Computations of the Flow around a Wind Turbine: Grid Sensitivity Study and the Influence of Inlet Conditions

2010 ◽  
pp. 345-352 ◽  
Author(s):  
R. Z. Szasz ◽  
L. Fuchs
Keyword(s):  
Wind Turbine ◽  
Sensitivity Study ◽  
Inlet Conditions

scholarly journals Sensitivity study of diffuser angle and brim height parameters for the design of 3 kW Diffuser Augmented Wind Turbine

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Michał Lipian ◽  
Maciej Karczewski ◽  
Krzysztof Olasek
Keyword(s):  
Numerical Model ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Sensitivity Study ◽  
Flow Speed ◽  
Diffuser Angle

AbstractThe Diffuser Augmented Wind Turbine (DAWT) is an innovative mean to increase the power harvested by wind turbine. By encompassing the rotor with a diffusershaped duct it is possible to increase the flow speed through the turbine by about 40-50%. The study presents the development of a numerical model and its validation by the experiments performed in the wind tunnel of the Institute of Turbomachinery, TUL. Then, the numerical model is used for the geometry sensitivity study to optimize the shape of a diffuser. The paper presents that the DAWT technology has the potential to even double the power outcome of wind turbine when compared to a bare rotor version.

A Review of Wind Turbine Polar Data and its Effect on Fatigue Loads Simulation Accuracy

2015 ◽  
Author(s):  
Matthew Lennie ◽  
Georgios Pechlivanoglou ◽  
David Marten ◽  
Christian Navid Nayeri ◽  
Oliver Paschereit
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Leading Edge ◽  
Sensitivity Study ◽  
Wind Turbine Blades ◽  
Simulation Code ◽  
Simulation Accuracy ◽  
Inflow Turbulence ◽  
Lift And Drag

To certify a Wind Turbine the standard processes set out by the GL guidelines and the IEC61400 demand a large number of simulations in order to justify the safe operation of the machine in all reasonably probable scenarios. The result of this rather demanding process is that the simulations rely on lower fidelity methods such as the Blade Element Momentum (BEM) method. The BEM method relies on a number of simplified inputs including the coefficient of lift and drag polar data (usually referred to as polars). These polars are usually either measured experimentally, generated using tools such as XFoil or, in some cases obtained using 2D CFD. It is typical to then modify these polars in order to make them suitable for aeroelastic simulations. Some of these modifications include 360° angle of attack extrapolation methods and polar modifications to account for 3D effects. Many of these modifications can be perceived to be a black art due to the manual selection of coefficients. The polars can misrepresent reality for many reasons, for example, inflow turbulence can affect measurements obtained in wind tunnels. Furthermore, on real wind turbine blades leading edge erosion can reduce performance. Simulated polars can even vary significantly due to the choice of turbulence models. Stack these effects on top of the uncertainties caused by yaw error, pitch error and dynamic stall and one can clearly see an operating environment hostile to accurate simulations. Colloquial evidence suggests that experienced designers would account for all of these sources of errors methodically, however, this is not reflected by the certification process. A review of experimental data and literature was performed to identify some of the inaccuracies in wind turbine polars. Significant variations were found between a range of 2D polar techniques and wind tunnel measurements. A sensitivity study was conducted using the aeroelastic simulation code FAST (National Renewable Energy Laboratory) with lift and drag polars sourced using different methods. The results were post-processed to give comparisons the rotor blade fatigue damage; variations in accumulated damages reached levels of 164%. This variation is not disastrous but is certainly enough to motivate a new approach for certifying the aerodynamic performance of wind turbines. Such an approach would simply see the source of polar data and all post-processing steps documented and included in the checks performed by certification bodies.

Flow Simulation Around a Rim-Driven Wind Turbine and in Its Wake

2013 ◽  
Author(s):  
Bryan E. Kaiser ◽  
Svetlana V. Poroseva ◽  
Michael A. Snider ◽  
Rob O. Hovsapian ◽  
Erick Johnson
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Flow Simulation ◽  
Wind Farms ◽  
Sensitivity Study ◽  
Onshore Wind ◽  
Flow Simulations ◽  
Turbine Design ◽  
The Impact

A relatively high free stream wind velocity is required for conventional horizontal axis wind turbines (HAWTs) to generate power. This requirement significantly limits the area of land for viable onshore wind farm locations. To expand a potential for wind power generation and an area suitable for onshore wind farms, new wind turbine designs capable of wind energy harvesting at low wind speeds are currently in development. The aerodynamic characteristics of such wind turbines are notably different from industrial standards. The optimal wind farm layout for such turbines is also unknown. Accurate and reliable simulations of a flow around and behind a new wind turbine design should be conducted prior constructing a wind farm to determine optimal spacing of turbines on the farm. However, computations are expensive even for a flow around a single turbine. The goal of the current study is to determine a set of simulation parameters that allows one to conduct accurate and reliable simulations at a reasonable cost of computations. For this purpose, a sensitivity study on how the parameters variation influences the results of simulations is conducted. Specifically, the impact of a grid refinement, grid stretching, grid cell shape, and a choice of a turbulent model on the results of simulation of a flow around a mid-sized Rim Driven Wind Turbine (U.S. Patent 7399162) and in its near wake is analyzed. This wind turbine design was developed by Keuka Energy LLC. Since industry relies on commercial software for conducting flow simulations, STAR-CCM+ software [1] was used in our study. A choice of a turbulence model was made based on the results from our previous sensitivity study of flow simulations over a rotating disk [2].

A Comparative Cost Analysis of Floating Wind Turbine Platforms

2013 ◽  
Author(s):  
Daniel A. Dwyer ◽  
Justin C. Emmerik
Keyword(s):  
Wind Turbine ◽  
Energy Production ◽  
Sensitivity Study ◽  
Operating Parameters ◽  
Floating Wind Turbine ◽  
Cost Of Energy ◽  
Wide Range ◽  
Anchoring System ◽  
Steel Weight ◽  
Cost Factors

This thesis presents a cost-of-energy (COE) analysis comparing three types of floating wind turbine platforms—spar-buoy, semi-submersible, and tension-leg platform (TLP)— based on existing commercial designs. The analysis develops the COE of a 500-MW reference wind plant at a reference offshore location using a merit-based criterion that integrates both lifecycle cost and turbine energy production. A sensitivity study examines how fluctuations in site-dependent operating parameters and fabrication cost factors affect results. The analysis demonstrates that while the COE of a floating wind plant can vary across a wide range ($0.10 to $0.22/kWh), the relative COE performance of the three platforms does not change. The TLP consistently enables the lowest COE across a range of operating parameters as a result of its comparatively low steel weight and less expensive mooring and anchoring system. The percent differences between the COE enabled by the TLP and that of the spar-buoy and semi-submersible are 4% and 19%, respectively, at the baseline reference site.

A Sensitivity Study of Gas Turbine Exhaust Diffuser-Collector Performance at Various Inlet Swirl Angles and Strut Stagger Angles

2017 ◽  
Author(s):  
Michal P. Siorek ◽  
Stephen Guillot ◽  
Song Xue ◽  
Wing F. Ng
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Flow Behavior ◽  
Exhaust System ◽  
Sensitivity Study ◽  
Inlet Swirl ◽  
Inlet Conditions ◽  
Gas Turbine Exhaust ◽  
The Impact ◽  
Turbine Exhaust

This paper describes studies completed using a quarter-scaled rig to assess the impact of turbine exit swirl angle and strut stagger on a turbine exhaust system consisting of an integral diffuser-collector. Advanced testing methods were applied to ascertain exhaust performance for a range of inlet conditions aerodynamically matched to flow exiting an industrial gas turbine. Flow visualization techniques along with complementary Computational Fluid Dynamics (CFD) predictions were used to study flow behavior along the diffuser endwalls. Complimentary CFD analysis was also completed with the aim to ascertain the performance prediction capability of modern day analytical tools for design phase and off-design analysis. The K-Epsilon model adequately captured the relevant flow features within both the diffuser and collector, and the model accurately predicted the recovery at design conditions. At off-design conditions, the recovery predictions were found to be pessimistic. The integral diffuser-collector exhaust accommodated a significant amount of inlet swirl without a degradation in performance, so long as the inlet flow direction did not significantly deviate from the strut stagger angle. Strut incidence at the hub was directly correlated with reduction in overall performance, whereas the diffuser-collector performance was not significantly impacted by strut incidence at the shroud.

Modeling and Analysis of a 5 MW Semi-Submersible Wind Turbine Combined With Three Flap-Type Wave Energy Converters

2014 ◽  
Author(s):  
Chenyu Luan ◽  
Constantine Michailides ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wave Energy ◽  
Sensitivity Study ◽  
Total Power ◽  
Rotational Axis ◽  
Horizontal Axis Wind Turbine ◽  
Type Wave ◽  
Wave Energy Converters ◽  
Energy Converters

Semi-submersible floating structures might be an attractive system to support wind turbines and wave energy converters (WECs) in areas with abundant wind and wave energy resources. The combination of wind turbines and WECs may increase the total power production and reduce the cost of the power. A concept of a semi-submersible with a 5 MW horizontal axis wind turbine combined with three flap-type WECs is presented in this paper. The concept is named as Semi-submersible Flap Combination (SFC). The WECs of the SFC are inspired by an optimized bottom-fixed rotating flap-type wave energy absorber. Each WEC of SFC includes an elliptical cylinder, two supporting arms, a rotational axis and a power take off (PTO) system. A time domain numerical modeling method for the SFC is presented. The numerical model is using the state-of-the-art code Simo/Riflex/Aerodyn. Linear rotational damping is introduced to model the effects of the PTO system. The choice of a PTO damping coefficient and of the mass of the elliptical cylinders has a significant effect on the power generated by the WECs. Such effects have been addressed and discussed in the paper through a sensitivity study.

A Sensitivity Study of Gas Turbine Exhaust Diffuser-Collector Performance at Various Inlet Swirl Angles and Strut Stagger Angles

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Michal P. Siorek ◽  
Stephen Guillot ◽  
Song Xue ◽  
Wing F. Ng
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Flow Behavior ◽  
Exhaust System ◽  
Sensitivity Study ◽  
Inlet Swirl ◽  
Inlet Conditions ◽  
Gas Turbine Exhaust ◽  
The Impact ◽  
Turbine Exhaust

This paper describes studies completed using a quarter-scaled rig to assess the impact of turbine exit swirl angle and strut stagger on a turbine exhaust system consisting of an integral diffuser-collector. Advanced testing methods were applied to ascertain exhaust performance for a range of inlet conditions aerodynamically matched to flow exiting an industrial gas turbine. Flow visualization techniques along with complementary computational fluid dynamics (CFD) predictions were used to study flow behavior along the diffuser end walls. Complimentary CFD analysis was also completed with the aim to ascertain the performance prediction capability of modern day analytical tools for design phase and off-design analysis. The K-Epsilon model adequately captured the relevant flow features within both the diffuser and collector, and the model accurately predicted the recovery at design conditions. At off-design conditions, the recovery predictions were found to be pessimistic. The integral diffuser-collector exhaust accommodated a significant amount of inlet swirl without degradation in performance, so long as the inlet flow direction did not significantly deviate from the strut stagger angle. Strut incidence at the hub was directly correlated with reduction in overall performance, whereas the diffuser-collector performance was not significantly impacted by strut incidence at the shroud.

Performance Specifications for Real-Time Hybrid Testing of 1:50-Scale Floating Wind Turbine Models

2014 ◽  
Author(s):  
Matthew Hall ◽  
Javier Moreno ◽  
Krish Thiagarajan
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Sensitivity Study ◽  
Scale Model ◽  
Testing System ◽  
Floating Platform ◽  
Hybrid Testing ◽  
Actuation Mechanism ◽  
Floating Wind Turbine ◽  
Performance Specifications

This paper presents performance requirements for a real-time hybrid testing system to be suitable for scale-model floating wind turbine experiments. In the wave basin, real-time hybrid testing could be used to replace the model wind turbine with an actuation mechanism, driven by a wind turbine simulation running in parallel with, and reacting to, the experiment. The actuation mechanism, attached to the floating platform, would provide the full range of forces normally provided by the model wind turbine. This arrangement could resolve scaling incompatibilities that currently challenge scale-model floating wind turbine experiments. In this paper, published experimental results and a collection of full-scale simulations are used to determine what performance specifications such a system would need to meet. First, an analysis of full-scale numerical simulations and published 1:50-scale experimental results is presented. This analysis indicates the required operating envelope of the actuation system in terms of displacements, velocities, accelerations, and forces. Next, a sensitivity study using a customization of the floating wind turbine simulator FAST is described. Errors in the coupling between the wind turbine and the floating platform are used to represent the various inaccuracies and delays that could be introduced by a real-time hybrid testing system. Results of this sensitivity study indicate the requirements — in terms of motion-tracking accuracy, force actuation accuracy, and system latency — for maintaining an acceptable level of accuracy in 1:50-scale floating wind turbine experiments using real-time hybrid testing.

scholarly journals Computational fluid dynamic (CFD) of vertical-axis wind turbine: mesh and time-step sensitivity study

2019 ◽  
Vol 13 (3) ◽  
pp. 5604-5624
Author(s):  
S. Ashwindran ◽  
A. A. Azizuddin ◽  
A. N. Oumer
Keyword(s):  
Wind Turbine ◽  
Numerical Study ◽  
Computational Cost ◽  
Vertical Axis ◽  
Sensitivity Study ◽  
Dynamic Mode ◽  
Vertical Axis Wind Turbine ◽  
Time Step ◽  
Sliding Mesh ◽  
Mesh Resolution

This paper presents mesh and time-step dependence study of newly designed drag type vertical axis wind turbine. Ansys FLUENT a commercially available CFD solver was used to perform CFD numerical study on the drag type wind turbine. In computational analysis, 2D models was simulated under unsteady flow fields using SST k-ω to achieve stabilized numerical convergence. The model was analyzed at static and dynamic mode, where sliding mesh technique was used to analyze the turbine in dynamic mode. Three main parameters were taken under careful consideration: mesh resolution, turbulence model and time-step. Aerodynamic force was used in mesh sensitivity study for both static and sliding mesh. A small discrepancy in results of 2D sliding mesh result at different time-step and mesh resolution was observed. The generated results showed good agreement between fine and medium mesh with small difference in the initial initialization. In time-step dependency study for static mesh, dt=0.0002 time-step size was chosen for economical computational cost.

scholarly journals AD/RANS Simulations of Wind Turbine Wake Flow Employing the RSM Turbulence Model: Impact of Isotropic and Anisotropic Inflow Conditions

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4026 ◽  
Author(s):  
Tian ◽  
Song ◽  
Zhao ◽  
Shen ◽  
Wang
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Isotropic Turbulence ◽  
Sensitivity Study ◽  
Wake Flow ◽  
Wake Region ◽  
Anisotropic Turbulence ◽  
Wide Range ◽  
Turbine Wake ◽  
Wind Turbine Wake

The Reynolds-averaged Navier–Stokes (RANS)-based generalized actuator disc method along with the Reynolds stress model (AD/RANS_RSM) is assessed for wind turbine wake simulation. The evaluation is based on validations with four sets of experiments for four horizontal-axis wind turbines with different geometrical characteristics operating in a wide range of wind conditions. Additionally, sensitivity studies on inflow profiles (representing isotropic and anisotropic turbulence) for predicting wake effects are carried out. The focus is on the prediction of the evolution of wake flow in terms of wind velocity and turbulence intensity. Comparisons between the computational results and the measurements demonstrate that in the near and transition wake region with strong anisotropic turbulence, the AD/RANS_RSM methodology exhibits a reasonably good match with all the experimental data sets; however, in the far wake region that is characterized by isotropic turbulence, the AD/RANS_RSM predicts the wake velocity quite accurately but appears to over-estimate the wake turbulence level. While the introduction of the overall turbulence intensity is found to give an improved agreement with the experiments. The performed sensitivity study proves that the anisotropic inflow condition is recommended as the profile of choice to represent the incoming wind flow.

Sign in / Sign up

Export Citation Format

Share Document