High-speed Video Recording System Research Articles

Experimental and Analytical Study of under Water Pressure Wave Induced by the Implosion of a Bubble Generated by Focused Laser.

In various domains of material processing, such as surface cleaning and surface treatment, cavitation phenomenon may become an alternative to traditional methods if this phenomenon is well understood. Due to experimental and mathematical difficulties in theoretical models, it is still a challenge to accurately measure the physical mechanism of the fluid/structure interactions. In this study, we verified the feasibility of using polyvinylidene fluoride (PVDF) sensors to quantitatively measure the under-water pressure wave generated by the collapse of a single cavitation bubble. The electrical signal obtained by PVDF can be converted into pressure information only by using the sensor material parameters provided by the supplier. During the conversion process, only the capacitance of the acquisition chain needs to be additionally measured. At the same time, a high-speed video recording system was used to visualize the evolution of the cavitation bubble. The Gilmore analytical model and an associated wave propagation model were used to simulate the pressure peak of the first collapse of the cavitation bubble. This theoretical pressure was compared with the experimental results. The result showed that, for bubbles with a normalized standoff distance larger than 5, the PVDF sensor had the ability to quantitatively measure the pressure wave generated by a single cavitation bubble.

The critical atomization conditions of high-potential fire suppressant droplets in an air flow

In this research, we used a high-speed video-recording system to experimentally study the surface transformation of droplets of water and water-based slurries, solutions, and emulsions exposed to the incoming air flow. The experimental parameters were varied in the following ranges: 0.3–3 mm for the initial droplet radius; 0.5–50 m/s for the air flow velocity; 10 vol% for the relative volume concentration of liquid additives to water; 10 wt% for the relative mass fraction of solid particles to water; 80–140 μm for the size of solid particles; 5–50 °C for the droplet temperature. Three regimes were identified: surface transformation without breakup; taking the bag shape followed by destruction; breakup into a cloud of small droplets. The novelty of the research lies in the maximum ratios of child droplet surface areas to the parent droplet surface area determined for the conditions typical of liquid discharge from various heights for fire suppression.

Percentage of single-stroke flashes related to different thunderstorm types

This study shows an analysis of data from measurements of natural cloud-to-ground lightning performed in Austria between 2009 and 2018. The measurement system consists of a high-speed Video and electric Field Recording System (VFRS). Over the whole period, 735 negative cloud-to-ground flashes were recorded at 33 different locations on 61 individual days. The measurement locations are scattered across the Austrian territory in Alpine and pre-Alpine terrain. Data from the Austrian Lightning Location System (LLS), ALDIS, are correlated with the collected VFRS ground truth data to complete the dataset. These datasets are used to analyze possible reasons for the detected variation of single-stroke flashes in Austria. The percentage of single-stroke flashes among all negative flashes is higher in this study (27 %) than in previous studies from different countries (12 to 24 %). A classification of thunderstorms does not show any dependency of the single-stroke flash occurrence on different thunderstorm types (based on radar data) or underlying meteorological characteristics (based on vertical wind shear computed from weather stations and radiosondes). In contrast, a possible dependency of the occurrence of single-stroke flashes on underlying terrain (Alpine versus pre-Alpine) is noted.

Investigation of Successful Eyedrop Instillation Rates and Analysis of Drop Positions Using High-speed Digital Video Recording System

We investigated the success rates of eyedrop instillation and the distance between the cornea and the dropper tip in 100 volunteers using high-speed digital video recording. Past eyedrop adherence studies assumed that instillation occurred without failure. The ideal distance between the cornea and dropper tip remained unclear, although the general estimate was approximately 2.54 cm (1 inch). This study was approved by the Institutional Review Boards of all participating medical institutions, and all volunteers provided written, informed consent. Successful instillation was defined as when 1 drop fell accurately into the eye on the first attempt. The instillation of ≥2 drops or drops delivered outside the eye was considered a failure. The distance between the eye and dropper tip was measured using still images from a paused digital video camera and a digital ruler. Forty percent of the volunteers instilled eyedrops without instructions from ophthalmologists, pharmacists, or other healthcare workers. When the images were analyzed, the success rate of the first instillation was 70.1%. When the eye was arbitrarily divided into 9 sections, most of the drop sites were the iris or the center of the eye. The distance between the dropper tip and cornea was 2.62±1.75 (median 2.20) cm. These results indicate that the generally recommended distance is usually followed. The successful instillation rate based on the distance from the dropper tip to the cornea was 77% at 1.6±0.88 cm and 54.9% at 4.8±1.25 cm.

Conditions and characteristics of droplets breakup for industrial waste-derived fuel suspensions ignited in high-temperature air

This research is focused on the ignition and combustion mechanisms and characteristics of single droplets of seven different composite liquid fuels, based on wet coal processing waste (fine coal + 50 wt% of water) with 40 wt% of vegetable oils (castor, rapeseed) and used petroleum-based oils (lubricants – motor, compressor, and turbine oils; working fluid – hydraulic oil; insulating fluid – transformer oil). The combustion of waste-derived fuel suspensions is initiated by introducing single droplets into heated motionless air with a temperature of 700–1,000 °C. Threshold conditions (component composition, concentration of combustible liquid, and temperature) were detected, for which micro-explosions during the induction period resulted in the full breakup of droplets, combustion of products (vapors and fine particles) and their subsequent rapid burnout. A high-speed video recording system is used to establish consistent patterns of physical and chemical processes, as well as ignition and combustion characteristics (ignition delay times, burnout time, velocity of breakup products, and size of their burnout area) for a group of fuels under the conditions of droplet breakup. A hypothesis about how the composition of the component affects the breakup of droplets during ignition was formulated based on the results of analyzing the properties (initial boiling point and evaporation rates of oils, their surface tension and surface free energy, as well as wettability of dry coal processing waste) of separate fuel components.

Rates of High-Temperature Evaporation of Promising Fire-Extinguishing Liquid Droplets

Differences in the rates of heating and evaporation of droplets with the component composition are important parameters of heat transfer processes and phase transformations. This paper presents the values of high-temperature (up to 600 °C) evaporation rates of droplets of promising fire-extinguishing compositions (water, bentonite suspension, bischofite solution, EA-5 solution, and foaming agent emulsion) at convective (in the air stream), conductive (on a heated surface), and radiation (in a muffle furnace) heating. A high-speed video recording system and tracking software algorithms are used. At identical initial sizes of droplets of fire-extinguishing suspensions, known as emulsions and solutions, the times of their complete evaporation are shown to differ 3.7 times when heating on the substrate, 1.25 times in the air flow, and 1.9 times in the muffle furnace. A general approximation expression is formulated, and the empirical constants are calculated to predict the evaporation rate of the droplets of extinguishing agents in a wide range of temperatures (up to 600 °C) and heat fluxes (up to 100 kW/m2), which are characteristic of forest fires. With the use of the experimental data obtained, it is possible to predict the completeness of evaporation of promising extinguishing liquids at different schemes of heat supply.

Co-combustion of coal processing waste, oil refining waste and municipal solid waste: Mechanism, characteristics, emissions

This experimental research studies co-combustion of wet coal processing waste (filter cakes) with typical municipal solid waste (wood, rubber, plastic, cardboard) and used turbine oil, as combustible components of composite liquid fuel. Ignition mechanisms and characteristics of single droplets of three fuel composition groups have been investigated in a motionless heated air with using a high-speed video recording system. Analyzing video frames, a physical model of the process under study was developed. The values of the guaranteed ignition delay times have been determined for three fuel groups with different compositions at the ambient temperature 600–1,000 °C. The minimum values of ignition delay times are about 3 s, the maximum ones are about 25 s. In addition to the established difference in the ignition delay times, the various fuel compositions also differ in combustion temperatures. Maximum values reaching 1,300 °C for compositions with 10% of used oil. It has also been determined that fuels with municipal solid waste are notable for lower nitrogen and sulfur oxide concentrations in flue gases as compared to filter cakes in initial state. Adding used oil to such fuel compositions increases the anthropogenic emissions but these worsening environmental characteristics do not exceed the regulated allowable limits of pollutants for solid fossil fuel combustion by thermal power plants. The obtained results are the backbone for the development of an environmentally friendly, cost- and energy-efficient co-combustion technology for municipal solid waste recovery by burning it as part of composite fuels, e.g., in boiler furnaces instead of coal.

High speed video recording system on a chip for detonation jet engine testing

This article describes system on a chip development for high speed video recording purposes. Current research was started due to difficulties in selection of FPGAs and CPUs which include wide bandwidth, high speed and high number of multipliers for real time signal analysis implementation. Current trend of high density silicon device integration will result soon in a hybrid sensor-controller-memory circuit packed in a single chip. This research was the first step in a series of experiments in manufacturing of hybrid devices. The current task is high level syntheses of high speed logic and CPU core in an FPGA. The work resulted in FPGA-based prototype implementation and examination.

Movement of water drops in a forest fuel layer in the course of its thermal decomposition

In this paper, we conducted an experimental investigation on water droplets gravitating in a layer of typical forest fuel (as illustrated by pine needle litter) in the course of its thermal decomposition. We used a high-speed (200 fps) video recording system, Tema Automotive software with continuous tracking of a moving object as well as a set of low-inertia (no more than 0.1 second) thermocouples. Similar experiments were performed at moderate temperatures (below the onset temperature of forest fuel pyrolysis, i. e. about 300 K). Two approaches were used: continuous tracking of a moving water droplet using high-speed video recording and registration of a droplet path using the readings of thermocouples placed at different levels in a forest fuel layer. We determined the typical depths of an forest fuel layer that water droplets reach with the initial volume of these droplets ranging from 90 to 900 μL. The typical velocities of water droplets were calculated at different depths of the forest fuel layer. We also determined the share of the mass of water spent in an forest fuel layer on evaporation and cooling of the material down to the temperatures below those of thermal decomposition. Finally, we identified the physical processes influencing water droplets moving through the layers of forest fuel heated up to the high temperatures similar to those of thermal decomposition.

Unsteady temperature fields of evaporating water droplets exposed to conductive, convective and radiative heating

In this paper, we present the rates and typical durations of high-temperature heating and evaporation of water droplets determined for the dominating conductive, convective or radiative energy supply. We developed three setups for heating a water droplet: on a substrate (conduction), in a muffle furnace (radiation), and in a heated airflow (convection). The heating temperature is up to 1000 °C to correspond high-temperature technologies, namely thermal cleaning of fluids, polydisperse fire extinguishing with low water consumption, etc. With the help using of a high-speed video recording system, we determine the water droplet lifetimes (the times of their complete evaporation). Using Planar Laser Induced Fluorescence, we establish the quantitative differences between the water droplet heating rates (heating time to lifetime ratios) on the three setups. Maximum temperatures are determined that the water droplets reach when exposed to different heating mechanisms. Furthermore, we obtain the criterial dependences to connect the main attributes of temperature field generation of an evaporating water droplet with the heating conditions. Finally, we identify possible implications of the research findings and ways to further improve the newly developed experimental approach.

Experimental Investigation of Droplet Evaporation of Suspension Based on Water with Subsurface Admixtures in a Flame Area

The influence of typical mixtures (clay, sand, soil, silt) on integral characteristics of droplet evaporation of suspension based on water in high-temperature (about 1100 K) gases was investigated experimentally by the optical methods and high-speed (to 10 5 frames per second) video recording system. The significant intensification of heat up and evaporation of suspension droplets was defined when varying the relative mass fraction of admixtures within the range γ=0−0.1 for a sand, γ=0−0.01 for clay, ground, and silt.

Ballistic and numerical simulation of impacting goods on conveyor belt rubber

Impact loading is an important process in the transport industry as it causes wear and failure of critical components. Conveyor belts are of particular importance as they are used in practically every industry where large quantities of goods are moved over short (<10 m) or long distances (>1 km). To investigate stress levels inside the material during impact loading, a gas gun was utilized to shoot 9 mm spherical steel balls onto the surface of a rubber conveyor belt. A high speed video recording system was employed in order to determine penetration depth and dissipated energy of the steel ball. Maximal penetration depths of up to 3.9 mm and maximal dissipated energies of up to 86.8 % were measured. Additionally, a numerical simulation using smooth particle applied mechanics was conducted and compared to the experimental results obtained with the gas gun. The calculated von Mises stresses affected the conveyor belts up to a maximum depth of 8.8 mm with at least 20 MPa. Maximum von Mises stresses were calculated to reach 60 MPa.

Energy Absorption Capabilities of a Square Tube System

In the present paper the authors refer about a series of experimental tests, where an aluminium alloy square tube, filled with an aluminium foam, was crushed by a longitudinal load at a speed of 10 m/s. The test apparatus consisted of a sled installed on a very stiff frame moving on appropriate guides, as the specimen was set on a home-made fixture. Two arrangements of square tubes were considered as specimens: a “standard” one and an “optimized” one. Both crushing behaviours and energy absorption capabilities were analyzed experimentally and numerically simulated by means of the explicit FE code LS-DYNA®; the complete numerical model consisted of the striker, the assemblage of square tubes and the base. A high-speed video recording system was used to capture the images from the physical test. The results from the numerical analyses were compared to those obtained from the experiments: those results showed that the force–deflection response had been overestimated by the numerical model. The authors attempted to justify this inconsistency by considering the influence of the strain rate parameters of the considered Cowper-Symonds analytical model on the results. It was shown that the “optimized” energy absorber exhibited a more desirable force–deflection response than the standard one due to some easy design changes, which involved the insertion of aluminium foam dampers.

Effects of Acetazolamide on Infantile Nystagmus Syndrome Waveforms: Comparisons to Contact Lenses and Convergence in a Well-Studied Subject

Aim:To determine if acetazolamide, an effective treatment for certain inherited channelopathies, has therapeutic effects on infantile nystagmus syndrome (INS) in a well-studied subject, compare them to other therapies in the same subject and to tenotomy and reattachment (T&R) in other subjects.Methods:Eye-movement data were taken using a high-speed digital video recording system. Nystagmus waveforms were analyzed by applying an eXpanded Nystagmus Acuity Function (NAFX) at different gaze angles and determining the Longest Foveation Domain (LFD).Results:Acetazolamide improved foveation by both a 59.7% increase in the peak value of the NAFX function (from 0.395 to 0.580) and a 70% broadening of the NAFX vs Gaze Angle curve (the LFD increased from 20° to 34°). The resulting U-shaped improvement in the percent NAFX vs Gaze Angle curve, varied from ~60% near the NAFX peak to over 1000% laterally. The therapeutic improvements in NAFX from acetazolamide (similar to T&R) were intermediate between those of soft contact lenses and convergence, the latter was best; for LFD improvements, acetazolamide and contact lenses were equivalent and less effective than convergence. Computer simulations suggested that damping the central oscillation driving INS was insufficient to produce the foveation improvements and increased NAFX values.Conclusion:Acetazolamide resulted in improved-foveation INS waveforms over a broadened range of gaze angles, probably acting at more than one site. This raises the question of whether hereditary INS involves an inherited channelopathy, and whether other agents with known effects on ion channels should be investigated as therapy for this condition.

Experimental Study and Numerical Simulation of Propellant Ignition and Combustion for Cased Telescoped Ammunition in Chamber

Cased telescoped ammunition (CTA) is a kind of charge structure with projectile embedded in the cartridge case. The advantages of CTA, compared with concepts using conventional ammunition, are: (1) reduced charge/ammunition volume, (2) improved performance, and (3) enhanced power and survivabillity of armament. The projectile is placed in the control tube of the cartridge before shooting. After the primer is struck, propellant product gases, generated by the igniter charge burning in the central igniter tube, drive the projectile to move forward along the control tube, and then causing the main propellants around the igniter tube and control tube to burn. Therefore, in the process of interior ballistics, there is a motion of the projectile in the control tube before the projectile engraves the rifles, in contrast with the traditional ammunition. The consistency of this motion has an important influence on the stability of CTA interior ballistic performance. The experiments on the ignition and combustion of propellants and motion of projectile in the control tube are carried out using a high-speed video recording system in this study. The projectile velocity at the entrance of the rifle is obtained from the recorded images. A two-phase flow model of CTA is also established and simulated by using the two-phase flow method and computational fluid dynamics technology. The calculated projectile velocity is in good agreement with the experimental data. The numerical results show that the developed mathematical model gives the correct trend and can provide useful calculated parameters for the structural design of CTA components.

Echolocating bats can use acoustic landmarks for spatial orientation

We investigated the echolocating bat's use of an acoustic landmark for orientation in a complex environment with no visual information. Three bats of the species Eptesicus fuscus were trained to fly through a hole in a mist net to receive a food reward on the other side. In all experiments, the vocal behavior of the bats was recorded simultaneously using a high-speed video recording system, allowing for a 3D reconstruction of the flight path. We ran three types of experiments, with different spatial relations between the landmark and net hole. In the first experiment, the bat's behavior was studied in test trials with the landmark placed 10 cm to the left of the net opening; between test trials, the positions of the net opening and landmark were moved, but the spatial relationship between the two remained fixed. With the landmark adjacent to the net opening, the bats quickly found the hole. In the second experiment, bats were tested in control trials in which the landmark was moved independently of the hole, breaking the established spatial relationship between the two. In control trials the bats repeatedly crashed into the net next to the landmark, and inspected the area around it. In the final experiment, the landmark was removed altogether from the set-up. Here the bats spent more time per trial searching for the net opening with an increased number of inspections as well as crashes into the net. However, over the course of a test day without the landmark, bats reduced the time spent per trial and focused inspections and crashes around the hole. The behavioral data show for the first time that the echolocating bat can learn to rely on an acoustic landmark to guide spatial orientation.

Video recording system for the measurement of eyelid movements during classical conditioning of the eyeblink response in the rabbit

Classical conditioning of the eyeblink response in the rabbit is a popular model for studying the neural substrates of associative learning. Most of the common eyeblink recording techniques require invasive procedures. To perform experiments in intact animals, a non-invasive, high-speed video recording system was developed to measure eyeblink responses of rabbits during classical conditioning experiments. Besides being non-invasive, this method does not require excessive restraint of the animal. The PC-based system combines a Pulnix video camera with National Instruments video capture and timing hardware to control the experiment and acquire images of the peri-ocular region. The software developed for controlling these experiments also detects the eyeblink by measuring the movement of the upper and lower eyelids, the area of the exposed surface of the eye, and head movements in the sagittal plane. The time resolution of this relatively inexpensive system is 8.33 ms, and at a working distance of 0.8 m, it can detect movements as small as 0.11 mm.

Visualization and measurements of periodic boiling in silicon microchannels

A simultaneous visualization and measurement investigation has been carried out on flow boiling of water in parallel silicon microchannels of trapezoidal cross-section. Two sets of parallel microchannels, having hydraulic diameters of 158.8 and 82.8 μm, respectively, were used. The visualization study shows that once boiling heat transfer is established, two-phase flow and single-phase liquid flow appear alternatively with time in the microchannels. Large-amplitude/long-period fluctuations with time in wall temperatures, fluid temperatures, fluid pressures, and fluid mass flux, are measured for the first time during flow boiling in the microchannels. The fluctuation periods are found to be dependent on channel size, heat flux, and mass flux. The mechanism of the periodic boiling fluctuations in this experiment as well as their comparisons with other boiling fluctuations phenomena reported previously, are also discussed. The experimental results confirm that large-amplitude/long-period boiling fluctuations can be sustained when the fluctuations of pressure drop and mass flux have phase differences.With the aid of a microscope and high-speed video recording system, bubbly flow, slug flow, churn flow, and other peculiar flow patterns, are observed during two-phase flow periods in the microchannels.

Structure-I and Structure-H Hydrate Formation Using Water Spraying

An attempt has been made to form continuously either a structure-I or a structure-H hydrate using methane as the common guest substance and methylcyclohexane as the second guest for the structure-H hydrate. The experimental technique we tested was to spray water into a high-pressure chamber charged with methane gas. In the experiments to form the structure-I hydrate, water droplets sprayed from a single nozzle at the top of the chamber coalesced into a water pool underlying the methane gas phase. In the experiments to form the structure-H hydrate, the water droplets fell onto a methylcyclohexane layer superposed on a pool of water then merged with the pool. Water was continuously drained from the bottom of the chamber and circulated back through the spray nozzle. During this circulation, the water passed through a heat exchanger outside the chamber to release the heat generated by hydrate formation. The pressure in the chamber was maintained at a prescribed level (typically 2.5−3.7 MPa) by supplying methane gas through a port at the top of the chamber. The rate of methane flowing into the chamber was continuously measured to determine the instantaneous rate of hydrate formation in the chamber. The results of the measurements indicate that comparable methane-storing rate may be obtained for structure-H and structure-I hydrates, but with the structure-H hydrate formed at lower pressures. The process of hydrate formation was observed visually through a pair of glass windows in the chamber wall, alternatively using a digital video camera and a microscope connected to a high-speed video-recording system. This paper discusses the mechanisms of hydrate formation revealed by these observations and by the measurements of the rate of hydrate formation.

Axial viewing studies of horizontal gas–liquid flows with low liquid loading

An axial viewing system is described which was used to investigate the behaviour of the liquid phase in two-phase gas–liquid flows in a 0.079 m diameter horizontal pipe. The region investigated was that of flows with relatively high gas velocities and low liquid loading. Such flows are typically experienced in gas-condensate lines. Axial images obtained using the new system, show that the bulk of the liquid flows within a layer at the bottom of the pipe; however, at higher gas or liquid velocities, a significant portion is entrained as droplets within the gas core and is seen to deposit around the pipe periphery. A process that appeared to contribute significantly to the entrainment was captured using a high speed video recording system. Waves on the liquid layer were observed to converge and breakup into rapidly moving spray droplets. This process appeared to be random, but more frequent with increase in gas or liquid velocities. Secondary droplet breakup was also observed; large droplets were seen to balloon out and burst. The video evidence obtained using the axial viewing method, clearly identified the process of entrainment and deposition as the dominant contributor to the liquid phase transfer to the upper part of the pipe wall.