High-speed Video Camera System Research Articles

Effects of Pipe Inclination on Global Two-Phase Flow Parameters

Inclined two-phase flow geometries can be found in advanced nuclear reactor systems, such as the helical coil steam generators being considered for use in current integral steam generator designs. While this geometry includes inclination and centrifugal effects coupled together on two-phase flow, there have been limited studies to separate these effects to develop robust models. The majority of two-phase flow research is conducted on vertical channels, with recent work being conducted in a horizontal orientation and limited work in inclined pipes. In the current work, experiments are conducted in an adiabatic two-phase flow test facility to investigate the inclination effect on an air-water flow in straight pipes near atmospheric pressure. The pipe is made of clear acrylic with an inner diameter of 25.4 mm. The inclination of the flow loop can be adjusted in increments of 0.1 deg. Measurement capabilities are included to obtain local two-phase flow parameters such as void fraction, interfacial area concentration, bubble velocity, and Sauter-mean diameter using a local multisensor conductivity probe, local two-phase flow static pressure and pressure drop using a pressure transducer, and flow visualization using a high-speed video camera system. The experimental studies performed in the current work demonstrate how changes in inclination angle can affect the gas distribution flow regime transition and two-phase frictional pressure drop. Based on these experimental results, existing correlations for frictional pressure drop are evaluated, and the modified Lockhart-Martinelli correlation is found to predict the two-phase frictional pressure drop for inclined two-phase flows. This method agrees with experimental data within 7% on average.

Magneto-Hydrodynamic effects on Diesel/CNG bubbly flow enhanced by Fe3O4 Nanoparticles: Experimental and mathematical assessments

In the present study, the magneto hydrodynamic (MHD) was applied to the motion analysis of compressed natural gas (CNG) bubbles in laminar diesel flow after enhancing the liquid fuel with iron oxide nanoparticles (Fe3O4) in a horizontal pipe using experimental and mathematical approaches. Two distinct techniques were adopted for the experimental measurements: High speed video camera system (HSVC) and particle image velocimetry (PIV). The result of the PIV investigation indicates that increasing the intensity of the magnetic field changed the axial velocity profile of the diesel/nanoparticle mixture from the parabolic to a relatively flat shape. Whilst to illustrate the effect of magnetic field on bubble velocity, the axial and vertical components of the bubble velocity were computed by keeping track of the geometric center of the bubble from frame to frame recorded by HSVC. Moreover, the fundamental equation of motion of a single CNG bubble based upon Newton’s law under a forced magnetic field were derived and presented. The origination processes of the velocity dispersion of the liquid and gas stages of the bubbly flow were equally discussed. The governing partial-differential equations were numerically determined by means of a 4th order Runge-Kutta method. The outcomes from the model solution indicate that at magnetic field intensity (B = 0), the comparison between mathematical and experimental results in literature for the average axial and perpendicular components of bubble velocity resulted in mean percentage differences of 10.4 % and 15.6 % respectively.

Experiment and Simulation for Sport Wellness Fukiya

In ancient times, blowgun was used as a simple ranged weapon to hunt small animals. Today it is mainly used for sport wellness in Japan and is called Fukiya. The underlying principles of blowgun, especially the dynamic behaviours of the dart and the airflow in a blowpipe have not been studied sufficiently. In order to assist the design of new sport wellness blowguns, in particular, to design a dart which can travel horizontally in the blowpipe with small air resistance and can fly along a desired direction and distance, experiment and computer simulation for sport wellness blowgun were carried out. The experimental apparatus consists of the blowing system and high-speed video camera system. The blowing system is composed of a dart, a blowpipe, a mini digital angle meter and a compressor. The high-speed video camera system is composed of a video camera, a control unit, a synchronizing unit, an analog-digital converter, and a personal computer.

Investigation of LNG Underwater Release and Combustion Behavior on Water Surface

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30646, “Experimental Investigation of LNG Underwater Release and Combustion Behavior on the Water Surface,” by Yixiang Zhang, Jianlu Zhu, and Youmei Peng, China University of Petroleum, et al., prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4-7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. Most liquefied natural gas (LNG) is transported by ship, creating opportunities for potential hazards to surrounding devices and the environment. Nevertheless, few studies have examined the characteristics of LNG underwater leakage and subsequent vapor flame. The paper considers transportation safety and risk evaluation for LNG, with emphasis on accidental release and vapor flame. Introduction The cryogenic nature of LNG, with a boiling point of -162°C, raises safety concerns with regard to vaporization gas hazards and the potential for pool fires. According to the literature devoted to LNG accidental release and spill, three puncture positions have been proposed: Category I, where the leakage point is above the water line; Category II, where the point is at or close to the water line; and Category III, where the point is below the water line. A need exists to investigate LNG underwater leakage and combustion behavior for risk assessment. This work focuses on experimental research of the dynamic behavior of LNG jet release under water and the immediate burning on the water surface using three orifices and different crosswinds. The main points of investigation include the following: - Liquid-rising process and microbehavior in the orifice - Flame geometry on the water surface under crosswinds - Flame-temperature distribution on the water surface Experimental Setup Experimental Facilities. Experiments were conducted in a rectangular tank measuring 1000 mm long, 500 mm wide, and 500 mm high, which was placed in a wind tunnel. The nozzles have diameters of 1, 3, and 5 mm in the middle of the discharge pipe. An inline cryogenic flow-meter with a measuring range of 0.06 - 0.6 m3/h was used to regulate the volume flow rate with an accuracy of 1.5 %. The pressure measurements were performed by a pressure gauge with a range from 0 to 4 MPa placed on the end of the discharged pipeline. The LNG jets were re-leased vertically into the bulk water at a depth of 0.6 m. Images were recorded using a high-speed video camera system. Experimental Conditions. The window was closed when LNG was released, and the discharged gas was quickly diffused from the wind tunnel. The temperature in the room was 17±1°C and 14±0.5°C in water. The relative humidity was approximately 50%. All tests were conducted three times.

Effects of electrode polarity on the droplet transfer mode in self-shielded flux-cored arc welding

Abstract Self-shielded flux-cored wires (AWS E71 T FCW) are widely applied in the fields of construction. In this study, the effect of the electrode polarity on the mode of droplet transfer and arc stability in self-shielded flux-cored arc welding was investigated by the high-speed video camera system and electric signal. The results showed that the change of electrode polarity determined different mode of droplet transfer. In direct current electrode positive (DCEP), droplet transfer mode presented the globular repelled transfer. And the area of the arc root decreased at the bottom of the droplet because of the metallurgical reaction effect of the flux core, it resulted in the relatively lager electromagnetic force acting on the droplet, which hindered the droplet transfer. Moreover, when the droplet was separated from the welding wire, the droplet was kept rotation state under the action of the resultant force couple. In the direct current electrode negative (DCEN), the electromagnetic force promoted the droplet transfer and droplet transfer mode shown spray transfer mode. Due to the particularity of the composition and distribution of the molten slag, the conductive path was generated easily at the connection between the droplet and the wire, it made the arc root climb up and wrap the droplet, the necking phenomenon appeared obviously. In DCEN or DCEP, arc voltage and arc current have little effect on the droplet transfer mode. At the same time, compared with the welding process in DCEP, the welding process in DCEN had the advantages of higher arc stability, fewer welding spatter.

Magic carpet breakup of a drop impacting onto a heated surface in a depressurized environment

Drop impact onto a hot substrate leads to various hydrodynamic outcomes depending on the substrate temperature and the impact parameters: deposition, drop dancing, thermal atomization, and finally rebound at temperatures above the dynamic Leidenfrost condition. In the present experimental study this parameter space has been extended to conditions of a depressurized environment (1–101 kPa), which are relevant to space applications such as a reentry spaceship or a rocket engine. The impact onto a superheated smooth substrate with relatively small impact velocities (0.1–0.46 m/s) has been captured using a high-speed video camera system. Under these conditions two new modes of drop outcome have been identified; magic carpet breakup, in which the drop splashes immediately after the impact, leading to extensively large lateral deformation and upward drop movement, and tiptoeing, in which the drop bounces back with a time scale similar to capillary rebound (so-called rebound) accompanied by a significant fluctuation of the outer shape and secondary droplet generation triggered by successive attach-and-detach cycles. These new modes occur at a temperature range between the deposition regime and the capillary rebound regime. Detailed regime maps indicating the type of drop outcome for different pressures and substrate temperatures have been constructed. Moreover, a hypothesis on the mechanism of magic carpet breakup is presented and a theoretical model, in which a classical bubble growth model for pool boiling is extended to bubble growth in a drop and correlated with drop kinematics, is developed. The numerical solution is in good qualitative agreement with the experimental data for the bubble burst time and for the change in drop velocity.

Study on the structure and behaviour of cavitation bubbles generated in a high-intensity focused ultrasound (HIFU) field.

In this study, structures and behaviours of acoustic cavitation bubbles induced by a high-intensity focused ultrasound (HIFU) transducer, operating at its resonance frequency of 250kHz, are experimentally explored with corresponding observations captured by a high-speed video camera system. The experiments were conducted in an open-top Perspex water tank with deionized water, and illumination was provided by a LED spotlight which is placed beside the water tank throughout the whole experiment. Experimental results show that the structure of ultrasonically generated bubbles forms in a conical shape with several concentric bubble rings above the transducer. The distance between the adjacent rings with equal spacing as determined by the driving frequency of the HIFU transducer is experimentally measured and compared with the theoretical value. Then, the distribution of acoustic pressure in the acoustically driven liquid is further studied to investigate the behaviours of cavitation bubbles generated in a HIFU field. Additionally, the analysis of Bjerknes forces on the bubble surface which are induced by the gradient of acoustic pressure and the adjacent oscillating bubbles is quantitatively carried out, and the radius and velocity of a typical larger bubble are measured to characterize the behaviours of ultrasonically induced bubbles. Particularly, the physical phenomena of large bubbles including the coalescence, attraction or repulsion between adjacent bubbles, as well as the jumping of an acoustic bubble from the lower concentric ring level to the higher level, are analysed. The moving trajectory of the bubble is next obtained, and some conclusions are summarized to provide a greater understanding of the complex behaviours of the ultrasonically generated bubbles.

An experimental study of the mechanical and fracturing behavior in PMMA specimen containing multiple 3D embedded flaws under uniaxial compression

This paper studies the mechanical and fracture behavior of poly methyl methacrylate (PMMA) specimens containing multiple embedded flaws, under uniaxial compression. The initiation, propagation, coalescence of cracks, and failure of specimens are captured by a high-speed digital video camera system. Six types of cracks and three modes of crack coalescence are captured in the PMMA specimens. The experimental observations show that the effects of the flaw angle on crack propagation and coalescence are stronger than the non-overlapping length. Furthermore, the peak strength and crack initiation stress show regular change with increasing in the flaw angle and the non-overlapping length.

Experimental study on crack coalescence behavior of double unparallel fissure-contained sandstone specimens subjected to freeze-thaw cycles under uniaxial compression

To study the rock fracturing characteristics in cold-region engineering, uniaxial compression tests are conducted on double unparallel fissure-contained sandstone specimens subjected to freeze-thaw (FT) cycles. First, the effects of FT cycles on the water absorption, peak strength, initiation stress and deformation behavior of flawed sandstone specimens are investigated. The water absorption, uniaxial compressive strength, initiation stress, elastic modulus and deformation modulus of flawed sandstone specimens decrease with an increase in the number of FT cycles. However, the peak strain of flawed sandstone specimens increases with an increase in the number of FT cycles. Second, the cracking processes of flawed sandstone specimens are investigated in detail via images captured by a high-speed digital video camera system. The relationship between the real-time crack coalescence and the axial stress-strain curve of flawed specimens, which evaluates the macroscopic deformation characteristics of precracked rock subjected to FT cycles well, is considered. Third, the interaction mechanism of fissures in rock specimens is discussed. Fourth, the influence of water and temperature on the rock-weakening process is discussed. In this study, during the rock FT cycle weakening process, the effect of water, including the dissolution effect and the stress effect, is analyzed, whereas temperature damages the rock by means of different temperature gradients and the phase transition of water. Finally, the local strong fatigue-damaged zones around the fissure tips of sandstone specimens are also analyzed. These experimental results are helpful to improve the understanding of fracture mechanisms of a rock mass in cold-region engineering.

Quantitative Evaluation of Mixing Characteristics of Static Mixers by Visualization Experiments

We propose a convenient way of evaluating the mixing performance of static mixers used for round pipe by conducting flow visualization experiments under the turbulent region and using water as the main stream. A fluorescent pigment, glycerin, two carboxymethyl cellulose solutions, and rapeseed oil were each injected upstream of the mixer. Three static mixer conditions were tested: 1) no static mixer; 2) a Kenics-type static mixer; and 3) a multi-stacked elements (MSE) static mixer. The mixing trend downstream of the mixer in each condition and with each injection fluid was monitored using a laser and high-speed video camera system to obtain cross-sectional images. We propose suitable indexes based on the images obtained for quantitative evaluations of the mixing characteristics of static mixers.

Motion-Blur-Free High-Speed Video Shooting Using a Resonant Mirror.

This study proposes a novel concept of actuator-driven frame-by-frame intermittent tracking for motion-blur-free video shooting of fast-moving objects. The camera frame and shutter timings are controlled for motion blur reduction in synchronization with a free-vibration-type actuator vibrating with a large amplitude at hundreds of hertz so that motion blur can be significantly reduced in free-viewpoint high-frame-rate video shooting for fast-moving objects by deriving the maximum performance of the actuator. We develop a prototype of a motion-blur-free video shooting system by implementing our frame-by-frame intermittent tracking algorithm on a high-speed video camera system with a resonant mirror vibrating at 750 Hz. It can capture 1024 × 1024 images of fast-moving objects at 750 fps with an exposure time of 0.33 ms without motion blur. Several experimental results for fast-moving objects verify that our proposed method can reduce image degradation from motion blur without decreasing the camera exposure time.

Multimodal sensor-based weight drop spinal cord impact system for large animals

Background ContextA conventional weight drop spinal cord (SC) impact system for large animals is composed of a high-speed video camera, a vision system, and other things. However, a camera with high speed at over 5,000 frames per second (FPS) is very expensive. In addition, the use of the vision system involves complex pattern recognition algorithms and accurate arrangement of the camera and the target. PurposeThe purpose of this study was to develop a large animal spinal cord injury (SCI) modeling system using a multimodal sensor instead of a high-speed video camera and vision system. Another objective of this study was to demonstrate the possibility of the developed system to measure the impact parameters in the experiments using different stiffness materials and an in vivo porcine SC. Study DesignA multimodal sensor-based SCI impact system was developed for large animals. The experiments to measure SC impact parameters were then performed using three different stiffness materials and a Yucatan miniature pig to verify the performance of system developed. MethodsA comparative experiment was performed using three different stiffness materials such as high-density (HD) sponge, rubber, and clay to demonstrate the system and perform measurement for impact parameters such as impact velocity, impulsive force, and maximally compressed displacement reflecting physical properties of materials. In the animal experiment, a female Yucatan miniature pig of 60-kg weight was used. Impact conditions for all experiments were fixed at freefalling object mass of 50 g and height of 20 cm. ResultsIn the impact test, measured impact velocities were almost the same for the three different stiffness materials at 1.84±0.0153 m/s. Impulsive forces for the three materials of rubber, HD sponge, and clay were 50.88 N, 32.35 N, and 6.68 N, respectively. Maximally compressed displacements for rubber, HD sponge, and clay were 1.93 mm, 3.35 mm, and 15.01 mm, respectively. In the pig experiment, impact velocity, impulsive force, and maximally compressed dural displacement were measured at 1.84 m/s, 13.35 N, and 3.04 mm, respectively. After 3 days from the experiment, paralysis was confirmed for the lower half body of the experimental pig. ConclusionsThrough experiments, it was verified that our proposed system could be used to measure the SC impact parameters and induce SCI for large animals.

Several surfaces with special wettability: Influence on spreading and motion of W/O emulsion droplets

ABSTRACTPhysical and chemical modifications were made on the surface of the aluminum sheet to change the surface properties and superhydrophobic–hydrophilic wettability gradient surface was made on the perspex surface by using microstructure-pattering technique and self-assembled-monolayer method. By using high-speed video camera system and optical tensiometer, this paper discusses the influence of special surfaces with different wettability on spreading and motion of water, oil, and W/O emulsion droplets both experimentally and theoretically. In addition, the paper also discusses the influence of the superhydrophobic–hydrophilic wettability gradient on fluidity of W/O emulsion droplets and the coalescence process of droplets. The results showed that the contact angle of W/O emulsion droplets on the modified surfaces was related to the water and oil distribution at the three-phase line. On the wettability gradient surface, the droplet moved spontaneously when the droplet was located at the junction of the gradient. A quasi-steady theoretical model was used to analyze the driving and resistant forces acting on a droplet to improve the understanding of the self-transport behavior of the droplets.

Dynamic Interfacial Phenomena at Water-Magnetic Fluid System Subject to Alternating Magnetic Field

Responses of a magnetic fluid interface adsorbed on a small permanent magnet in water container subjected to an alternating magnetic field were studied with a high-speed video camera system. The directions of the external alternating magnetic field were parallel and anti-parallel to that of the permanent magnet. It was found that the interface of water-magnetic fluid responds to the external alternating magnetic field in elongation and contraction with Rosensweig instability at the interface. Frequency characteristics of the interface response of water-magnetic fluid system subjected to alternating magnetic field were revealed over a wide frequency band experimentally.

Characteristics in the Opening and Closing Operations of Micro Magnetic Fluid Diaphragm Mechanism by Alternating Magnetic Field

Response characteristics in the opening and closing operations of the micro magnetic fluid diaphragm mechanism by the alternating magnetic field are described. The micro magnetic fluid diaphragm mechanism was composed of a ring shaped permanent magnet and kerosene-based magnetic fluid. The driving principle of micro magnetic fluid device was based on the surface phenomena of magnetic fluid adsorbed on a permanent magnet. The opening and shutting time of diaphragm mechanism in the alternating magnetic field was measured by high-speed video camera system. The details of magnetic fluid surface response in the opening and closing operations of magnetic fluid hole were revealed experimentally.

Voltage-Mediated Control of Bundle Dynamics in Hair Cells

Hair cells of the vertebrate vestibular and auditory end organs convert mechanical inputs into electrical responses. This mechano-electrical transduction (MET) involves the gating of mechanically sensitive ion channels, thus modulating the conductance and the membrane potential of the cell. MET includes one or more energy consuming feedback mechanisms that keep the channels in their most sensitive operating range. Coupling between the gating of the channels and this adaptation mechanism has been proposed to follow dynamics of a system that is close to a Hopf or other bifurcations. Such systems exhibit high responsiveness to external stimuli in the proximity of a critical point, and exhibit spontaneous limit-cycle oscillations when the system crosses a bifurcation. We present optical and electrophysiological recordings from hair cells that exhibit such spontaneous oscillations and explore how the cell's membrane potential may control the system's tuning near the critical point. Sacculi from the American bullfrog were mounted in a two-compartment chamber such that the natural fluid separation between the apical and basolateral surfaces of the hair cells was maintained. Spontaneous hair bundle oscillations were monitored using a high-speed video camera system, and the hair cell membrane potential was controlled using standard patch-clamp techniques. We found that the membrane potential of the hair cell can modulate or fully suppress innate oscillations, thus controlling the dynamic state of the bundle. This control is mediated by the cell's internal calcium concentration, which sets the resting open probability of the mechanosensitive channels. The auditory and vestibular systems could control the membrane potential of hair cells to tune the dynamic states of the system near (or away from) the critical point, thereby affecting the responsiveness of the hair cells. This work was supported by NIH grant RO1DC011380 to DB.

Slug flow in a vertical narrow rectangular channel – Laminar and turbulent regimes in the main flow and turbulent regime in the wake region of the Taylor bubble

Using a high-speed video-camera system, the hydrodynamics of gas–liquid two-phase slug flow in a vertical narrow rectangular channel with the cross section of 2.2 mm × 43 mm is investigated for laminar and turbulent regimes in the main flow and turbulent regime in the wake region of the Taylor bubble. The Taylor bubble velocity is the function of the liquid slug length ahead of it, and the interaction of Taylor bubbles for turbulent flow in main flow is weaker than that for laminar flow. Thus, two correlations are proposed for laminar and turbulent flows, respectively. The distributions of Taylor bubble velocity, lengths of liquid slug and Taylor bubble are all positively skewed. The lengths of Taylor bubble and the liquid slug decrease with the liquid flow rate. The Taylor bubble length increases with the gas flow rate, whereas the influence of the gas flow rate on the liquid slug length is insignificant.

Three-Dimensional Optical Reconstruction of Vocal Fold Kinematics Using High-Speed Video With a Laser Projection System.

Vocal fold kinematics and its interaction with aerodynamic characteristics play a primary role in acoustic sound production of the human voice. Investigating the temporal details of these kinematics using high-speed videoendoscopic imaging techniques has proven challenging in part due to the limitations of quantifying complex vocal fold vibratory behavior using only two spatial dimensions. Thus, we propose an optical method of reconstructing the superior vocal fold surface in three spatial dimensions using a high-speed video camera and laser projection system. Using stereo-triangulation principles, we extend the camera-laser projector method and present an efficient image processing workflow to generate the three-dimensional vocal fold surfaces during phonation captured at 4000 frames per second. Initial results are provided for airflow-driven vibration of an ex vivo vocal fold model in which at least 75% of visible laser points contributed to the reconstructed surface. The method captures the vertical motion of the vocal folds at a high accuracy to allow for the computation of three-dimensional mucosal wave features such as vibratory amplitude, velocity, and asymmetry.

J0260104 フタモンアシナガバチの翅展開と離陸飛行に関する研究

Most of insects that walk about on the ground have structures to fold their wings. In this study, the take-off motion of a paper wasp, Polistes chinensis, was observed with a high-speed video camera system, and the unfolding sequence of the wings was investigated. A paper wasp with a body length of 13.8 mm was used. The wasp opened the folded wings and started flapping, and then the wing unfolding was completed at the third down stroke. The down stroke time decreased and upstroke time increased until each third stroke. Therefore, the initial several up and down strokes seem to be conducted to unfold the wings. The behavior of the vertical climbing flight following to the take-off was also investigated. The incline of the body to the horizontal was kept at around π/4 in the whole period of the vertical flight. Although the up and down stroke directions were almost parallel to the horizontal, the trajectories were different from each other. The trajectories of up and down strokes were convex upward and downward, respectively.

永久磁石に吸着したマイクロ磁性流体リングの交流磁場応答の研究

This paper is concerned with the development of micro magnetic fluid diaphragm driven by alternating magnetic field. The micro magnetic fluid diaphragm is composed of a ring-shaped permanent magnet and kerosene-based magnetic fluid. The response characteristics on the relations between input and output signals were examined by using a photodiode detector system and a digital high-speed video camera system. Sinusoidal, triangle, square, and saw tooth waves as input signals were examined. The magnetic fluid device showed good responses even at the frequency f0=1000 Hz in alternating field.