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Dataset for thesis "Effects of turbulence on the performance and wake of a model-scale wind turbine"
No full textThis dataset contains all the data used for the Southampton Doctoral thesis entitled : "Effects of turbulence on the performance and wake of a model-scale wind turbine". It consists of two archives: the first one, piv-insta.zip, contains the instantaneous PIV snapshots acquired in the turbine wake, while the second, data.zip, contains all other data.
It is a large dataset 258Gb available on request via https://library.soton.ac.uk/datarequest.</span
Effects of turbulence on the performance and wake of a model-scale wind turbine
No full textThis thesis work presents experimental results on the effects of different ambient turbulence conditions on the performance and wake development of a model-scale wind turbine, focusing on two main parameters to characterise the nature of the incoming nature: these are its intensity I∞ and its spectral distribution, represented by the integral time scale of the free-stream T0. The power generated by the model-scale turbine is seen to increase with the intensity of the velocity fluctuations, as well as with the free-stream integral time scale; the former finding is in line with established literature, albeit the magnitude of the increase is higher than what expected, while the latter confirms some recent works that model the turbines as low-pass filters, more apt to harvest energy from low-frequency fluctuations. The wake evolution under turbulence is also observed to be highly affected by the atmospheric conditions: wakes developed under higher turbulence intensity evolve more rapidly under the condition that the free-stream T0 is low; in other words, for the same I∞, conditions that are favourable for power harvesting generate longer wakes, unfavourable from the point of view of a wind farm. The predictions of some analytical wake models are compared to the obtained wake, highlighting how fine-tuning of the model parameters can result in very accurate predictions. The results obtained stress the need to include a virtual origin in the wake models, a practice customary for bluff-bodies but seldom employed for wind turbines; this quantity has been seen to relate to the stability of the helical tip-vortex structure, and thus conveys a physical meaning. The rate at which the mean velocity field evolves in the streamwise direction has been related to the Reynolds shear stress in the turbine wake by means of an analytical relation; this allows to predict the mean velocity field in the turbine wake with knowledge limited to the second-order statistics. This last finding has been leveraged to formulate a framework using proper orthogonal decomposition to predict the full-scale wake from limited probe data; preliminary results show that this is possible with acceptable results, correctly predicting both the intensity of the turbulence in the turbine wake from limited data and the mean wake velocity
Dataset for paper "The effects of free-stream turbulence on the performance of a model wind turbine"
No full textThis archive contains the minimal dataset necessary to reproduce the plots reported in the paper "The effects of free-stream turbulence on the performance of a model wind turbine", in the process of being published on the Journal of Renewable and Sustainable Energy.
Data for all figures, as well as scripts necessary to reproduce these, are included in the archive.</span
Supporting data for the journal article "The influence of freestream turbulence on the development of a wind turbine wake
No full textThis dataset contains:
The scripts needed to reduce the raw data (available at doi: http://dx.doi.org/10.5258/SOTON/D2197) to the content of the plots of the related publication.
Relationship between files, if important for context: The folder data/piv-insta needs the contents of the main dataset (doi: http://dx.doi.org/10.5258/SOTON/D2197) for the scripts in scripts-postprocess to work.
Additional related data collected that was not included in the current data package: (doi: http://dx.doi.org/10.5258/SOTON/D2197) not included because of space reasons (achive is over 200GB)</span
The effects of free-stream turbulence on the performance of a model wind turbine
No full textFree-stream turbulence characteristics play an important role in the mechanisms of power harvesting for wind turbines. Acquisitions of power and thrust from a model wind turbine of diameter 0.18 m have been carried out in a wind tunnel for a wide range of turbulent base flows, with varying free-stream turbulence intensity in the range between 3% and 16% and integral timescale spanning from 0.1 to 10 times the turbine rotation period. The results demonstrate that power is significantly affected by both the inflow turbulence scales and its intensity, while thrust is scarcely affected by free-stream turbulence. Fluctuations in the generated torques are also measured, with their behavior dominated by the free-stream turbulence scale, and only moderately affected by turbulence intensity. The frequency response of thrust fluctuations has been measured for a selected subset of operating conditions, demonstrating that the turbine thrust is unaffected by high-frequency components in the inflow. Conclusions are drawn on the necessity to match both turbulence intensity and base flow frequency content in wind tunnel studies if realistic results are to be obtained from small-scale studies.</p
The influence of freestream turbulence on the development of a wind turbine wake
Get PDFThe wake of an isolated model-scale wind turbine is analysed in a set of
inflow conditions having freestream turbulence intensity between 3 % and 12 %,
and integral time scales in the range of 0.1 to 10 times the convective
timescale based on the turbine diameter. It is observed that the wake generated
by the turbine evolves more rapidly, with the onset of the wake evolution being
closer to the turbine, for high turbulence intensity and low integral time
scale flows, in accordance with literature, while flows at higher integral time
scales result in a slow wake evolution, akin to that generated by
low-turbulence inflow conditions despite the highly-turbulent ambient
condition. The delayed onset of the wake evolution is connected to the
stability of the shear layer enveloping the near wake, which is favoured for
low-turbulence or high-integral time scale flows, and to the stability of the
helical vortex set surrounding the wake, as this favours interaction events and
prevents momentum exchange at the wake boundary which hinder wake evolution.
The rate at which the velocity in the wake recovers to undisturbed conditions
is instead analytically shown to be a function of the Reynolds shear stress at
the wake centreline, an observation that is confirmed by measurements. The rate
of production of Reynolds shear stress in the wake is then connected to the
power harvested by the turbine to explain the differences between flows at
constant turbulence intensity and different integral time scales.Comment: 26 pages, 21 figures. Velocity snapshots available at
https://doi.org/10.5258/SOTON/D219
Replication Data for: The far wake of porous disks and a model wind turbine: Similarities and differences assessed by hot wire anemometry
No full textThis dataset contains all data necesary to produce the figures containing original data in the paper "The far wake of porous disks and a model wind turbine: Similarities and differences assessed by hot wire anemometry". It contains single wire hot-wire anemometry (HWA) of the far wakes of four wake generationg objects, one solid disk (SD), two different porous disks (non-uniform disk, ND, and uniform disk, UD) used as static wind turbine models, and a wind turbine (WT).</span
The far wake of porous disks and a model wind turbine: Similarities and differences assessed by hot-wire anemometry
No full textThe wakes of two different porous disks have been evaluated experimentally. Such disks are commonly used as physical actuator disk analogs for wind turbines. One disk is made of a uniform wire mesh, while the other has a nonuniform design with radial spars connected by rings. The disks have the same solidity and produce approximately the same drag. The wakes have also been compared to the wake of a model wind turbine and a solid disk. In contrast to earlier studies, the far wake, up to 30 diameters downstream, is included in the comparison. In the near wake, the velocity deficit and turbulence intensity profiles of the disk wakes differ significantly. High levels of turbulence intensity in the wake of the nonuniform disk increase the transverse transport in the wake, which leads to faster spreading and lower velocity deficits in the far wake, compared to the uniform disk and the wind turbine. High velocity gradients in the wake of the uniform disk give rise to turbulence production farther downstream, maintaining higher turbulence levels in the far wake. In addition, coherent vortex shedding is only identified in the wake of the nonuniform disk. None of the disks were able to replicate the asymmetric features of the wind turbine wake. Nonetheless, the results highlight important flow physics that should be considered in the design process of a porous disk used as a wind turbine surrogate
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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