scholarly journals Vortex identification methods applied to wind turbine tip vortices

2021 ◽  
Author(s):  
Rodrigo Soto-Valle ◽  
Stefano Cioni ◽  
Sirko Bartholomay ◽  
Marinos Manolesos ◽  
Christian Navid Nayeri ◽  
...  
Keyword(s):  
Velocity Field ◽  
Wind Turbine ◽  
Tip Vortex ◽  
Vortex Center ◽  
Vortex Identification ◽  
Tip Vortices ◽  
Identification Methods ◽  
Image Velocimetry ◽  
The Impact ◽  
Selection Of

Abstract. This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using Particle Image Velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and its derivatives. They are applied to each instantaneous velocity field from the dataset and also to the calculated average velocity field. The methodologies are compared through the vortex center location, vortex core radius and jittering zone. Results show that the tip vortex center locations and radius have good comparability and can vary only a few grid spacings between methods. Conversely, the convection velocity and the jittering surface, defined as the area where the instantaneous vortex centers are located, vary between identification methods. Overall, the examined parameters depend significantly on the post-processing method and selected vortex identification criteria. Therefore, this study proves that the selection of the most suitable postprocessing methods of PIV data is pivotal to ensure robust results.

scholarly journals Research on Rotorcraft Blade Tip Vortex Identification and Motion Characteristics in Hovering State

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 196
Author(s):  
Hai Du ◽  
Wenjie Kong ◽  
Yan Wang ◽  
Wenjing Liu ◽  
Mingqi Huang ◽  
...  
Keyword(s):  
High Speed ◽  
Tip Vortex ◽  
Axial Position ◽  
Aerodynamic Load ◽  
Vortex Center ◽  
Vortex Identification ◽  
Identification Methods ◽  
Study Results ◽  
Blade Tip ◽  
Motion Characteristics

The rotorcraft blade tip vortex rolled up by the blade tip when the rotor rotates at high speed will produce a complex induced velocity field, which will have an important impact on the aerodynamic load and performance of the rotor. For this reason, this paper carries out the research on the identification of blade tip vortex and the motion characteristics of the vortex. Through the time-resolved particle image velocimetry (TR-PIV) experiment, the flow field of the rotor at a fixed rotate speed (2100 r/min) with a collective pitch of 6° and 9° was obtained. Based on the vorticity field, Q criterion, and Ω criterion, the research on vortex identification and vortex motion characteristics are realized. The results show that with the increase of blade motion azimuth, the radial position of blade tip vortex gradually contracts inward and the axial position moves downward in hovering state. As the collective pitch of the rotor increases, the radial contraction becomes more obvious, and the axial displacement increases, at the same time, the blade tip vortex intensity increases. Comparative study results show that different vortex identification methods have obtained certain deviations in the vortex center. Compared with other vortex identification methods, the Ω criterion method has a smaller deviation and can accurately identify the vortex core radius and vortex boundary.

Effect of Upstream Rotor Vortical Disturbances on the Time-Averaged Performance of Axial Compressor Stators: Part 1—Framework of Technical Approach and Wake–Stator Blade Interactions

1999 ◽  
Vol 121 (3) ◽  
pp. 377-386 ◽  
Author(s):  
T. V. Valkov ◽  
C. S. Tan
Keyword(s):  
Total Pressure ◽  
Axial Compressor ◽  
Tip Vortex ◽  
Technical Approach ◽  
Tip Vortices ◽  
Tip Leakage ◽  
Unsteady Interaction ◽  
Flow Approximation ◽  
Stator Blade ◽  
The Impact

In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stators with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-averaged performance of the stator. Detailed interrogation of the computed flow field showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically, there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated nontransitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.

scholarly journals Towards reduced order modelling for predicting the dynamics of coherent vorticity structures within wind turbine wakes

2017 ◽  
Vol 375 (2091) ◽  
pp. 20160108 ◽  
Author(s):  
M. Debnath ◽  
C. Santoni ◽  
S. Leonardi ◽  
G. V. Iungo
Keyword(s):  
Boundary Layer ◽  
Velocity Field ◽  
Atmospheric Boundary Layer ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Dynamic Mode ◽  
Decomposition Techniques ◽  
Modal Decomposition ◽  
Tip Vortices ◽  
Reduced Order

The dynamics of the velocity field resulting from the interaction between the atmospheric boundary layer and a wind turbine array can affect significantly the performance of a wind power plant and the durability of wind turbines. In this work, dynamics in wind turbine wakes and instabilities of helicoidal tip vortices are detected and characterized through modal decomposition techniques. The dataset under examination consists of snapshots of the velocity field obtained from large-eddy simulations (LES) of an isolated wind turbine, for which aerodynamic forcing exerted by the turbine blades on the atmospheric boundary layer is mimicked through the actuator line model. Particular attention is paid to the interaction between the downstream evolution of the helicoidal tip vortices and the alternate vortex shedding from the turbine tower. The LES dataset is interrogated through different modal decomposition techniques, such as proper orthogonal decomposition and dynamic mode decomposition. The dominant wake dynamics are selected for the formulation of a reduced order model, which consists in a linear time-marching algorithm where temporal evolution of flow dynamics is obtained from the previous temporal realization multiplied by a time-invariant operator. This article is part of the themed issue ‘Wind energy in complex terrains’.

scholarly journals Impact of Surface Roughness on the Turbulent Wake Flow of a Turbine Blade

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
K. Mulleners ◽  
P. Gilge ◽  
S. Hohenstein
Keyword(s):  
Surface Roughness ◽  
Velocity Field ◽  
Turbine Blade ◽  
Field Measurements ◽  
Wake Flow ◽  
Vortical Structures ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
The Individual ◽  
The Impact

Roughened aeroengine blade surfaces lead to increased friction losses and reduced efficiency of the individual blades. The surface roughness also affects the wake flow of the blade and thus the inflow conditions for the subsequent compressor or turbine stage. To investigate the impact of surface roughness on a turbulent blade wake, we conducted velocity field measurements by means of stereo particle image velocimetry in the wake of a roughened turbine blade in a linear cascade wind tunnel. The turbine blade was roughened at different chordwise locations. The influence of the chordwise location of the added surface roughness was examined by comparing their impact on the width and depth of the wake and, the positions and distribution of vortical structures in the wake. Additionally, the friction loss coefficients for different surface roughness positions were estimated directly from the velocity field.

scholarly journals The Rolled-up and Tip Vortices Studies in the CFD Model of the 3-D Swept-Backward Wind Turbine Blades

2017 ◽  
Vol 11 (12) ◽  
pp. 118 ◽  
Author(s):  
Sutrisno . ◽  
Deendarlianto . ◽  
Tri Agung Rochmat ◽  
Indarto . ◽  
Setyawan Bekti Wibowo ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Tip Vortex ◽  
Dynamics Simulation ◽  
Vortex Center ◽  
Wind Turbine Blades ◽  
Detailed Measurement ◽  
Vortex Effect ◽  
Strong Vortex

In this paper, the method to analyze of vortex dynamics simulation of 3-D (three dimensional) backward wind turbine blades is introduced, consisted of flow visualization part and detailed measurement part. With this method, one could explain visually and by calculation the role of 3-D flow vortex mechanism patterns on 3-D backward wind turbine blade, the interchange between kinetic and potential energies, the utilization of very strong vortex, which could lose energy, generate lift, and produce tangential mechanical power. The method could be elucidated by analyzing the appearance of rolled-up vortex effect on the 3-D backward wind turbine blades. A sharp pointed backward blade, generally has a weak tip vortex, may generate a second weak vortex center, and appears due to the rolled-up vortex effect, which is quite difficult to identify. The weakness of tip vortex makes the sharp pointed blade more efficient to exchange energy. Blunt backward turbine blades generally have a strong vortex center, a tip vortex; which in the form of a vortex core. Due to the rolled-up vortex effect, it could generate a second weak vortex center that is clearly visible. 

Computational analysis of vortices near casing in a transonic axial compressor rotor

2017 ◽  
Vol 233 (2) ◽  
pp. 710-724
Author(s):  
Yanhui Wu ◽  
Guangyao An ◽  
Zhiyang Chen ◽  
Bo Wang
Keyword(s):  
Shock Wave ◽  
Graphical Representation ◽  
Boundary Layer Separation ◽  
Tip Vortex ◽  
Vortex Identification ◽  
Tip Leakage Flow ◽  
Tip Leakage Vortex ◽  
Identification Methods ◽  
Tip Leakage ◽  
Compressor Rotor

Complicated flowfields near casing in a transonic axial flow compressor rotor have been numerically investigated in this paper. Two vortex identification methods, namely the Eigenvector Method and Lambda 2 Method, are introduced as important tools for the graphical representation of the concentrated vortices arising from tip leakage flow and blade boundary layer separation. The analysis of the numerical results reveals that multiple tip vortices whose development are dependent on the variation of shock wave configuration are observed at conditions around the peak efficiency point. However, with the decrease of the massflow rate, only the well-known tip leakage vortex and the second tip vortex are left in the tip region due to the disappearance of the second shock wave. Then when the massflow rate further decreases to the stall limit, an deceleration flow region emerges downstream of the shock wave due to an increasing interaction between the first shock wave and the well-known tip leakage vortex. The tip leakage vortex further experiences a bubble-type and then spiral-type breakdown at near stall flow conditions. In addition, the validity of the two vortex identification methods is also discussed in this paper. It is found that both methods are able to identify and accentuate the concentrated streamwise vortices near casing when a vortex is not disrupted. However, if the vortex breakdown occurs, only Eigenvector Method can describe the breakdown region in a deep view.

On the Use of Velocity Data for Load Estimation of a VAWT in Dynamic Stall

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
Carlos J. Simão Ferreira ◽  
Gerard J. W. van Bussel ◽  
Gijs A. M. van Kuik ◽  
Fulvio Scarano
Keyword(s):  
Velocity Field ◽  
Wind Turbine ◽  
Turbine Blades ◽  
Pressure Sensors ◽  
Vertical Axis ◽  
Dynamic Stall ◽  
Velocity Data ◽  
Vertical Axis Wind Turbine ◽  
Wind Turbine Blades ◽  
Image Velocimetry

This paper focuses on evaluating the feasibility of estimating loads on vertical axis wind turbine blades in dynamic stall with velocity data acquired with Particle Image Velocimetry. The study uses numerical simulation data of a 2D Vertical Axis Wind Turbine in dynamic stall to verify sources of error and uncertainty and estimate the accuracy of the method. The integration of the forces from the velocity field overcomes the difficulties and limitations presented by pressure sensors for estimating the local section loads, but adds the difficulty in determining the correct velocity field and its time and spatial derivatives. The analysis also evaluates the use of phase-locked average data as an estimator of average loads.

scholarly journals Measurement of the Flow Field Generated by Multicopter Propellers

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5537
Author(s):  
Zbigniew Czyż ◽  
Paweł Karpiński ◽  
Wit Stryczniewicz
Keyword(s):  
Velocity Field ◽  
Particle Image ◽  
Angle Of Attack ◽  
Vertical Plane ◽  
Airflow Velocity ◽  
Field Distributions ◽  
Image Velocimetry ◽  
Plane Passing ◽  
The Impact ◽  
Qualitative Analyses

This paper presents the results of research on the airflow around a multirotor aircraft. The research consisted of the analysis of the velocity field using particle image velocimetry. Based on the tests carried out in a wind tunnel, the distribution of the velocity and its components in the vertical plane passing through the propeller axis were determined for several values of the angle of attack of the tested object for two values of airflow velocity inside the tunnel, i.e., vwt = 0 m/s and vwt = 12.5 m/s. Determining the velocity value as a function of the coordinates of the adopted reference system allowed for defining the range of impact of the horizontal propellers and the fuselage of the research object itself. The tests allowed for quantitative and qualitative analyses of the airflow through the horizontal rotor. Particular attention was paid to the impact of the airflow and the angle of attack on the obtained velocity field distributions.

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