Kamera-Ethnographie ist ein filmischer Ansatz zur Gestaltung der Wahrnehmungs- und Wissensprozesse beim ethnographischen Forschen. Dabei wird im Unterschied zur Logik der Aufzeichnung angenommen, ...dass Forschungsgegenstände zunächst noch gar nicht sichtbar sind. Kameraführung, Schnitt und Montage tragen als experimentelle Praktiken zur Beobachtbarkeit und Sichtbarkeit epistemischer Dinge bei. Bina Elisabeth Mohns repräsentationskritische Programmschrift zeigt, wie die Methode der Kamera-Ethnographie auch nonverbale Praktiken in ihren Choreographien und bildhaften Figuren in den Blick rückt. Eine situierte Methodologie und reflexive Pragmatik leiten zum positionierten Hinschauen und Sehenlernen an und binden selbst das Publikum in eine forschende Rezeption ein.
•Fuel’s ignition and combustion characteristics are measured by different method.•Diesel blends containing 20% and 40% n-pentanol are examined.•D60P40 advances ignition phase over D80P20 under low ...oxygen content conditions.•Flame luminosity is reduced with the increase of pentanol ratio in most conditions.•Pentanol could significantly accelerate soot oxidation under all conditions.
Pentanol is considered as one of the most promising alternative biofuels due to its excellent physicochemical properties. The objective of this work was to compare the ignition and combustion characteristics of different n-pentanol/diesel blends in an optical constant volume combustion chamber. The tested fuels included 20% (D80P20) and 40% (D60P40) of n-pentanol blended with diesel in volume, and pure diesel (D100). Broadband chemiluminescence technique was used to measure the timing and location of spray ignition. A high-speed CCD camera with two ND8 dimmer lenses was used to capture the incandescence radiated from the soot particles during combustion. A wide range of experimental conditions was investigated. The ambient temperature ranged from 800K to 1200K and the oxygen concentration ranging from 10% to 21%, covering both the conventional and low temperature combustion regimes. The results show that pure diesel has shorter ignition delay and distance comparing to pentanol blends. A larger blending proportion of pentanol D60P40 advances the ignition phase more than the D80P20 in low oxygen concentration conditions. Due to the fuel-borne oxygen and the dilution effect, the natural flame luminosity is reduced significantly with the increase of pentanol ratio in most conditions except under the intermediate temperature region of 1000K. In that condition, the shorter ignition delay and flame lift-off length of pentanol blends cause a slightly increase in the natural flame luminosity. The natural flame luminosity images showed that the oxygen-contained structure of pentanol could accelerate soot oxidation under all conditions. This indicates that pentanol blends could decrease final soot emissions in internal combustion engines.
Infrared thermal camera is an alternative and non-invasive method used to identify various physiological and pathological process related to body surface temperature changes. The aim of this ...research was to study the body surface temperature pattern based on the observed regios. Three horses were randomly selected as animal experiments. Thermal image data was collected at 17.00 – 19.00 WIB for five days. Images were retrieved from seven regios: head, thorax, abdomen, and four lower legs. The result of horse A’s surface temperature in five days on head, thorax, abdomen, front left leg, front right leg, rear left leg, and rear right leg regios were 33.42, 33.49, 33.56, 31.30, 31.48, 31. 33.14, 31.34 °C, respectively. The resulf of horse B’s surface tempereture were 33.55, 33.65, 33.64, 31.45, 31.35, 31.53, 31.48 °C, respectively. The resulf of horse C’s surface tempereture were 33.45, 33.55, 33.60, 31.37, 31.45, 31.34, 31.42 °C, respectively. The result showed that difference on horse A’s rear left leg (p<0.05) because of inflamation. Inflamation recovery process on horse A occured on the fifth day, indicated by a drop in temperature and a change in colors on thermal image. Color noises on some images were color difference between objects and poor color saturation. Color noises on thermal images did not affect the results of temperature interpretation.
•The droplet flow over horizontal tubes under 8/23/38 mm tube spacing is studied experimentally.•The droplet flow between tubes can be divided into the following four processes: droplet formation, ...droplet falling, droplet impact, neck break and retraction.•A parameter in the droplet formation process independent of flow rate and tube spacing—``escape length" is proposed.•A new correlation has been suggested to describe the primary droplet diameter.•The increase of viscosity can retard the droplets falling and the decrease of surface tension can predate the appearance of the droplet detaching.
Droplet flow is one of the most significant flow patterns in horizontal tubes falling film flow, which is widely observed in industrial equipment. Flow visualization of water/ethanol/30% glycerol-water solution falling in 8/23/38 mm tube spacing using high-resolution and high-speed digital video camera is presented here. The image edges detection algorithm of Sobel is developed to quantify falling distance and velocity for each frame of a sequence. The results illustrate that the droplet flow between tubes can be divided into the following four processes: droplet formation, droplet falling, droplet impact, neck break and retraction. The “escape length” is proposed in droplet formation process. The falling process can be divided into three stages according to the appearance and break of liquid neck. The droplet in different tube spacing displays different falling stages, which affect the processes of droplet impact and neck break and retraction eventually. The droplets falling velocity increases linearly with the falling distance in the first and second stages of falling process. The increase of viscosity can retard the droplets falling and the decrease of surface tension can predate the appearance of the droplet detaching. In addition, a new correlation has been suggested to predict the primary droplet diameter. When 9mm < s < 15 mm and 25ms < τa < 40 ms, there is a phenomenon of ``liquid globule rebound".
The graphene oxide (GO) nanocoating surface was fabricated by GO nanoparticles self-assembly on plain copper surface under nucleate pool boiling. Saturated and subcooled pool boiling experiments on ...GO nanocoating surface with distilled water at atmospheric pressure were conducted. Saturated pool boiling performance indicated enhancements of 78% in critical heat flux (CHF) and 41% in maximum heat transfer coefficient (HTC) when compared with the plain copper surface. It was found that the enhancement was mainly attributed to the improved wettability and high thermal conductivity of GO nanocoating, as well as the increased surface roughness. Subcooled pool boiling results showed that the liquid subcooling had significant effect on heat transfer performance of GO nanocoating surface. The CHF increased linearly with the increased subcooling degree, and the maximum HTC increased almost linearly with the increased subcooling degree. The CHF reached 274 W/cm2 at subcooling degree of 19 K, which translated an enhancement of 128% when compared with the plain copper surface. This high CHF can address the heat dissipation bottleneck in ultra high-power density electronic devices. To better understand the subcooling effect on nucleate boiling, visualization studies on bubble growth characteristics at subcooled pool boiling were investigated with a high-speed digital camera. It was shown that bubbles were smaller and grew more slowly with the increase of liquid subcooling, and microbubble jets were observed at moderate heat flux regime.
•Graphene oxide (GO) surface was fabricated by GO nanoparticles self-assembly.•GO surface improve critical heat flux (CHF) by 78% under saturated boiling.•The enhancement is caused by improved wettability, roughness and thermal conductivity of GO surface.•GO surface improve critical heat flux (CHF) by 128% under 19 K subcooling.•Enhanced boiling heat transfer is analyzed by bubble images on subcooled GO surface.
Fatigue cracks developed under repetitive loads are one of the major threats to structural integrity of steel bridges. Human inspection is the most commonly applied approach for fatigue crack ...detection, but is time consuming, labor intensive, and lacks reliability. In this study, we propose a computer vision‐based fatigue crack detection approach using a short video stream taken by a consumer‐grade digital camera. A feature tracking technology is applied to the video for tracking the surface motion of the monitored structure under repetitive load. Then, a crack detection and localization algorithm is established to effectively search differential features at different video frames caused by the crack opening and closing. The effectiveness of the proposed approach is validated through testing two experimental specimens with in‐plane and out‐of‐plane fatigue cracks, respectively. Results indicate that the proposed approach can robustly identify the fatigue crack, even when the crack is under ambient lighting conditions, surrounded by other crack‐like edges, covered by complex surface textures, or invisible to human eyes due to crack closure. Furthermore, our proposed approach enables accurate quantification of the crack opening under fatigue loading with submillimeter accuracy. However, due to the capacity of the camera resolution in this study, accurate detection of crack tip remains challenging.
Liquid transfer and drop formation/deposition processes involve complex free-surface flows including the formation of columnar necks that undergo spontaneous capillary-driven instability, thinning ...and pinch-off. For simple (Newtonian and inelastic) fluids, a complex interplay of capillary, inertial and viscous stresses determines the nonlinear dynamics underlying finite-time singularity as well as self-similar capillary thinning and pinch-off dynamics. In rheologically complex fluids, extra elastic stresses as well as non-Newtonian shear and extensional viscosities dramatically alter the nonlinear dynamics. Stream-wise velocity gradients that arise within the thinning columnar neck create an extensional flow field, and many complex fluids exhibit a much larger resistance to elongational flows than Newtonian fluids with similar shear viscosity. Characterization of pinch-off dynamics and the response to both shear and extensional flows that influence drop formation/deposition in microfluidic and printing applications requires bespoke instrumentation not available, or easily replicated, in most laboratories. Here we show that dripping-onto-substrate (DoS) rheometry protocols that involve visualization and analysis of capillary-driven thinning and pinch-off dynamics of a columnar neck formed between a nozzle and a sessile drop can be used for measuring shear viscosity, power law index, extensional viscosity, relaxation time and the most relevant processing timescale for printing. We showcase the versatility of DoS rheometry by characterizing and contrasting the pinch-off dynamics of a wide spectrum of simple and complex fluids: water, printing inks, semi-dilute polymer solutions, yield stress fluids, food materials and cosmetics. We show that DoS rheometry enables characterization of low viscosity printing inks and polymer solutions that are beyond the measurable range of commercially-available capillary break-up extensional rheometer (CaBER). We show that for high viscosity fluids, DoS rheometry can be implemented relatively inexpensively using an off-the-shelf digital camera, and for many complex fluids, similar power law scaling exponent describes both neck thinning dynamics and the shear thinning response.
•The Venturi nozzle design with entry and exit angles, which leads the self-sucked air flow.•Microbubbles generation regarding to entry and exit angles.•High speed visualization study to track the ...self-sucked air flow stream broken into microbubbles.
We studied the effect of varying the entry and exit angles of Venturi nozzles on the formation of microbubbles in Venturi nozzle-type microbubble generators. We 3D-printed nozzles with five entry angles (15, 22, 30, 38 and 45°) and five exit angles (15, 22, 30, 38 and 45°). For the visualization experiment, we inserted the nozzles into a cover case made of aluminum and transparent acrylic. We measured the pressure drop and the air flow rate with respect to the entry and exit angles, determined the diameters of the bubbles using a digital camera, and analyzed bubble breakage by observing the behavior of the bubbles using a high-speed camera. We confirmed that the exit angle (not the entry angle) is dependent on the pressure drop and found that the air flow rate did not vary linearly with the fluid flow rate, as expected according to Bernoulli's theorem. Instead, it tended to remain constant or decrease as the fluid flow rate increased due to the abnormal flow. The sizes of the bubbles decreased as the exit angle increased, except in cases where the outlet angle was greater than 30° at high flow rates (260–300 LPM). We observed a change in bubble size with respect to exit angle. According to our visualization, the bubbles were broken by the flow separation at the beginning of the divergence at the exit.
The effects of up to 30% H2O and CO2 replacement of N2 in air on the structure and shape of laminar coflow syngas (COH2) diffusion flames were experimentally and numerically studied. Temperatures ...along the flame centerline were measured using a type-B thermocouple. The OH*-chemiluminescence and flame luminance were captured respectively by an intensified CCD camera and a CCD camera to determine the flame height and radii. The syngas diffusion flames were numerically modeled using detailed thermal and transport properties and the chemical reaction mechanism of Davis et al. (2005). Four pairs of artificial species were introduced in additional numerical calculations to isolate the chemical, thermal, transport, and radiative effects of H2O and CO2. The experimental and numerical results show that H2O and CO2 replacement of N2 in the oxidizer reduce the peak flame temperature, but they influence the flame centerline temperature distributions differently. The thermal and radiative effects of both H2O and CO2 addition decrease the flame temperatures. The chemical and transport effects of CO2 and H2O affect flame temperatures differently. H2O addition promotes the OH concentration though H+O2=O+OH and O+H2O=2OH, while CO2 addition decreases the OH concentration by suppressing those reactions. The higher concentrations of OH under H2O addition signify higher combustion intensity and hence lead to decreased flame height and radius. In contrast, the addition of CO2 suppresses flame temperature and the overall combustion process, resulting in increased flame height and radius.
•Increasing the magnetic field strength reduces the mixing length.•By increasing the volume flow rate, the mixing efficiency decreases.•The mixing length is linearly related to the flow rate with a ...slope of 0.3.•Increasing the nanoparticle mass fraction improves the mixing efficiency.
In this paper, the rapid mixing of deionized water and Fe3O4 ferrofluid in a Y-shaped microchannel using a permanent magnet is studied both numerically and experimentally. The microchannel has a rectangular cross section with 500μm in width and 1mm in depth. The process, assumed to be two-dimensional and steady state, is simulated by COMSOL numerical software. In the numerical simulation, the Maxwell equations are solved to obtain the magnetic potential. Then, the magnetic force can be calculated. Knowing the magnetic force, the momentum and transport-diffusion equations are solved. A setup is designed and fabricated to carry out the experiments. The mixing process is photographed by a CCD camera for 5min until the mixing process reached a steady state condition. The numerical results are compared with the corresponding measurements to validate the simulations. The effect of different parameters such as magnetic field’s strength (1280G, 2000G and 3000G), volume flow rate (30cc/min, 40cc/min, and 60cc/min), and mass fraction of nanoparticles (0.0125, 0.025 and 0.05) is investigated on the mixing efficiency. Applying magnetic field considerably improves the mixing efficiency of the micromixer and reduces the mixing length. Increasing the mass fraction of nanoparticles and magnetic field strength increases the mixing efficiency until the magnetization of the ferrofluid reaches its saturated level. Increasing the fluid flow, however, lowers the mixing efficiency and increases the mixing length.
