scholarly journals Investigation of the bag-breakup phenomena of the spray generation processes during wind-wave interaction in the laboratory experiments with optical methods

2021 ◽  
Vol 2127 (1) ◽  
pp. 012015
Author(s):  
A A Kandaurov ◽  
D A Sergeev ◽  
Yu I Troitskaya
Keyword(s):  
High Speed ◽  
Laboratory Experiments ◽  
Wind Wave ◽  
Wave Interaction ◽  
Optical Methods ◽  
Imaging Method ◽  
Thin Membrane ◽  
Spray Formation ◽  
High Speed Video ◽  
Shadow Imaging

Abstract Present paper devoted to the investigations with optical methods processes of artificially induced bag-breakup type of spray formation phenomenon within wind-wave interaction. Experiments were carried out on the Thermostratified Wind-Wave Tank of the IAP RAS. High-speed video filming with the shadow imaging method demonstrated that it was possible to artificially reproduce all the main stages of this phenomenon, which are also observed for the sporadically occurred ones: inflation of a thin membrane surrounded by a thicker rim, rupture of the membrane leading to the formation of small droplets, fragmentation of the rim with the formation of large droplets. Special processing of the images allowed us to estimate typical lifetimes and sizes of membrane for artificial bag-breakup events which turned out to be close to the same parameters for sporadically occurred ones.

scholarly journals An Application of the Visualization Methods for Investigation Small Scale Processes in the Atmosphere-hydrosphere Boundary Layer within Laboratory Experiments on the Wind-wave Facilities

2021 ◽  
Author(s):  
Daniil Sergeev ◽  
Anatoly Suvorov ◽  
Alexander Kandaurov
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Wind Wave ◽  
Weather Conditions ◽  
Optical Methods ◽  
Small Scale ◽  
Imaging Method ◽  
Shadow Imaging ◽  
Laboratory Modelling ◽  
The Waves

Hydro/aerodynamic laboratory experiment aimed at the laboratory modelling of the physical processes marine atmospheric boundary layer is one of the most complicated. Especial features as spray of droplets, the bubbles in the water and foam generated during the breaking of the waves should be taken into account when modelling extreme weather conditions caused by severe winds. Thus, in the experiment we are dealing with a multiphase turbulent flow with a free boundary. This investigation describes developing approaches to the use of optical methods based on visualization for performing these investigations. Presented results were obtained in experiments carried out on wind-wave facilities. To study the processes of fragmentation of the water surface leading to the formation of droplets and foam, high-speed multi-angle video taking is used in combination with the shadow imaging method.

scholarly journals The Anna's hummingbird chirps with its tail: a new mechanism of sonation in birds

2008 ◽  
Vol 275 (1637) ◽  
pp. 955-962 ◽  
Author(s):  
Christopher James Clark ◽  
Teresa J Feo
Keyword(s):  
High Frequency ◽  
High Speed ◽  
Laboratory Experiments ◽  
Wild Birds ◽  
High Speed Video ◽  
Calypte Anna

A diverse array of birds apparently make mechanical sounds (called sonations) with their feathers. Few studies have established that these sounds are non-vocal, and the mechanics of how these sounds are produced remains poorly studied. The loud, high-frequency chirp emitted by a male Anna's hummingbird ( Calypte anna ) during his display dive is a debated example. Production of the sound was originally attributed to the tail, but a more recent study argued that the sound is vocal. Here, we use high-speed video of diving birds, experimental manipulations on wild birds and laboratory experiments on individual feathers to show that the dive sound is made by tail feathers. High-speed video shows that fluttering of the trailing vane of the outermost tail feathers produces the sound. The mechanism is not a whistle, and we propose a flag model to explain the feather's fluttering and accompanying sound. The flag hypothesis predicts that subtle changes in feather shape will tune the frequency of sound produced by feathers. Many kinds of birds are reported to create aerodynamic sounds with their wings or tail, and this model may explain a wide diversity of non-vocal sounds produced by birds.

scholarly journals Fluttering wing feathers produce the flight sounds of male streamertail hummingbirds

2008 ◽  
Vol 4 (4) ◽  
pp. 341-344 ◽  
Author(s):  
Christopher James Clark
Keyword(s):  
High Speed ◽  
Laboratory Experiments ◽  
Morphological Changes ◽  
Wingbeat Frequency ◽  
Primary Feather ◽  
Mean Frequency ◽  
High Speed Video ◽  
Males And Females ◽  
Avian Communication ◽  
Lines Of Evidence

Sounds produced continuously during flight potentially play important roles in avian communication, but the mechanisms underlying these sounds have received little attention. Adult male Red-billed Streamertail hummingbirds ( Trochilus polytmus ) bear elongated tail streamers and produce a distinctive ‘whirring’ flight sound, whereas subadult males and females do not. The production of this sound, which is a pulsed tone with a mean frequency of 858 Hz, has been attributed to these distinctive tail streamers. However, tail-less streamertails can still produce the flight sound. Three lines of evidence implicate the wings instead. First, it is pulsed in synchrony with the 29 Hz wingbeat frequency. Second, a high-speed video showed that primary feather eight (P8) bends during each downstroke, creating a gap between P8 and primary feather nine (P9). Manipulating either P8 or P9 reduced the production of the flight sound. Third, laboratory experiments indicated that both P8 and P9 can produce tones over a range of 700–900 Hz. The wings therefore produce the distinctive flight sound, enabled via subtle morphological changes to the structure of P8 and P9.

scholarly journals Investigation of the mechanisms of sea spray generation induced by wind-wave interaction in laboratory conditions

2019 ◽  
Vol 213 ◽  
pp. 02036
Author(s):  
Alexander Kandaurov ◽  
Daniil Sergeev ◽  
Yuliya Troitskaya ◽  
Olga Ermakova
Keyword(s):  
High Speed ◽  
Wind Wave ◽  
Wave Interaction ◽  
Wave Crest ◽  
Applied Physics ◽  
Wave Flume ◽  
Wind Speeds ◽  
Laboratory Conditions ◽  
Academy Of Sciences

The paper presents the results of investigations of the mechanisms of spray of droplets generation within wind wave interaction obtained under laboratory conditions on the High-speed Wind-Wave Flume of the Institute of Applied Physics of the Russian Academy of Sciences. For the research, a multi-angle high-speed video system used together shadow method, including underwater illumination. The results allowed for the classification of mechanismsleading to the formation of droplets. Three main types of phenomena responsible for the generation of the spume droplets near the wave crest were specified: breakage of liquid ligaments, bursting of large submerged bubbles, and bag breakup. The last and less known mechanism claims to be dominant for high wind speeds and it was described in detail.

scholarly journals Research on Target Deviation Measurement of Projectile Based on Shadow Imaging Method in Laser Screen Velocity Measuring System

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 554 ◽  
Author(s):  
Wenbo Chu ◽  
Donge Zhao ◽  
Baowei Liu ◽  
Bin Zhang ◽  
Zhiguo Gui
Keyword(s):  
High Speed ◽  
Target Position ◽  
Measuring System ◽  
Laser Source ◽  
Imaging Method ◽  
Aspherical Lens ◽  
Timing Pulse ◽  
Shadow Imaging ◽  
Deviation Measurement ◽  
Velocity Measuring

In the laser screen velocity measuring (LSVM) system, there is a deviation in the consistency of the optoelectronic response between the start light screen and the stop light screen. When the projectile passes through the light screen, the projectile’s over-target position, at which the timing pulse of the LSVM system is triggered, deviates from the actual position of the light screen (i.e., the target deviation). Therefore, it brings errors to the measurement of the projectile’s velocity, which has become a bottleneck, affecting the construction of a higher precision optoelectronic velocity measuring system. To solve this problem, this paper proposes a method based on high-speed shadow imaging to measure the projectile’s target deviation, ΔS, when the LSVM system triggers the timing pulse. The infrared pulse laser is collimated by the combination of the aspherical lens to form a parallel laser source that is used as the light source of the system. When the projectile passes through the light screen, the projectile’s over-target signal is processed by the specially designed trigger circuit. It uses the rising and falling edges of this signal to trigger the camera and pulsed laser source, respectively, to ensure that the projectile’s over-target image is adequately exposed. By capturing the images of the light screen of the LSVM system and the over-target projectile separately, this method of image edge detection was used to calculate the target deviation, and this value was used to correct the target distance of the LSVM to improve the accuracy of the measurement of the projectile’s velocity.

scholarly journals A study on Behavior of Vortices near Wind Wave Surfaces by Using High-speed Video Camera and MLS

2008 ◽  
Vol 55 ◽  
pp. 51-55
Author(s):  
Kohsei TAKEHARA ◽  
T. Goji ETOH ◽  
Takaaki SHIGEMATSU ◽  
Vu Truong Son DAO
Keyword(s):  
High Speed ◽  
Wind Wave ◽  
Video Camera ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Wave Surfaces

scholarly journals Optical method for fuel atomization control using high-speed video

2020 ◽  
Vol 16 (2) ◽  
pp. 19-26
Author(s):  
Alexander V. Eskov ◽  
Ivan I. Kiryushin
Keyword(s):  
Optical Method ◽  
High Speed ◽  
Video Camera ◽  
Optical Methods ◽  
Atmospheric Conditions ◽  
High Speed Video ◽  
Fuel Atomization ◽  
High Speed Video Camera ◽  
Fuel Jet ◽  
Surface Diameter

The article discusses the description of one of the optical methods for determining the parameters of fuel atomization in atmospheric conditions and recording the results using a high-speed video camera. The possibility of interpreting images of a fuel jet in development over time as the distribution of the concentration of a dispersed medium with a constant volume-surface diameter (Sauter), which is an optical method for controlling fuel atomization, is shown.

scholarly journals TECHNICAL DEVELOPMENT OF THE MAGNETO-OPTICAL IMAGING METHOD IN THE RESEARCH OF RELIEF SIGNS OF THE METAL OBJECTS

2021 ◽  
pp. 746-768
Author(s):  
O. Koshel
Keyword(s):  
Optical Imaging ◽  
High Speed ◽  
High Efficiency ◽  
Science Studies ◽  
Operating Conditions ◽  
Optical Methods ◽  
Imaging Method ◽  
Practical Application ◽  
Near Surface ◽  
Non Destructive

The study of relief marking of metal objects is one of the constantly demanded areas of expert research, especially for objects such as weapons and vehicles. The question of choosing a research method for these objects, which is constantly topical for an expert, acquires particular relevance in the case of rare and historical objects, new expensive products. In the last decade, a non-destructive method of magneto-optical imaging, which was developed at the Kyiv Polytechnic Institute more than 20 years ago, has been successfully applied abroad for these studies in 40 countries. During this time, the technical implementation of the method has been developed, the technical components of the complex have been significantly improved and changed. In 2008 basing on the results of practical application on specially designed test objects, including those with three thicknesses of paint coatings, the developers carried out studies in which they assessed the sensitivity of magnetic powder, electrochemical and magneto-optical methods. Obtained results demonstrated a higher sensitivity of the magneto-optical method for thin-walled objects and the sensitivity for thick-walled objects is not worse than other methods. Practical application of the modern REGULA 7517 complex in expert studies under various operating conditions confirms its high sensitivity, testifies to the high speed of operation, reliability, autonomy of the complex and wide temperature conditions of use. The high efficiency of the non-destructive method of magneto-optical imaging makes it possible to consider it as one of the most promising methods in trace studies, as well as in materials science studies, where information on the state and structure of the surface and near-surface layers of metal objects is needed.

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