Determination of the effectiveness of high-speed cameras for identifying ejection particles during splash with regard to the sticky paper method

2020 ◽  
Author(s):  
Agata Sochan ◽  
Michał Beczek ◽  
Rafał Mazur ◽  
Magdalena Ryżak ◽  
Zbigniew Łagodowski ◽  
...  
Keyword(s):  
High Speed ◽  
Water Drop ◽  
Reference Method ◽  
Drop Impact ◽  
Glass Beads ◽  
Time Interval ◽  
Time Frequency ◽  
The Impact ◽  
Paper Method

<p>The phenomenon of splash caused by water drop has been widely studied in recent years. There are many measurement methods, including the method based on the use of so-called high-speed cameras. Due to the possibility of recording of the phenomenon with a high time frequency (thousands of recorded frames per second), this method provides detailed information about the process of splashed particles, which were previously unavailable. These include, among others, precise tracking of single ejected particles, determination of their ejection angle, displacement distance, and division of splashed elements into groups depending on the place or moment of ejection from the particle bedding. Despite the numerous advantages of the method, there is no information about the percentage of splashed particles that the cameras are able to detect and identify. In order to determine such effectiveness, it is necessary to have a reference method that guarantees 100% identification of splashed particles.</p><p>The aim of this work was to determine the effectiveness of high-speed cameras in identification of particles ejected from the granular bedding during the water drop impact. Sticky paper was used as a reference method.</p><p>Dry spherical glass beads (425–600 μm size range), which were placed into an aluminium ring (30mm diameter, 10mm height) were used in the experiments. The aluminum ring was placed in a drilled hole (only slightly larger than the ring) in a horizontal wooden plate, and therefore, the surface of the beads was at the same level as the surrounding plane. Drops (d=4.2mm) of distilled water were created in a peristaltic pump and fell free from 1.5m. The final velocity of each drop was 4.98 m/s.</p><p>Three synchronized Phantom Miro M310 cameras were used to register the splash phenomenon (307 μs time interval, 1280x800 px resolution). The camera calibration process facilitated analysis of the trajectories of the splashed particles and determination of their velocities, ejection angles, and displacement distances. The analysis of the recorded images was carried out using the Dantec Dynamics Studio software. The particles were tracked by the Volumetric 3DPTV module, and the trajectories were further analyzed by our script written in LabVIEW.</p><p>A hole (30mm diameter) was cut out of a piece of sticky paper, and the paper was placed concentrically over the ring. This allowed recording of all splashed particles while avoiding their rebounding or rolling from the plane. Following the impact, the beads were photographed using a Nikon D7100 camera, and images were analyzed using ImageJ software. The number of particles and the distance from the geometrical center of the drop impact were recorded.</p><p>Measurements using the high-speed cameras and the sticky paper method were carried out in 16 repetitions.</p><p>The results obtained with both methods were compared with each other. Regarding the sticky paper method as a reference, the efficiency of identification with the high-speed cameras for the splash of glass beads was determined, which was estimated at 53%.</p><p>The study was partially funded by the National Science Centre, Poland, in the frame of the project no. 2017/26/D/ST10/01026.</p>

Impact patterns and temporal evolutions of water drops impinging on a rotating disc

2011 ◽  
Vol 226 (4) ◽  
pp. 956-967 ◽  
Author(s):  
J-Y Li ◽  
X-F Yuan ◽  
Q Han ◽  
G Xi
Keyword(s):  
High Speed ◽  
Water Drop ◽  
Video Camera ◽  
Drop Impact ◽  
Rossby Number ◽  
Rotating Disc ◽  
Factors Affecting ◽  
Radial Spread ◽  
Spread Factor ◽  
The Impact

The impact process of a water drop colliding with a rotating disc was recorded and analysed using a high-speed video camera. Four falling velocities of the drop, eight rotational speeds, and four impacting radii of the disc were chosen to study their influences on the outcomes of drop impact. The correlation of the deposition–splash boundary was found to be the function of Reynolds number, Weber number, and Rossby number. Four kinds of impact processes were classified in terms of Rossby number and several new stages of the impact outcomes not present in drop impact on a stationary plate were recognized. For deposition processes, the temporal evolutions of two spread factors, the tangential and radial spread factors, were analysed in detail. It was found that the Rossby number and the falling velocity of the drop are the major factors affecting the tangential spread factor. In contrast, the Rossby number has little effect on the radial spread factor while the falling velocity of the drop still exerts a considerable influence on it.

Splash formation by spherical drops

2001 ◽  
Vol 427 ◽  
pp. 73-105 ◽  
Author(s):  
LIOW JONG LENG
Keyword(s):  
High Resolution ◽  
Quantitative Data ◽  
Water Surface ◽  
High Speed ◽  
Scaling Laws ◽  
Capillary Wave ◽  
Water Drop ◽  
Qualitative And Quantitative ◽  
High Resolution Images ◽  
The Impact

The impact of a spherical water drop onto a water surface has been studied experimentally with the aid of a 35 mm drum camera giving high-resolution images that provided qualitative and quantitative data on the phenomena. Scaling laws for the time to reach maximum cavity sizes have been derived and provide a good fit to the experimental results. Transitions between the regimes for coalescence-only, the formation of a high-speed jet and bubble entrapment have been delineated. The high-speed jet was found to occur without bubble entrapment. This was caused by the rapid retraction of the trough formed by a capillary wave converging to the centre of the cavity base. The converging capillary wave has a profile similar to a Crapper wave. A plot showing the different regimes of cavity and impact drop behaviour in the Weber–Froude number-plane has been constructed for Fr and We less than 1000.

scholarly journals Experimental Study of Drop Impact on Deep-Water Surface in the Presence of Wind

2018 ◽  
Vol 48 (2) ◽  
pp. 329-341 ◽  
Author(s):  
Xinan Liu
Keyword(s):  
Deep Water ◽  
Water Surface ◽  
Water Drop ◽  
Threshold Value ◽  
Impact Angle ◽  
Drop Impact ◽  
Wind Speeds ◽  
Secondary Droplets ◽  
Low Wind Speeds ◽  
The Impact

AbstractThe effects of wind on the impact of a single water drop on a deep-water surface are studied experimentally in a wind tunnel. Experiments are performed by varying impacting drop diameters, ranging from 2.5 to 4.1 mm and wind speeds up to 6.7 m s−1. The sequence of splashing events that occurred during drop impacts is recorded with a backlit, cinematic shadowgraph technique. The experimental results show that for low wind speeds, an asymmetrical crown forms on the leeward of the periphery of the colliding region after the drop hits the water surface, while a wave swell forms on the windward. Secondary droplets are generated from the crown rim. For high wind speeds with large drop diameters, ligaments are generated from the crown rim on the leeward of the drop impact site. The ligaments grow, coalesce, and fragment into secondary droplets. It is found that both the drag force and surface tension play important roles in the evolution process of the ligaments. The nondimensional K number (K = WeOh−0.4, where We is the Webber number and Oh is the Ohnesorge number) is used to describe the splashing-deposition limit of drop impact. The threshold value of this K number changes with the wind velocity and/or drop impact angle.

A 10-Bit Column-Parallel Single Slope ADC Based on Two-Step TDC with Error Calibration for CMOS Image Sensors

2015 ◽  
Vol 24 (04) ◽  
pp. 1550054 ◽  
Author(s):  
Jiangtao Xu ◽  
Jing Yu ◽  
Fujun Huang ◽  
Kaiming Nie
Keyword(s):  
Analog Circuits ◽  
High Speed ◽  
Propagation Delay ◽  
Image Sensors ◽  
Time Interval ◽  
Cmos Process ◽  
Digital Converter ◽  
Cmos Image Sensors ◽  
Time Problem ◽  
The Impact

This paper presents a 10-bit column-parallel single slope analog-to-digital converter (SS ADC) with a two-step time-to-digital converter (TDC) to overcome the long conversion time problem in conventional SS ADC for high-speed CMOS image sensors (CIS). The time interval proportional to the input signal is generated by a ramp generator and a comparator, which is digitized by a two-step TDC consisting of coarse and fine conversions to achieve a high-precision time-interval measurement. To mitigate the impact of propagation delay mismatch, a calibration circuit is also proposed to calibrate the delay skew within -T/2 to T/2. The proposed ADC is designed in 0.18 μm CMOS process. The power dissipation of each column circuit is 232 μW at supply voltages of 3.3 V for the analog circuits and 1.8 V for the digital blocks. The post simulation results indicate that the ADC achieves a SNDR of 60.89 dB (9.82 ENOB) and a SFDR of 79.98 dB at a conversion rate of 2 MS/s after calibration, while the SNDR and SFDR are limited to 41.52 dB and 67.64 dB, respectively before calibration. The differential nonlinearity (DNL) and integral nonlinearity (INL) without calibration are +15.80/-15.29 LSB and +1.68/-15.34 LSB while they are reduced down to +0.75/-0.25 LSB and +0.76/-0.78 LSB with the proposed calibration.

An experimental investigation of fluid flow resulting from the impact of a water drop with an unyielding dry surface

1981 ◽  
Vol 373 (1755) ◽  
pp. 419-441 ◽  
Keyword(s):  
Water Drop ◽  
Roughness Parameter ◽  
Fluid Velocities ◽  
Spatial Dimensions ◽  
Water Drops ◽  
The Moment ◽  
High Degree ◽  
First Contact ◽  
The Impact

The flow of fluid associated with the impact of water drops of radius R at a speed V onto unyielding dry metal surfaces of known roughness R a is described. Spatial dimensions of the deforming drop are normalized by transformations of the kind x ' — x/R , and time scales are normalized according to t ' = tV/R , to permit comparison of events where or differ. It is shown that the primary influence of the surface roughness parameter R a is the determination of the condition for the ejection of secondary droplets by the excitation of an instability in the developing watersheet; provided R a ≪ R , it is possible to evaluate the condition to a high degree of accuracy, and for R a = 0.84 μm it is found to be α4/3 RV 1.69 > 7.4, where α is the eccentricity of the drop at the moment of impact. Deceleration of the drop apex does not commence until > 0.6, contrary to the prediction of Engel (1955) but in good agreement with that of Savic & Boult (1957). Close examination of the very early stages of impact suggests strongly that the so-called watersheet originates at a moment t ' — 0.01 after first contact, regardless of the absolute values of R, V or R a ; the initial normalized watersheet velocity is of order 5. Where there is ejected material, its normalized velocity at the moment of ejection is of the order of 20 % greater than that of the watersheet substrate. Simple calculations also suggest that initial fluid velocities greater than 10 are required immediately before the initiation of the watersheet ( t '< 0.01). Impacts at speeds considerably greater than the appropriate terminal fall speed in air show no deviations in character from those investigated at much lower speeds. A simple subsidiary experiment also suggests that greater impact velocities are required to produce splashing on inclined targets.

Studies of two-dimensional liquid-wedge impact and their relevance to liquid-drop impact problems

1985 ◽  
Vol 401 (1821) ◽  
pp. 225-249 ◽  
Keyword(s):  
High Speed ◽  
Liquid Drop ◽  
Time History ◽  
Drop Impact ◽  
High Speed Photography ◽  
Two Dimensional ◽  
Surface Geometry ◽  
Repeated Impact ◽  
Liquid Impact ◽  
The Impact

In the initial stage of liquid-drop impact, the contact region expands faster than the wave speed in the liquid. This causes compressible behaviour in the liquid, and high transient pressures. High-velocity jetting results when the wave motion in the liquid overtakes the expanding contact edge and moves up the free surface of the drop. The detailed pressure fields in this early time history of impact have been calculated by Lesser ( Proc . R . Soc . Lond . 377, 289 (1981)) for both two and three-dimensional liquid masses and for targets of finite admittance. An important result is that the edge pressures exceed the central ‘water-hammer’ pressure 3ρ 0 CU i and at the time of shock-detachment approach ca . 3ρ 0 CU i . At this stage the edge pressures, for both spherical drops and two-dimensional liquid wedges, depend only on the impact velocity and the instantaneous angle between the liquid and solid surfaces. This suggests that the essential features of the early stage of liquid impact can be usefully studied by producing impacts with two-dimensional liquid wedges, and predicted data for pressures, shock angles and velocities are presented. Experiments are described for producing impacts with preformed shapes by using water-gelatine mixtures and observing the impact events with high-speed photography. The results confirm the main features of the model and give information on edge pressures, jetting, cavitation in the liquid and the effect of the admittance of the solid. The relevance of the results to the damage and erosion of materials subjected to liquid impact is discussed. In particular, it is possible to explain the apparently low damage-threshold of some materials, the form of damage and its development with repeated impact. The study highlights the importance of the detailed surface geometry in the region of contact.

scholarly journals INFLUENCE OF ERRORS IN DETERMINATION OF TRACING SLOPE ON THE ACCURACY OF GEODETIC BASE FOR ROUTE

2021 ◽  
pp. 111-117
Author(s):  
Kostiantyn Mamonov ◽  
Svitlana Kamchatnaya ◽  
Yevhen Orel ◽  
Oleksandr Saiapin
Keyword(s):  
High Speed ◽  
Methodological Approach ◽  
Line Length ◽  
Route Length ◽  
The Difference ◽  
Artificial Development ◽  
The Right ◽  
The Impact ◽  
Further Development

The purpose of this article is to study and develop a methodological approach tosolving the problem of accuracy of the geodetic base of the route. For this purpose, the followingtasks are set: mathematical substantiation the dependence of the line length on the ratio of the traceslope and the guide slope; description of the function of optimal use of the guiding slope at highspeed; determination of the impact of errors in the course of the geodetic justification on the routelength. Starting from the determined point and further to the right, artificial development of the lineis required. Because when a trace is planed using level curves, this point can be reached sooner orlater, and in some cases, this point can not be reached not at all, the line length designed accordingto the plan will be slightly different than in the case of tracing with usage the exact data. Thus, theobtained results indicate the following. If the error positions during a high-speed segment are suchthat the ordnance datum of the passage is less than the truth, the route length will be less than thetrue and vice versa. This trivial result indicates that the location of geodetic support points ondifferent sides of the pass is not recommended. It is established that due to the accumulation of errorsin the transmission of coordinates in the working substantiation networks, the conditions of the linedesign and the amount of operating costs change. It is mathematically substantiated that the linelength depends on the depth of the excavation on the pass and the height of the embankment at thepoint, and also on the difference of ordnance datum at these points. The difference between the traceslope and the guiding slope has an inversely proportional effect. In addition, the function of optimaluse of the guide slope at a high-speed segment has the form of a broken line according to its fracturesthe need for artificial development of the route can be established. The influence of errors in the course of the working justification is manifested in the discrepancy between the true and projectedroute length. If this error is not taken into account, it will lead to significant overspending duringbuilding a longer line than necessary. Further development of the problem of increasing the accuracyof tracing and reducing the impact of errors is planned in the direction of creating methods of digitalmodelling and automated programs.

A discussion on deformation of solids by the impact of liquids, and its relation to rain damage in aircraft and missiles, to blade erosion in steam turbines, and to cavitation erosion - Conclusion

1966 ◽  
Vol 260 (1110) ◽  
pp. 311-315
Keyword(s):  
High Speed ◽  
Rear Surface ◽  
Peak Load ◽  
Brittle Materials ◽  
Front Surface ◽  
Drop Impact ◽  
Surface Flow ◽  
Steam Turbines ◽  
Brittle Solids ◽  
The Impact

Basic studies show that the measured impact pressure can be accounted for by assuming compressible deformation of the liquid drop in the first stages of impact. The distribution of pressure under a drop produces a shallow indentation in the surface of ductile solids and a ring fracture in brittle materials. The flow of liquid across the surface from under the drop leads to erosive shearing along the edges of the deformed area. Although in theory erosion due to surface flow would not occur on perfectly smooth surfaces, ideal conditions of this kind are impracticable. The smallest discontinuities (step heights down to about 1000 A) have been shown to act as nuclei for erosion pits. The short duration of the peak load during drop impact gives the impact an explosive character. In brittle materials the reflexion and interference of stress waves can cause extensive fracture in regions remote from the initial impact area. Spalling of the rear surface of a thin plate due to drop impact on the front surface could be an important mechanism in the failure of ceramic radomes in high speed aircraft and missiles. To some extent the strength of brittle solids can be improved by treatments which alter the size or number of surface flaws.

scholarly journals A Method of FPGA-Based Extraction of High-Precision Time-Difference Information and Implementation of Its Hardware Circuit

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5067
Author(s):  
Li ◽  
Yan ◽  
Li ◽  
Meng ◽  
Yan
Keyword(s):  
High Precision ◽  
High Speed ◽  
Source Location ◽  
Blast Waves ◽  
Time Difference ◽  
P Wave ◽  
Sensor Data ◽  
Time Interval ◽  
Time Frequency ◽  
Precision Time

Abstract: The positioning technology to find shallow underground vibration sources based on a wireless sensor network is receiving great interest in the field of underground position measurements. The slow peaking and strong multi-waveform aliasing typical of the underground vibration signal result in a low extraction accuracy of the time difference and a poor source-positioning accuracy. At the same time, the transmission of large amounts of sensor data and the host computer’s slow data processing speed make locating a source a slow process. To address the above problems, this paper proposes a method for high-precision time-difference measurements in near-field blasting and a method for its hardware implementation. First, based on the broadband that is typical of blast waves, the peak frequency of the P-wave was obtained in the time–frequency domain, taking advantage of the difference in the propagation speed of the P-wave, S-wave, and the surface wave. Second, the phase difference between two sensor nodes was found by means of a spectral decomposition and a correlation measurement. Third, the phase ambiguity was eliminated using the time interval of the first break and the dynamic characteristics of the sensors. Finally, following a top-down design idea, the hardware system was designed using Field Programmable Gate Array(FPGA). Verification, using both numerical simulations and experiments, suggested that compared with generalized cross-correlation-based time-difference measurement methods, the proposed method produced a higher time-difference resolution and accuracy. Compared with the traditional host computer post-position positioning method, the proposed method was significantly quicker. It can be seen that the proposed method provides a new solution for solving high-precision and quick source-location problems, and affords a technical means for developing high-speed, real-time source-location instruments.

scholarly journals Drop Impact on Textile Material: Effect of Fabric Properties

2014 ◽  
Vol 14 (3) ◽  
pp. 145-151 ◽  
Author(s):  
Zouhaier Romdhani ◽  
Ayda Baffoun ◽  
Mohamed Hamdaoui ◽  
Sadok Roudesli
Keyword(s):  
Water Drop ◽  
Free Fall ◽  
Spreading Rate ◽  
Drop Impact ◽  
Drop Deformation ◽  
Coating Film ◽  
Drop Shape ◽  
Coated Fabric ◽  
Fabric Construction ◽  
The Impact

Abstract This paper presents an experimental study of impact of water drop on a surface in a spreading regime with no splashing. Three surfaces were studied: virgin glass, coating film and woven cotton fabric at different construction parameters. All experiments were carried out using water drop with the same free fall high. Digidrop with high-resolution camera is used to measure the different parameters characterising this phenomenon. Results show an important effect of the height of the free fall on the drop profile and the spreading behaviour. An important drop deformation at the surface impact was observed. Then, fabric construction as the weft count deeply affects the drop impact. For plain weave, an increase of weft count causes a decrease in penetration and increase in the spreading rate. The same result was obtained for coated fabric. Therefore, the impact energy was modified and the drop shape was affected, which directly influenced the spreading rate.

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