scholarly journals Numerical analyses and optimizations on the flow in the nacelle region of a wind turbine

2018 ◽  
Vol 3 (2) ◽  
pp. 503-531
Author(s):  
Pascal Weihing ◽  
Tim Wegmann ◽  
Thorsten Lutz ◽  
Ewald Krämer ◽  
Timo Kühn ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Flow Separation ◽  
Navier Stokes ◽  
Local Flow ◽  
Aerodynamic Efficiency ◽  
Blade Root ◽  
Root Region ◽  
Flow Features ◽  
Flat Back ◽  
The Impact

Abstract. The present study investigates flow dynamics in the hub region of a wind turbine focusing on the influence of nacelle geometry on the root aerodynamics by means of Reynolds averaged Navier–Stokes simulations with the code FLOWer. The turbine considered is a generic version of the Enercon E44 converter incorporating blades with flat-back-profiled root sections. First, a comparison is drawn between an isolated rotor assumption and a setup including the baseline nacelle geometry in order to elaborate the basic flow features of the blade root. It was found that the nacelle reduces the trailed circulation of the root vortices and improves aerodynamic efficiency for the inner portion of the rotor; on the other hand, it induces a complex vortex system at the juncture to the blade that causes flow separation. The origin of these effects is analyzed in detail. In a second step, the effects of basic geometric parameters describing the nacelle have been analyzed with the purpose of increasing the aerodynamic efficiency in the root region. Therefore, three modification categories have been addressed: the first alters the nacelle diameter, the second varies the blade position relative to the nacelle and the third comprises modifications in the vicinity of the blade–nacelle junction. The impact of the geometrical modifications on the local flow physics are discussed and assessed with respect to aerodynamic performance in the blade root region. It was found that increasing the nacelle diameter deteriorates the root aerodynamics, since the flow separation becomes more pronounced. Possible solutions identified to reduce the flow separation are a shift of the blade in the direction of the rotation or the installation of a fairing fillet in the junction between the blade and the nacelle.

scholarly journals Numerical Analyses and Optimizations on the Flow in the Nacelle Region of a Wind Turbine

2018 ◽  
Author(s):  
Pascal Weihing ◽  
Tim Wegmann ◽  
Thorsten Lutz ◽  
Ewald Krämer ◽  
Timo Kühn ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Flow Separation ◽  
Navier Stokes ◽  
Vortex System ◽  
Local Flow ◽  
Aerodynamic Efficiency ◽  
Blade Root ◽  
Root Region ◽  
Flow Features ◽  
The Impact

Abstract. The present study investigates the flow dynamics in the hub region of a wind turbine focusing on the influence of the nacelle geometry on the root aerodynamics by means of Reynolds averaged Navier-Stokes simulations with the code FLOWer. The turbine considered is a generic version of the Enercon E44 converter incorporating blades with flatback-profiled root sections. First, a comparison is drawn between an isolated rotor assumption and a setup including the baseline geometry, in order to elaborate the basic flow features of the blade root. It was found that the nacelle reduces the trailed circulation of the root vortices and improves aerodynamic efficiency for the inner portion of the rotor, but on the other hand induces a complex vortex system in the junction of the blade and the nacelle that causes flow separation. The origin of these effects is analyzed in detail. In a second step, effects of basic geometric nacelle properties have been analyzed with the purpose to increase the aerodynamic efficiency in the root region. Therefore, three modification categories have been addressed, where the first alters the nacelle diameter, the second varies the blade position relative to the nacelle and the third comprises modifications in the vicinity of the blade-nacelle junction. The impact of the geometrical modifications on the local flow physics are discussed and assessed with respect to aerodynamic performance in the blade root region. It was found that increasing the nacelle diameter deteriorates the root aerodynamics, since the flow separation gets more pronounced. Possible solutions identified to reduce the flow separation are a shift of the blade in direction of the rotation or the installation of a fairing fillet in the junction between the blade and the nacelle.

scholarly journals Detailed analysis of the blade root flow of a horizontal axis wind turbine

2016 ◽  
Vol 1 (2) ◽  
pp. 89-100 ◽  
Author(s):  
Iván Herráez ◽  
Buşra Akay ◽  
Gerard J. W. van Bussel ◽  
Joachim Peinke ◽  
Bernhard Stoevesandt
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Aerodynamic Performance ◽  
Negative Influence ◽  
Navier Stokes ◽  
Wind Turbine Blades ◽  
Force Coefficient ◽  
Horizontal Axis Wind Turbine ◽  
Blade Root ◽  
Root Region

Abstract. The root flow of wind turbine blades is subjected to complex physical mechanisms that influence significantly the rotor aerodynamic performance. Spanwise flows, the Himmelskamp effect, and the formation of the root vortex are examples of interrelated aerodynamic phenomena that take place in the blade root region. In this study we address those phenomena by means of particle image velocimetry (PIV) measurements and Reynolds-averaged Navier–Stokes (RANS) simulations. The numerical results obtained in this study are in very good agreement with the experiments and unveil the details of the intricate root flow. The Himmelskamp effect is shown to delay the stall onset and to enhance the lift force coefficient Cl even at moderate angles of attack. This improvement in the aerodynamic performance occurs in spite of the negative influence of the mentioned effect on the suction peak of the involved blade sections. The results also show that the vortex emanating from the spanwise position of maximum chord length rotates in the opposite direction to the root vortex, which affects the wake evolution. Furthermore, the aerodynamic losses in the root region are demonstrated to take place much more gradually than at the tip.

scholarly journals Detailed Analysis of the Blade Root Flow of a Horizontal Axis Wind Turbine

2016 ◽  
Author(s):  
I. Herráez ◽  
B. Akay ◽  
G. J. W. van Bussel ◽  
J. Peinke ◽  
B. Stoevesandt
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Navier Stokes ◽  
Wind Turbine Blades ◽  
Force Coefficient ◽  
Horizontal Axis Wind Turbine ◽  
Physical Mechanisms ◽  
Blade Root ◽  
Root Region ◽  
Image Velocimetry

Abstract. The root flow of wind turbine blades is subjected to complex physical mechanisms that influence significantly the rotor aerodynamic performance. Spanwise flows, the Himmelskamp effect and the formation of the root vortex are examples of interrelated aerodynamic phenomena observed in the blade root region. In this study we address those phenomena by means of Particle Image Velocimetry (PIV) measurements and Reynolds Averaged Navier–Stokes (RANS) simulations. The numerical results obtained in this study are in very good agreement with the experiments and unveil the details of the intricate root flow. The Himmelskamp effect is shown to delay the stall onset and enhance the lift force coefficient Cl even at a moderate angle of attack (AoA ≈ 13°). The results also show that the vortex emanating from the spanwise position of maximum chord length rotates in the opposite direction of the root vortex, what affects the wake evolution.

scholarly journals Numerical analysis of high-lift configurations with oscillating flaps

2021 ◽  
Author(s):  
Johannes Ruhland ◽  
Christian Breitsamter
Keyword(s):  
Reynolds Number ◽  
Flow Separation ◽  
Separated Flow ◽  
Navier Stokes ◽  
Rotational Axis ◽  
High Lift ◽  
Hinge Point ◽  
Reduced Frequency ◽  
Flap Deflection ◽  
The Impact

AbstractThis study presents two-dimensional aerodynamic investigations of various high-lift configuration settings concerning the deflection angles of droop nose, spoiler and flap in the context of enhancing the high-lift performance by dynamic flap movement. The investigations highlight the impact of a periodically oscillating trailing edge flap on lift, drag and flow separation of the high-lift configuration by numerical simulations. The computations are conducted with regard to the variation of the parameters reduced frequency and the position of the rotational axis. The numerical flow simulations are conducted on a block-structured grid using Reynolds Averaged Navier Stokes simulations employing the shear stress transport $$k-\omega $$ k - ω turbulence model. The feature Dynamic Mesh Motion implements the motion of the oscillating flap. Regarding low-speed wind tunnel testing for a Reynolds number of $$0.5 \times 10^{6}$$ 0.5 × 10 6 the flap movement around a dropped hinge point, which is located outside the flap, offers benefits with regard to additional lift and delayed flow separation at the flap compared to a flap movement around a hinge point, which is located at 15 % of the flap chord length. Flow separation can be suppressed beyond the maximum static flap deflection angle. By means of an oscillating flap around the dropped hinge point, it is possible to reattach a separated flow at the flap and to keep it attached further on. For a Reynolds number of $$20 \times 10^6$$ 20 × 10 6 , reflecting full scale flight conditions, additional lift is generated for both rotational axis positions.

Impact of three-dimensional phenomena on the design of rotodynamic pumps

1999 ◽  
Vol 213 (1) ◽  
pp. 59-70 ◽  
Author(s):  
J. F. Gülich
Keyword(s):  
Three Dimensional ◽  
Flow Distribution ◽  
Navier Stokes ◽  
Specific Work ◽  
Preliminary Design ◽  
Present Contribution ◽  
Part Load ◽  
Starting Point ◽  
Flow Features ◽  
The Impact

Three-dimensional Navier—Stokes calculations are expected to be increasingly applied in the future for performance improvement of rotodynamic pumps. Frequently such an optimization process involves a preliminary design—based on one-dimensional methods and empirical data—which is subsequently optimized by computational fluid dynamics (CFD). Employing an empirical database is not only necessary in order to provide a good starting point for the CFD analysis but also to ensure that the design has a good chance of fulfilling part load requirements, since recirculating flows at the impeller inlet and outlet are not easily handled by CFD programs. CFD calculations provide the specific work input to the fluid and information on losses and reveal the complex three-dimensional flow patterns. The designer is faced with the task of interpreting such data and drawing conclusions for the optimization of the impeller. It is the purpose of the present contribution to analyse and describe the impact of various geometric parameters and flow features on the velocity distribution in the impeller and their influence on performance and part load characteristics. Criteria are also provided to select the parameters for the preliminary design. Hydraulic impeller losses calculated by CFD programs may often be misleading if the non-uniformity of the flow distribution at the impeller outlet is ignored. Procedures to quantify such mixing losses in the diffuser or volute downstream of the impeller are discussed.

Development of a Stall Barrier with Internal Flow Channel for Effective, Highly Separated Boundary Layer and Flow Control in the Rotor Blade Root Region

2013 ◽  
Vol 597 ◽  
pp. 29-35
Author(s):  
Frank Kortenstedde ◽  
Benjamin Stanke ◽  
Christian Wendler ◽  
Bernd Steckemetz
Keyword(s):  
Boundary Layer ◽  
Wind Turbine ◽  
Rotor Blade ◽  
Radial Flow ◽  
Internal Flow ◽  
Aerodynamic Efficiency ◽  
Aerospace Research ◽  
Root Region ◽  
Model Rotor ◽  
Flow Element

As part of a cluster project in the Aerospace research cluster at the Hochschule Bremen, the model rotor blade of a wind turbine is to be aerodynamically optimized with a more effective stall barrier. The flow element to be developed should provide very effective interruption of the radial flow on the rotor blade. A combination of this flow element and the "Splitflap" flow element allows the aerodynamic efficiency of the rotor blade to be further improved.

scholarly journals The Suction Control Characteristics of Flow Separation on NACA 23012

2020 ◽  
Vol 2 (1) ◽  
pp. 1-15
Author(s):  
Moses Oluwatosin Julius ◽  
Saheed Adewale Adio ◽  
Adam Olatunji Muritala ◽  
Oluwasanmi Alonge
Keyword(s):  
Flow Separation ◽  
Aerodynamic Characteristics ◽  
Control Technique ◽  
Navier Stokes ◽  
Suction Control ◽  
Lift Enhancement ◽  
Stall Angle ◽  
The Impact ◽  
Drag Ratio ◽  
Lift To Drag Ratio

The enormous loss of momentum leads to stall and adversely affects the aerodynamic performance of aeroplane wings which may lead to a disaster, more importantly, risking the safety of the aeroplane by putting lives of passengers on it in danger. Therefore, this paper focuses on the enhancement of aerodynamic characteristics of NACA 23012 through the mitigation of flow separation and delay of the stall at higher angles of attack by using suction for Reynolds number (Re) = 3.4 x 106 . Considering the different suction features such as suction width, suction position, and suction coefficient, the separation delay capability of a suction control is studied. Also, the lift to drag ratio and the impact of energy consumption variation during the control technique are used for estimating the control effects. The Reynolds Average Navier-Stokes (RANS) equations are employed together with the Menter’s shear stress turbulent model. The result of this study revealed that the jet position just behind the separation point at 0.2 % of the chord length shows an outstanding control outcome on the separation and stall, thereby increasing the lift. The lift to drag ration increased proportionately when the suction jet coefficient was increased. At suction coefficient Cq = 0.00225, a 92.1% drag reduction and 72.7% lift enhancement is observed. Hence, the stall angle is moved beyond 21.5o from an initial angle of 16° and the more energy was saved at a high angle of attack.

scholarly journals Numerical Investigation of Jet Angle Effect on Airfoil Stall Control

2019 ◽  
Vol 9 (15) ◽  
pp. 2960 ◽  
Author(s):  
Junkyu Kim ◽  
Young Min Park ◽  
Junseong Lee ◽  
Taesoon Kim ◽  
Minwoo Kim ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Separation Control ◽  
Angle Effect ◽  
Stall Control ◽  
The Impact

Numerical study on flow separation control is conducted for a stalled airfoil with steady-blowing jet. Stall conditions relevant to a rotorcraft are of interest here. Both static and dynamic stalls are simulated with solving compressible Reynolds-averaged Navier-Stokes equations. It is expected that a jet flow, if it is applied properly, provides additional momentum in the boundary layer which is susceptible to flow separation at high angles of attack. The jet angle can influence on the augmentation of the flow momentum in the boundary layer which helps to delay or suppress the stall. Two distinct jet angles are selected to investigate the impact of the jet angle on the control authority. A tangential jet with a shallow jet angle to the surface is able to provide the additional momentum to the flow, whereas a chord-normal jet with a large jet angle simply averts the external flow. The tangential jet reduces the shape factor of the boundary layer, lowering the susceptibility to the flow separation and delaying both the static and dynamic stalls.

scholarly journals Effects of Wind-Wave Misalignment on a Wind Turbine Blade Mating Process: Impact Velocities, Blade Root Damages and Structural SafetyAssessment

2020 ◽  
Vol 19 (2) ◽  
pp. 218-233
Author(s):  
Amrit Shankar Verma ◽  
Zhiyu Jiang ◽  
Zhengru Ren ◽  
Zhen Gao ◽  
Nils Petter Vedvik
Keyword(s):  
Wind Turbine ◽  
Failure Modes ◽  
Wind Wave ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Alignment Procedure ◽  
Blade Root ◽  
Wave Conditions ◽  
The Impact ◽  
Relative Motions

Abstract Most wind turbine blades are assembled piece-by-piece onto the hub of a monopile-type offshore wind turbine using jack-up crane vessels. Despite the stable foundation of the lifting cranes, the mating process exhibits substantial relative responses amidst blade root and hub. These relative motions are combined effects of wave-induced monopile motions and wind-induced blade root motions, which can cause impact loads at the blade root’s guide pin in the course of alignment procedure. Environmental parameters including the wind-wave misalignments play an important role for the safety of the installation tasks and govern the impact scenarios. The present study investigates the effects of wind-wave misalignments on the blade root mating process on a monopile-type offshore wind turbine. The dynamic responses including the impact velocities between root and hub in selected wind-wave misalignment conditions are investigated using multibody simulations. Furthermore, based on a finite element study, different impact-induced failure modes at the blade root for sideways and head-on impact scenarios, developed due to wind-wave misalignment conditions, are investigated. Finally, based on extreme value analyses of critical responses, safe domain for the mating task under different wind-wave misalignments is compared. The results show that although misaligned wind-wave conditions develop substantial relative motions between root and hub, aligned wind-wave conditions induce largest impact velocities and develop critical failure modes at a relatively low threshold velocity of impact.

Numerical Simulation of the Resistance and Self-Propulsion Model Tests1

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Adrian Lungu
Keyword(s):  
Complex Structure ◽  
Turbulence Models ◽  
Open Water ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Local Flow ◽  
Complex Investigation ◽  
Flow Features ◽  
Thrust And Torque

Abstract The paper proposes a series of numerical investigations performed to test and demonstrate the capabilities of a Reynolds-averaged Navier–Stokes equation (RANSE) solver in the area of complex ship flow simulations. The focus is on a complete numerical model for hull, propeller, and rudder that can account for the mutual interaction between these components. The paper presents the results of a complex investigation of the flow computations around the hull model of the 3600 TEU MOERI containership (KCS hereafter). The resistance for the hull equipped with a rudder, the propeller open-water (POW hereafter) computations, as well as the self-propulsion simulation are presented. Comparisons with the experimental data provided at the Tokyo 2015 Workshop on Computational Fluid Dynamics (CFD) in Ship Hydrodynamics are given to validate the numerical approach in terms of the total and wave resistance coefficients, sinkage and trim, thrust and torque coefficients, propeller efficiency, and local flow features. Verification and validation based on the grid convergence tests are performed for each computational case. Discussions on the efficiency of the turbulence models used in the computations as well as on the main flow features are provided aimed at clarifying the complex structure of the flow around the ship stern.

Sign in / Sign up

Export Citation Format

Share Document