共查询到20条相似文献，搜索用时 15 毫秒
1.
This work presents an analysis of vortex‐induced vibrations of a DU96‐W‐180 airfoil in deep stall at a 90° angle of attack, based on 2D and 3D Reynolds Averaged Navier Stokes and 3D Detached Eddy Simulation unsteady Computational Fluid Dynamics computations with non‐moving, prescribed motion and elastically mounted airfoil suspensions. Stationary vortex‐shedding frequencies computed in 2D and 3D Computational Fluid Dynamics differed. In the prescribed motion computations, the airfoil oscillated in the direction of the chord line. Negative aerodynamic damping, found in both 2D and 3D Computational Fluid Dynamics computations with moving airfoil, showed in the vicinity of the stationary vortex‐shedding frequency computed by 2D Computational Fluid Dynamics. A shorter time series was sufficient to verify the sign of the aerodynamic damping in the case of the elastic computations than the prescribed motion. Even though the 2D computations seemed to be capable of indicating the presence of vortex‐induced vibrations, the 3D computations seemed to reflect the involved physics more accurately. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
2.
Vortex‐induced and stall‐induced vibrations of a 2D elastically mounted airfoil at high angles of attack in the vicinity of 90° are investigated using a vortex type model. Such conditions are encountered in parked or idling operation at extreme yaw angles provoked by control system failures. At very high angles of attack, massive flow separation takes place over the entire blade span, and vortex shedding evolves downstream of the blade giving rise to periodically varying loads at frequencies corresponding to the Strouhal number of the vortices shed in the wake. As a result, vortex‐induced vibrations may occur when the shedding frequency matches the natural frequency of the blade. A vortex type model formulated on the basis of the ‘double wake’ concept is employed for the modelling of the stalled flow past a 2D airfoil. By tuning the core size of the vortex particles in the wake, the model predictions are successfully validated against averaged 2D measurements on a DU‐96‐W‐180 airfoil at high angles of attack. In order to assess the energy fed to the airfoil by the aerodynamic loads, the behaviour under imposed sinusoidal edgewise motions is analysed for various oscillation frequencies and amplitudes. Moreover, stall‐induced and vortex‐induced vibrations of an elastically mounted airfoil section are assessed. The vortex model predicts higher aeroelastic damping as compared with that obtained using steady‐state aerodynamics. Excessive combined vortex‐induced and stall‐induced edgewise vibrations are obtained beyond the wind speed of 30 m s?1. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
This paper presents a newly developed high‐fidelity fluid–structure interaction simulation tool for geometrically resolved rotor simulations of wind turbines. The tool consists of a partitioned coupling between the structural part of the aero‐elastic solver HAWC2 and the finite volume computational fluid dynamics (CFD) solver EllipSys3D. The paper shows that the implemented loose coupling scheme, despite a non‐conservative force transfer, maintains a sufficient numerical stability and a second‐order time accuracy. The use of a strong coupling is found to be redundant. In a first test case, the newly developed coupling between HAWC2 and EllipSys3D (HAWC2CFD) is utilized to compute the aero‐elastic response of the NREL 5‐MW reference wind turbine (RWT) under normal operational conditions. A comparison with the low‐fidelity but state‐of‐the‐art aero‐elastic solver HAWC2 reveals a very good agreement between the two approaches. In a second test case, the response of the NREL 5‐MW RWT is computed during a yawed and thus asymmetric inflow. The continuous good agreement confirms the qualities of HAWC2CFD but also illustrates the strengths of a computationally cheaper blade element momentum theory (BEM) based solver, as long as the solver is applied within the boundaries of the employed engineering models. Two further test cases encompass flow situations, which are expected to exceed the limits of the BEM model. However, the simulation of the NREL 5‐MW RWT during an emergency shut down situation still shows good agreements in the predicted structural responses of HAWC2 and HAWC2CFD since the differences in the computed force signals only persist for an insignificantly short time span. The considerable new capabilities of HAWC2CFD are finally demonstrated by simulating vortex‐induced vibrations on the DTU 10‐MW wind turbine blade in standstill. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
Witold Robert Skrzypiński Mac Gaunaa Niels Sørensen Frederik Zahle Joachim Heinz 《风能》2014,17(4):641-655
This work presents an analysis of two‐dimensional (2D) and three‐dimensional (3D) non‐moving, prescribed motion and elastically mounted airfoil computational fluid dynamics (CFD) computations. The elastically mounted airfoil computations were performed by means of a 2D structural model with two degrees of freedom. The computations aimed at investigating the mechanisms of both vortex‐induced and stall‐induced vibrations related to a wind turbine blade at standstill conditions. In this work, a DU96‐W‐180 airfoil was used in the angle‐of‐attack region potentially corresponding to stall‐induced vibrations. The analysis showed significant differences between the aerodynamic stability limits predicted by 2D and 3D CFD computations. A general agreement was reached between the prescribed motion and elastically mounted airfoil computations. 3D computations indicated that vortex‐induced vibrations are likely to occur at modern wind turbine blades at standstill. In contrast, the predicted cut‐in wind speed necessary for the onset of stall‐induced vibrations appeared high enough for such vibrations to be unlikely. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
A brief summary of the main challenges of rotor design in wind energy conversion (WEC) systems, most notably the horizontal axis wind turbine (HAWT), are presented. One of the limiting factors in HAWT design is choosing the rated capacity to maximize power output and turbine longevity. One such strategy to accomplish this goal is to widen the operational range of the WEC system by using pitch or torque control, which can be costly and subject to mechanical failure. We present a morphing airfoil concept, which passively controls airfoil pitch through elastic deformation. As a justification of the concept, a two‐dimensional fluid‐structure interaction routine is used to simulate the aeroelastic response of a symmetric NACA 0012 blade subjected to variable loading. The results suggest that the morphing blade can be designed to offer superior average lift to drag ratios over a specified range of attack angles by up to 4.2%, and possibly even higher. This infers that the morphing blade design can increase the power production of WEC systems while conceivably reducing cost because the passive deformation of the morphing turbine does not require active control systems that come at an added upfront and maintenance cost. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
The prediction of dynamic characteristics for a floating offshore wind turbine (FOWT) is challenging because of the complex load coupling of aerodynamics, hydrodynamics, and structural dynamics. These loads should be accurately calculated to yield reliable analysis results in the design phase of a FOWT. In this study, a high‐fidelity fluid‐structure interaction simulation that simultaneously considers the influence of aero‐hydrodynamic coupling due to the dynamic motion of a FOWT has been conducted using computational fluid dynamics based on an overset grid technique. The DeepCwind semisubmersible floating platform with the NREL 5‐MW baseline wind turbine model is considered for objective numerical verification with the NREL FAST code. A state‐of‐the‐art computational model based on the coupled computational fluid dynamics and dynamic structure analysis is constructed and analyzed to solve multiphase flow, 6 degrees of freedom motions of OC4 semisubmersible FOWT. A quasi‐static mooring solver is also applied to resolve the constraint motion of floater because of a 3‐line mooring system. The influence of tower shadow on the unsteady aerodynamic performance and loads is also demonstrated. Finally, complex unsteady flow fields considering blade and tower interference effects among blade‐tip vortices, shedding vortices, and turbulent wakes are numerically visualized and investigated in detail. 相似文献
7.
对弹性支撑单圆柱在均匀流作用下的涡激运动特性进行数值模拟,捕捉到\"锁定区\"、\"拍\"、\"频率变换\"等现象。柱体周围流场采用Fluent求解,将4阶Runge-Kutta方法代码写入用户自定义函数(UDF)求解运动微分方程,运用动网格技术更新流场,实现圆柱与流场的非线性耦合作用。发现随着折合速度的增大,涡激运动响应可分为锁定前支、锁定区、锁定后支3个阶段,在进入锁定区前(折合速度Ur=3)横向运动响应发生拍现象,当跨过锁定区后(折合速度Ur=10)发生频率变换现象。结果表明,横向涡激运动有较大范围的频率锁定现象,频率解锁前后圆柱涡激运动轨迹由\"右8字\"形变换为\"左8字\"形。 相似文献
8.
The present study investigated physical phenomena related to stall‐induced vibrations potentially existing on wind turbine blades at standstill conditions. The study considered two‐dimensional airfoil sections while it omitted three‐dimensional effects. In the study, a new engineering‐type computational model for the aeroelastic response of an elastically mounted airfoil was used to investigate the influence of temporal lag in the aerodynamic response on the aeroelastic stability in deep stall. The study indicated that even a relatively low lag significantly increases the damping of the model. A comparison between the results from a model with lag imposed on all force components with the results from a model with lag imposed exclusively on the lift showed only marginal difference between the damping in the two cases. A parameter study involving positions of the elastic hinge point and the center of gravity indicated that the stability is relatively independent of these parameters. Another parameter study involving spring constants showed that the stability of each mode is dependent only on the spring constant acting in the direction of the leading motion of the mode. An investigation of the influence of the added mass terms showed that only the pitch‐rate and flapwise‐acceleration terms have any influence on the stability. An investigation of three different profiles showed that the stability is heavily dependent on the aerodynamic characteristics of the profiles—mainly on the lift. It was also shown that only the edgewise mode is unstable in deep stall. Moreover, independent of the amount of temporal lag in the aerodynamic response of the model, the inflow‐angle region in the vicinity of 180° remains unstable in the edgewise mode. Therefore, this inflow‐angle region may create stability problems in real life. The other type of vibrations potentially present at standstill conditions is vortex‐induced, being outside the scope of the present study. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Analysis results, obtained from numerical simulation, for non-linear and unsteady aeroelastic behavior of large horizontal-axis wind turbines are presented in this paper. Simulations are carried out using a partitioned scheme of weak interaction that allows dealing with the fluid–structure interaction problem by using one method to solve the structural-dynamic problem and another method for the aerodynamic problem. 相似文献
10.
For a better design of tidal stream turbines operated in off-design conditions, analyses considering the effects of blade deformation and yawed inflow conditions are necessary. The flow load causes deformation of the blade, and the deformation affects the turbine performance in return. Also, a yawed inflow influences the performance of the turbine. As a validation study, a computational fluid dynamics (CFD) simulation was carried out to predict the performance of a horizontal axis tidal stream turbine (HATST) with rigid blades. The numerical uncertainty for the turbine performance with blade deformation and a yawed inflow was evaluated using the concept of the grid convergence index (GCI). A fluid–structure interaction (FSI) analysis was carried out to estimate the performance of a turbine with flexible composite blades, with the results then compared to those of an analysis with rigid blades. The influence of yawed inflow conditions on the turbine performance was investigated and found to be important in relation to power predictions in the design stages. 相似文献
11.
Masato Taguchi ;Naoki Semba ;Koichi Mori ;Yoshiaki Nakamura ;Keiichi Ishiko 《能源与动力工程:英文版》2014,(8):1386-1392
The flow field of 3D （three-dimensional） wall-jet is investigated. Jet-blast from airplane is simulated by wall-jet setup using a sonic nozzle at a laboratory scale. Farfield velocity and fluctuation distributions are measured by using X-type hot wire anemometer at four measurement planes. As a result, the flow properties of streamwise component are consistent with data which are obtained in previous researches. The secondary flow is also measured on each measurement plane. Reynolds stresses, v＇v＇ and w＇ w＇, are analyzed from the fluctuation of the secondary flow. The law of similarity is observed in the dimensionless distributions of mean velocity and fluctuation. However, the distributions in nearer field （i.e., in the measurement plane at X/D = 100） tend to disobey the similarity law, especially in the cases of fluctuation. It seems that jet-blast is not fully developed by reaching X/D = 100. The experimental results are compared with computational results which are obtained by CFD （computational fluid dynamics） with SST （shear-stress transport） turbulence model. And it is shown that the results by the simulation with SST turbulence model do not follow the similarity law. The present database of the Reynolds stresses is critically important for development of a new turbulence model of RANS （reynolds-averaged navier-atokes） simulations on wall-jet. 相似文献
12.
13.
M.-A. Dufour;G. Pinon;E. Rivoalen;F. Blondel;G. Germain; 《风能》2024,27(7):633-666
This paper presents a lifting-line implementation in the framework of a Lagrangian vortex particle method (LL-VP). The novelty of the present implementation lies in the fluid particles properties definition and in the particles shedding process. In spite of mimicking a panel method, the LL-VP needs some peculiar treatments described in the paper. The present implementation converges rapidly and efficiently during the shedding sub-iteration process. This LL-VP method shows good accuracy, even with moderate numbers of sections. Compared to its panel or vortex filaments counterparts, more frequently encountered in the literature, the present implementation inherently accounts for the diffusion term of the Navier-Stokes equations, possibly with a turbulent viscosity model. Additionally, the present implementation can also account for more complex onset flows: upstream ambient turbulence and upstream turbine wakes. After validation on an analytical elliptic wing configuration, the model is tested on the Mexnext-III wind turbine application, for three reduced velocities. Accurate results are obtained both on the analytical elliptic wing and on the New MEXICO rotor cases in comparison with other similar numerical models. A focus is made on the Mexnext-III wake analysis. The numerical wake obtained with the present LL-VP is close to other numerical and experimental results. Finally, a last configuration with three tidal turbines in interaction is considered based on an experimental campaign carried out at the IFREMER wave and current flume tank. Enhanced turbine-wake interactions are highlighted, with favourable comparisons with the experiment. Hence, such turbine interactions in a farm are accessible with this LL-VP implementation, be it wind or tidal energy field. 相似文献
14.
Unai Fernández‐Gámiz Clara Marika Velte Pierre‐Elouan Réthoré Niels N. Sørensen Eduard Egusquiza 《风能》2016,19(6):1043-1052
Vortex generators (VGs) are used increasingly by the wind turbine industry as flow control devices to improve rotor blade performance. According to experimental observations, the vortices generated by VGs have previously been observed to be self‐similar for both the axial (uz) and azimuthal (uθ) velocity components. Furthermore, the measured vortices have been observed to obey the criteria for helical symmetry. These are powerful results, as it reduces the highly complex 3‐D flow to merely four parameters and therefore significantly facilitates the modeling of this type of flow, which in a larger perspective can assist in parametric studies to increase the total power output of wind turbines. In this study, corresponding computer simulations using Reynolds‐averaged Navier–Stokes equations have been carried out and compared with the experimental observations. The main objective is to investigate how well the simulations can reproduce these aspects of the physics of the flow, i.e., investigate if the same analytical model can be applied and therefore significantly facilitate the modeling of this type of flow, which in a larger perspective can assist in parametric studies to increase the total power output of wind turbines. This is especially interesting since these types of flows are notoriously difficult for the turbulence models to predict correctly. Using this model, parametric studies can be significantly reduced, and moreover, reliable simulations can substantially reduce the costs of the parametric studies themselves. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
15.
FSI效应对管道水击运动特性的影响分析 总被引：1，自引：3，他引：1
使用哈密顿变分原理和变形体流体运动的基本方程建立了输流固耦合运动方程,由此构造出描述管道波－波－振动系统的动力耦合效应的4－方程模型,并得到了相应的复频解析解,将该模型与经典模型做了对比分析,结果表明,改进模型能更好地反映管道水击运动的特性。 相似文献
16.
The aim of this report is to present a model of a rigid‐rotor system based on computational fluid dynamics (CFD), which is applied on a vertical axis wind turbine (VAWT) research. Its originality results from the use of the average value of the variable rotational speed method taken in a periodic steady‐state (PSS) of the VAWT rotor instead of the classical fixed rotational speed method. This approach was chosen in order to determine the mechanical and aerodynamic parameters of the wind turbine. The modeling method uses an implicit Euler iterative solution strategy, which resolves the coupling between fixed and moving rotor domains. The main methods that were adopted are based on the three‐dimensional modeling of the interaction of the fluid flow with a rigid‐rotor. The strategy consists of using the Reynolds averaged Navier Stokes (RANS) equations with the standard k‐ ? and SST k‐ ω models to solve the fluid flow problem. To perform the rigid‐rotor motion in a fluid, the one degree of freedom (1‐DOF) method was applied. In the present study, the steady‐state and dynamic CFD simulations of the Savonius rotor are adopted to contribute to the validation elements of the VAWT models that are used. The dynamic study allows the investigation of the rotor behavior and the relation between velocity, pressure, and vorticity fields in and around the rotor blades. The flow fields generated by the rotation of the Savonius rotor were investigated in the half revolution period of the rotor angle θ from 0° to 180°. In this range of θ, the focus is on generating and dissipating vortices. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
17.
风力机翼型颤振及射流减振技术的气动弹性研究 总被引：1，自引：0，他引：1
采用流固耦合的数值计算方法研究了S80 9风力机翼型在大攻角 (15°～ 5 0°)范围的颤振 ,以及在翼型背部部分引入射流的减振技术。在流体区域用高精度、高分辨率算法求解Farve平均的Navier Stokes方程 ,在固体区域用四阶Runge Kutta法求解振动方程 ,并且每一个时间步后都在两个区域之间传递边界条件。计算结果表明在翼型背部引入适当射流会降低振动 ,并且基本上不影响翼型的升力系数。但如果引入射流的速度过高 ,会在叶背处形成新的分离流 ,升力会大幅度下降 相似文献
18.
对一冷却塔风机支承结构附近的流场进行CFD分析。支承结构造成的流体绕流现象在风机进口处形成涡流，造成风机风量减少，噪声增加，浪费能源。期望通过数值模拟计算结果为解决以上问题提出理论上的可行性指导，达到节约能源的最终目的。主要措施：在宽梁上增加额外送风；在平台上下方各加一导流罩装置。计算结果显示，这两项措施对风机进口处流场的改善起到了一定的作用。 相似文献
19.
沉沙池冲沙是复杂的固—液两相流瞬态过程,其数值模拟对校核冲沙能力、优化池型和布置等均具有重要意义。利用CFD商用软件FLOW-3D对冲沙池的冲沙过程进行模拟,并通过与物理模型试验进行对比,在确认其可靠性的基础上,以某水电站实际沉沙池为例进行流态和冲沙过程模拟,分析了不同冲沙底板开启方式对冲沙效果的影响。结果表明,沉沙池冲沙从冲沙底板开启段向两侧发展,初始时冲沙速率较快,冲沙量非常大,随后逐渐减小,冲沙也趋于平缓,FLOW-3D软件应用于沉沙池冲沙过程模拟可行,能较好地反映沉沙池冲沙过程中沙粒的运动规律。 相似文献
20.
M. Peksen 《International Journal of Hydrogen Energy》2018,43(1):354-362
Heating-up strategies of full scale solid oxide fuel cell (SOFC) systems still affect the safe operation of the system and incorporation of the technology into the global energy sector. To ensure rapid start-up times whilst retaining the structural reliability of the SOFC system components, requires a safe heating-up operation. To master a controlled heating-up stage, detailed understanding of the component interaction and multiphysics within a fuel cell system is required. State of the art dynamic fuel cell system modelling comprises sub-models of the assembly, or is based on empirical nature. However, invaluable information of the multiphysics inside the system is lost. Therefore, it is of paramount importance to understand and improve the knowledge of the detailed processes, occurring within the interacting components. The effect of integrating different electrical heater cartridges at different locations has been thoroughly investigated to optimise the heating-up of the system. The study utilises a previously developed and experimentally validated full scale three dimensional planar type SOFC system model to mitigate experimental costs and shed light on the details, occurring within the system. A comparison to a simplified variant of the model has been added to shed light on its effect on the results. 相似文献