scholarly journals Assessing Spacing Impact on Coherent Features in a Wind Turbine Array Boundary Layer

2017 ◽  
Author(s):  
Naseem Ali ◽  
Nicholas Hamilton ◽  
Raul Cal
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flow ◽  
Wind Turbine ◽  
Reynolds Stress ◽  
Flow Structure ◽  
Energy Content ◽  
Turbulence Kinetic Energy ◽  
Flow Structures ◽  
Spanwise Direction ◽  
The Impact

Abstract. As wind farms become larger, the spacing between turbines becomes a significant design element that imposes serious economic constraints. Effects of turbine spacing on the power produced and flow structure are crucial for future development of wind energy. To investigate the turbulent flow structures in a 4 × 3 Cartesian wind turbine array, a wind tunnel experiment was carried out parameterizing the streamwise and spanwise wind turbine spacing. Four cases were chosen spacing turbines by 6 diameters (D) or 3D in the streamwise, and 3D or 1.5D in the spanwise direction. Data were obtained experimentally using stereo particle-image velocimetry. Mean streamwise velocity showed maximum values upstream of the turbine with the spacing of 6D and 3D, in the streamwise and spanwise direction, respectively. Fixing the spanwise turbine spacing to 3D, variations in the streamwise spacing influence the turbulent flow structure and the power available to following wind turbines. Quantitative comparisons were made through spatial averaging, shifting measurement data and interpolating to account for the full range between devices to obtain data independent of array spacing. The largest averaged Reynolds stress is seen in cases with spacing of 3D and 3D, in the streamwise and spanwise direction, respectively. Snapshot proper orthogonal decomposition was employed to identify the flow structures based on the turbulence kinetic energy content. The maximum turbulence kinetic energy content in the first POD mode compared with other cases is seen for turbine spacing of 6D × 1.5D. The flow upstream of each wind turbine converges faster than the flow downstream according to accumulation of turbulence kinetic energy by POD modes, regardless of spacing. The streamwise-averaged profile of the Reynolds stress is reconstructed using a specific number of modes for each case; the case of 6D × 1.5D spacing shows the fastest reconstruction. Intermediate modes are also used to reconstruct the averaged profile and show that the intermediate scales are responsible for features seen in the original profile. The variation in streamwise and spanwis spacing leads to changing the background structure of the turbulence, where the color map based on barycentric map and anisotropy stress tensor provides a new perspective on the nature of the perturbations within the wind turbine array. The impact of the streamwise and spanwise spacings on power produced is quantified, where the maximum production corresponds with the case of greatest turbine spacing.

scholarly journals Assessing spacing impact on coherent features in a wind turbine array boundary layer

2018 ◽  
Vol 3 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Naseem Ali ◽  
Nicholas Hamilton ◽  
Dominic DeLucia ◽  
Raúl Bayoán Cal
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Flow ◽  
Wind Turbine ◽  
Reynolds Stress ◽  
Energy Content ◽  
Turbulence Kinetic Energy ◽  
Flow Structures ◽  
Spanwise Direction ◽  
The Impact

Abstract. As wind farms become larger, the spacing between turbines becomes a significant design consideration that can impose serious economic constraints. To investigate the turbulent flow structures in a 4 × 3 Cartesian wind turbine array boundary layer (WTABL), a wind tunnel experiment was carried out parameterizing the streamwise and spanwise wind turbine spacing. Four cases are chosen spacing turbines by 6 or 3D in the streamwise direction, and 3 or 1.5D in the spanwise direction, where D = 12 cm is the rotor diameter. Data are obtained experimentally using stereo particle image velocimetry. Mean streamwise velocity showed maximum values upstream of the turbine with the spacing of 6 and 3D in the streamwise and spanwise direction, respectively. Fixing the spanwise turbine spacing to 3D, variations in the streamwise spacing influence the turbulent flow structure and the power available to following wind turbines. Quantitative comparisons are made through spatial averaging, shifting measurement data and interpolating to account for the full range between devices to obtain data independent of array spacing. The largest averaged Reynolds stress is seen in cases with spacing of 3D × 3D. Snapshot proper orthogonal decomposition (POD) was employed to identify the flow structures based on the turbulence kinetic energy content. The maximum turbulence kinetic energy content in the first POD mode is seen for turbine spacing of 6D × 1.5D. The flow upstream of each wind turbine converges faster than the flow downstream according to accumulation of turbulence kinetic energy by POD modes, regardless of spacing. The streamwise-averaged profile of the Reynolds stress is reconstructed using a specific number of modes for each case; the case of 6D × 1.5D spacing shows the fastest reconstruction to compare the rate of reconstruction of statistical profiles. Intermediate modes are also used to reconstruct the averaged profile and show that the intermediate scales are responsible for features seen in the original profile. The variation in streamwise and spanwise spacing leads to changes in the background structure of the turbulence, where the color map based on barycentric map and Reynolds stress anisotropy tensor provides an alternate perspective on the nature of the perturbations within the wind turbine array. The impact of the streamwise and spanwise spacings on power produced is quantified, where the maximum production corresponds with the case of greatest turbine spacing.

Turbulent characteristics of flow in the vicinity of mid-channel braid bar

2020 ◽  
Author(s):  
Mohammad Amir Khan ◽  
Nayan Sharma ◽  
MANISH PANDEY ◽  
Mohd Obaid Qamar
Keyword(s):  
Turbulent Flow ◽  
Flow Structure ◽  
Turbulent Intensity ◽  
Flow Area ◽  
Fluvial Processes ◽  
Relative Dominance ◽  
Turbulent Characteristics ◽  
Turbulent Flow Structure ◽  
The Impact ◽  
Channel Bar

The impact of a mid-channel bar on the turbulent flow structure has been investigated in this research. A new Dominance Function S_(i,H) is proposed in this study as a measure of the relative dominance of ejection and sweep events in turbulent flow structure. Occurrence of the kolk-boil phenomenon is observed due to interaction of ejection and sweep events.. A new parameter Movement Ratio is formulated in this study which is found to faithfully reflect the fluvial processes of sedimentation and scouring on the channel bed.. Acceleration of flow is seen to occur at adjoining regions close to the upstream end of the bar. Due to the presence of the bar, the flow area in its proximity decreases which has caused increment in the velocity at sections located near the upstream end of the mid-channel bar. For model runs with bars, a distinct bulge in the turbulent intensity graph is observed.

scholarly journals The Impact of Three-Dimensional Effects on the Simulation of Turbulence Kinetic Energy in a Major Alpine Valley

2018 ◽  
Vol 168 (1) ◽  
pp. 1-27 ◽  
Author(s):  
Brigitta Goger ◽  
Mathias W. Rotach ◽  
Alexander Gohm ◽  
Oliver Fuhrer ◽  
Ivana Stiperski ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Three Dimensional ◽  
Turbulence Kinetic Energy ◽  
Alpine Valley ◽  
Dimensional Effects ◽  
The Impact

Three-Dimensional Computations of Turbulent Flow in a Turbine-Rotor Passage

1997 ◽  
Author(s):  
B. Song ◽  
R. S. Amano ◽  
S. Sitarama ◽  
B. Lin
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flow ◽  
Isotropic Turbulence ◽  
Numerical Study ◽  
Interpolation Method ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Turbulence Kinetic Energy ◽  
Wall Region ◽  
Staggered Grids

Numerical study on a three-dimensional turbulent flow in a turbine-rotor passage is presented in this paper. The standard k-ε model was used for the first phase of the turbulence computations. The computations were further extended by employing the full Reynolds-stress closure model (RSM). The computational results obtained using these models were compared in order to investigate the turbulence effect in the near-wall region. The governing equations in a generalized curvilinear coordinate system are discretized by using the SIMPLEC method with non-staggered grids. The oscillations in pressure and velocity due to non-staggered grids are eliminated by using a special interpolation method. The predicted midspan pressure coefficients using the k-ε model and the RSM are compared with the experimental data. It was shown that the present results obtained by using either model are fairly reasonable. Computations were then extended to cover the entire blade-to-blade flow passage, and the three-dimensional effects on pressure and turbulence kinetic energy were evaluated. It was observed that the two turbulence models predict different results for the turbulence kinetic energy. This variation was identified as being related to some non-isotropic turbulence occurring near the blade surface due to the severe acceleration of the flow. It was thus proven that the models based on the RSM give more realistic predictions for highly turbulent cascade flow computations than a Boussinesq viscosity model.

scholarly journals Turbulent Kinetic Energy in Bolt Fishway

2019 ◽  
Vol 1 (2) ◽  
pp. 265-282
Author(s):  
Marta Puzdrowska ◽  
Tomasz Heese
Keyword(s):  
Spatial Distribution ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Laboratory Tests ◽  
Flow Structures ◽  
3D Flow ◽  
Velocity Magnitude ◽  
Biological Development ◽  
The Impact ◽  
Channel Development

The paper presents an analysis the spatial distribution of turbulent kinetic energy (TKE) for bolt fishways, including the impact of additional spillway slots and fixed channel development. The research was done for two models, each containing a different arrangement of slots. The presented results of research for bolt fishways were obtained as an effect of laboratory tests. The measurements were done for three components of instant flow velocity magnitude (speed). Analysis of the results was done for a 3D flow structure using Matlab software. In the case of bolt fishways, significant differences were noted for the method of velocity and TKE distribution, in reference to research comprising channels with biological development. It was stated that a reason for this is the flexible development of the channel. The occurrence of extreme TKE values in the chamber (pool) is strictly associated with the characteristics of interaction zones between various flow structures. It was also stated that the lower the parapet of the slot’s spillway shelf is in the fishway’s partition, the higher TKE could be expected just downstream of the section. These establishments may be important for the designing process in the case of fish passes of various types of construction.

scholarly journals Analysis of Turbulent Flow Structure with Its Fluvial Processes around Mid-Channel Bar

2021 ◽  
Vol 14 (1) ◽  
pp. 392
Author(s):  
Md. Amir Khan ◽  
Nayan Sharma ◽  
Jaan Pu ◽  
Faisal M. Alfaisal ◽  
Shamshad Alam ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Turbulent Flow ◽  
Flow Velocity ◽  
Turbulent Kinetic Energy ◽  
Production Rate ◽  
Energy Transport ◽  
Vertical Distance ◽  
Scour Hole ◽  
The Impact ◽  
Channel Bar

Researchers have recognized that the successive growth of mid-channel bar deposits can be entertained as the raison d’être for the initiation of the braiding process, which is closely interlinked with the growth, decay, and vertical distribution of fluvial turbulent kinetic energy (TKE). Thus, focused analysis on the underlying mechanics of turbulent flow structures in the proximity of a bar deposit occurring in the middle of the channel can afford crucial scientific clues for insight into the initiating fluvial processes that give rise to braiding. In the study reported herein, a physical model of a mid-channel bar is constructed in an experimental flume to analyze the turbulence parameters in a region close to the bar. Notably, the flow velocity plays an important role in understanding the flow behavior in the scour-hole location in the upstream flow divergence zone as well as near the downstream zone of flow convergence in a mid-channel bar. Therefore, the fluctuating components of turbulent flow velocity are herein discussed and analyzed for the regions located close to the bar. In the present study, the impact of the mid-channel bar, as well as its growth in turbulent flow, on higher-order velocity fluctuation moments are investigated. For near-bed locations, the results show the dominance of ejection events in upstream zones and the dominance of sweep events at locations downstream of the mid-channel bar. In scour-hole sections, the negative value of the stream-wise flux of turbulent kinetic energy and the positive value of the vertical flux of turbulent kinetic energy indicate energy transport in downward and forward directions, respectively. The downward and forward energy transport processes lead to scouring at these locations. The maximum turbulent production rate occurs in the wake region of the bar. The high rate of turbulence production has occurred in that region, which can be ascribed to the process of shedding turbulent vortices. The results show that the impact of the presence of the bar is mainly restricted to the lower layers of flow. The turbulent dissipation rate monotonically decreases with an increase in the vertical distance from the bed. The turbulent production rate first increases and then decreases with successive increases in the vertical distance from the bed. The paper concludes with suggestions for the future potential use of the present research for the practical purpose of examining braid bar occurrences in alluvial rivers to develop an appropriate response through training measures.

scholarly journals Assessing Spacing Impact on the Wind Turbine Array Boundary Layer via Proper Orthogonal Decomposition

2016 ◽  
Author(s):  
Naseem Ali ◽  
Nicholas Hamilton ◽  
Raúl Bayáon Cal
Keyword(s):  
Proper Orthogonal Decomposition ◽  
Energy Content ◽  
Region Of Interest ◽  
Orthogonal Decomposition ◽  
Spanwise Direction ◽  
Mean Velocity ◽  
Stereo Particle Image Velocimetry ◽  
Downstream Flow ◽  
Proper Orthogonal ◽  
The Impact

Abstract. A 4 × 3 array of wind turbines was assembled in a wind tunnel with four cases to study the influence based on streamwise and spanwise spacings. Data are extracted using stereo particle-image velocimetry and analyzed statistically. The maximum mean velocity is displayed at the upstream of the turbine with the spacing of 6D and 3D, in streamwise and spanwise direction, respectively. The region of interest downstream to the turbine confirms a notable influence of the streamwise spacing is shown when the spanwise spacing equals to 3D. Thus the significant impact of the spanwise spacing is observed when the streamwise spacing equals to 3D. Streamwise averaging is performed after shifting the upstream windows toward the downstream flow. The largest and smallest averaged Reynolds stress, and flux locates at cases 3D × 3D and 6D × 1.5D, respectively. Snapshot proper orthogonal decomposition is employed to identify the flow coherence depending on the turbulent kinetic energy content. The case of spacing 6D × 1.5D possesses highest energy content in the first mode compared with other cases. The impact of the streamwise and spanwise spacings in power produce is quantified, where the maximum power is found in the spacing of 6D × 3D.

Turbulence Kinetic Energy Performance on Wind Turbine Blade Using CFD

2013 ◽  
Vol 315 ◽  
pp. 523-526 ◽  
Author(s):  
Azmahani Sadikin ◽  
M.R. Shamsudin ◽  
A. Wahab
Keyword(s):  
Kinetic Energy ◽  
Wind Energy ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Lift Coefficient ◽  
Energy Performance ◽  
Wind Turbine Blade ◽  
Turbulence Kinetic Energy ◽  
Good Design ◽  
The World

Wind represents the kinetic energy of the atmosphere. Wind energy is currently supplying as much as 1% of the world electricity used, and could supply as much as 20% of global electricity in power and can be created through the use of wind turbines. Wind turbine blade is the most promising technology for the production of energy by using wind energy. Good design of wind turbine blade depends on performance of increasing to generate electricity which related with drag coefficient , lift coefficient and turbulence kinetic energy. However, the efficiency of wind turbine blade could be predicted by simulation due to flow streamline on wind turbine blade. This paper discuss the result obtain from simulation in CFD using CFX on NACA 4412 and NACA 4415.

Effect of moisture percentage on the wind turbine performance

2018 ◽  
Vol 2 (1) ◽  
Author(s):  
Suad Danook ◽  
Kamal Tawfeeq ◽  
Esraa Mansoor
Keyword(s):  
Kinetic Energy ◽  
Wind Turbine ◽  
Electric Energy ◽  
Energy System ◽  
Alternative Source ◽  
Dry Air ◽  
Turbine Performance ◽  
Wind Energy System ◽  
Moisture Percentage ◽  
The Impact

This paper incorporates the utilization of the wind energy system as an alternative source for Traditional source of energy, where it has been studied convert the kinetic energy in the wind to electric energy and the impact of humidity which effect on the density of air and the density of dry air is higher from humid. So the humid air meaning lower density then lower power from wind turbine.

scholarly journals Atmospheric teleconnection patterns and eddy kinetic energy content: wavelet analysis

2004 ◽  
Vol 11 (3) ◽  
pp. 295-301 ◽  
Author(s):  
V. N. Khokhlov ◽  
A. V. Glushkov ◽  
I. A. Tsenenko
Keyword(s):  
Kinetic Energy ◽  
North Atlantic ◽  
Energy Content ◽  
Southern Oscillation ◽  
Eddy Kinetic Energy ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
The Relationship

Abstract. In this paper, we employ a non-decimated wavelet decomposition to analyse long-term variations of the teleconnection pattern monthly indices (the North Atlantic Oscillation and the Southern Oscillation) and the relationship of these variations with eddy kinetic energy contents (KE) in the atmosphere of mid-latitudes and tropics. Major advantage of using this tool is to isolate short- and long-term components of fluctuations. Such analysis allows revealing basic periodic behaviours for the North Atlantic Oscillations (NAO) indices such as the 4-8-year and the natural change of dominant phase. The main results can be posed as follows. First, if the phases of North Atlantic and Southern Oscillations vary synchronously with the 4-8-year period then the relationship between the variations of the NAO indices and the KE contents is the most appreciable. Second, if the NAO phase tends to abrupt changes then the impact of these variations on the eddy kinetic energy contents in both mid-latitudes and tropics is more significant than for the durational dominance of certain phase.

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