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 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.

Experimental Investigation of Boundary Layer Instabilities on the Free Surface of Non-Turbulent Jet

2012 ◽  
Author(s):  
Matthieu A. Andre ◽  
Philippe M. Bardet
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Capillary Waves ◽  
Wave Growth ◽  
Image Velocimetry ◽  
Planar Laser ◽  
Surface Visualization ◽  
The Waves

Shear instabilities induced by the relaxation of laminar boundary layer at the free surface of a high speed liquid jet are investigated experimentally. Physical insights into these instabilities and the resulting capillary wave growth are gained by performing non-intrusive measurements of flow structure in the direct vicinity of the surface. The experimental results are a combination of surface visualization, planar laser induced fluorescence (PLIF), particle image velocimetry (PIV), and particle tracking velocimetry (PTV). They suggest that 2D spanwise vortices in the shear layer play a major role in these instabilities by triggering 2D waves on the free surface as predicted by linear stability analysis. These vortices, however, are found to travel at a different speed than the capillary waves they initially created resulting in interference with the waves and wave growth. A new experimental facility was built; it consists of a 20.3 × 146.mm rectangular water wall jet with Reynolds number based on channel depth between 3.13 × 104 to 1.65 × 105 and 115. to 264. based on boundary layer momentum thickness.

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.

Whitecap coverage measurements in laboratory modeling of wind-wave interaction

2020 ◽  
Author(s):  
Alexander Kandaurov ◽  
Yuliya Troitskaya ◽  
Daniil Sergeev ◽  
Dmitry Kozlov
Keyword(s):  
High Speed ◽  
Wind Wave ◽  
Surface Condition ◽  
Vertical Direction ◽  
Water Volume ◽  
Small Scale ◽  
Unit Surface Area ◽  
Mode Water ◽  
Whitecap Coverage ◽  
Manual Processing

<p>Whitecap coverage were retrieved from high-speed video recordings of the water surface obtained on the unique laboratory faculty Heidelberg Small-Scale Air-Sea Interaction Facility, the Aeolotron (annular wind-wave facility, 60 cm width, 2.4 m height, circumference of 27.3 m at the inner wall; water depth during experiments 1.0 m, water volume 18.0 m³, air space volume 24 m³; wind was generated by two axial fans mounted into the ceiling).</p><p>Records were made in the vertical direction (from top to bottom) in a shadowgraph configuration with backlight located under the channel. On the annular channel, regimes with an abrupt start of wind under an unperturbed surface condition were implemented, including the case of butanol presence in water simulating salinity. At the same time, the wave parameters varying depending on the time elapsed after the wind was turned on, made it possible to study the characteristics of the generation of spray at various effective fetches.<br>As a result of semi-automatic processing of image sequences using specially developed software that allows marking the moment and position of the bag-breakup formation on the videos, the dependences of the frequency of occurrence of these phenomena per unit surface area versus time after turning on the wind were obtained. From the same images, using the developed software for automatic detection of areas of wave breaking, the values of the whitecap coverage area were obtained. In this case, automatic image processing was performed using morphological analysis in combination with manual processing of part of the frames for tweaking the algorithm parameters: for each mode (water characteristics and wind speed), manual processing of several frames was performed, based on the results of which automatic algorithm parameters were selected to ensure that the resulting whitecap coverage corresponded. Since the same high-speed surface images were used to study the statistics of occurrence of events leading to the spray generation and the dependences of the whitecap coverage on time after turning on the wind for each regime were obtained, we were able to estimate the average number of fragmentation events per unit area of the collapse area.</p><p>The work was supported by the RFBR grant 18-35-20068 (conducting an experiment), President grant for young scientists MK-3184.2019.5 (software development) and the RSF grant No. 18-77-00074 (data processing).</p>

Auxiliary Kite Propulsion Contribution to Ship Thrust

2013 ◽  
Author(s):  
Heng Ran ◽  
Carl-Erik Janson ◽  
Björn Allenström
Keyword(s):  
Fuel Consumption ◽  
Energy Efficient ◽  
High Speed ◽  
Wind Wave ◽  
Control Mechanism ◽  
Weather Conditions ◽  
Power Reduction ◽  
Computer Based ◽  
Rudder Angle ◽  
Engine Power

Low speed transportation is more energy efficient than high speed transportation in general. At the same time of maintain speed, ships with lower design speeds provide possibilities for further reducing fuel consumption by using auxiliary wind propulsion devices. A kite is one type of auxiliary wind propulsion device that can be used for this purpose. The aim of this study is to investigate the influence of auxiliary kite propulsion on the performance of a Panamax tanker, specifically on engine power reduction, maneuverability in different wind/wave directions and on course-keeping ability of the ship. The study was carried out by means of computer-based simulations. Scenario combinations are established for various ship speeds, headings and weather conditions. For the purpose of simulation, a simplified auxiliary kite propulsion model was built. Throughout the simulations, forces, moments and motions of the tanker were recorded, and so were rudder angle, ship thrust and engine power. The result shows that auxiliary kite propulsion can play a significant role in reducing engine power in following up to beam sea conditions. The present study is a first step towards a fully dynamic kite model where a control mechanism will be introduced to find the most favorable flying trajectory.

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.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

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