Simultaneous Visualizations Research Articles

Simulating atmospheric freezing of single aqueous droplets to ice in a cryogenically cooled ultrasonic levitator.

Atmospheric freezing of water droplets suspended in air followed by cloud formation and precipitation represent fundamental steps of the terrestrial water cycle. These aqueous droplets exhibit distinct freezing mechanisms and thermodynamic requirements compared to bulk water often forming metastable supercooled water at subzero temperatures on the Celsius scale (<273 K) prior to crystallization. Here, we report on a real-time spectroscopic investigation combined with simultaneous visualizations of single aqueous droplet freezing events inside a cryogenically cooled ultrasonic levitation chamber with the ultimate goal of probing the molecular structure evolution and stages of ice formation. The observed droplet freezing follows a pseudoheterogeneous ice nucleation mechanism mimicking the process that occurs for atmospherically supercooled water droplets at the air-water interface. This proof-of-concept experimental setup allows future crystallization studies of homo- and heterogeneously doped aqueous droplets under simulated atmospheric environments-also in the presence of reactive trace gases, thus untangling dynamic molecular interactions and chemical reactions, which are of fundamental interest to low-temperature atmospheric chemistry delineating with ice nucleation mechanisms.

Evaluating online and tangible interfaces for engaging stakeholders in forecasting and control of biological invasions.

Ecological forecasts will be best suited to inform intervention strategies if they are accessible to a diversity of decision‐makers. Researchers are developing intuitive forecasting interfaces to guide stakeholders through the development of intervention strategies and visualization of results. Yet, few studies to date have evaluated how user interface design facilitates the coordinated, cross‐boundary management required for controlling biological invasions. We used a participatory approach to develop complementary tangible and online interfaces for collaboratively forecasting biological invasions and devising control strategies. A diverse group of stakeholders evaluated both systems in the real‐world context of controlling sudden oak death, an emerging forest disease killing millions of trees in California and Oregon. Our findings suggest that while both interfaces encouraged adaptive experimentation, tangible interfaces are particularly well suited to support collaborative decision‐making. Reflecting on the strengths of both systems, we suggest workbench‐style interfaces that support simultaneous interactions and dynamic geospatial visualizations.

BATTLE: Genetically Engineered Strategies for Split-Tunable Allocation of Multiple Transgenes in the Nervous System

SummaryElucidating fine architectures and functions of cellular and synaptic connections requires development of new flexible methods. Here, we created a concept called the “battle of transgenes,” based on which we generated strategies using genetically engineered battles of multiple recombinases. The strategies enabled split-tunable allocation of multiple transgenes. We demonstrated the versatility of these strategies and technologies in inducing strong and multi-sparse allocations of multiple transgenes. Furthermore, the combination of our transgenic strategy and expansion microscopy enabled three-dimensional high-resolution imaging of whole synaptic structures in the hippocampus with simultaneous visualizations of endogenous synaptic proteins. These strategies and technologies based on the battle of genes may accelerate the analysis of whole synaptic and cellular connections in diverse life science fields.

Flow visualization study of a diffusion flame under acoustic excitation

The behavior of a diffusion flame under acoustic excitation was experimentally studied with the aid of simultaneous flow visualizations of the flame combining Mie scattering and schlieren/shadowgraph imaging. The Mie scattering imaging showed the periodic formation of a vortex street along the flame axis, while the schlieren/shadowgraph images indicated the formation of a high-amplitude density fluctuation near the burner exit. Furthermore, mean velocity and temperature along the flame axis were measured for evaluating the flame behavior by acoustic excitation. These experimental results showed that the acoustic excitation led to a density fluctuation near the burner and promoted the flame behavior near the burner. This behavior resulted in enhanced mixing and combustion in the flame near the burner, which grew as the oscillation amplitude of the acoustic excitation increased. In addition, the flame height, oscillation amplitude and luminosity decreased as the acoustic excitation amplitude is highly increased because of the formation of the increased velocity region with high-temperature near the burner associated with the initiation of laminar-to-turbulent transition of the flame.

Geographical information system software as in-house chemical indexing database for catalyst screening of alkene metathesis catalysts

Abstract Large amounts of chemical information can be indexed on various databases. If these databases store information in an appropriate format for specific search queries, we can perform a catalyst screening from intelligent searches. However, little to no database applications are flexible enough to allow for simultaneous screening and comparable visualizations. Therefore, for setting up a flexible in-house database, we propose the use of geographical information system (GIS) software. GIS includes an attribute table that can be populated with text and numerical information. From this table, we could selectively screen our data as well as visualize the different values on an intelligently created grid pattern. Consequently, 11 types of alkene metathesis catalysts together with 9 Grubbs-type catalysts were investigated using GIS techniques. GIS proved to be an efficient and versatile tool whereby quick and successful catalyst screening could be done.

Infrared analysis of the two phase flow in a single closed loop pulsating heat pipe

A Single Loop Pulsating Heat Pipe (SLPHP) filled at 60% vol. with pure ethanol, having an inner diameter of 2 mm, is designed with two sapphire tubes mounted between the evaporator and the condenser. Being the sapphire almost transparent in the infrared spectrum, such inserts allow simultaneous high-speed visualizations and infrared analysis of the fluid regimes. Two highly accurate pressure transducers measure the pressure at the two ends of one of the sapphire inserts. Three heating elements are controlled independently, in such a way to vary the heating distribution at the evaporator. It is found that particular heating distributions promote the slug/plug flow motion in a preferential direction, allowing to establish a self-sustained circulatory motion. It is demonstrated that a direct infrared visualization of the two-phase flow passing through the sapphire inserts is a valuable technique to measure the liquid slug bulk temperature after a proper calibration of the camera, with uncertainty of 1.5 °C (99.7% confidence level). Additionally, the fluid infrared visualization allows to appreciate the liquid film dynamics (wetting and dewetting phenomena) during the device operation, and to map the temperature gradients of liquid slugs thanks to the high-sensivity of the infrared measurements (0.05 K).

Meta-Representational Fluency: Math Majors’ Visualization of the l’Hospital’s Rule in a Dynamic Geometry Environment

The present qualitative study on mathematics majors’ visualization of the l’Hospital’s Rule in a dynamic geometry environment highlights student-generated representations in a theoretical framework drawn from visual thinking in calculus and meta-representational competences perspectives. Students developed their own personal meanings of the l’Hospital’s formalism; their expression of meta-representational fluency occurred in different, yet not necessarily hierarchical modes of visualizations. Whereas global tangential visualization appeared in the form of static, successive, or simultaneous visualizations of the tangency points on both function graphs; functional visualization (local-tangential functional, static derivative functional, dynamic derivative functional) appeared as an additional key construct in students' treatment of the l’Hospital’s Rule by primarily focusing on the function graphs, without taking tangent lines into account.

Experiments on localized secondary instability in bypass boundary layer transition

An experimental study on localized secondary instability of unsteady streamwise streaks in bypass boundary layer transition under an elevated level of free-stream turbulence has been carried out mainly using the particle image velocimetry (PIV) technique. Simultaneous orthogonal dual-plane PIV measurements were performed for a concurrent examination of the transitional flow features in both wall-normal and spanwise planes. These quantitative and simultaneous visualizations clearly show the wall-normal view of a low-speed streak undergoing sinuous/varicose motion in the spanwise plane. An oscillating shear layer in the wall-normal plane is found to be associated with the sinuous/varicose streak oscillation in the spanwise plane. Further, these measurements indicate that a localized secondary instability wavepacket can originate near the boundary layer edge. The time-resolved PIV measurements in the wall-normal plane clearly show how an instability develops on a lifted-up inclined shear layer and leads to flow breakdown. The estimated wavelength and convection velocity of such instabilities are found to compare well with those calculated from the one-dimensional linear stability analysis of the spatially averaged velocity profiles associated with the lifted-up shear layers. The time-resolved PIV measurements in the spanwise plane also facilitate quantitative visualizations of sinuous and varicose instabilities. These measurements experimentally confirm that a varicose instability at the juncture of an incoming high-speed streak and a downstream low-speed streak can eventually lead to the formation of lambda structures. The estimated convection velocity, wavelength and growth rate of these instabilities are found to be consistent with the numerical results reported in the literature. Moreover, the streak secondary instability is found to be apparent in the velocity contours, while the estimated streak amplitude is approximately 30 % of the free-stream velocity.

Effect of venting the periodic reverse vapor flow on the performance of a microchannel evaporator in air-conditioning systems

This paper proposes a novel solution to reduce the impacts of periodic reverse flow and induced boiling fluctuations on the performance of a microchannel evaporator used in an air-conditioning or other similar refrigeration system. Reverse vapor trapped within the inlet header is continuously vented bypassing microchannels. Simultaneous flow visualizations and measurements quantified the effects of venting the reverse vapor on the evaporator performance. The vapor–liquid interface in the inlet header is elevated above all the microchannel inlets, resulting in more uniform liquid distribution among channels. Evaporator surface temperatures measured by an infrared camera oscillate with reduced amplitude (less than 1°C) compared to the situation without venting, indicating more stable boiling heat transfer and two-phase flow within the microchannels. The evaporator pressure drop is reduced up to about 15% due to removal of the reversed vapor flow. In addition, the reverse vapor flow is characterized for the first time through this method. Both its average flow rate and oscillation amplitude increase with average heat flux, while the oscillation period is reduced. Compared to the total refrigerant flow rate supplied to the evaporator, the average reverse vapor flow is in the range of 2–8% at the conditions explored.

Periodical reverse flow and boiling fluctuations in a microchannel evaporator of an air-conditioning system

This paper presents the phenomenon of periodic reverse flow and associated boiling fluctuation found in experiments with a parallel microchannel evaporator used in an R134a air conditioning system. A simultaneous flow visualizations and measurements confirmed the periodic flow reversal. It caused synchronized oscillations of the evaporator inlet pressure and the pressure drop. The magnitude and frequency of oscillations increased with heat flux. Three potential impacts of flow reversal on evaporator performance are identified: 1) moderate liquid maldistribution; 2) reduced heat transfer coefficient; 3) increased refrigerant side pressure drop. Finally, to mitigate impacts of periodic reverse flow, a solution is proposed: to vent and bypass backflow vapor accumulated in the inlet header.

Simultaneous Measurement of Wind Pressures and Flow Patterns for Buildings with Interference Effect

This present study investigated interference effects of local peak pressure on a principal building for various locations of an interfering building for various wind directions. To obtain further information and to explain the interference mechanism for enhanced local peak pressure due to the interfering building, simultaneous pressure measurements and flow visualizations using a dynamic particle image velocimetry (DPIV) system were performed in the wind tunnel of the Shimizu Institute of Technology. Experimental results have been examined and presented of effects of an interfering building and wind direction on local peak pressures. DPIV results have shown that, for an oblique configuration, a strong shear layer generated by the interfering building directly hits the principal building, which increases the momentum over its upper surface, resulting in a high pressure coefficient near the leading edge of its upper surface.

Experimental investigation of local flow boiling heat transfer and pressure drop characteristics in microgap channel

Two-phase microgap channel cooling concept has been recently proposed for cooling the heat sources directly in application of electronic devices thermal management. This concept is relatively new and more research should be carried out systematically to investigate the size effects of microgap channel on heat transfer and pressure drop mechanisms. In this study, local flow boiling phenomenon in different microgap sizes has been investigated experimentally. Experiments are performed in silicon based microgap heat sink having microgap of depth 190μm, 285μm and 381μm, using deionized water with inlet temperature of 86°C. The effects of mass flux and heat flux on heat transfer coefficient and pressure drop characteristics are examined by using three different mass fluxes 420kg/m2s, 690kg/m2s and 970kg/m2s and effective heat flux varying from 0 to 110W/cm2. An array of integrated micro-temperature sensors are used in this study to obtain the local temperatures and subsequently local heat transfer coefficients are determined. Apart from these experimental investigations, simultaneous high speed visualizations are conducted to observe and explore the mechanism of flow boiling in microgap channel. The results of this study show that flow boiling heat transfer coefficient is dependent on gap size, and the lower the gap size, higher the heat transfer coefficient. Moreover, it has been observed that confined slug and annular boiling are the dominant heat transfer mechanisms in microgap channels after the onset of nucleate boiling. Hence, local heat transfer coefficient increases significantly because of thin film evaporation during confined boiling at high heat flux. This study also evaluates the effectiveness of microgap cooling technology, to eliminate temperature gradient and hotspots.

GIS and Intra-Site Spatial Analyses: An Integrated Approach for Recording and Analyzing the Fossil Deposits at Casablanca Prehistoric Sites (Morocco)

The Mio-Plio-Pleistocene sequence at Casablanca, covering the last six million years, is well known in scientific literature. The variability and the chronology of the Acheulian sequence is documented by systematic, modern and controlled investigations in various sites (Unit L and Hominid Cave at Thomas I Quarry, Rhinoceros Cave at Oulad Hamida 1 Quarry, Sidi Abderrahman Extension Quarry, Bear’s Cave and Cap Chatelier at Sidi Abderrahman Quarry) which have taken place within the framework of the Franco-Moroccan co-operative project “Casablanca”. In order to manage the excavation data and to explore the taphonomic nature of Unit L, Hominid Cave and Rhinoceros Cave, where research is still in progress, an approach combining a Geographic Information System (GIS) and spatial analysis techniques was developed, incorporating all existing information produced from previous excavations and recent surveys of the sites. The amalgamation of this data into a GIS has resulted in a digital database that allows the production of simultaneous or separate visualizations and analyses of the fossils, artifacts and geological materials within their original spatial contexts and also permits intra-site spatial analyses that allow a comprehensive investigation of the site formation processes.

GPGPU computation and visualization of three-dimensional cellular automata

This paper presents a general-purpose simulation approach integrating a set of technological developments and algorithmic methods in cellular automata (CA) domain. The approach provides a general-purpose computing on graphics processor units (GPGPU) implementation for computing and multiple rendering of any direct-neighbor three-dimensional (3D) CA. The major contributions of this paper are: the CA processing and the visualization of large 3D matrices computed in real time; the proposal of an original method to encode and transmit large CA functions to the graphics processor units in real time; and clarification of the notion of top-down and bottom-up approaches to CA that non-CA experts often confuse. Additionally a practical technique to simplify the finding of CA functions is implemented using a 3D symmetric configuration on an interactive user interface with simultaneous inside and surface visualizations. The interactive user interface allows for testing the system with different project ideas and serves as a test bed for performance evaluation. To illustrate the flexibility of the proposed method, visual outputs from diverse areas are demonstrated. Computational performance data are also provided to demonstrate the method’s efficiency. Results indicate that when large matrices are processed, computations using GPU are two to three hundred times faster than the identical algorithms using CPU.

Volume visualization and exploration through flexible transfer function design

Direct volume rendering (DVR) is a well-known method for exploring volumetric data sets. Optical properties are assigned to the volume data and then a DVR algorithm produces visualizations by sampling volume elements and projecting them into the image plane. The mapping from voxel values to optical attribute values is known as transfer function (TF). Therefore, the quality of a visualization is highly dependent on the TF employed, but its specification is a non-trivial and unintuitive task. Without any help during the TF design process, the user goes through a frustrating and time-consuming trial-and-error cycle. This paper presents a useful combination of TF design techniques in an interactive workspace for volume visualization. Our strategy relies on semi-automatic TFs generation methods: boundary emphasis, stochastic evolutive search in TF space, and manual TF specification aided by dual domain interaction. A two-level user interface was also developed. In the first level, it provides multiple simultaneous interactive visualizations of the volume data using different TFs, while in the second one, a detailed visualization of a single TF and the respective rendered volume are displayed. Moreover, in the second level, the TF can be manually refined and the volume can be further inspected through geometric tools. The techniques combined in this work are complementary, allowing easy and fast TF design and data exploration.

On the fate of thermally buoyant mantle plumes at density interfaces

The 660-km depth endothermic phase transition is expected to delay upwelling plumes and modify their morphology. The interaction of thermal starting plumes with a density boundary is investigated experimentally by using simultaneous visualizations of temperature, composition and velocity fields. In a tank initially stratified with two viscous fluids with different densities and viscosities, a thermal starting plume was generated by using a circular plate heater at the bottom of the tank. Its interaction mode with the inner interface depends on the local buoyancy number (BL: the ratio of the stabilizing chemical buoyancy to the plume thermal buoyancy at the interface), the Rayleigh number (Ra), the viscosity contrast between the chemical layers (γ), and the local viscosity ratio of the ambient material to the plume head (γp). For BL<0.6, the “pass-through mode” develops, whereby a large volume of the lower material rises through the upper layer and reaches the top surface, since the plume head has a large thermal buoyancy compared to the stabilizing density contrast between the two layers. When BL>0.6, the “rebirth mode” occurs, where the thermal plume ponds and spreads under the chemical boundary and secondary thermal plumes are generated from the interface. Depending on the magnitude of BL, these plumes can entrain upwards by viscous coupling a significant amount of lower layer material. Scaling laws are determined for the onset of secondary plumes, their number and wavelength, the amount of entrainment and the topography of the interface. Our results could explain the hotspots' distribution above superswells and the peculiar time evolution of La Réunion hotspot.

Turbulence Structures and the Acoustic Far Field of a Mach 1.3 Jet

The temporal characteristics of the acoustic far field of a Mach 1.3, high-Reynolds-number, ideally expanded axisymmetric jet and their potential correlation with large-scale turbulence structures within the jet were explored. A dual microphone array, placed approximately 30 deg from the jet axis in the acoustic far field, was used to determine the temporal variations of the acoustic field and the approximate locations of intense noise sources within the jet, as well as the time of noise emission with respect to the acquired planar flow images. Simultaneous double-pulse flow visualizations were used to identify turbulence structures, as well as their development and interaction in the region of intense noise generation. The time history of the acoustic data showed individual large-amplitude noise events, periodic large-amplitude noise events, and long periods of relative quiet without any large-amplitude noise production

Forced convection boiling in a microchannel heat sink

Micromachining technology was utilized to fabricate a transparent microchannel heat-sink system by bonding glass to a silicon wafer. The micro heat sink consisted of a microchannel array, a heater, and a temperature sensor array. This integrated microsystem allowed simultaneous qualitative visualizations of the flow pattern within the microchannels and quantitative measurements of temperature distributions, flow rates, and input power levels. Boiling curves of temperature as a function of the input power were established. No boiling plateau was observed in the boiling curves, consistent with our previously reported data but different from results reported for macrochannel heat sinks. Three stable boiling modes, depending on the input power level, have been distinguished from the flow patterns. Local nucleation boiling was observed in microchannels with a hydraulic diameter as small as 26 /spl mu/m at the lower input power range. At the higher input power range, a stable annular flow was the dominant boiling mode. Bubbly flow, commonly observed in macrochannels, could not be developed in the present microchannels. Consequently, no boiling plateau was detected in the boiling curves.

VORTEX SHEDDING RESONANCE FROM A ROTATIONALLY OSCILLATING CYLINDER

Vortex shedding resonance of a circular cylinder wake to a forced rotational oscillation has been investigated experimentally by measuring the velocity fluctuations in the wake, pressure distributions over the cylinder surface, and visualizing the flow field with respect to cylinder oscillations. The vortex shedding resonance occurs near the natural shedding frequency at small amplitude of cylinder oscillations, while the peak resonance frequency shifts to a lower value with an increase in oscillation amplitude. The drag and lift forces acting on the cylinder at fixed forcing Strouhal number indicate that the phase lag of fluid forces to the cylinder oscillations increases with an increase in oscillation amplitude, supporting the variation of resonance frequency with oscillation amplitude. The comparative study of the measured pressure distributions and the simultaneous flow visualizations with respect to cylinder rotation shows the mechanisms of phase lag, which is due to the strengthened vortex formation and the modification of the surface pressure distributions.

Comparison of NO and OH planar fluorescence temperature measurements in scramjet model flowfield

The use of nitric oxide (NO) and the hydroxyl radical (OH) as temperature tracers, in a two-line planar laser-induced fluorescence technique, is examined in the context of a supersonic mixing and combustion flowfield. The temperature measurements were based on the sequential excitation of two transitions, either in the A implied by X (0,0) band of NO near 226 nm or the A implied by X (1,0) band of OH near 283 nm. The measurements were obtained for each species through the use of two lasers and two cameras, with each camera integrating signal induced from only one of the lasers. Both temporally resolved and frame-averaged temperature measurements of each species are presented. Additional results include simultaneous NO and OH visualizations, in which seeded NO marks the fuel jet fluid and nascent OH marks the reaction zones and convected combustion gases. A detailed temperature comparison shows good agreement in the common measurement regions and indicates that shot noise is the largest source of uncertainty. The comparison also illustrates the importance of a careful interpretation of the measurements, since, depending on the origin of the tracer and the degree of mixing, the measurements may be biased toward the fuel, freestream, or reactionmore » zone temperatures. 33 refs.« less