scholarly journals Interferometric Ice Particle Imaging in a Wind Tunnel

Optics ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 216-227
Author(s):  
Mohamed Talbi ◽  
Romain Duperrier ◽  
Barbara Delestre ◽  
Gilles Godard ◽  
Marc Brunel
Keyword(s):  
Wind Tunnel ◽  
Single Particle ◽  
Particle Sizing ◽  
High Wind ◽  
Wind Speeds ◽  
Ice Particles ◽  
Particle Imaging

We report interferometric ice particle imaging and sizing in an icing wind tunnel with wind speeds of 70 m/s. Single particle interferograms are first analysed, size measurements are performed, and examples of possible reconstructed shapes are deduced from the interferometric images. Particle sizing is also performed in the case of ice particles whose out-of-focus images overlap, with or without Moiré phenomena. Results show that the IPI technique can be carried out for irregular rough particles in a critical environment such as in an icing wind tunnel with high wind speeds.

scholarly journals Mitigating Large Vibrations of Stayed Cables in Wind and Rain Hazards

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Hung Vo-Duy ◽  
Cung H. Nguyen
Keyword(s):  
Experimental Investigation ◽  
Wind Tunnel ◽  
Significant Role ◽  
Low Frequency ◽  
Vortex Flows ◽  
Complex Mechanism ◽  
High Wind ◽  
Wind Speeds ◽  
Cable Vibrations

This paper presents an experimental investigation of stayed cable vibrations in dry-wind and rain-wind coupling hazards. To mitigate large vibrations of the cable, the use of spiral wires wrapped around the cable is proposed. By testing two cable models in a wind tunnel in dry and rain conditions for different yaw angles and wind speeds, the effectiveness of using the spiral wires to mitigate large vibrations is clarified. Finally, the paper provides a further understanding of the complex mechanism of wind-induced and rain-wind-induced vibrations. It is found that the low-frequency vortex flows in the wake play a significant role in the excitation of large responses of the cable in high wind speeds. The spiral wires dismiss these low-frequency flows and then reduce the large vibrations.

scholarly journals Dependence of Power Characteristics on Savonius Rotor Segmentation

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2912
Author(s):  
Krzysztof Doerffer ◽  
Janusz Telega ◽  
Piotr Doerffer ◽  
Paulina Hercel ◽  
Andrzej Tomporowski
Keyword(s):  
High Wind ◽  
Horizontal Axis Wind Turbine ◽  
Savonius Rotor ◽  
Power Characteristics ◽  
Wind Speeds ◽  
Single Segment ◽  
High Elongation ◽  
Low Wind Speeds ◽  
Number Of Segments ◽  
Rotor Type

Savonius rotors are large and heavy because they use drag force for propulsion. This leads to a larger investment in comparison to horizontal axis wind turbine (HAWT) rotors using lift forces. A simple construction of the Savonius rotor is preferred to reduce the production effort. Therefore, it is proposed here to use single-segment rotors of high elongation. Nevertheless, this rotor type must be compared with a multi-segment rotor to prove that the simplification does not deteriorate the effectiveness. The number of segments affects the aerodynamic performance of the rotor, however, the results shown in the literature are inconsistent. The paper presents a new observation that the relation between the effectiveness of single- and multi-segment rotors depends on the wind velocity. A single-segment rotor becomes significantly more effective than a four-segment rotor at low wind speeds. At high wind speeds, the effectiveness of both rotors becomes similar.

scholarly journals An encryption–decryption framework to validating single-particle imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhou Shen ◽  
Colin Zhi Wei Teo ◽  
Kartik Ayyer ◽  
N. Duane Loh
Keyword(s):  
Conceptual Framework ◽  
Single Particle ◽  
Latent Variables ◽  
Ground Truth ◽  
Resolving Power ◽  
Validation Measure ◽  
Encryption Decryption ◽  
Diffraction Patterns ◽  
Particle Imaging ◽  
Single Particle Imaging

AbstractWe propose an encryption–decryption framework for validating diffraction intensity volumes reconstructed using single-particle imaging (SPI) with X-ray free-electron lasers (XFELs) when the ground truth volume is absent. This conceptual framework exploits each reconstructed volumes’ ability to decipher latent variables (e.g. orientations) of unseen sentinel diffraction patterns. Using this framework, we quantify novel measures of orientation disconcurrence, inconsistency, and disagreement between the decryptions by two independently reconstructed volumes. We also study how these measures can be used to define data sufficiency and its relation to spatial resolution, and the practical consequences of focusing XFEL pulses to smaller foci. This conceptual framework overcomes critical ambiguities in using Fourier Shell Correlation (FSC) as a validation measure for SPI. Finally, we show how this encryption-decryption framework naturally leads to an information-theoretic reformulation of the resolving power of XFEL-SPI, which we hope will lead to principled frameworks for experiment and instrument design.

Midlatitude cyclones in convection permitting climate simulations: the added value offered for extreme wind speeds and sting-jets

2021 ◽  
Author(s):  
Colin Manning ◽  
Elizabeth Kendon ◽  
Hayley Fowler ◽  
Nigel Roberts ◽  
Segolene Berthou ◽  
...  
Keyword(s):  
Climate Model ◽  
Surface Wind ◽  
Added Value ◽  
Large Contribution ◽  
High Wind ◽  
Wind Speeds ◽  
Wind Gusts ◽  
Climate Simulations ◽  
Extreme Wind ◽  
Extreme Wind Speeds

<p>Extra-tropical windstorms are one of the costliest natural hazards affecting Europe, and windstorms that develop a phenomenon known as a sting-jet account for some of the most damaging storms. A sting-jet (SJ) is a mesoscale core of high wind speeds that occurs in particular types of cyclones, specifically Shapiro-Keyser (SK) cyclones, and can produce extremely damaging surface wind gusts. High-resolution climate models are required to adequately model SJs and so it is difficult to gauge their contribution to current and future wind risk. In this study, we develop a low-cost methodology to automate the detection of sting jets, using the characteristic warm seclusion of SK cyclones and the slantwise descent of high wind speeds, within pan-European 2.2km convection-permitting climate model (CPM) simulations. Following this, we quantify the contribution of such storms to wind risk in Northern Europe in current and future climate simulations, and secondly assess the added value offered by the CPM compared to a traditional coarse-resolution climate model. This presentation will give an overview of the developed methods and the results of our analysis.</p><p>Comparing with observations, we find that the representation of wind gusts is improved in the CPM compared to ERA-Interim reanalysis data. Storm severity metrics indicate that SK cyclones account for the majority of the most damaging windstorms. The future simulation produces a large increase (>100%) in the number of storms exceeding high thresholds of the storm metric, with a large contribution to this change (40%) coming from windstorms in which a sting-jet is detected. Finally, we see a systematic underestimation in the GCM compared to the CPM in the frequency of extreme wind speeds at 850hPa in the cold sector of cyclones, likely related to better representation of sting-jets and the cold conveyor belt in the CPM. This underestimation is between 20-40% and increases with increasing wind speed above 35m/s. We conclude that the CPM adds value in the representation of severe surface wind gusts, providing more reliable future projections and improved input for impact models.</p>

Study on the Relation Between Side Ratios of Rectangular Cross Sections and Secondary Vortices at Trailing Edge in Motion-Induced Vortex Excitation

2017 ◽  
Author(s):  
Kazutoshi Matsuda ◽  
Kusuo Kato ◽  
Kouki Arise ◽  
Hajime Ishii
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Cross Sections ◽  
Leading Edge ◽  
Trailing Edge ◽  
Wind Speeds ◽  
Smoke Flow ◽  
Flow Visualizations ◽  
Institute Of Technology ◽  
Secondary Vortices

According to the results of conventional wind tunnel tests on rectangular cross sections with side ratios of B/D = 2–8 (B: along-wind length (m), D: cross-wind length (m)), motion-induced vortex excitation was confirmed. The generation of motion-induced vortex excitation is considered to be caused by the unification of separated vortices from the leading edge and secondary vortices at the trailing edge [1]. Spring-supported test for B/D = 1.18 was conducted in a closed circuit wind tunnel (cross section: 1.8 m high×0.9 m wide) at Kyushu Institute of Technology. Vibrations were confirmed in the neighborhoods of reduced wind speeds Vr = V/fD = 2 and Vr = 8 (V: wind speed (m/s), f: natural frequency (Hz)). Because the reduced wind speed in motion-induced vortex excitation is calculated as Vr = 1.67×B/D = 1.67×1.18 = 2.0 [1], vibrations around Vr = 2 were considered to be motion-induced vortex excitation. According to the smoke flow visualization result for B/D = 1.18 which was carried out by the authors, no secondary vortices at the trailing edge were formed, although separated vortices from the leading edge were formed at the time of oscillation at the onset wind speed of motion-induced vortex excitation, where aerodynamic vibrations considered to be motion-induced vortex excitation were confirmed. It was suggested that motion-induced vortex excitation might possibly occur in the range of low wind speeds, even in the case of side ratios where secondary vortices at trailing edge were not confirmed. In this study, smoke flow visualizations were performed for ratios of B/D = 0.5–2.0 in order to find out the relation between side ratios of rectangular cross sections and secondary vortices at trailing edge in motion-induced vortex excitation. The smoke flow visualizations around the model during oscillating condition were conducted in a small-sized wind tunnel at Kyushu Institute of Technology. Experimental Reynolds number was Re = VD/v = 1.6×103. For the forced-oscillating amplitude η, the non-dimensional double amplitudes were set as 2η/D = 0.02–0.15. Spring-supported tests were also carried out in order to obtain the response characteristics of the models.

The retention of ammonia and sulfur dioxide during riming of ice particles and dendritic snow flakes: laboratory experiments in the Mainz vertical wind tunnel

2013 ◽  
Vol 70 (2) ◽  
pp. 131-150 ◽  
Author(s):  
Nadine v. Blohn ◽  
Karoline Diehl ◽  
Anke Nölscher ◽  
Alexander Jost ◽  
Subir K. Mitra ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Sulfur Dioxide ◽  
Laboratory Experiments ◽  
Vertical Wind ◽  
Ice Particles

A stochastic model for sand sorting in a wind-tunnel

1981 ◽  
Vol 13 (2) ◽  
pp. 282-297 ◽  
Author(s):  
O. Barndorff-Nielsen ◽  
J. N. Darroch
Keyword(s):  
Wind Tunnel ◽  
Stochastic Model ◽  
Single Particle ◽  
Hyperbolic Type ◽  
Size Distributions ◽  
Wind Tunnel Experiments ◽  
Stable Conditions ◽  
Hyperbolic Form ◽  
Experimental Findings

The wind exerts a sorting effect on particles of sands and, under certain stable conditions that occur frequently but whose nature is little understood, the sorting results in log-size distributions of the hyperbolic form, first noted by R. A. Bagnold. Here, for wind-tunnel experiments a stochastic model is constructed which exhibits a sorting effect deriving from the dependence of distance travelled on the size of the single particle. Under rather specific, experimentally testable assumptions the model reproduces log-size distributions which are of the hyperbolic type and show a variation with distance along the wind tunnel that accords with experimental findings of R. A. Bagnold.

Wind Tunnel Model Study of the Hot Exhaust Plume From the Compressor Research Facility at Wright-Patterson Air Force Base, OH

1979 ◽  
Author(s):  
G. R. Ludwig
Keyword(s):  
Wind Tunnel ◽  
Air Force ◽  
Research Facility ◽  
Wind Tunnel Model ◽  
Wind Speeds ◽  
Model Study ◽  
Tunnel Model ◽  
Concentration Measurements ◽  
Building Ventilation ◽  
Air Force Base

This paper presents the results of a wind tunnel model study to determine temperatures at various locations generated by the hot exhaust air from the Compressor Research Facility [CRF] which is being built at Wright-Patterson Air Force Base, Ohio. The study was designed to provide data at the inlet to the CRF and at other nearby locations where pedestrians, building ventilation systems, and vegetation might be affected. The test program, which was conducted in the Calspan Atmospheric Simulation Facility, included flow visualization studies and quantitative concentration measurements of a tracer gas from which full-scale temperature could be calculated. The concentration measurements were performed for a number of wind speeds at each of twelve different wind directions. Two exhaust flows and two exhaust stack configurations were studied.

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