Transactions of Nanjing University of Aeronautics & Astronautics
Volume 33,Issue 1,2016 Table of Contents
2016, 33(1).
Abstract:
It is well known that wind turbine blades will be eroded in wind-sand environment, so it is crucial to confirm what operating condition the erosion will occur in. In this paper, the effect of sand diameter on the wind turbine airfoil erosion is studied firstly. It is found that the sands bypass the airfoil and no erosion appears on it when the sand diameter is less than 3μm, and the sands impact on the airfoil and the erosion occurs when the sand diameter is greater than 4μm. So there is a critical sand diameter between 3μm and 4μm that just causes erosion of the airfoil. In order to find out the critical value, the particle Stokes number is introduced into discussion as an important non-dimensional parameter describing two-phase flow. According to the critical sand diameter above, it can be assumed that there is a critical value of particle Stokes number between 0.0078 and 0.014 to judge whether erosion will occur on wind turbine airfoil. And then, some other factors are taken into account to validate the assumption, such as angle of attack, relative thickness of the airfoil, different series airfoil, and inflow velocity, it is confirmed to be correct
It is well known that wind turbine blades will be eroded in wind-sand environment, so it is crucial to confirm what operating condition the erosion will occur in. In this paper, the effect of sand diameter on the wind turbine airfoil erosion is studied firstly. It is found that the sands bypass the airfoil and no erosion appears on it when the sand diameter is less than 3μm, and the sands impact on the airfoil and the erosion occurs when the sand diameter is greater than 4μm. So there is a critical sand diameter between 3μm and 4μm that just causes erosion of the airfoil. In order to find out the critical value, the particle Stokes number is introduced into discussion as an important non-dimensional parameter describing two-phase flow. According to the critical sand diameter above, it can be assumed that there is a critical value of particle Stokes number between 0.0078 and 0.014 to judge whether erosion will occur on wind turbine airfoil. And then, some other factors are taken into account to validate the assumption, such as angle of attack, relative thickness of the airfoil, different series airfoil, and inflow velocity, it is confirmed to be correct
2016, 33(1).
Abstract:
A 2-blade HAWT model is simulated at various tip speed ratios to study its wake characteristics by analyzing the tip and root vortex trajectory in near-wake, and the vertical profiles of axial velocity. The results show the pitch of the tip vortices varies inversely with the tip-speed-ratio. Diametric expansion of tip vortices becomes more obvious as the tip-speed-ratio increases. Tip vortices shed from the blade in the range of 97.5%-99.7% radius of the rotor. The axial velocity profiles transform from W-shaped to V-shaped at the distance downstream of eight rotor diameters due to momentum recovery.
A 2-blade HAWT model is simulated at various tip speed ratios to study its wake characteristics by analyzing the tip and root vortex trajectory in near-wake, and the vertical profiles of axial velocity. The results show the pitch of the tip vortices varies inversely with the tip-speed-ratio. Diametric expansion of tip vortices becomes more obvious as the tip-speed-ratio increases. Tip vortices shed from the blade in the range of 97.5%-99.7% radius of the rotor. The axial velocity profiles transform from W-shaped to V-shaped at the distance downstream of eight rotor diameters due to momentum recovery.
3 Modeling methods and Test verification of the root insert contact interface for wind turbine blade
2016, 33(1).
Abstract:
Two modeling methods of the root insert for wind turbine blade are presented in this paper, which are local mesh optimization method (LMOM) and global modeling method (GMM). Based on the optimized mesh of the local model for the metal contact interface, LMOM is proposed to analyze the load path and stress distribution characteristics. While GMM is used to calculate and analyze the stress distribution characteristics of the resin which is established between the bushing and composite layers of root insert. To validate the GMM, the tension test is carried out. The result successfully shows the shear strain expresses a similar strain distribution tendency with the GMM’s results.
Two modeling methods of the root insert for wind turbine blade are presented in this paper, which are local mesh optimization method (LMOM) and global modeling method (GMM). Based on the optimized mesh of the local model for the metal contact interface, LMOM is proposed to analyze the load path and stress distribution characteristics. While GMM is used to calculate and analyze the stress distribution characteristics of the resin which is established between the bushing and composite layers of root insert. To validate the GMM, the tension test is carried out. The result successfully shows the shear strain expresses a similar strain distribution tendency with the GMM’s results.
2016, 33(1).
Abstract:
A hybrid method is presented to numerically investigate the wind turbine aerodynamic characteristics. The wind turbine blade is replaced by an actuator line model. Turbulence is treated using a dynamic one-equation sudgrid-scale model in large eddy simulation. Detailed information about the basic characteristics of the wind turbine wake is obtained and discussed. The rotor aerodynamic performance compares well with the measurements. The ALM-LES technique demonstrates its high potential in providing accurate load prediction and high resolution of turbulent fluctuations in the wind turbine wakes and the interactions within a feasible cost.
A hybrid method is presented to numerically investigate the wind turbine aerodynamic characteristics. The wind turbine blade is replaced by an actuator line model. Turbulence is treated using a dynamic one-equation sudgrid-scale model in large eddy simulation. Detailed information about the basic characteristics of the wind turbine wake is obtained and discussed. The rotor aerodynamic performance compares well with the measurements. The ALM-LES technique demonstrates its high potential in providing accurate load prediction and high resolution of turbulent fluctuations in the wind turbine wakes and the interactions within a feasible cost.
2016, 33(1).
Abstract:
Fatigue strength assessment of a horizontal axis wind turbine(HAWT) composite blade is considered. Fatigue load cases are identified and loads are calculated by GH Bladed software which are specified at the IEC61400 international specification and GL(Germanisher Lloyd) regulations for the wind energy conversion system. Stress analysis is performed with a 3-D finite element method(FEM). Take Saint-Venant’s principle into consideration, uniform cross section FEM models are built at each critical zone. Stress transformation matrix(STM) are set up by applied six unit load components on these models in the linear elastic range, and STM can be used to convert the load into stress components. The main material of composite wind turbine blade is fiber reinforced plastics(FRP). In order to evaluate the degree of fatigue damage of FRP, the well known strength criterion—Puck theory is used and the stresses of fiber direction are extracted. The total fatigue damage of each laminate on the critical point are counted by rain-flow counting method and Miner’s damage law based on general S-N curves. Several sections of a 45.3m blade were studied using the new fatigue evaluation method. A comparison of the performance of this method is made with a far more costly business software FOCUS. The fatigue damage of multi-axis FRP could be assessed conveniently by this FEM_STM method. This proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.
Fatigue strength assessment of a horizontal axis wind turbine(HAWT) composite blade is considered. Fatigue load cases are identified and loads are calculated by GH Bladed software which are specified at the IEC61400 international specification and GL(Germanisher Lloyd) regulations for the wind energy conversion system. Stress analysis is performed with a 3-D finite element method(FEM). Take Saint-Venant’s principle into consideration, uniform cross section FEM models are built at each critical zone. Stress transformation matrix(STM) are set up by applied six unit load components on these models in the linear elastic range, and STM can be used to convert the load into stress components. The main material of composite wind turbine blade is fiber reinforced plastics(FRP). In order to evaluate the degree of fatigue damage of FRP, the well known strength criterion—Puck theory is used and the stresses of fiber direction are extracted. The total fatigue damage of each laminate on the critical point are counted by rain-flow counting method and Miner’s damage law based on general S-N curves. Several sections of a 45.3m blade were studied using the new fatigue evaluation method. A comparison of the performance of this method is made with a far more costly business software FOCUS. The fatigue damage of multi-axis FRP could be assessed conveniently by this FEM_STM method. This proposed method gives a reliable and efficient method to analyze the fatigue damage of slender composite structure with variable cross-sections.
2016, 33(1).
Abstract:
In this paper, an unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on Fluent software platform. Firstly, the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution. Then the wave evolution is simulated by solving the unsteady incompressible N-S equations coupled with the volume of fluid method. For the small amplitude wave with reasonable wave parameters, the numerical wave agrees well with the given wave model. Finally, a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under combined action of wave and wind. The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with the Morison formula. The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under combined action of small amplitude wave and wind.
In this paper, an unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on Fluent software platform. Firstly, the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution. Then the wave evolution is simulated by solving the unsteady incompressible N-S equations coupled with the volume of fluid method. For the small amplitude wave with reasonable wave parameters, the numerical wave agrees well with the given wave model. Finally, a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under combined action of wave and wind. The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with the Morison formula. The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under combined action of small amplitude wave and wind.
2016, 33(1).
Abstract:
A hybrid Cartesian structured grid method is proposed for solving moving boundary unsteady problems. In the present method, the near body region is discretized by using body-fitted structured grids, while the remaining computational domain is tessellated with generated Cartesian grids. As the body moves, the structured grids move with the body and the outer boundaries of inside grids are used to generate new holes in the outside adaptive Cartesian grid to facilitate data communication. By using the alternating digital tree (ADT) algorithm, the computational time of hole-cutting and identification of donor cells could be reduced significantly. A compressible solver for unsteady flow problems is developed. A cell-centered, 2nd-order accurate finite volume method is employed in spatial discretization and an implicit dual-time stepping LU-SGS approach is employed in temporal discretization. Geometry-based adaptation is used during unsteady simulation time steps when boundary moves and the flow solution is interpolated from the old Cartesian grids to the new one with inverse distance weighting interpolation formula. Both laminar and turbulent unsteady cases are tested to demonstrate the accuracy and efficiency of the proposed method. Then, a 2d store separation problem is simulated. The result shows that the hybrid Cartesian grid method can handle the unsteady flow problems involving large-scale moving boundaries.
A hybrid Cartesian structured grid method is proposed for solving moving boundary unsteady problems. In the present method, the near body region is discretized by using body-fitted structured grids, while the remaining computational domain is tessellated with generated Cartesian grids. As the body moves, the structured grids move with the body and the outer boundaries of inside grids are used to generate new holes in the outside adaptive Cartesian grid to facilitate data communication. By using the alternating digital tree (ADT) algorithm, the computational time of hole-cutting and identification of donor cells could be reduced significantly. A compressible solver for unsteady flow problems is developed. A cell-centered, 2nd-order accurate finite volume method is employed in spatial discretization and an implicit dual-time stepping LU-SGS approach is employed in temporal discretization. Geometry-based adaptation is used during unsteady simulation time steps when boundary moves and the flow solution is interpolated from the old Cartesian grids to the new one with inverse distance weighting interpolation formula. Both laminar and turbulent unsteady cases are tested to demonstrate the accuracy and efficiency of the proposed method. Then, a 2d store separation problem is simulated. The result shows that the hybrid Cartesian grid method can handle the unsteady flow problems involving large-scale moving boundaries.
2016, 33(1).
Abstract:
In combination with the assumption of Park Model that the wake region is in linear expansion and that the cross-wind is in multinomial and Gaussian distribution in wake region, this paper respectively developed the Park-Polynomial Model and the Park-Gaussian Model, to conduct wake flow field numerical simulation study for a single wind turbine. By comparison with the measured data of wind farm and the wind tunnel test, it shows that the prediction precision of wake field has been improved obviously under the modified initial wake radius; both of the newly modified two models could well simulate the wind velocity in wake region, for which not only the accuracy is approximately consistent with the test result, but also the cross-wind distribution conforms to the real flow field. At the same time, the two models have inherited many advantages of engineering models, such as simple form, easy-to-code, and computational efficiency; However, The Park - Gaussian Model is the best in overall performance among them.
In combination with the assumption of Park Model that the wake region is in linear expansion and that the cross-wind is in multinomial and Gaussian distribution in wake region, this paper respectively developed the Park-Polynomial Model and the Park-Gaussian Model, to conduct wake flow field numerical simulation study for a single wind turbine. By comparison with the measured data of wind farm and the wind tunnel test, it shows that the prediction precision of wake field has been improved obviously under the modified initial wake radius; both of the newly modified two models could well simulate the wind velocity in wake region, for which not only the accuracy is approximately consistent with the test result, but also the cross-wind distribution conforms to the real flow field. At the same time, the two models have inherited many advantages of engineering models, such as simple form, easy-to-code, and computational efficiency; However, The Park - Gaussian Model is the best in overall performance among them.
2016, 33(1).
Abstract:
Stall delay is an important phenomenon on wind turbine blades. It makes the maximum aerodynamic load of a rotating blade much higher than that predicted without a correction. A new stall delay model is established in the present paper based on investigations into the flow around a rotating blade. The investigations indicate that the shrink of separation vortex caused by centrifugal force is the major reason for stall delay. Multiple factors relating to the rotational effects are considered in the model, including rotating speed, inflow velocity, local chord length and radial position. Validations for the model are made on the NREL Phase Ⅳ blade and the results show that the accuracy of the aerodynamic prediction for the blade is significantly improved as the model is applied.
Stall delay is an important phenomenon on wind turbine blades. It makes the maximum aerodynamic load of a rotating blade much higher than that predicted without a correction. A new stall delay model is established in the present paper based on investigations into the flow around a rotating blade. The investigations indicate that the shrink of separation vortex caused by centrifugal force is the major reason for stall delay. Multiple factors relating to the rotational effects are considered in the model, including rotating speed, inflow velocity, local chord length and radial position. Validations for the model are made on the NREL Phase Ⅳ blade and the results show that the accuracy of the aerodynamic prediction for the blade is significantly improved as the model is applied.
2016, 33(1).
Abstract:
The offshore wind energy presents a good solution for the green energy demand. The floating offshore wind turbine is one of the most potential choices of the basement construction for offshore wind turbines in deep water. Hydrodynamic performances of multi-column tension-leg-type floating wind turbine are investigated numerically, particularly at its motion responses. Based on the Navior-Stokes equations and the volume of fluid method, a numerical wave tank (NWT) is established to simulate the floating structure system. The analytical relaxation method is adopted to generate regular waves. Dynamic mesh method is used to calculate the motion of the floating body. Hydrostatic decay of motion and hydrodynamic forces in the regular wave are provided. The computation results agree with the experimental data available. Numerical results show that the wave force on the lower pontoon of the system is the greatest while that on the center column is the smallest. Detailed information about the changes of the wave forces on different elements of the floating system is discussed.
The offshore wind energy presents a good solution for the green energy demand. The floating offshore wind turbine is one of the most potential choices of the basement construction for offshore wind turbines in deep water. Hydrodynamic performances of multi-column tension-leg-type floating wind turbine are investigated numerically, particularly at its motion responses. Based on the Navior-Stokes equations and the volume of fluid method, a numerical wave tank (NWT) is established to simulate the floating structure system. The analytical relaxation method is adopted to generate regular waves. Dynamic mesh method is used to calculate the motion of the floating body. Hydrostatic decay of motion and hydrodynamic forces in the regular wave are provided. The computation results agree with the experimental data available. Numerical results show that the wave force on the lower pontoon of the system is the greatest while that on the center column is the smallest. Detailed information about the changes of the wave forces on different elements of the floating system is discussed.
2016, 33(1).
Abstract:
The fatigue limit state are critical for most offshore wind turbines, to minimize the development of fatigue damage, dynamic amplification of the response must be avoided. Thus, it is importance that the first natural frequency of the offshore wind turbine does not coincide with the excitation frequencies related to wind turbine and wave loadings. Currently, there is few study related to offshore wind turbine frequencies considering self-gravity influences including turbine, tower and part pile foundation. In order to evaluate the self-gravity influence on the first natural frequency of wind turbine support structures, the offshore wind turbine system vibration was modeled using an Euler-Bernoulli beam with axial force and horizontal force. The real data from five wind turbines available in the market are considered. The wind turbines size is from 2.3MW to 6MW, the tubular steel tower height are from 83m to 100m. Based on the research results, it indicated that the average influence of gravity on the natural frequency is nearly 1.8%. Considering the first natural frequency should lies between 1p and 3p, which is a relatively narrow range, the design procedure requires an accurate evaluation of the first natural frequency. From this perspective, the first natural frequency is reduced due to gravity need to be considered for design of offshore wind turbine support structures, especially for the design first natural frequency of the offshore wind turbine close to the lower limit 1P.
The fatigue limit state are critical for most offshore wind turbines, to minimize the development of fatigue damage, dynamic amplification of the response must be avoided. Thus, it is importance that the first natural frequency of the offshore wind turbine does not coincide with the excitation frequencies related to wind turbine and wave loadings. Currently, there is few study related to offshore wind turbine frequencies considering self-gravity influences including turbine, tower and part pile foundation. In order to evaluate the self-gravity influence on the first natural frequency of wind turbine support structures, the offshore wind turbine system vibration was modeled using an Euler-Bernoulli beam with axial force and horizontal force. The real data from five wind turbines available in the market are considered. The wind turbines size is from 2.3MW to 6MW, the tubular steel tower height are from 83m to 100m. Based on the research results, it indicated that the average influence of gravity on the natural frequency is nearly 1.8%. Considering the first natural frequency should lies between 1p and 3p, which is a relatively narrow range, the design procedure requires an accurate evaluation of the first natural frequency. From this perspective, the first natural frequency is reduced due to gravity need to be considered for design of offshore wind turbine support structures, especially for the design first natural frequency of the offshore wind turbine close to the lower limit 1P.
2016, 33(1).
Abstract:
Aiming at the CFD simulation of floating offshore wind turbine in coupled wind–wave domain, the NREL 5 MW wind turbine supported by the OC3-Hywind Spar platform is modeled in STAR-CCM+ software. Based on the RANS equations and RNG k-ε turbulence model, the rotor aerodynamic simulation for wind turbine is conducted. Numerical results show good agreement with NREL data. Taking advantage with VOF method and Dynamic Fluid Body Interaction (DFBI) technology, the dynamic responses of the floating system with mooring lines are simulated under coupled wind-wave sea condition. The free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests in regular wave are conducted to validate the numerical model through comparing with the results simulated by FAST. Finally, the simulations of the overall FOWT system in coupled wind-wave flow field are carried out. The relationship between the power output and dynamic motion responses of the platform is investigated. The numerical results show that the dynamic response of wind turbine performance and platform motions all vary as the same frequency with inlet wave. During platform motion, power output of wind turbine is more sensitive than thrust force. This study may provide some reference for further research in coupled aero-hydro simulation of FOWT.
Aiming at the CFD simulation of floating offshore wind turbine in coupled wind–wave domain, the NREL 5 MW wind turbine supported by the OC3-Hywind Spar platform is modeled in STAR-CCM+ software. Based on the RANS equations and RNG k-ε turbulence model, the rotor aerodynamic simulation for wind turbine is conducted. Numerical results show good agreement with NREL data. Taking advantage with VOF method and Dynamic Fluid Body Interaction (DFBI) technology, the dynamic responses of the floating system with mooring lines are simulated under coupled wind-wave sea condition. The free-decay tests for rigid-body degrees of freedom (DOF) in still water and hydrodynamic tests in regular wave are conducted to validate the numerical model through comparing with the results simulated by FAST. Finally, the simulations of the overall FOWT system in coupled wind-wave flow field are carried out. The relationship between the power output and dynamic motion responses of the platform is investigated. The numerical results show that the dynamic response of wind turbine performance and platform motions all vary as the same frequency with inlet wave. During platform motion, power output of wind turbine is more sensitive than thrust force. This study may provide some reference for further research in coupled aero-hydro simulation of FOWT.
2016, 33(1).
Abstract:
Noil discarded fibers from producing fibers for textile industry have short length and are always considered less valuable. In this paper, noil ramie fibers/HDPE composite was prepared using twin-screw extruder and the thermal and dynamic mechanical properties were studied. The influence of ramie fibre and maleic anhydride-grafted polyolefin (MA-g-PO) on mechanical, thermal and dynamic mechanical properties was investigated. It is observed that the tensile, flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites. Dynamic mechanical properties of the composite with MA-g-PO show an increase in storage modulus and a higher α relaxation peak of the treated composites, which indicates a improved interfacial bonding between fiber and matrix by the MA-g-PO addition. Furthermore, the change in TGA thermograms of composite caused by MA-g-PO exhibit that addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.
Noil discarded fibers from producing fibers for textile industry have short length and are always considered less valuable. In this paper, noil ramie fibers/HDPE composite was prepared using twin-screw extruder and the thermal and dynamic mechanical properties were studied. The influence of ramie fibre and maleic anhydride-grafted polyolefin (MA-g-PO) on mechanical, thermal and dynamic mechanical properties was investigated. It is observed that the tensile, flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites. Dynamic mechanical properties of the composite with MA-g-PO show an increase in storage modulus and a higher α relaxation peak of the treated composites, which indicates a improved interfacial bonding between fiber and matrix by the MA-g-PO addition. Furthermore, the change in TGA thermograms of composite caused by MA-g-PO exhibit that addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.
2016, 33(1).
Abstract:
Prediction of droplet impingement on wind turbine blade accurately is one of the most important premises of anti-icing and de-icing system design. In SLD conditions, droplet no longer maintains the sphere shape, it may deform, break up, and splash when it is moving or impinging on the surface. Semi-empirical models of droplet dynamic behaviours are embedded into the Eulerian droplet model to improve the accuracy of the numerical simulation of droplet impingement limits and local collection efficiency. Eulerian droplet model ( Model1) for small droplets and improved Eulerian droplet model ( Model2) for large droplet are both validated by comparing to the wind tunnel experiment results. Using the methods mentioned in this paper, droplet impingement limitation and local collection efficiency on the S809 airfoil are calculated in various conditions. A detailed derivation of Model1 and Model2 is presented along with a comparison of numerical trajectories, drag coefficient and collection efficiency distributions. The results show that droplet dynamic behaviours including splashing, breaking up and deforming must be considered to accurately simulate the impingement behaviour in SLD conditions. And with the increasing of the droplet diameters, the effects of the droplet dynamic behaviors on the impingement characteristics are more obvious.
Prediction of droplet impingement on wind turbine blade accurately is one of the most important premises of anti-icing and de-icing system design. In SLD conditions, droplet no longer maintains the sphere shape, it may deform, break up, and splash when it is moving or impinging on the surface. Semi-empirical models of droplet dynamic behaviours are embedded into the Eulerian droplet model to improve the accuracy of the numerical simulation of droplet impingement limits and local collection efficiency. Eulerian droplet model ( Model1) for small droplets and improved Eulerian droplet model ( Model2) for large droplet are both validated by comparing to the wind tunnel experiment results. Using the methods mentioned in this paper, droplet impingement limitation and local collection efficiency on the S809 airfoil are calculated in various conditions. A detailed derivation of Model1 and Model2 is presented along with a comparison of numerical trajectories, drag coefficient and collection efficiency distributions. The results show that droplet dynamic behaviours including splashing, breaking up and deforming must be considered to accurately simulate the impingement behaviour in SLD conditions. And with the increasing of the droplet diameters, the effects of the droplet dynamic behaviors on the impingement characteristics are more obvious.
2016, 33(1).
Abstract:
A novel multi-objective optimization algorithm incorporating vector method and evolution strategies, referred as VD-MOEA, has been established and applied in the field of aerodynamic-structure integrative design of wind turbine blades. The main characteristics of the new algorithm are that a set of virtual vectors are elaborately constructed guiding population to fast move forward to the Pareto optimal front and dominating the distribution uniformity with high efficiency. In comparison with conventional methods, VD-MOEA displays dramatic improvement of algorithm performance in both convergence and diversity preservation for handling complex problems of multi-variables, multi-objectives and multi-constraints. Subsequently as an example, a 1.5MW wind turbine blades are designed and analyzed taking maximum annual energy production, minimum blade mass, and minimum blade root thrust as the optimization objectives. The results indicate that the Pareto optimal set can be obtained in one single simulation run, and the obtained solutions in the optimal set distribute quite uniform which maximally maintains the population diversity. The efficiency of VD-MOEA has been elevated about two orders of magnitude in comparison with classical NSGA-II. This provides a reliable high-performance optimization approach for the aerodynamic-structure integrative design for wind turbine blade.
A novel multi-objective optimization algorithm incorporating vector method and evolution strategies, referred as VD-MOEA, has been established and applied in the field of aerodynamic-structure integrative design of wind turbine blades. The main characteristics of the new algorithm are that a set of virtual vectors are elaborately constructed guiding population to fast move forward to the Pareto optimal front and dominating the distribution uniformity with high efficiency. In comparison with conventional methods, VD-MOEA displays dramatic improvement of algorithm performance in both convergence and diversity preservation for handling complex problems of multi-variables, multi-objectives and multi-constraints. Subsequently as an example, a 1.5MW wind turbine blades are designed and analyzed taking maximum annual energy production, minimum blade mass, and minimum blade root thrust as the optimization objectives. The results indicate that the Pareto optimal set can be obtained in one single simulation run, and the obtained solutions in the optimal set distribute quite uniform which maximally maintains the population diversity. The efficiency of VD-MOEA has been elevated about two orders of magnitude in comparison with classical NSGA-II. This provides a reliable high-performance optimization approach for the aerodynamic-structure integrative design for wind turbine blade.
16 Aeroelastic responses calculation for wind turbine blade considering the bend-twist coupled effect
2016, 33(1).
Abstract:
The Euler-Bernoulli beam model coupled with the sectional properties achieved by the VABS method was used to construct the blade structure model. Combined the aerodynamic loads calculated by the unsteady blade element momentum model with dynamic inflow and dynamic stall correction, the dynamics equations of blade was built. The Newmark implicit algorithm was used to solve the dynamics equations. Results of the sectional properties and blade structure model were compared with the multi-cell beam method and the ANSYS using shell elements. It was proved that the method was very effective and had high precision. And the effects on the aeroelastic response caused by bend-twist coupling were analyzed. The coupling effects made the torsional direction deform toward to the upwind direction. The aerodynamic loads and the displacement were reduced.
The Euler-Bernoulli beam model coupled with the sectional properties achieved by the VABS method was used to construct the blade structure model. Combined the aerodynamic loads calculated by the unsteady blade element momentum model with dynamic inflow and dynamic stall correction, the dynamics equations of blade was built. The Newmark implicit algorithm was used to solve the dynamics equations. Results of the sectional properties and blade structure model were compared with the multi-cell beam method and the ANSYS using shell elements. It was proved that the method was very effective and had high precision. And the effects on the aeroelastic response caused by bend-twist coupling were analyzed. The coupling effects made the torsional direction deform toward to the upwind direction. The aerodynamic loads and the displacement were reduced.
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