38 results on '"Zhong, Shen"'
Search Results
2. Development of a streamline wake model for wind farm performance predictions
- Author
-
Ju Feng, Yun Xu, Mikkel Friis-Møller, Wen Zhong Shen, Mengying Xu, and Matias Sessarego
- Subjects
History ,Computer science ,Wake ,Computer Science Applications ,Education ,Marine engineering - Abstract
In the present paper a new streamline model for wake development based on a streamline topology is applied and compared with different approaches for modeling the wind turbine wakes. The contribution of the present work is the comparison of the streamline-and straight-wake models as well as the different wake models, e.g., Jensen and Gaussian. The models have been applied to two wind farm cases. The results from the first case are compared against SCADA measurements and computational fluid dynamics simulations (CFD). The CFD simulations are performed using Reynolds-Averaged Navier Stokes (RANS) together with the actuator disc (AD) approach. The mean percent difference in power using the different wake models ranged between 19-20%. Mean percent difference in power for the AD-RANS was approximately 20%. For the second wind farm case only wake models are compared and approximately ±1% difference exists between them. The present work shows that the streamline topology of the wind turbine wake flow as well as the wake models have an effect on the performance prediction of wind farms.
- Published
- 2020
3. Co-optimization of the shape, orientation and layout of offshore wind farms
- Author
-
Wen Zhong Shen and Ju Feng
- Subjects
History ,Offshore wind power ,Environmental science ,Orientation (graph theory) ,Computer Science Applications ,Education ,Marine engineering - Abstract
Previous studies on wind farm design optimization usually assume that the wind farm boundary is fixed. However, due to the uneven distribution of energy for different wind directions, the wind farm boundary, which determines the possible shape and orientation of the wind farm, can have large influences on the wind farm’s energy production. Towards an overall design optimization, the shape and orientation of wind farm should also be considered as part of the design variables. To tackle this problem, we formulate a co-optimization problem of the wind farm’s shape, orientation and layout to maximize AEP under several realistic constraints. As an initial effort, we limit the wind farm boundary to parallelogram shapes. A two-stage optimization method is then proposed to solve the co-optimization problem. The case study on the Horns Rev 1 offshore wind farm demonstrates the importance of choosing proper shape and orientation and the effectiveness of the proposed optimization method.
- Published
- 2020
4. Noise Propagation Calculations of a Wind Turbine in Complex Terrain
- Author
-
Matias Sessarego and Wen Zhong Shen
- Subjects
History ,Environmental science ,Terrain ,Turbine ,Computer Science Applications ,Education ,Marine engineering ,Noise propagation - Abstract
This paper describes numerical noise propagation calculations of a single wind turbine in complex terrain near a town in Central Denmark. The purpose of the work is to estimate the noise level at increasing distances from a single wind turbine and investigate the effect of complex terrain. Results indicate that time varying numerical noise propagation predictions of wind turbines in complex terrain can be achieved by using computational fluid dynamics via large-eddy simulation (LES) and the Technical University of Denmark’s noise propagation tool based on the parabolic equation. The wind turbine is modeled using the actuator line approach. The results from this project will have significant social, environmental, and economic impact, since accurate predictions of wind turbine noise propagation can be used to develop noise mitigation strategies to increase the public acceptance of wind energy.
- Published
- 2020
5. Evaluation of different methods of determining the angle of attack on wind turbine blades under yawed inflow conditions
- Author
-
Eva Jost, Daniel Micallef, H. Rahimi, Wen Zhong Shen, K. Vimalakanthan, C.J. Simao Ferreira, J.G. Schepers, and L. Klein
- Subjects
History ,Turbine blade ,Energy Efficiency ,020209 energy ,Energy / Geological Survey Netherlands ,02 engineering and technology ,Inflow ,Turbines -- Aerodynamics ,Computational fluid dynamics ,01 natural sciences ,7. Clean energy ,010305 fluids & plasmas ,Education ,law.invention ,Aerodynamics ,Horizontal axis wind turbines -- Blades ,law ,Angle of attack (Aerodynamics) ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,QC ,Mathematics ,Energy ,Angle of attack ,business.industry ,Rotor (electric) ,Wind turbines -- Aerodynamics ,Computer Science Applications ,Aerodynamic force ,Line (geometry) ,business ,Marine engineering - Abstract
As part of the AVATAR and Mexnext projects, this study compares several methods used to derive lifting line variables from CFD simulations of the MEXICO rotor in yawed inflow. The results from six partners within the AVATAR/Mexnext consortium using five different methods of extraction were compared. Overall comparison of the induced velocities at the mid and tip parts of blade shows fairly good agreement between the tested methods, where the derived angle of attack differs within 1°, within the linear range this accounts to ˂ 10% uncertainty on the aerodynamic forces. The presented comparison shows inadequate agreement between the methods for application towards the root., peer-reviewed
- Published
- 2018
6. An integrated numerical method for wind turbine flow simulation, sound generation and propagation
- Author
-
Jun Zhu, Wei, primary, Cao, Jiufa, additional, Barlas, Emre, additional, Zhong Shen, Wen, additional, Zhang, Lei, additional, Sun, Zhenye, additional, Yang, Hua, additional, and Xu, Haoran, additional
- Published
- 2018
- Full Text
- View/download PDF
7. An integrated numerical method for wind turbine flow simulation, sound generation and propagation
- Author
-
Emre Barlas, Wen Zhong Shen, Zhenye Sun, Cao Jiufa, Wei Jun Zhu, Yang Hua, Haoran Xu, and Lei Zhang
- Subjects
History ,business.industry ,Numerical analysis ,Thrust ,Aerodynamics ,Computational fluid dynamics ,Turbine ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Noise ,Computer Science::Systems and Control ,Computer Science::Computational Engineering, Finance, and Science ,Frequency domain ,Physics::Space Physics ,Environmental science ,business ,Actuator ,Physics::Atmospheric and Oceanic Physics ,Marine engineering - Abstract
The scope of the paper is to present an efficient numerical method that predicts: (a) wind turbine aerodynamic loads and power; (b) wind turbine noise source; (c) long distance wind turbine noise source propagation. The numerical methods involved in this study are a combination of Computational Fluid Dynamics (CFD) and wind turbine aeroacoustic methods. The results from the CFD simulation provide necessary information of wind turbine power and thrust etc. The 2D Actuator Disc (AD) theory is applied for such a purpose. The computational efficiency becomes very high while using a steady 2D CFD approach. The flow geometry at each blade element is required for wind turbine noise source calculations. The predicted wind turbine noise source is the starting field for long distance noise propagation model which is based on solving the Parabolic Equations (PE) in the frequency domain. Results showed that the integrated wind turbine flow-acoustic prediction method is capable of calculating wind turbine aerodynamic, aerodynamic noise source and long range sound propagation.
- Published
- 2018
8. Analysis of winglets and sweep on wind turbine blades using a lifting line vortex particle method in complex inflow conditions
- Author
-
Wen Zhong Shen, Matias Sessarego, and Néstor Ramos-García
- Subjects
History ,Blade (geometry) ,Turbine blade ,Turbulence ,020209 energy ,02 engineering and technology ,Aerodynamics ,Inflow ,01 natural sciences ,Turbine ,010305 fluids & plasmas ,Computer Science Applications ,Education ,Vortex ,law.invention ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Wingtip device ,Geology ,Marine engineering - Abstract
An in-house aero-elastic vortex code, called MIRAS, is used to investigate the aerodynamic performance of winglets and sweep on horizontal-axis wind turbine (HAWT) blades in simple and complex inflow conditions. Previous studies using vortex codes applied to study winglets and blade sweep on HAWTs have typically not considered complex inflow conditions such as turbulent wind and shear. The reasons may include the absence of modeling capability, the computational cost associated with simulating long turbulent time series, and/or the computational cost associated with resolving the blade tips to a very fine level. A preliminary study is performed here, where the MIRAS code is applied on the NREL 5MW wind turbine with an arbitrary winglet shape and blade sweep. Results indicate that wind turbine blades with sweep or winglets might be better in performance compared to their straight blade counterparts.
- Published
- 2018
9. Numerical Fluid-Structure Interaction Study on the NREL 5MW HAWT
- Author
-
Amr M. Halawa, Shigeo Yoshida, Wen Zhong Shen, and Matias Sessarego
- Subjects
History ,020209 energy ,0103 physical sciences ,Fluid–structure interaction ,0202 electrical engineering, electronic engineering, information engineering ,02 engineering and technology ,Mechanics ,01 natural sciences ,Geology ,010305 fluids & plasmas ,Computer Science Applications ,Education - Published
- 2018
10. Aero-structural optimization of wind turbine blades using a reduced set of design load cases including turbulence
- Author
-
Wen Zhong Shen and Matias Sessarego
- Subjects
Set (abstract data type) ,History ,Turbine blade ,law ,Computer science ,Turbulence ,Design load ,Computer Science Applications ,Education ,law.invention ,Marine engineering - Published
- 2018
11. Large Wind Turbine Rotor Design using an Aero-Elastic / Free-Wake Panel Coupling Code
- Author
-
Sessarego, Matias, primary, Ramos-García, Néstor, additional, Zhong Shen, Wen, additional, and Sørensen, Jens Nørkær, additional
- Published
- 2016
- Full Text
- View/download PDF
12. LES tests on airfoil trailing edge serration
- Author
-
Wen Zhong Shen and Wei Jun Zhu
- Subjects
Airfoil ,History ,Engineering ,Angle of attack ,business.industry ,020209 energy ,Acoustics ,Reynolds number ,02 engineering and technology ,Starting vortex ,01 natural sciences ,010305 fluids & plasmas ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Noise ,symbols.namesake ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,symbols ,Trailing edge ,business ,Wind tunnel ,Large eddy simulation - Abstract
In the present study, a large number of acoustic simulations are carried out for a low noise airfoil with different Trailing Edge Serrations (TES). The Ffowcs Williams-Hawkings (FWH) acoustic analogy is used for noise prediction at trailing edge. The acoustic solver is running on the platform of our in-house incompressible flow solver EllipSys3D. The flow solution is first obtained from the Large Eddy Simulation (LES), the acoustic part is then carried out based on the instantaneous hydrodynamic pressure and velocity field. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FWH approach. For all the simulations, the chord based Reynolds number is around 1.5x106. In the test matrix, the effects from angle of attack, the TE flap angle, the length/width of the TES are investigated. Even though the airfoil under investigation is already optimized for low noise emission, most numerical simulations and wind tunnel experiments show that the noise level is further decreased by adding the TES device.
- Published
- 2016
13. Extension of Goldstein's circulation function for optimal rotors with hub
- Author
-
Valery Okulov, Wen Zhong Shen, and Jens Nørkær Sørensen
- Subjects
Physics::Physics and Society ,History ,Engineering ,Blade (geometry) ,02 engineering and technology ,01 natural sciences ,010305 fluids & plasmas ,Education ,law.invention ,Physics::Fluid Dynamics ,0203 mechanical engineering ,law ,0103 physical sciences ,Cylinder ,Slipstream ,020301 aerospace & aeronautics ,business.industry ,Rotor (electric) ,Aerodynamics ,Mechanics ,Computer Science Applications ,Vortex ,Circulation (fluid dynamics) ,Classical mechanics ,Flow (mathematics) ,business - Abstract
The aerodynamic interaction or interference between rotor blades and hub body is usually very complicated, but some useful simplifications can be made by considering the hub with an infinite cylinder. Various attempts to find the optimum distribution of circulation by the lifting vortex lines method have been previously proposed to describe the blade interaction with the hub modeled by the infinite cylinder. In this case, the ideal distribution of bound circulation on the rotor blades is such that the shed vortex system in the hub-area is a set of helicoidal vortex sheets moving uniformly as if rigid, exactly as in the case where there is no influence of the streamtube deformations by the central hub-body. In the present investigation, we consider a more specific problem of the rotor-hub interaction where the initial flow streamtubes and the rotor slipstream submitted strong deformations at the nose-area of the semi-infinite hub.
- Published
- 2016
14. Multi-Objective Random Search Algorithm for Simultaneously Optimizing Wind Farm Layout and Number of Turbines
- Author
-
Wen Zhong Shen, Chang Xu, and Ju Feng
- Subjects
History ,Mathematical optimization ,Engineering ,business.industry ,020209 energy ,Pareto principle ,Boundary (topology) ,02 engineering and technology ,Wake ,Minimum spanning tree ,021001 nanoscience & nanotechnology ,Turbine ,Computer Science Applications ,Education ,Power (physics) ,Genetic algorithm ,0202 electrical engineering, electronic engineering, information engineering ,Range (statistics) ,0210 nano-technology ,business - Abstract
A new algorithm for multi-objective wind farm layout optimization is presented. It formulates the wind turbine locations as continuous variables and is capable of optimizing the number of turbines and their locations in the wind farm simultaneously. Two objectives are considered. One is to maximize the total power production, which is calculated by considering the wake effects using the Jensen wake model combined with the local wind distribution. The other is to minimize the total electrical cable length. This length is assumed to be the total length of the minimal spanning tree that connects all turbines and is calculated by using Prim's algorithm. Constraints on wind farm boundary and wind turbine proximity are also considered. An ideal test case shows the proposed algorithm largely outperforms a famous multi-objective genetic algorithm (NSGA-II). In the real test case based on the Horn Rev 1 wind farm, the algorithm also obtains useful Pareto frontiers and provides a wide range of Pareto optimal layouts with different numbers of turbines for a real-life wind farm developer.
- Published
- 2016
15. Wind Turbine Noise Propagation Modelling: An Unsteady Approach
- Author
-
Emre Barlas, Wen Zhong Shen, Søren Juhl Andersen, and Wei Jun Zhu
- Subjects
History ,Engineering ,Turbine blade ,business.industry ,Turbulence ,Acoustics ,Flow (psychology) ,Turbine ,Computer Science Applications ,Education ,law.invention ,Physics::Fluid Dynamics ,Dependent source ,law ,Wind shear ,Sound pressure ,business ,Large eddy simulation - Abstract
Wind turbine sound generation and propagation phenomena are inherently time dependent, hence tools that incorporate the dynamic nature of these two issues are needed for accurate modelling. In this paper, we investigate the sound propagation from a wind turbine by considering the effects of unsteady flow around it and time dependent source characteristics. For the acoustics modelling we employ the Parabolic Equation (PE) method while Large Eddy Simulation (LES) as well as synthetically generated turbulence fields are used to generate the medium flow upon which sound propagates. Unsteady acoustic simulations are carried out for three incoming wind shear and various turbulence intensities, using a moving source approach to mimic the rotating turbine blades. The focus of the present paper is to study the near and far field amplitude modulation characteristics and time evolution of Sound Pressure Level (SPL).
- Published
- 2016
16. Aeroacoustic calculations of a full scale Nordtank 500kW wind turbine
- Author
-
Harald Debertshäuser, Wen Zhong Shen, and Wei Jun Zhu
- Subjects
Body force ,History ,Engineering ,business.industry ,Acoustics ,Mathematics::Analysis of PDEs ,Full scale ,Inflow ,Turbine ,Wind speed ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Incompressible flow ,Wind shear ,business ,Actuator - Abstract
The Actuator Line/ Navier-stokes technique is used to compute the incompressible flow around a full scale Nordtank 500kW wind turbine under different complex flow conditions such as atmospheric turbulence and wind shear. The flow field is used as an input to aeroacoustic calculations based on; a semi empirical noise model; and a Navier-Stokes based computational aeroacoustic code (CAA). The Navier-Stokes based approach is solving acoustic perturbation equations and is capable of taking propagation and ground effects into account, but is limited to low frequency noise due to feasible mesh resolution, and due to the simplification in the actuator line method using body forces to represent the blade. Noise levels are compared to field measurements of a Nordtank 500kW wind turbine at different wind speeds and inflow profiles.
- Published
- 2016
17. The Collection of The Main Issues for Wind Farm Optimisation in Complex Terrain
- Author
-
Wen Zhong Shen, Chen Dandan, Pan Hangping, Han Xingxing, and Chang Xu
- Subjects
History ,Mathematical optimization ,Engineering ,021103 operations research ,Optimization problem ,Series (mathematics) ,Operations research ,business.industry ,020209 energy ,0211 other engineering and technologies ,Terrain ,02 engineering and technology ,Minimum spanning tree ,Turbine ,Computer Science Applications ,Education ,Genetic algorithm ,0202 electrical engineering, electronic engineering, information engineering ,business ,Dijkstra's algorithm ,Electronic circuit - Abstract
The paper aims at establishing the collection of the main issues for wind farm optimisation in complex terrain. To make wind farm cost effective, this paper briefly analyses the main factors influencing wind farm design in complex terrain and sets up a series of mathematical model that includes micro-siting, collector circuits, access roads design for optimization problems. The paper relies on the existing one year wind data in the wind farm area and uses genetic algorithm to optimize the micro-siting problem. After optimization of the turbine layout, single-source shortest path algorithm and minimum spanning tree algorithm are used to optimize collector circuits and access roads. The obtained results can provide important guidance for wind farms construction.
- Published
- 2016
18. Noise model for serrated trailing edges compared to wind tunnel measurements
- Author
-
Andreas Fischer, Franck Bertagnolio, Jesper Madsen, and Wen Zhong Shen
- Subjects
Airfoil ,History ,Engineering ,business.industry ,Acoustics ,Structural engineering ,Computational fluid dynamics ,01 natural sciences ,010305 fluids & plasmas ,Computer Science Applications ,Education ,Serration ,Noise ,0103 physical sciences ,Trailing edge ,business ,Sound pressure ,Reynolds-averaged Navier–Stokes equations ,010301 acoustics ,Wind tunnel - Abstract
A new CFD RANS based method to predict the far field sound pressure emitted from an aerofoil with serrated trailing edge has been developed. The model was validated by comparison to measurements conducted in the Virginia Tech Stability Wind Tunnel. The model predicted 3 dB lower sound pressure levels, but the tendencies for the different configurations were predicted correctly. Therefore the model can be used to optimise the serration geometry. A disadvantage of the new model is that the computational costs are significantly higher than for the Amiet model for a straight trailing edge. However, it is by decades faster than LES methods.
- Published
- 2016
19. A quasi-3D viscous-inviscid interaction code:Q3UIC
- Author
-
Wen Zhong Shen, Jens Nørkær Sørensen, and Néstor Ramos García
- Subjects
Airfoil ,Physics ,History ,Mechanics ,Aerodynamics ,Rotation ,Turbine ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Momentum ,Boundary layer ,Classical mechanics ,Inviscid flow ,Parametric statistics - Abstract
A computational model for predicting the aerodynamic behavior of wind turbine airfoils under rotation and subjected to steady and unsteady motions developed in [1] is presented herein. The model is based on a viscous-inviscid interaction technique using strong coupling between the viscous and inviscid parts. The rotational effects generated by centrifugal and Coriolis forces are introduced in Q3UIC via the streamwise and spanwise integral boundary layer momentum equations. A special inviscid version of the code has been developed to cope with massive separation. To check the ability of the code wind turbine airfoils in steady and unsteady conditions for a large range of angles of attack are considered here. Further, the new quasi-3D code Q3UIC is used to perform a parametric study of a wind turbine airfoil under rotation confined to its boundary layer.
- Published
- 2014
20. Validation of the CQU-DTU-LN1 series of airfoils
- Author
-
Jesper Madsen, Wei Jun Zhu, Jin Chen, Wen Zhong Shen, Andreas Fischer, Néstor Ramos García, and Jiangtao Cheng
- Subjects
Airfoil ,History ,XFOIL ,Engineering ,Series (mathematics) ,business.industry ,Computation ,Acoustics ,Aerodynamics ,Structural engineering ,Computer Science Applications ,Education ,NACA airfoil ,Noise ,business ,Wind tunnel - Abstract
The CQU-DTU-LN1 series of airfoils were designed with an objective of high lift and low noise emission. In the design process, the aerodynamic performance is obtained using XFOIL while noise emission is obtained with the BPM model. In this paper we present some validations of the designed CQU-DTU-LN118 airfoil by using wind tunnel measurements in the acoustic wind tunnel located at Virginia Tech and numerical computations with the inhouse Q3uic and EllipSys 2D/3D codes. To show the superiority of the new airfoils, comparisons with a NACA64618 airfoil are made. For the aerodynamic features, the designed Cl and Cl/Cd agrees well with the experiment and are in general higher than those of the NACA airfoil. For the acoustic features, the noise emission of the LN118 airfoil is compared with the acoustic measurements and that of the NACA airfoil. Comparisons show that the BPM model can predict correctly the noise changes.
- Published
- 2014
21. Study of tip loss corrections using CFD rotor computations
- Author
-
Wei Jun Zhu, Jens Nørkær Sørensen, and Wen Zhong Shen
- Subjects
Airfoil ,History ,Engineering ,Wind power ,business.industry ,Angle of attack ,Rotor (electric) ,Computation ,Structural engineering ,Mechanics ,Computational fluid dynamics ,Turbine ,Computer Science Applications ,Education ,Momentum theory ,law.invention ,law ,business - Abstract
Tip loss correction is known to play an important role for engineering prediction of wind turbine performance. There are two different types of tip loss corrections: tip corrections on momentum theory and tip corrections on airfoil data. In this paper, we study the latter using detailed CFD computations for wind turbines with sharp tip. Using the technique of determination of angle of attack and the CFD results for a NordTank 500 kW rotor, airfoil data are extracted and a new tip loss function on airfoil data is derived. To validate, BEM computations with the new tip loss function are carried out and compared with CFD results for the NordTank 500 kW turbine and the NREL 5 MW turbine. Comparisons show that BEM with the new tip loss function can predict correctly the loading near the blade tip.
- Published
- 2014
22. Design of low noise wind turbine blades using Betz and Joukowski concepts
- Author
-
Wei Jun Zhu, Wen Zhong Shen, Iva Hrgovan, Jesper Madsen, and Valery Okulov
- Subjects
Airfoil ,History ,Engineering ,Turbine blade ,business.industry ,Rotor (electric) ,Noise reduction ,Acoustics ,Blade element momentum theory ,Structural engineering ,Aerodynamics ,Turbine ,Computer Science Applications ,Education ,law.invention ,law ,business ,Wind tunnel - Abstract
This paper presents the aerodynamic design of low noise wind turbine blades using Betz and Joukowski concepts. The aerodynamic model is based on Blade Element Momentum theory whereas the aeroacoustic prediction model is based on the BPM model. The investigation is started with a 3MW baseline/reference turbine rotor with a diameter of 80 m. To reduce the noise emission from the baseline rotor, the rotor is reconstructed with the low noise CQU-DTU-LN1 series of airfoils which has been tested in the acoustic wind tunnel located at Virginia Tech. Finally, 3MW low noise turbine rotors are designed using the concepts of Betz and Joukowski, and the CQU-DTU-LN1 series of airfoils. Performance analysis shows that the newly designed turbine rotors can achieve an overall noise reduction of 6 dB and 1.5 dB(A) with a similar power output as compared to the reference rotor.
- Published
- 2014
23. Numerical Investigation of Flow Control Feasibility with a Trailing Edge Flap
- Author
-
Wen Zhong Shen, Wei Jun Zhu, and Jens Nørkær Sørensen
- Subjects
Airfoil ,History ,Engineering ,Finite volume method ,business.industry ,Turbulence ,Mechanics ,Immersed boundary method ,Starting vortex ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Lift (force) ,Incompressible flow ,Control theory ,Trailing edge ,business - Abstract
This paper concerns a numerical study of employing an adaptive trailing edge flap to control the lift of an airfoil subject to unsteady inflow conditions. The periodically varying inflow is generated by two oscillating airfoils, which are located upstream of the controlled airfoil. To establish the control system, a standard PID controller is implemented in a finite volume based incompressible flow solver. An immersed boundary method is applied to treat the problem of simulating a deformable airfoil trailing edge. The flow field is solved using a 2D Reynolds averaged Navier-Stokes finite volume solver. In order to more accurately simulate wall bounded flows around the immersed boundary, a modified boundary condition is introduced in the k- ω turbulence model. As an example, turbulent flow over a NACA 64418 airfoil with a deformable trailing edge is investigated. Results from numerical simulations are convincing and may give some highlights for practical implementations of trailing edge flap to a wind turbine rotor blade
- Published
- 2014
24. Fully consistent CFD methods for incompressible flow computations
- Author
-
Niels N. Sørensen, Wen Zhong Shen, Jens Nørkær Sørensen, and Dmitry Kolmogorov
- Subjects
Airfoil ,History ,Mathematical optimization ,business.industry ,Turbulence ,Computation ,Computational fluid dynamics ,Turbine ,SIMPLEC algorithm ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,Rate of convergence ,Incompressible flow ,Applied mathematics ,business ,Mathematics - Abstract
Nowadays collocated grid based CFD methods are one of the most efficient tools for computations of the flows past wind turbines. To ensure the robustness of the methods they require special attention to the well-known problem of pressure-velocity coupling. Many commercial codes to ensure the pressure-velocity coupling on collocated grids use the so-called momentum interpolation method of Rhie and Chow [1]. As known, the method and some of its widely spread modifications result in solutions, which are dependent of time step at convergence. In this paper the magnitude of the dependence is shown to contribute about 0.5% into the total error in a typical turbulent flow computation. Nevertheless if coarse grids are used, the standard interpolation methods result in much higher non-consistent behavior. To overcome the problem, a recently developed interpolation method, which is independent of time step, is used. It is shown that in comparison to other time step independent method, the method may enhance the convergence rate of the SIMPLEC algorithm up to 25 %. The method is verified using turbulent flow computations around a NACA 64618 airfoil and the roll-up of a shear layer, which may appear in wind turbine wake.
- Published
- 2014
25. Aerodynamic Analysis of Trailing Edge Enlarged Wind Turbine Airfoils
- Author
-
Wei Jun Zhu, Haoran Xu, Wen Zhong Shen, Yang Hua, and Chao Liu
- Subjects
Airfoil ,Lift-to-drag ratio ,History ,Chord (geometry) ,Lift coefficient ,Materials science ,business.industry ,Stall (fluid mechanics) ,Structural engineering ,Mechanics ,Computer Science Applications ,Education ,Drag ,Vortex lift ,Trailing edge ,business - Abstract
The aerodynamic performance of blunt trailing edge airfoils generated from the DU- 91-W2-250, DU-97-W-300 and DU-96-W-350 airfoils by enlarging the thickness of trailing edge symmetrically from the location of maximum thickness to chord to the trailing edge were analyzed by using CFD and RFOIL methods at a chord Reynolds number of 3 × 106. The goal of this study is to analyze the aerodynamic performance of blunt trailing edge airfoils with different thicknesses of trailing edge and maximum thicknesses to chord. The steady results calculated by the fully turbulent k-ω SST, transitional k-ω SST model and RFOIL all show that with the increase of thickness of trailing edge, the linear region of lift is extended and the maximum lift also increases, the increase rate and amount of lift become limited gradually at low angles of attack, while the drag increases dramatically. For thicker airfoils with larger maximum thickness to chord length, the increment of lift is larger than that of relatively thinner airfoils when the thickness of blunt trailing edge is increased from 5% to 10% chord length. But too large lift can cause abrupt stall which is profitless for power output. The transient characteristics of blunt trailing edge airfoils are caused by blunt body vortices at low angles of attack, and by the combined effect of separation and blunt body vortices at large angles of attack. With the increase of thickness of blunt trailing edge, the vibration amplitudes of lift and drag curves increase. The transient calculations over-predict the lift at large angles of attack and drag at all angles of attack than the steady calculations which is likely to be caused by the artificial restriction of the flow in two dimensions.
- Published
- 2014
26. Wind farm layout optimization in complex terrain: A preliminary study on a Gaussian hill
- Author
-
Wen Zhong Shen and Ju Feng
- Subjects
History ,Mathematical optimization ,Engineering ,Wind power ,Optimization problem ,business.industry ,Gaussian ,Terrain ,Inflow ,Computational fluid dynamics ,Wake ,Computer Science Applications ,Education ,Random search ,symbols.namesake ,symbols ,business ,Simulation - Abstract
One of the crucial problems for wind farm (WF) development is wind farm layout optimization. It seeks to find the optimal positions of wind turbines (WTs) inside a WF, so as to maximize and/or minimize a single objective or multiple objectives, while satisfying certain constraints. Although this problem for WFs in flat terrain or offshore has been investigated in many studies, it is still a challenging problem for WFs in complex terrain. In this preliminary study, the wind flow conditions of complex terrain without WTs are first obtained from computational fluid dynamics (CFD) simulation, then an adapted Jensen wake model is developed by considering the terrain features and taking the inflow conditions as input. Using this combined method, the wake effects of WF in complex terrain are properly modelled. Besides, a random search (RS) algorithm proposed in previous study is improved by adding some adaptive mechanisms and applied to solve the layout optimization problem of a WF on a Gaussian shape hill. The layout of the WF with a certain number of WTs is optimized to maximize the total power output, which obtained steady improvements over expert guess layouts.
- Published
- 2014
27. Investigation of modified AD/RANS models for wind turbine wake predictions in large wind farm
- Author
-
Wei Jun Zhu, Jens Nørkær Sørensen, Wen Zhong Shen, Ning Zhao, and Linlin Tian
- Subjects
History ,Engineering ,Meteorology ,Turbulence ,business.industry ,Inflow ,Wake ,Wind direction ,Turbine ,Computer Science Applications ,Education ,Offshore wind power ,Wind profile power law ,business ,Reynolds-averaged Navier–Stokes equations - Abstract
Average power losses due to multiple wind turbine wakes in the large offshore wind farm is studied in this paper using properly modified k-ω SST turbulence models. The numerical simulations are carried out by the actuator disc methodology implemented in the flow solver EllipSys3D. In these simulations, the influence of different inflow conditions such as wind direction sectors are considered and discussed. Comparisons with measurements in terms of wake speed ratio and the corresponding power outputs show that the modified turbulence models had significant improvements; especially the SST-Csust model reflects the best ability in predicting the wake defect. The investigations of various inflow angles reveal that the agreement between predicted and measured data is improved for the wider sector case than the narrow case because of the wind direction uncertainty.
- Published
- 2014
28. Simulations of the Yawed MEXICO Rotor Using a Viscous-Inviscid Panel Method
- Author
-
Wen Zhong Shen, Néstor Ramos-García, and Jens Nørkær Sørensen
- Subjects
History ,Engineering ,Field (physics) ,Rotor (electric) ,business.industry ,Structural engineering ,Aerodynamics ,Mechanics ,Wake ,Computer Science Applications ,Education ,law.invention ,Physics::Fluid Dynamics ,Aerodynamic force ,Boundary layer ,Pressure measurement ,law ,Inviscid flow ,business - Abstract
In the present work the viscous-inviscid interactive model MIRAS is used to simulate flows past the MEXICO rotor in yawed conditions. The solver is based on an unsteady three-dimensional free wake panel method which uses a strong viscous-inviscid interaction technique to account for the viscous effects inside the boundary layer. Calculated wake velocities have been benchmarked against field PIV measurements, while computed blade aerodynamic characteristics are compared against the load calculated from pressure measurements at different locations along the blade span. Predicted and measured aerodynamic forces are in overall good agreement, however discrepancies appear in the root region which could be related to an underestimation of the rotational effects arising from Coriolis and centrifugal forces. The predicted wake velocities are generally in good agreement with measurements along the radial as well as the axial traverses performed during the experimental campaign.
- Published
- 2014
29. Aero-Acoustic Modelling using Large Eddy Simulation
- Author
-
Wen Zhong Shen and Jens Nørkær Sørensen
- Subjects
Physics ,Airfoil ,History ,Angle of attack ,Turbulence ,K-epsilon turbulence model ,Acoustics ,Reynolds number ,Reynolds stress equation model ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,symbols.namesake ,Flow separation ,Mach number ,symbols - Abstract
The splitting technique for aero-acoustic computations is extended to simulate three-dimensional flow and acoustic waves from airfoils. The aero-acoustic model is coupled to a sub-grid-scale turbulence model for Large-Eddy Simulations. In the first test case, the model is applied to compute laminar flow past a NACA 0015 airfoil at a Reynolds number of 800, a Mach number of 0.2 and an angle of attack of 20°. The model is then applied to compute turbulent flow past a NACA 0015 airfoil at a Reynolds number of 100 000, a Mach number of 0.2 and an angle of attack of 20°. The predicted noise spectrum is compared to experimental data.
- Published
- 2007
30. Prediction and Reduction of Noise from a 2.3 MW Wind Turbine
- Author
-
Giorgos Leloudas, Wei Jun Zhu, Jens Nørkær Sørensen, Wen Zhong Shen, and S Hjort
- Subjects
History ,Engineering ,Momentum (technical analysis) ,Wind power ,business.industry ,Acoustics ,Acoustic model ,Turbine ,Computer Science Applications ,Education ,Power (physics) ,Noise ,Noise emission ,business ,Reduction (mathematics) - Abstract
We address the issue of noise emission from a 2.3 MW SWT-2.3-93 wind turbine and compare simulations from a semi-empirical acoustic model with measurements. The noise measurements were taken at the Hovsore test site for large wind turbines. The acoustic model is based on the Blade-Element Momentum (BEM) technique and various semi-empirical acoustic relations. The comparison demonstrates a generally good agreement between predicted and measured noise levels. The acoustic model is further employed to carry out a parametrical study to optimize the performance/noise of the wind turbine by changing tip speed and pitch setting. We show that it is possible to reduce the noise level up to 2 dB(A) without sacrificing too much the power yield.
- Published
- 2007
31. Computational Aero-Acoustic Using High-order Finite-Difference Schemes
- Author
-
Wen Zhong Shen, Wei Jun Zhu, and Jens Nørkær Sørensen
- Subjects
History ,Finite volume method ,Independent equation ,Mathematical analysis ,Finite difference ,Finite difference method ,Compact finite difference ,Computer Science Applications ,Education ,Euler equations ,Physics::Fluid Dynamics ,symbols.namesake ,Pressure-correction method ,Simultaneous equations ,symbols ,Mathematics - Abstract
In this paper, a high-order technique to accurately predict flow-generated noise is introduced. The technique consists of solving the viscous incompressible flow equations and inviscid acoustic equations using a incompressible/compressible splitting technique. The incompressible flow equations are solved using the in-house flow solver EllipSys2D/3D which is a second-order finite volume code. The acoustic solution is found by solving the acoustic equations using high-order finite difference schemes. The incompressible flow equations and the acoustic equations are solved at the same time levels where the pressure and the velocities obtained from the incompressible equations form the input to the acoustic equations. To achieve low dissipation and dispersion errors, either Dispersion-Relation-Preserving (DRP) schemes or optimized compact finite difference schemes are used for spatial discretizations of the acoustic equations. The classical fourth-order Runge-Kutta time scheme is applied to the acoustic equations for time discretization.
- Published
- 2007
32. Oscillatory instability in a closed cylinder with rotating top and bottom
- Author
-
Wen Zhong Shen and Jens Nørkær Sørensen
- Subjects
History ,Finite volume method ,Rotational symmetry ,Reynolds number ,Geometry ,Aspect ratio (image) ,Instability ,Computer Science Applications ,Education ,Physics::Fluid Dynamics ,symbols.namesake ,symbols ,Cylinder ,Spectral method ,Galerkin method ,Mathematics - Abstract
A numerical investigation of oscillatory instability is presented for axisymmetric swirling flow in a closed cylinder with rotating top and bottom. The critical Reynolds number and frequency of the oscillations are evaluated as function of the ratio of angular velocities of the bottom and the top (ξ = Ωbottom/Ωtop). Earlier Linear Stability Analysis (LSA) using the Galerkin spectral method by Gelfgat et al. [Phys. Fluids, 8, 2614-2625 (1996)] revealed that the curve of the critical Reynolds number behaves like an "S" around ξ = 0.54 in the corotation branch and around ξ = −0.63 in the counter-rotation branch. Additional finite volume computations, however, did not show a clear "S" behaviour. In order to check the existence of the "S" shape, computations are performed using an axisymmetric finite volume Navier-Stokes code at aspect ratios (λ = H/R) 1.5 and 2.0. Comparisons with LSA at λ = 1.5 show that the "S" shape does exist. At an aspect ratio λ = 2, our results show that the critical Reynolds number curve has a "beak" shape in the counter-rotation region and a much wider "S" shape in the co-rotation region. This transformation of the "S" shape is caused by the change in aspect ratio from 1.5 to 2 and therefore the corresponding topological behaviour of the transition is different.
- Published
- 2007
33. Aero-structural optimization of wind turbine blades using a reduced set of design load cases including turbulence.
- Author
-
Matias Sessarego and Wen Zhong Shen
- Published
- 2018
- Full Text
- View/download PDF
34. Analysis of winglets and sweep on wind turbine blades using a lifting line vortex particle method in complex inflow conditions.
- Author
-
Matias Sessarego, Néstor Ramos-García, and Wen Zhong Shen
- Published
- 2018
- Full Text
- View/download PDF
35. An integrated numerical method for wind turbine flow simulation, sound generation and propagation.
- Author
-
Wei Jun Zhu, Jiufa Cao, Emre Barlas, Wen Zhong Shen, Lei Zhang, Zhenye Sun, Hua Yang, and Haoran Xu
- Published
- 2018
- Full Text
- View/download PDF
36. Large Wind Turbine Rotor Design using an Aero-Elastic / Free-Wake Panel Coupling Code.
- Author
-
Matias Sessarego, Néstor Ramos-García, Wen Zhong Shen, and Jens Nørkær Sørensen
- Published
- 2016
- Full Text
- View/download PDF
37. Multi-Objective Random Search Algorithm for Simultaneously Optimizing Wind Farm Layout and Number of Turbines.
- Author
-
Ju Feng, Wen Zhong Shen, and Chang Xu
- Published
- 2016
- Full Text
- View/download PDF
38. LES tests on airfoil trailing edge serration.
- Author
-
Wei Jun Zhu and Wen Zhong Shen
- Published
- 2016
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.