cfd Simulation ◽  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Wind Turbine Blade ◽  
Aerodynamic Load ◽  
Published Data ◽  
Skin Thickness ◽  
Numeric Investigation

The current work is focused on numeric investigation of aerodynamic load developed on a wind turbine blade and its effects on aeroelastic characteristics of a wind turbine blade. In order to do that proper turbulent model along with appropriate assumptions need to be determined. Geometry is modeled with actual blade data for both twist and tapper. The blade tip is not considered during the modeling. Validation is done by NREL phase VI wind turbine blade data as well as other published data. Finally the aerodynamic load obtained from the CFD simulation is transferred to perform the structural analysis. It has been found that the load distribution along the blade span is not linear. It varies with the span length and it also varies along the chord of the blade airfoil. Due to this varying load the stresses developed in the blade are dissimilar which dictates the skin thickness of the blade and the shape of the spur inside the blade. It has also been observed that the aerodynamic characteristics such as lift coefficient (CL) and pressure coefficient (CP) changes with the deflection of the blade which affects the power output of the wind turbine. Finally a pre-bent blade model has been analyzed and the effect due to the bent on the performance of the wind turbine has been observed and presented. It has been found that the pre-bent blade has better Cp distribution than deflected blade and the deviation of Cp from the actual straight blade reduce significantly in pre-bent blade compare to deflected blade. The pressure distribution along the chord of the blade airfoil at different locations have been observed and presented.

Detached-Eddy Simulation With Compressibility Corrections Applied to a Supersonic Axisymmetric Base Flow

2002 ◽  
Vol 124 (4) ◽  
pp. 911-923 ◽  
Author(s):  
James R. Forsythe ◽  
Klaus A. Hoffmann ◽  
Russell M. Cummings ◽  
Kyle D. Squires
Keyword(s):  
Shear Stress ◽  
Large Eddy Simulation ◽  
Base Flow ◽  
Navier Stokes ◽  
Future Application ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Shear Stress Transport ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Detached-eddy simulation is applied to an axisymmetric base flow at supersonic conditions. Detached-eddy simulation is a hybrid approach to modeling turbulence that combines the best features of the Reynolds-averaged Navier-Stokes and large-eddy simulation approaches. In the Reynolds-averaged mode, the model is currently based on either the Spalart-Allmaras turbulence model or Menter’s shear stress transport model; in the large-eddy simulation mode, it is based on the Smagorinski subgrid scale model. The intended application of detached-eddy simulation is the treatment of massively separated, high-Reynolds number flows over complex configurations (entire aircraft, automobiles, etc.). Because of the intented future application of the methods to complex configurations, Cobalt, an unstructured grid Navier-Stokes solver, is used. The current work incorporates compressible shear layer corrections in both the Spalart-Allmaras and shear stress transport-based detached-eddy simulation models. The effect of these corrections on both detached-eddy simulation and Reynolds-averaged Navier-Stokes models is examined, and comparisons are made to the experiments of Herrin and Dutton. Solutions are obtained on several grids—both structured and unstructured—to test the sensitivity of the models and code to grid refinement and grid type. The results show that predictions of base flows using detached-eddy simulation compare very well with available experimental data, including turbulence quantities in the wake of the axisymmetric body.

scholarly journals Investigating of Flow Field and Power Performance on a Straight-blade Vertical Axis Wind Turbine with CFD Simulation

2021 ◽  
pp. 32-42
Author(s):  
Yanfeng Zhang ◽  
Zhiping Guo ◽  
Xiaowen Song ◽  
Xinyu Zhu ◽  
Chang Cai ◽  
...  
Keyword(s):  
Flow Field ◽  
Wind Turbine ◽  
Cfd Simulation ◽  
Tangential Velocity ◽  
Vertical Axis ◽  
Blade Surface ◽  
Vertical Axis Wind Turbine ◽  
Power Performance ◽  
Freestream Velocity ◽  
Straight Blade

Forecasting the power performance and flow field of straight-blade vertical axis wind turbine (VAWT) and paying attention to the dynamic stall can enhance more adaptability to high turbulence and complicated wind conditions in cities environment. According to the blade element-momentum theory, the force of blade is analyzed in one period of revolution based on the structural characteristics of straight blade airfoil. The power performance of VAWT obtained by computational fluid dynamics (CFD) simulation is compared with experiment to estimate the accuracy about the numerical simulation results. As a result, the trend of average value of simulation Cpower is entirely consistent with the value of experiment data, and the extreme value of average Cpower of VAWT is 0.225 for tip speed ration (TSR) λ=2.19 when the freestream velocity is 8 m/s. The flow separation around the blade surface also gradually changes with the azimuth angle increasing, and the maximum pressure difference on the blade surface appears in the upstream. In the case of high leaf tip velocity, the synthetic velocity is much larger than the incoming wind velocity, and the angle of synthetic velocity increases slightly with the increase of blade tangential velocity. Thus, the angles of attack are very close in two TSRs λ=2.19 and 2.58. The research provides a computational model and theoretical basis for predicting wind turbine flow field to improve wind turbine power performance.

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