Showing papers in "Journal of Visualization in 2015"

Visualization of arc and plasma flow patterns for advanced material processing

Abstract: Results are presented for physical experiments that illustrate the possibilities and efficiency of visualization for studying the effect of operating conditions (backward-facing stepped forming nozzle, exit diameter of anode, mass flow, and composition of working gas) on plasma flows at low Reynolds numbers for advanced coating and powder processing In particular, the shadow method, based on adaptive visualization transparency, is used for imaging electric arc and plasma jet flow patterns for different operating conditions Because of visualization, the optimal geometrical characteristics of the backward-facing stepped forming nozzle, mass flow rate of the working gas, and its composition were found These provide: (1) the absence of micro-shunting of the arc inside the backward-facing stepped nozzle for a transfer arc and twin arcs; and (2) compared to transient and turbulent jets, a higher density for the heat flux from a quasi-laminar flow to the surface of a flat substrate and the powder material to be treated, for nontransfer arc DC (direct current) torches and DC–RF (direct current and radio frequency) hybrid plasma flow system

SocialHelix: visual analysis of sentiment divergence in social media

Abstract: Social media allow people to express and promote different opinions, on which people’s sentiments to a subject often diverge when their opinions conflict. An intuitive visualization that unfolds the process of sentiment divergence from the rich and massive social media data will have far-reaching impact on various domains including social science, politics and economics. In this paper, we propose a visual analysis system, SocialHelix, to achieve this goal. SocialHelix is a novel visual design which enables the users to detect and trace topics and events occurring in social media, and to understand when and why divergences occurred and how they evolved among different social groups. We demonstrate the effectiveness and usefulness of SocialHelix by conducting in-depth case studies on tweets related to the national political debates.

Performance evaluation of an overdriven LED for high-speed schlieren imaging

Abstract: A quantitative comparison of an overdriven light-emitting diode (LED) and a high-intensity discharge (HID) lamp as illumination sources for high-speed schlieren imaging is presented A custom pulser circuit utilizing a new and improved driver circuit was developed to overdrive the LED by a factor of ten while simultaneously reducing pulse widths to sub-microsecond durations The LED system has been developed as a simple and inexpensive alternative light source to discharge lamps and pulsed laser systems, which are typical for high-speed schlieren imaging Image quality of a decaying spherical shock wave, produced from the unsteady release of an under-expanded helium jet, is analyzed to assess comparative performance The effects of framing rate, camera exposure time, and pulse duration on image quality were assessed and compared for the novel LED and an HID Framing rates of 10,000 and 50,000 fps and exposure times of 1 and 10 µs were tested Image quality was assessed qualitatively through side-by-side comparisons of fluid dynamic features such as the resolution of shock waves, compression waves, and shear layers Quantitative analysis was performed through the comparison of the signal-to-noise ratio at the various conditions LED performance was found to be superior when imaging fast events and inferior when imaging slower events Results and potential system improvements indicate that the LED system is ideal for low-cost, high-speed flow imaging

Large-scale taxi O/D visual analytics for understanding metropolitan human movement patterns

Abstract: It is very useful to understand metropolitan human movement patterns for better city planning and traffic management. As the most accessible and wide-coverage data source for probing the laws behind city pulse and human movement, taxi O/D data have been receiving more and more attention from road traffic administration offices. In this paper, we design a visual analysis system for big taxis O/D data for assisting understanding the spatio-temporal patterns of human mobility. The system first helps users determine the regions of interest for further investigation by the global heat map view of O/D distributions; visually encodes the spatio-temporal patterns of the O/D data of the to-be-analyzed regions chosen by lasso or rectangle region selection tools; and provides a multi-dimensidoneonal analysis of the latent spatio-temporal patterns of taxis O/D data through interactions between multiple coordinated views of visualizations including circular pixel graph, spatio-temporal stacked graph and nested pixel bar. The proposed system of taxis O/D data visual analysis gets interesting findings about the metropolitan residents’ movement behavior when applied to large-scale real taxis GPS data in Hangzhou and receives good user feedbacks.

A smoke visualization study of the flow over a square cylinder at incidence and tandem square cylinders

Abstract: An experimental investigation of flow around a square cylinder placed at various incidence angles (0–45) with respect to the approach flow is reported (Re d = 2,033, 6,776, 7,575, 8,246). Also flow over two square cylinders in a tandem arrangement at zero incidence is studied for different gap spacing values ranging from 1d to 6d, where d is cylinder side length (Re d = 2,033). A low-speed vertical smoke tunnel is used to visualize flow patterns. For single cylinder, the flow patterns, stagnation and separations points, separation angle, attachment point, transient and turbulence lengths of the shear layer, wake length, frequency and Strouhal number for various incidence angles are determined quantitatively using flow visualization and image digitization process. It is found that a critical value appears around α = 15° for aforementioned parameters due to occurrence of the reattachment of the separated shear layer on the lateral face of the cylinder.For tandem cylinders, the effect of gap spacing between cylinders on the flow patterns, separation angle, wake length, and transient and turbulence lengths of the shear layer of the upstream cylinders is investigated. The results showed that there are three flow patterns when the gap spacing values are varied from 1d to 6d. Also it is observed that the aforementioned parameters for the upstream cylinder become approximately similar to those for single cylinder due to reduction in the flow interference of the cylinders at higher gap spacing values, i.e., 5d and 6d.

Visualization study of hybrid synthetic jets

Abstract: A synthetic jet (SJ) is a fluid flow that is created from an oscillatory process of suction and blowing. A hybrid synthetic jet (HSJ) combines this principle with fluidic pumping through a valveless pump. The present study addresses round HSJs issuing into quiescent surroundings from an actuator orifice 8 mm in diameter. For comparison purposes, a common (zero-net-mass-flux) SJ is used. The working fluid is air, and the maximum Reynolds numbers are 11,000 and 9,000 for HSJs and SJs, respectively. The following five experimental methods are employed: flow visualization using a smoke wire technique, velocity measurements using a hot-wire anemometer, velocity measurements using a Pitot tube, impedance measurements of the actuators, and measurements of the jet momentum using precision scales. Flow visualization demonstrates phase-locked flow fields. The first resonance frequencies are theoretically derived to be 79 and 98 Hz for an SJ and HSJ, respectively. These values are confirmed by all of the experimental methods used. The results demonstrate the advantages of HSJs. The tested HSJ achieves a 24 % higher pumped volume flow rate in comparison to the SJ at a maximum volumetric efficiency of 33 %. Moreover, the overall energy efficiency of the HSJ actuator is 1.8 times higher than that of the SJ actuator. These promising HSJ features, including significantly higher efficiencies, can be useful for various heat transfer applications such as the cooling of highly loaded electronic devices.

Feature expectation heightens visual sensitivity during fine orientation discrimination.

Abstract: Attending to a stimulus enhances the sensitivity of perceptual decisions. However, it remains unclear how perceptual sensitivity varies according to whether a feature is expected or unexpected. Here, observers made fine discrimination judgments about the orientation of visual gratings embedded in low spatial-frequency noise, and psychophysical reverse correlation was used to estimate decision ‘kernels' that revealed how visual features influenced choices. Orthogonal cues alerted subjects to which of two spatial locations was likely to be probed (spatial attention cue) and which of two oriented gratings was likely to occur (feature expectation cue). When an expected (relative to unexpected) feature occurred, decision kernels shifted away from the category boundary, allowing observers to capitalize on more informative, “off-channel” stimulus features. By contrast, the spatial attention cue had a multiplicative influence on decision kernels, consistent with an increase in response gain. Feature expectation thus heightens sensitivity to the most informative visual features, independent of selective attention.

Visualization of flow instabilities in supersonic ejectors using Large Eddy Simulation

Abstract: Graphical Abstract

Quantification of transient behavior of wind-driven surface droplet/rivulet flows using a digital fringe projection technique

Abstract: A digital fringe projection (DFP) system is developed to achieve non-intrusive thickness measurements of wind-driven water droplet/rivulet flows over a test plate to quantify the unsteady surface water transport process pertinent to various atmospheric icing phenomena. The DFP technique is based on the principle of structured light triangulation in a similar manner as a stereo vision system but replacing one of the cameras for stereo imaging with a digital projector. The digital projector projects line patterns of known characteristics onto the test specimen (i.e., a water droplet/rivulet on a test plate for the present study). The pattern of the lines is modulated from the surface of the test object. By comparing the modulated pattern and a reference image, the 3D profile of the test object with respect to the reference plane (i.e., the thickness distribution of the water droplet/rivulet flow) can be retrieved quantitatively and instantaneously. The feasibility and implementation of the DFP system is first demonstrated by measuring the thickness distribution of a small flat-top pyramid over a test plate to evaluate the measurement accuracy level of the DFP system. After carefully calibrated and validated, the DFP system is applied to achieve time-resolved thickness distribution measurements of a water droplet/rivulet to quantify the transient behavior of a water droplet/rivulet flow driven by a boundary layer air flow over a test plate. The dynamic shape changes and stumbling runback motion of the wind-driven water droplet/rivulet flow were measured in real time in terms of film thickness distribution, contact line moving velocity, wet surface area and droplet evaporation rate.

Pressure-sensitive paint technique for surface pressure measurements in a low-density wind tunnel

Abstract: A low-density wind tunnel called the Mars wind tunnel, has been developed at Tohoku University that can produce a high subsonic flow at low pressures for aerodynamic measurements of low-Reynolds-number aircraft wings aimed at developing aircraft applicable to the atmosphere on the planet Mars. Accurate surface pressure measurements on the wing are essential for analysis of not only aerodynamic performance, including lift and drag, but also the flow fields around the wing. This paper presents a surface pressure measurement technique using pressure-sensitive paint (PSP) applicable for Mars wind tunnel tests under low-pressure conditions. The results show that a PSP composed of palladium tetra(pentafluorophenyl) porphyrin (PdTFPP) and poly[1-(trimethylsilyl)-propyne] [poly(TMSP)] exhibits a high-pressure sensitivity at pressures as low as 1 kPa, and the absolute values of the static pressures measured by the PSP accorded well with the values derived from static pressure sensors used as a reference. A calibration methodology for the non-uniform pressure sensitivity on the test model, including a temperature calibration, is also established. The PSP technique clearly demonstrated pressure sensitivity over a distinctive low-pressure region inside a leading edge separation bubble on a flat plate at low Reynolds numbers.

Gaze constancy in upright and inverted faces.

Abstract: The dual-route model (Otsuka, Mareschal, Calder, & Clifford, 2014) posits that constancy in the perception of gaze direction across lateral head rotation depends on the integration of information from the eye region and information about head rotation. Incorporation of information about head rotation serves to compensate for the change in eye-region information when viewing a rotated head. We tested the ability of this model to predict the magnitude of Wollaston's effect: When eyes from a frontal pose are inserted into an angled face, the perceived direction of gaze appears attracted towards the direction of the head. The framework of the dual-route model explains Wollaston's effect as a result of the misapplication of this same integration operation without any change in eye-region information. To test this explanation, we compared the magnitude of the integration occurring for Wollaston's effect to that for normal faces. Here, participants performed categorical judgment of gaze direction across head rotation poses in three image conditions: normal face, eyes-only, and Wollaston. Integration of eye and head information was inferred by comparing the effect of pose between the eyes-only condition and the normal face condition, and by examining the effect of pose in the Wollaston condition. Consistent with the dual-route model, the magnitude of integration was similar between the normal face condition and the Wollaston condition. Further, upright and inverted faces yielded similar levels of gaze constancy, showing that the dual-route model applies to the perception of gaze direction in inverted faces as well as in upright faces.

Flow visualization of Mach 3 compression ramp with different upstream boundary layers

Abstract: Experimental studies of supersonic flow over several compression ramps are carried out in a Mach 3.0 wind tunnel; the upstream boundary layers include laminar flow, transitional flow, and turbulent flow. Fine flow structures are obtained via nano-tracer planar laser scattering (NPLS) technique, typical flow structures such as boundary layer, shear layer, and shock wave are visible distinctly. The angle of shock wave and the development of boundary layer are measured by time-averaged flow field, the spatiotemporal evolutions of flow field are revealed by two time-dependent NPLS images. Results indicate that when ramp angles are 25°, a typical separation occurs in laminar flow, and a certain extent separation occurs in transitional flow, while separation does not occur in turbulent flow. When ramp angles are 28°, laminar flow separates further, a typical separation occurs in transitional flow, by comparison, separation region in turbulent flow is small. Significant differences of the three types of ramp flows can be found in shock wave structure and flow separation.

The effects of grouping on speed discrimination thresholds in adults, typically developing children, and children with autism.

Abstract: Adult observers show elevated speed discrimination thresholds when comparing the speeds of objects moving across a boundary compared to those moving parallel to a boundary (Verghese & McKee, 2006)-an effect that has been attributed to grouping processes in conjunction with a prior for smooth motion. Here, we extended Verghese and McKee's (2006) paradigm to typically developing children (n = 35) and children with autism (n = 26) and compared their performance with that of typical adults (n = 19). Speed discrimination thresholds were measured in three conditions: (a) with dots moving parallel to a boundary, (b) with dots moving perpendicular to a boundary, and (c) with dots in each stimulus half moving in orthogonal, oblique directions. As expected, participants had higher speed discrimination thresholds when dots appeared to cross a boundary compared to when dots moved parallel to the boundary. However, participants had even higher thresholds when dots moved in oblique, orthogonal directions, where grouping should be minimal. All groups of participants showed a similar pattern of performance across conditions although children had higher thresholds than adult participants overall. We consider various explanations for the pattern of performance obtained, including enhanced sensitivity for shearing motions and reduced sensitivity for discriminating different directions. Our results demonstrate that the speed discrimination judgments of typically developing children and children with autism are similarly affected by spatial configuration as those of typical adults and provide further evidence that speed discrimination is unimpaired in children with autism.

Visualization of synthetic jet formation in air

Abstract: This experimental study deals with a round synthetic jet (SJ) issuing into quiescent surroundings. Flow visualization in air is used to identify different flow field regimes. Hot-wire anemometry and theoretical evaluations are used to quantify parameters in terms of the Reynolds (Re) and Stokes (S) numbers. To verify the theoretical evaluation, additional experiments were performed using the laser Doppler vibrometry. Four regimes of oscillatory suction and extrusion are distinguished and presented by means of a Re–S parameter map: (a) creeping flow without SJ formation, (b) SJ formation and propagation without vortex rollup, (c) SJ with vortex rollup, and (d) vortex structure breakdown, instability and transition to turbulence. Differences in the SJ regimes at low, moderate and high Stokes numbers are found. While all four (a–d) regimes are identified for lower (S < 10) and moderate (S = 10–30) Stokes numbers, the SJ formation process for higher Re and S is coupled with the laminar–turbulent transition. The results are reasonably consistent with those in the available literature.

Real-time planar flow velocity measurements using an optical flow algorithm implemented on GPU

Abstract: This paper presents a high-speed implementation of an optical flow algorithm which computes in real-time planar velocity fields in an experimental flow. Real-time computations of the flow velocity field allow the experimentalist to have instantaneous access to quantitative features of the flow. This can be very useful in many situations: fast evaluation of the performances and characteristics of a new setup, design optimization, easier and faster parametric studies, etc. It can also be used as a visual sensor for an input in closed-loop flow control experiments where fast estimation of the state of the flow is needed. The algorithm is implemented on a graphics processor unit. The accuracy of the computation is demonstrated. Computation speed and scalability of the processing are highlighted along with guidelines for further improvements. The system architecture is flexible, scalable and can be adapted on the fly in order to process higher resolutions or achieve higher precision. The setup is applied on a backward-facing step flow in a hydrodynamic channel. For validation purposes, classical particle image velocimetry (PIV) is used to compare with instantaneous optical flow measurements. The important flow characteristics like the dynamics of the recirculation bubble, computed in real time for the first time, are well recovered. The accuracy of real-time optical flow measurements is comparable to off-line PIV computations.

Sunburst with ordered nodes based on hierarchical clustering: a visual analyzing method for associated hierarchical pesticide residue data

Abstract: According to the characteristics of pesticide residue data and analyzing requirements in food safety fields, we presented a visual analyzing method for associated hierarchical data, called sunburst with ordered nodes based on hierarchical clustering (SONHC). SONHC arranged the leaf nodes in sunburst in order using hierarchical clustering algorithm, put the associated dataset as a node in center of the sunburst, and connected it with the associated leaf nodes in sunburst using colored lines. So, it can present not only two hierarchical structures but also the relationships between them. Based on SONHC and some interaction techniques (clicking, contraction and expansion, etc) we developed an associated visual analyzing system (AVAS) for pesticide residues detection results data, which can help users to inspect the hierarchical structure of pesticide and agricultural products and to explore the associations between pesticides and agricultural products, and associations between different pesticides. The results of user experience test showed that SONHC algorithm overperforms than SA and SR algorithm in ULE and ULE’s variance. AVAS system is effective in helping users to analyze the pesticide residues data. Furthermore, SONHC algorithm can also be adopted to analyze associated hierarchical data in other fields, such as finance, insurance and e-commerce.

Scatterplot layout for high-dimensional data visualization

Abstract: Multi-dimensional data visualization is an important research topic that has been receiving increasing attention. Several techniques that apply scatterplot matrices have been proposed to represent multi-dimensional data as a collection of two-dimensional data visualization spaces. Typically, when using the scatterplot-based approach it is easier to understand relations between particular pairs of dimensions, but it often requires too large display spaces to display all possible scatterplots. This paper presents a technique to display meaningful sets of scatterplots generated from high-dimensional datasets. Our technique first evaluates all possible scatterplots generated from high-dimensional datasets, and selects meaningful sets. It then calculates the similarity between arbitrary pairs of the selected scatterplots, and places relevant scatterplots closer together in the display space while they never overlap each other. This design policy makes users easier to visually compare relevant sets of scatterplots. This paper presents algorithms to place the scatterplots by the combination of ideal position calculation and rectangle packing algorithms, and two examples demonstrating the effectiveness of the presented technique.

Study on the particle traceability in transonic and supersonic flows using molecular tagging velocimetry

Abstract: Particle image velocimetry (PIV) has become a powerful tool for flow velocity measurements in wind tunnel testing. However, it is generally difficult to apply the PIV technique to supersonic flows because of unreliable particle traceability. In the present study, the PIV and MTV (molecular tagging velocimetry) techniques are applied to transonic and supersonic flows, in which a normal shock wave appears, to evaluate particle traceability. Based on this work, it is found that the PIV data largely deviate from the MTV data behind a normal shock wave for both flows. The drag coefficient is also estimated for a particle from the velocity data measured by the two techniques. Its value is then compared to the drag coefficient value calculated from an empirical formula for particle Mach numbers ranging between 0.1 and 0.9. Based on the results, it is found that the experimental data can be reproduced reasonably well by the formula for particle Reynolds numbers higher than ~1. However, the data associated with particle Reynolds numbers lower than ~1 deviate largely from the formula.

Nose shape effect on the visualized flow field around an axisymmetric body of revolution at incidence

Abstract: The flow over an axisymmetric body of revolution at incidence angle is investigated to explore the nature of complex vortical flow structures around it. The crossflow pressure gradient causes the separated sheet to rollup and extend to the flow at the leeward side of the body. The oil and smoke flow visualization techniques are conducted to explore and describe such complicated flow patterns over and around the axisymmetric body under investigation considering two different nose shapes. The results show the formation of primary and secondary crossflow vortices around the model surface. Furthermore, the effects of nose shape on the vortical flow structure and separation and reattachment locations are also investigated. Moreover, longitudinal and circumferential surface pressure measurements are conducted to further explain the nature of the separation pattern observed in the flow visualization experiments. The comparison of the surface flow visualization results for the model indicates that the nose curvature has influenced on the separation position along the model length. Moreover, the nose separation occurs in smaller incidence angles for the model with blunter nose shape.

High resolution GPU-based flow simulation of the gaseous methane-oxygen detonation structure

Abstract: Graphical abstract

Visualization of supersonic flow around a sharp-edged, sub-boundary-layer protuberance

Abstract: Innovations in conventional surface and planar laser scattering visualizations revealed complex structures in the Mach 2.5 flow past a sharp-edged, sub-boundary-layer ramp with swept sides that is one type of micro vortex generator (MVG). The incoming flow separated over the leading edge despite the ramp angle being below the threshold for incipient separation. The separation produced a weak trailing horseshoe vortex system. The flow over the top of the MVG separated off the slant edges to produce a large primary vortex pair. Extra details were revealed at the trailing edge with at least two pairs of singularities. Vortex filaments spring from these singularities. Symmetry breaking from the confluence of the two primary vortices was observed as an unsteady wake to result in a train of possibly ring or hairpin vortices trailing downstream.

Flow visualization for the evolution of the slipstream in steady shock reflection

Abstract: As an important part of the basic research on shock wave, shock reflection phenomena which appear in many practical situations, ranging from supersonic aircraft wings to hypersonic vehicles and engines, always receive a great deal of attention. Generally speaking, the slipstream which is an important part of shock reflection structures has a significant effect on the flow property. On the one hand, better understanding of the slipstream is beneficial to flow control which aims to reduce the stagnation pressure loss. On the other hand, it also provides a reasonable way in mixing enhancement. In view of these structures, the schlieren method and the shadow method are widely applied for flow visualization so far. However, the photographs which are obtained by the above methods merely reflect the flow field that is through temporal and spatial integration, rather than high-spatiotemporal resolution images. Also, the evolution of the slipstream cannot be fully investigated by means of the traditional methods of flow visualization. Garrison and Settles (1992) trace the evolution of the slipstream which emanates from the triple point of the k-shock system using the Planar Laser Scattering (PIS) technique. Afterwards, to describe the steady Mach reflection configuration approximately, Azevedo and Liu (1993) and Li and Ben-Dor (1997) investigate shape of the slipstream ignoring the viscous effect respectively. Then, Rikanati et al. (2006) indicate that the slipstream thickening of the pseudo-steady Mach reflection is caused by small-scale growth of the Kelvin–Helmholtz shear flow instability using the interferometry technique. Afterwards, Rubidge et al. (2013a, b; Rubidge and Skews 2014) point out that Kelvin–Helmholtz instability do form on the pseudo-steady Mach reflection slipstream, and describe the Kelvin–Helmholtz instability evolution using the schlieren images. However, little work has been conducted on the development of the slipstream in steady shock reflection. Hence, a series of experiments are performed to observe the fine structures of the steady shock reflection and investigate the evolution of the slipstream in this paper, using Nano-tracer Planar Laser Scattering (NPLS) technique.

A semantic-enhanced trajectory visual analytics for digital forensic

Abstract: With the increasing application of GPS devices, trajectory data have been frequently adopted in digital forensics because it can encompass spatial and temporal aspects of suspects’ movements. However, a lack of semantic information causes difficulty of linking the trajectories with the activities of suspects. Using the situation of a kidnapping, this paper proposes a semantic-enhanced method in trajectory analysis, which categorizes the daily activities of suspects into different semantic types by connecting trajectory data with transaction data. In the meantime, we present an interactive visualization system with four inner-linked views to provide a collaborative visual analytics of trajectory and transaction data in multiple perspectives. In the case study, the kidnapping investigation is used to demonstrate how the system works on the routine pattern analysis of suspects, the detection of abnormal behaviors, and the association exploration among suspects and their abnormal behaviors.

Multi-scale vortical structure analysis on large eddy simulation of dune wake flow

Abstract: The three-dimensional dune wake flow is evaluated by large eddy simulation at a Reynolds number of 5,534, and validated by time-averaged results of particle image velocimetry measurement at a central streamwise plane. To reveal multi-scale characteristics of vortical structure, the instantaneous velocity, vorticity, and pressure were decomposed into the large-, intermediate- and small-scale components by three-dimensional wavelet multi-resolution technique, the scale of each wavelet component is quantified by two-point autocorrelation function with the central scale of 43, 20 and 9.6 mm, respectively. It is found that large-scale structure determines the formation of separation bubble and makes the most significance to the vorticity. Some intermediate-scale and small-scale streamwise vortices cause the upwelling of vortical structures, and they tend to be more active at the downstream. By visualization of pressure distribution, we can find that pressure distribution is mainly characterized by large-scale structure, and the distribution of small-scale structure can be interfered as a reason why large-scale vortical structure breaks into small vortices at the near outlet region.

Evaluation of cavitation in injector nozzle and correlation with liquid atomization

Abstract: Present paper describes the correlation between occurrence of cavitation inside injector nozzle and progress of atomization in discharged liquid jet flow. A transparent two-dimensional shape nozzle was designed and it was used for flow visualization. The visualized images both of cavitation and atomization were obtained simultaneously. The cavitation was evaluated by applying image analysis. The quantitative analysis on length, thickness and their fluctuations of cavitation was made, and the correlation with atomization was examined. The authors proposed an evaluation method of atomization in the previous study, and it was combined with evaluation method of cavitation developed in this study. It is found that the change of cavitation and progress of atomization are synchronized, and that a strong correlation between them exists. The best performance of atomization may be obtained by controlling the cavitation inside nozzle, and obtained aspects with this study will be utilized for the design of fuel injection nozzle of internal combustion engines.

Quantitative density measurement of the lateral jet/cross-flow interaction field by colored-grid background oriented schlieren (CGBOS) technique

Abstract: The colored-grid background oriented schlieren (CGBOS) technique is applied to the measurement of the interaction field of lateral jet and cross-flow. The test model is designed based on DLR’s generic model. Experiments were carried out in supersonic blow-down wind tunnel of JAXA/ISAS with 0.6 m × 0.6 m test section. Free-stream Mach number is set to 2.0. The quantitative experimental data obtained by CGBOS technique and the reconstruction results of the density for the interaction field between cross-flow and lateral jet are described. Unsteady phenomena in the lateral jet/cross-flow interaction field are also measured using color high-speed camera. The growth of the interaction field is reconstructed and visualized three dimensionally.

Damping of liquid sloshing by foams: from everyday observations to liquid transport

Abstract: Author(s): Cappello, J; Sauret, A; Boulogne, F; Dressaire, E; Stone, HA | Abstract: We perform experiments on the sloshing dynamics of liquids in a rectangular container submitted to an impulse. We show that when foam is placed on top of the liquid the oscillations of the free interface are significantly damped. The ability to reduce sloshing and associated splashing could find applications in numerous industrial processes involving liquid transport.

Visualization of bipartite relations between graphs and sets

Abstract: In many application domains, we encounter data which involves a graph encoding certain relationships and a set of items related to the graph One example is in social websites where the users interact with each other, and share their interests on different items such as music or books In this case, the direct interactions among the users can be represented as a graph, and the items like music or books can be represented as a set People are often interested in the bipartite relation between the graph and the set They might want to know the similarity or difference of the items liked by themselves and by their friends In this paper, we propose a visualization framework designed for the micro-exploration and detailed analysis of relations involving a graph and a set Our system consists of two major components: an enhanced graph view and a radial view The enhanced graph view shows a social network of people and statistical information about the items which people are interested in, and the radial view is designed to show people’s interests, the overlapping of their interests, and recommended items based on their interests The combined use of the two visualization components can facilitate the discovery of various relational patterns underlying the links connecting the graph and the set The experiment on the real dataset demonstrates the effectiveness of our technique

Visualization of tornado-like vortex interacting with wide tornado-break wall

Abstract: A three-dimensional CFD model, based on large eddy simulation, is utilized to numerically simulate a perpendicular interaction between a traveling tornado-like vortex and a wide rigid wall. The tornado-like flow is modeled by the Rankine-Combined Vortex Model. The case, where the wall width is much larger than the tornado vortex core diameter is examined. The main goal of the paper is to improve the understanding of the dynamics of the tornado–wall interaction. The conclusions drawn in this study are supported by various visualizations. During the tornado impact, the structure of the tornado-like vortex is substantially mitigated by the wide wall. The low-level portion of the vortex is disturbed both in front of the wall and behind the wall. When the vortex is approaching the wall, the vortex-induced velocities cause a boundary layer separation from the leading face of the wall. The ejected, from the wall, vorticity patches wrap around the tornado-like vortex causing its weakening. Behind the wall the tornado vortex is subjected to the turbulent flow that further disrupts the tornado vortex structure. The tornado-like vortex mitigation results in a low wind speed region behind the tornado-break wall, where the wind velocities are reduced by more than 50 %.

Horizontal two-phase jet behavior with an annular nozzle ejector in the water tank

Abstract: The behavior of gas–liquid two-phase jets has been extensively studied over many years, due to their fundamental importance in many multiphase systems. Understanding jet behaviors is essential for predicting many processes of practical importance. The objective of this study is to investigate horizontal air–water jet behavior with an annular nozzle ejector in a shallow water tank and to present the effect of overall jet behavior on oxygen transfer characteristics from air bubbles to water. The experimental apparatus consisted of an electric motor-pump, an annular nozzle ejector assembly, a high-speed camera unit, a circulation water tank, and measuring or controlling accessories. The images of the air–water mixed jet issuing from the ejector are analyzed qualitatively, and the dissolved oxygen concentration is measured using the clean water unsteady state technique. The horizontal mixed jet behaves like a buoyancy jet, a quasi-horizontal bubble jet, or a horizontal momentum jet owing to the momentum of the primary flow and air bubble size. It can be concluded that the higher the momentum of primary water flow and the lower the entrainment ratio, the smaller the air bubble size. The buoyancy force of the air bubble and the penetration of the mixed flow are found to be important parameters for the oxygen transfer rate owing to the contact area and time of the two phases.