High-speed Video System Research Articles

Effect of mechanical prosthetic heart valve orientation on the flow field inside the simulated ventricle: Comparison between St. Jude Medical Valve and Medtronic-Hall Valve

Two typical contemporary mechanical heart valves, with different designs (St. Jude Medical and Medtronic-Hall), were tested in the mitral position under pulsatile flow conditions. The test program used the flow visualization technique to map the velocity field inside the simulated ventricle. The study was carried out using a sophisticated cardiac simulator in conjunction with a highspeed video system (200 frames/s). The continuous monitoring of velocity vector time histories revealed useful details about the complex flow and helped establish the location and time of the peak parameter values. We conclude that (1) the SJM valve with antianatomical position creates a large single circulatory flow; and (2)the configuration of the MH valve seems to affect the flow characteristics more dramatically, and the posterior orientation exhibits a simple and stable circulatory flow.

Evaluation of Intra-Aneurysmal Blood Flow: Investigation of the Flow in Experimental Aneurysms

We evaluated the flow in experimental pig aneurysms using a high speed video system with tracer particles and digital subtraction angiography (DSA). We found that flow velocity in experimental aneurysms was fast on the inflow of aneurysms. There was a certain correlation between mean transit time (MTT) and velocity in experimental aneurysms. Therefore, the differences of flow velocity in aneurysms will be detected using DSA. The flow in aneurysms was much changed by platinum coil embolization.

Experiments on Saltation of Sand in Water

A high-speed video system was used to study saltation of sand in an open channel flow. High rates of image acquisition provided the information needed to resolve details of the Lagrangian properties of particle motion. Saltation of sand is described in terms of statistical properties of particle trajectories such as mean values and standard deviations of saltation length, height, and streamwise particle velocity. Results are compared with available empirical data. Saltation height seems to be independent of particle size when made dimensionless with the particle diameter; however, the dimensionless saltation length appears to increase as the particle size decreases. Particle collision with the bed is also analyzed. Observations of this process indicate that most of the interactions between saltating particles and the bed are of the collision-rebound type, which contradicts previous discussions on the subject. The estimated value of the dynamic friction coefficient is about half that proposed by Bagnold, i...

Coordination of wing motion and walking suggests common control of zigzag motor program in a male silkworm moth

The male silkworm moth, Bombyx mori, exhibits a zigzagging pattern as it walks upwind to pheromones. This species usually does not fly, but obvious wing-beating accompanies the pheromone-mediated walking. Males supported by a `sled', after having their legs removed, also moved upwind in a pheromone plume along zigzagging tracks, indicating that wing-generated thrust and torque result in locomotory paths similar to those observed from walking moths. Using a high-speed video system we investigated the correlation between the wing movements and zigzag walking. The wing ipsilateral to the direction of the turn showed a greater degree of retraction with respect to the contralateral wing. The timing of the wing retraction pattern was synchronized with changes of direction in the walking track. Coordination of wing movements and walking pattern was not dependent on visual feedback or sensory feedback generated from neck movements associated with turning. The results presented here, taken together with our previous studies of descending interneurons suggest that the coordination of wing movements with the walking pattern may result from the activity of a set of identified interneurons descending from the brain to the thoracic ganglia and/or may be coordinated by coupling of oscillating circuits for walking and wing beating.

Simultaneous Measurements of Collapsing Behavior and Erosion Pits for Vortex Cavitation Bubble.

One of the authors has made clear the bubble behaviors around the bubble collapsing period as well as the patterns of bubble collapse near solid wall through instantaneous measurement of an impulsive force and bubble appearance under a really flowing condition using a high speed video system composed of an impulsive force sensor and a high speed video camera. In this report, a simultaneous observation of bubble collapsing behavior and cavitation erosion pits is tried in separated vortex flow behind a circular cylinder to experimentally prove the ability of damage for the bubble collapsing patterns reported in the previous papers. As a result, the simultaneous observation of the bubble collapsing behavior and the erosion pits are successfully conducted with the present measurement system so that the damage ability is confirmed, at least, for a collapsing pattern of the axial collapse type, and the details of its collapsing behavior are also shown at the same time.

Do Flatfish Feed Like Other Fishes? a Comparative Study of Percomorph Prey-Capture Kinematics

The kinematics of prey capture in two bilaterally asymmetrical pleuronectiform flatfish species (Pleuronichthys verticalis and Xystreurys liolepis) and two symmetrical percomorph species (Lepomis macrochirus, a centrarchid, and Cheilinus digrammus, a labrid) were compared to test the hypothesis that flatfish have distinct prey-capture kinematics from those quantified for other percomorph fishes. Size-matched individuals of both flatfish species were video-taped feeding using a high-speed video system. Cephalic displacement and timing variables were quantified and compared with data from similarly sized L. macrochirus and C. digrammus previously collected by other researchers using similar experimental methodology. Nested multivariate analyses of variance indicated that there was no significant difference in prey-capture kinematics between flatfish and non-flatfish taxa, but that prey-capture kinematics did differ among the four taxa. Multiple nested analyses of variance revealed that the taxa differed in 7 of 11 kinematic variables. Post-hoc tests and comparisons with other fish taxa suggest that individuals of P. verticalis possess an unusual combination of prey-capture kinematics including large hyoid depression, large neurocranial rotation, large upper jaw protrusion and small gape. Previous research has suggested that this combination of traits is associated with suction-based prey capture. Correspondingly, the ram­suction index calculated for P. verticalis is more negative (indicating a greater use of suction) than that calculated for the other taxa. When homologous kinematic variables are compared across these four taxa, flatfish do not appear to have similar prey-capture kinematics. However, both flatfish species are distinct from the two symmetrical percomorph species in their asymmetrical jaw movements.

Reduction of pollutants from diesel exhaust by high pressure gas injection

Abstract In order to reduce the pollutants from diesel exhaust, high-pressure gas was injected during combustion into a modified pre-chamber of an IDI diesel engine at a varied load and gas injection timing. The result shows that high-pressure gas injection can reduce the particulates and NO x simultaneously, with little influence on the engine performance. The combustion process in the pre-chamber was visualized by means of an ultra high-speed video system and image analysis of the pictures obtained. The results of the visualization show that by injecting gas, the flame is first quenched, followed by the reduction of NO x in the pre-chamber by hydrocarbon. Although high-pressure gas injection could have caused a substantial increase in HC as a result of temperature quenching, this seems to be controlled by the consumed portion of HC during the recycling of NO x . Chemical analysis of polycyclic aromatics compounds was carried out for the purpose of establishing its variations with gas injection. It was established that gas injection not only reduces PM by oxidation of solid carbon, but also the PAH component.

Determination of residual stress distribution from in situ curvature measurements for thermally sprayed WC/Co coatings

An in situ monitoring of curvature of the specimen during spraying using a high speed video system was implemented to determine stresses in thermally sprayed WC/Co coatings. Influences of different spray-ing techniques (atmospheric plasma spraying and high-velocity oxygen fuel) and cooling levels were con-sidered using a mathematical model. Results show that temperature history of a part is of paramount importance in stress generation and distribution.

Analysis of isolated outer hair cell motility using high speed video system

Analysis of isolated outer hair cell motility using high speed video system

Contact time during impact of a spherical particle against a plane gas-liquid interface: experiment

The impact interaction of a solid sphere against an initially plane gas-liquid interface is experimentally studied with a new experimental principle. The interface is formed at the bottom of a capillary of about 8 mm inner diameter. The sphere impacts the interface inside the capillary. The new principle is based on video imaging of the grey levels of the gas-liquid interface using light beam reflection. The grey levels are recorded by a CCD high-speed video system. Collision time is determined as the time between the first two maxima of the grey levels and obtained by means of Fourier analysis. The dependence of collision time on the diameter and density of impacting particles is investigated and compared with the available theoretical models. The experimentally determined collision time is longer than the collision time predicted by the available theories. The reasons for this disagreement are discussed. The disagreement may be affected by the dependence of the restoring force on the radius of the plane gas-liquid interface.

Analysis of Isolated Outer Hair Cell Motility Using Patch-Clamp Technique.

Although the amplitude of tympanic membrane vibrations is only a few nanometers when we speak in a low voice, we can understand clearly what is being said. This is speculated to be due to the cochlear amplification which is based on outer hair cell (OHC) motility. However, the mechanism of OHC motility in the cochlea is unclear. In order to understand this mechanism, motility of an isolated OHC in response to step voltage stimuli is measured using a high-speed video system. Results indicate that the generation force of the short OHC taken from the basal region of the cochlea was larger than that of the long OHC taken from its apical region.

Aggregate disintegration in turbulent jets

A state-of-the-art, high-speed video system has been used to observe floc disintegration occurring in the thin shear layer of a turbulent jet. The macrovideographic images have provided details of the breakage process that were heretofore unavailable. This information has been used to validate and quantify a force balance model that establishes a more rational framework for the description of floc breakage. It also has provided a much more detailed picture of the threshold levels of stress required for the breakage of specific floc structural types. The ultimate objective of this line of research is to use this framework to successfully describe the response of floc structures to hydrodynamic stress in coagulation processes and to provide a means by which substantial improvements can be made in solid-liquid separation processes.

冠動脈マッスルブリッジの冠動脈動脈硬化促進作用の臨床とモックサーキットによる実験的検討

During a total of 518 coronary bypass surgery cases, we encountered 144 incidence (28%) of muscle briges overriding the coronary artery. Of these 144 cases, we found 111 in the left anterior descending coronary artery (77%). As opposed to the control group, the muscle bridge group was found 32% more in the female-to-male ratio, which suggests atherosclerotic progressive factors for female patients. During coronary bypass grafting, we preferred to excise muscle bridges and select this as the site of graft-to-coronary bypass anastomosis, due to the absence of atherosclerosis within this segment. By constructing a mock circuit, which contains a muscle bridge that was actuated by compressing a silastic tube periodically, we observed movement of microspheres using a microscope and a high-speed video system. We suspected, based on the movement of microspheres, the possibility of intimal cell damage. We concluded that muscle bridges are one of the contributing factors of atherosclerotic progression, particullarly in the region of the left anterior descending coronary artery.

Measurement of two dimensional velocity profile using a high-speed color video camera

Color pictures from a high-speed color video system was used in measurement of the internal velocity fields by the correlation method. Color pictures provide three-times more information than monochromatic pictures, allowing more detailed analysis of fluid motion under breaking waves. By taking this advantage, the comparative investigation was made on the internal velocity fields of solitary wave on a fixed bed and on a movable bed.

Experiments on particle—turbulence interactions in the near–wall region of an open channel flow: implications for sediment transport

A high-speed video system was used to study the interaction between sediment particles and turbulence in the wall region of an open channel flow with both smooth and transitionally rough beds. In smooth flows, particles immersed within the viscous sublayer were seen to accumulate along low-speed wall streaks; apparently due to the presence of quasi-streamwise vortices in the wall region. Larger particles did not tend to group along streaks, however their velocity was observed to respond to the streaky structure of the flow velocity in the wall region. In transitionally rough flows particle sorting was not observed. Coherent flow structures in the form of shear layers typically observed in the near-wall region interacted with sediment particles lying on the channel bottom, resulting in the particles being entrained into suspension. Although there has been some speculation that this process would not be effective in entraining particles totally immersed in the viscous sublayer, the results obtained demonstrate the opposite. The entrainment mechanism appears to be the same independent of the roughness condition of the bottom wall, smooth or transitionally rough. In the latter case, however, hiding effects tend to preclude the entrainment of particles with sizes finer than that of the roughness elements. The analysis of particle velocity during entrainment shows that the streamwise component tends to be much smaller than the local mean flow velocity, while the vertical component tends to be much larger than the local standard deviation of the vertical flow velocity fluctuations, which would indicate that such particles are responding to rather extreme flow ejection events.

The effects of temperature on “S‐Strike” feeding of larval herring,Clupea Harengus L.

Both Manx autumn‐spawning and Clyde spring‐spawning stocks of Atlantic herring were reared at a range of temperatures (Manx 10 and 13°C;Clyde 5, 8 and 12°C). The behaviour of larvae, feeding on Anemia nauplii at a range of test temperatures (7.0, 10.0 and 13.0°C for Manx and 6.8,9.3 and 13.0°C for Clyde herring) was recorded using a high speed video system at 200 frames per second. The maximum velocities of feeding ‘S‐strikes’ (measured during frame‐by‐frame analyses) were positively correlated with body length, capture time and attack distance. In contrast to burst swimming speeds reported elsewhere, strike velocities showed only a weak relationship with test temperature. Both strike behaviour and velocity altered as larvae developed and both were modified by rearing temperature.

A Critical Study of the Applicability of Rigid-Body Collision Theory

This article deals with the collision of steel bars with external surfaces. The central issue of the article is the investigation of the fundamental concepts that are used to solve collision problems by using rigid-body theory. We particularly focus on low-velocity impacts of relatively rigid steel bars to test the applicability of these concepts. An experimental analysis was conducted to study the rebound velocities of freely dropped bars on a large external surface. A high-speed video system was used to capture the kinematic data. The number of contacts and the contact time were determined by using an electrical circuit and an oscilloscope. Tests were performed by using six bar lengths and varying the pre-impact inclinations and the velocities of the bars. The experimental results were used to verify the applicability of Coulomb’s law of friction and the invariance of the coefficient of restitution in the class of impacts considered in this study. Then, given the unusual variation the coefficient of restitution as a result of changing pre-impact inclinations, a theoretical model was developed to explain this variation. A discrete model of the bar was used to obtain the equations of motion during impact. Computed and experimental results were compared to establish the accuracy of numerical model. The internal vibrations of the bar and multi impacts between the bar and the surface were found to be two main factors that cause the variation of the coefficient of restitution. Furthermore, a slenderness factor was proposed to identify the subset of collision problems where the coefficient of restitution was invariant to the inclination angle.

Three-Dimensional Particle Tracking Velocimetry With Laser-Light Sheet Scannings

This paper describes three-dimensional particle tracking velocimetry (3D PTV), which enables us to obtain remarkably larger number of velocity vectors than previous techniques. Instead of the usual stereoscopic image recordings, the present 3D PTV visualizes an entire three-dimensional flow with the scanning laser-light sheets generated from a pair of optical scanners and the images are taken by a high-speed video system synchronized with the scannings. The digital image analyses to derive velocity components are based on the numerical procedure (Ushijima and Tanaka, 1994), in which several improvements have been made on the extraction of particle images, the determination of their positions, the derivation of velocity components and others. The present 3D PTV was applied to the rotating fluids, accompanied by Ekman boundary layers, and their complicated secondary flow patterns, as well as the primary circulations, are quantitatively captured.

Wind tunnel simulation of ammonia gas release transport processes

This work reports on experimental data and generalized correlations, which display the modification of a scalar field by the presence of obstacles. The data were obtained by means of a triple hot-wire probe in a wind tunnel. The global picture of the flow was visualized and recorded by a high-speed video system. The flow studied was a buoyant jet in a cross wind. This flow simulates an accidental ammonia release from a pressurized containment. The obstacle is found to enhance scalar turbulent dispersion and mixing. The simulated ammonia plume exhibits similar dynamic behavior with and without the obstacle, obtaining a self-similar state at distances downwind predicted by dimensional arguments. The scalar probability density functions display deviations from Gaussian distribution, depending upon their distance from the jet center. The data support a gradient transport hypothesis modeling. Recirculation patterns contributing to the entrainment processes were identified in the near wake of the obstacle.

Bubble Behavior and Mean Diameter in Subcooled Flow Boiling

Bubble behavior and mean bubble diameter in subcooled upward flow boiling in a vertical annular channel were investigated under low pressure and mass flux conditions. A high-speed video system was used to visualize the subcooled flow boiling phenomenon. The high-speed photographic results indicated that, contrary to the common understanding, bubbles tend to detach from the heating surface upstream of the net vapor generation point. Digital image processing technique was used to measure the mean bubble diameter along the subcooled flow boiling region. Data on the axial area-averaged void fraction distributions were also obtained using a single-beam gamma densitometer. Effects of the liquid subcooling, applied heat flux, and mass flux on the mean bubble size were investigated. A correlation for the mean bubble diameter as a function of the local subcooling, heat flux, and mass flux was obtained.