Camera Imaging Technique Research Articles

Horizontal buoyant jets into viscoplastic ambient fluids

This study investigates the horizontal injection of a heavy Newtonian fluid into a lighter viscoplastic ambient fluid, in a large reservoir. The flow dynamics is experimentally captured via camera imaging, laser-induced fluorescence, and particle image velocimetry techniques. The flow parameters include various density differences, injection velocities, and ambient fluid viscoplastic properties. Our analysis identifies two key dimensionless numbers, the Froude number (Fr) and the effective viscosity ratio (m), which includes the rheology of the viscoplastic fluid. Our study also examines the effects of these dimensionless numbers on critical jet characteristics, such as bifurcation length, transition length, deviation length, and jet trajectory, and provides correlations using Fr and m, to predict these characteristic lengths. A regime classification based on the bifurcation phenomenon is also presented in the Fr−m plane.

Buoyant miscible viscoplastic displacements in vertical pipes: Flow regimes and their characterizations

We experimentally study miscible displacement flows of a light Newtonian fluid by a heavy viscoplastic fluid, in a vertical pipe with a large aspect ratio (δ−1≫1). We use camera imaging, laser-induced fluorescence, and ultrasound Doppler velocimetry techniques, to capture and process data. Four dimensionless parameters, namely, the Reynolds (Re), Bingham (B), viscosity ratio (M), and densimetric Froude (Fr) numbers (or their combinations), mainly govern the flow dynamics. We identify and characterize three distinct flow regimes, including plug, separation, and mixing regimes, while we describe each regime's dynamics in detail, particularly in terms of the velocity and concentration fields as well as the displacement front velocity. In addition, we analyze the plug regime concerning the residual wall layers, the separation regime in terms of the separation dynamics, spatiotemporal separation zone, and viscoplastic layer thinning, and the mixing regime regarding the mixing index and macroscopic diffusion. Finally, we develop a simplified model to help delineate the flow regime classification, in the plane of Re/Fr2 and M.

Spray and deposition characteristics of unsaturated polyester resin applied for impregnating long fiber preform composites

AbstractSpray up is a method intensively applied for short fiber reinforced plastic (FRP) products manufacturing. The current study investigated the application of spray up for impregnation and manufacturing of long fiber FRP products, which can bring major advantages of minimized impregnation time and fewer product defects. Computational fluid dynamics (CFD) modeling was applied to investigate the spray and deposition characteristics of the viscous general‐purpose unsaturated polyester resin on a glass fiber preform. Validation of CFD results was done using phase Doppler anemometer and camera imaging techniques, and errors were calculated. Droplet velocity distributions 30 cm from the nozzle tip showed an average absolute percentage error of 4.3% and root mean square error value of 0.68 m/s, which are minimal. CFD and experimental values of sprayed resin area coverage (main area) after 4 s of spray were 17 and 16.3 cm in diameter, respectively; this is a relatively small error. Resin pool thickness on the target surface was variable, values predicted numerically. Non‐uniformity of pool thickness can be compensated by using appropriate compaction mechanisms. It is also possible to impregnate large size and complex shape products using multiple nozzles of proper arrangement.

Immersed buoyant viscoplastic injections

In this study, the injection of a viscoplastic (yield stress) fluid into a quiescent Newtonian medium is experimentally investigated, using a range of experimental methods, including high-speed camera imaging, laser-induced fluorescence (LIF), and ultrasound Doppler velocimetry (UDV) techniques. The case of our consideration is the continuous downward injection of a Carbopol solution, as a core fluid, through an eccentric inner pipe, placed inside a vertical closed-end pipe filled with a glycerin–water solution. The injected fluid is always heavier than the in-situ fluid and the fluids are miscible. As the injection continues, a filament of the core fluid immersed in the in-situ fluid is formed, for which it has been shown that there exist three distinct flow patterns, namely, the breakup, coiling, and bulging (buckling) regimes. Our focus in this study is to analyse the detailed flow features and sub-regimes at longer times, from an experimental perspective. To generalize our results, they are presented versus the governing dimensionless numbers of the flow, i.e. the buoyancy number, the Bingham number, the viscosity ratio, and the falling height. The breakup regime is analysed in terms of the yielding, necking and pinch-off process, the length of filaments, and their subsequent falling behaviours, the coiling regime in terms of the regular, free and irregular coiling behaviours, and the bulging (buckling) regime in terms of the appearance of a detached falling part and the maximum penetration depth. The results of this work can find applications, in particular, in the plug and abandonment (e.g. cementing processes) of oil and gas wells and 3D printing technologies. • Experimental analysis of immersed buoyant viscoplastic injection in Newtonian fluid. • Observed flow regimes classified into breakup, coiling, and bulging. • Analysis of yielding, necking/pinch-off, and length of filaments for breakup regime. • Coiling subregimes categorized as regular, free, and irregular coiling. • Analysis of maximum penetration depth and subregimes in bulging regime.

An experimental study of displacement flows in stationary and moving annuli for reverse circulation cementing applications

We present an experimental study of buoyant displacement flows in vertical narrow centric/eccentric annular configurations, representing the oilfield primary cementing process, from a fluid mechanics perspective. In this study, we consider the reverse circulation cementing case, i.e. the case in which the cementing fluids are pumped down from the surface into the annulus and the in-situ fluids are taken through the casing or tubing. The fluid proxies used to represent the industrial fluids are miscible, with different rheological behaviours, i.e. salt-water (Newtonian), Xanthan (shear-thinning) and Carbopol (viscoplastic) solutions, and they have various density contrasts. Our dimensional analysis and systematic simplifications allow us to describe the flow using five dimensionless numbers: m (viscosity ratio), Fr (densimetric Froude number, quantifying effects of the density difference or buoyancy), Re (Reynolds number, quantifying the effects of the imposed flow rate), e (eccentricity) and f (reciprocation frequency). We examine the effects of the aforementioned parameters in stationary and moving annuli, wherein we change the frequency of the inner pipe reciprocation motion, over a fixed amplitude. Using mainly high-speed camera imaging techniques, we analyse displacement flow patterns and mixing between the fluids. We show that the density-stable or density-unstable configurations, the non-Newtonian effects, and the annulus eccentricity exert a significant impact on the displacement flow features, which we explain through a detailed comparison between Newtonian and non-Newtonian displacements. In addition, we demonstrate that an interplay between the yield stress and the annulus motion can remarkably change the displacement flow behaviour, particularly the wall residual layer thicknesses of the displaced fluid. Finally, we quantify the effects of different flow parameters on the leading front velocity, representing the displacement efficiency in the reverse circulation cementing.

Development of Image Reconstruction Algorithm in Realtime for Compton Camera Systems

Compton Camera is a imaging technique that uses the principle of Compton scattering interaction to reproduce the distribution image of the radiation source. Compton Camera is a 3-D imaging technique, which has a high sensitivity, wide viewing angle and a range of shooting energy that is much higher than the transmissive imaging technique. In addition, the Compton Camera imaging technique does not use a mechanical collimation system, so it is compact in size, suitable for mobile applications, security control, radiation source detection and medical applications. In this paper, the authors built an image reconstruction algorithm for Compton Camera imaging equipment using data from Monte Carlo simulation. The image quality and the parameters of the algorithm will be evaluated in detail to determine the practical applicability.

Experimental study of the flow structure around Taylor bubbles in the presence of dispersed bubbles

This work presents an experimental study focusing on the interactions between the dispersed and Taylor bubbles in a slug flow pattern. In order to better investigate these interactions, a quasi-real slug flow was studied, where a single Taylor bubble is injected in a bubbly flow background stream, under controlled and repeatable conditions, controlling the bubbly flow superficial gas and liquid velocity, and also the Taylor bubble length. In this way, ensemble averaged results can be obtained over several Taylor bubbles. The flow was analyzed through the laser diode photocell, high-speed camera imaging and PIV techniques. Results revealed that the terminal Taylor bubble velocity is affected by the gas volume fraction of the bubbly background flow. Ensemble average velocity profiles are presented for Taylor bubble nose and tail regions. Since the experimental apparatus used in the present work allowed a large number of instantaneous PIV acquisitions, the turbulent statistics around the Taylor bubble can also be calculated. These experimental results can be used for the implementation and validation of multidimensional CFD models for flows with different interface length scales.

Saha Şartlarında Aerobik Stabilite Süresince Mikrobiyal Kompozisyondaki Değişikliklerin Termal Kamera Görüntüleme Tekniği ile Değerlendirilmesi

Amaç: Araştırmanın ana amacı; Termal Kamera Görüntüleme Tekniğinin, silajdaki aerobik dönemde meydana gelen bozulmanın boyutları hakkında güvenilir ve pratik bir ölçü aracı olarak kullanılıp kullanılamayacağını tespit etmektir. Materyal ve Metot: Araştırma Tekirdağ ilinde mısır silajı yapan bir işletmede yürütülmüştür. Bu amaçla toprak üstü silonun yüzey alanı (sağ, orta ve sol bölge) olmak üzere 3 örnekleme bölgesine ayrılmıştır. Her bir bölgedeki sıcaklık değerleri ve ortam sıcaklığı 40 gün süreyle sıcaklık sensörleri ile ölçülüp kaydedilmiştir. Araştırmanın 0., 7., 14., 21. 30. ve 40. günlerinde silonun belirlenen 3 farklı noktasından 5 tekerrür olmak üzere alınan silaj örneklerinde kimyasal ve mikrobiyolojik parametrelere ilişkin analizler yürütülmüştür. Aynı zamanda, Fluke Ti9 IR (160x120) marka termal kamera ile 1 m mesafeden silo yüzeyinin belirlenen bölgelerinden görüntüleme yapılarak değerlendirme sonuçları kaydedilmiştir. Daha sonra elde edilen veriler SmartView®software programında değerlendirilmiştir. Bulgular: Araştırma sonucunda, termal kamera görüntüleme tekniği ve sıcaklık sensörlerine ilişkin değerlerin paralellik gösterdiği tespit edilmiştir. Sonuç: Termal kameranın, aerobik stabilitenin erken döneminde bozulmanın boyutlarını belirleyebilmek ve silaj amenajmanını geliştirmek amacı ile saha şartlarında pratik bir yöntem olarak kullanılabileceği sonucuna varılmıştır.

Flame temperature reconstruction through a multi-plenoptic camera technique

Due to the variety of burner structure and fuel mixing, flame temperature distribution is not only irregular but also complex. Therefore, it is necessary to develop an advanced temperature measurement technique, which can provide not only adequate flame radiative information but also reconstruct complex flame temperature accurately. In this paper, a novel multi-plenoptic camera imaging technique is proposed which provides adequate flame radiative information from two different directions and also reconstructs the complex flame temperature distribution accurately. An inverse algorithm, i.e. non-negative least squares, is used to reconstruct the flame temperature. The bimodal asymmetric temperature distribution is considered to verify the feasibility of the proposed system. Numerical simulations and experiments were carried out to evaluate the performance of the proposed technique. Simulation results demonstrate that the proposed system is able to provide higher reconstruction accuracy although the reconstruction accuracy decreases with the increase of noise levels. Meanwhile, compared to the single plenoptic and conventional multi-camera techniques, the proposed method has the advantages of a lower relative error and better reconstruction quality even with higher noise levels. The proposed technique is further verified by experimental studies. The experimental results also demonstrate that the proposed technique is effective and feasible for the reconstruction of flame temperature. Therefore, the proposed multi-plenoptic camera imaging technique is capable of reconstructing complex flame temperature fields more precisely.

Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST

Intensity fluctuations are investigated using the fast camera imaging technique in the slab annular plasma as a function of magnetic shear and connection length in the spherical tokamak QUEST. Note that here QUEST is operated as a simple magnetized torus with a tight aspect ratio. Slab annular plasmas feature open magnetic field lines and can mimic the tokamak edge-scrape off layer (SOL)-like plasma attributes reasonably well. Three magnetic shear regimes are realized using three poloidal magnetic field (PF) coil pairs. A whole range of connection lengths (∼∞ ≥ Lc ≥ 5.5 m) is scanned by varying the PF strength for a given toroidal field for each magnetic shear regime. For the first time a systematic study of the effect of magnetic shear and field line pitch together on edge-SOL-like plasma fluctuations is being reported. Slab plasmas with intermediate magnetic shear are observed to be more susceptible to generate distinct blobs when Lc is reduced by increasing the PF strength. A distinct coherent mode appears only at the lowest magnetic shear slab featuring a deep potential well. Such mode is not apparent at other magnetic shear cases even at the same Lc. Finally, with a combination of PF coil pairs, both the features of intermediate and low magnetic shear slabs are shown to be realizable simultaneously. Significantly stronger blobs are observed with such combination of PF mirror ratios in the presence of a coherent mode. This study may provide better insight into the effect of magnetic configuration in the tokamak edge and SOL turbulence and can help in searching for better tools to control cross-field convective intermittent transport in tokamaks.

Autoradiography and biopsy measurements of a resected hepatocellular carcinoma treated with 90 yttrium radioembolization demonstrate large absorbed dose heterogeneities

PurposeRadioembolization is an alternative palliative treatment for hepatocellular carcinoma. Here, we examine the uptake differences between tumor tissue phenotypes and present a cross-section of the absorbed dose throughout a liver tissue specimen. Methods and materialsA patient with hepatocellular carcinoma was treated with 90Y radioembolization followed by liver tissue resection. Gamma camera images and autoradiographs were collected and biopsy tissue samples were analyzed using a gamma well counter and light microscopy. ResultsAn analysis of 25 punched biopsy tissue samples identified 4 tissue regions: Normal tissue, viable tumor tissue with and without infarcted areas, and tumor areas with postnecrotic scar tissue. Autoradiography and biopsy tissue sample measurements showed large dose differences between viable and postnecrotic tumor tissue (159 Gy vs 23 Gy). ConclusionsRadioembolization of 90 yttrium with resin microspheres produces heterogeneous-absorbed dose distributions in the treatment of unifocal hepatic malignancies that could not be accurately determined with current gamma camera imaging techniques.

Streak Tubes for Diagnostics of Lasers and Plasmas

Designing a facility for laser fusion research requires sufficient advancement in diagnostics techniques for lasers and plasmas, including those involving streak camera imaging. Maximum specifications of streak cameras depend on the parameters of streak tubes. The paper illustrates how these devices function, and which of their parameters are limiting. The paper presents a novel technological platform designed at VNIIA, which was used to develop a new generation of streak tubes. Using these streak tubes in streak cameras, the efficiency of streak camera imaging techniques can be improved by several orders of magnitude, and new techniques can be designed.

Dynamic fracturing of strengthened glass under biaxial tensile loading

A high speed camera imaging technique is used to capture the dynamic fracturing process of thin strengthened glass under biaxial tensile loading with modified ring-on-ring configurations. Crack fronts emit radially from the fracture origin. The crack front velocity depends on the load-bearing capacity of the specimen and can be as high as 0.76cR, where cR is the Rayleigh wave speed. Finite element analysis (FEA) is used to analyze the stress distribution associated with large deflections accounting for the specific loading fixture geometry.

Role of stochasticity in turbulence and convective intermittent transport at the scrape off layer of Ohmic plasma in QUEST

Statistical features of fluctuations are investigated using the fast camera imaging technique in the scrape of layer (SOL) of electron cyclotron resonance heated Ohmic plasma. Fluctuations in the SOL towards low field side are dominated by coherent convective structures (blobs). Two dimensional structures of the higher order moments (skewness s and kurtosis k) representing the shape of probability density function (PDF) are studied. s and k are seen to be functions of the magnetic field lines. s and k are consistently higher towards the bottom half of the vessel in the SOL showing the blob trajectory along the field lines from the top towards bottom of the vessel. Parabolic relation (k=As2+C) is observed between s and k near the plasma boundary, featuring steep density gradient region and at the far SOL. The coefficient A, obtained experimentally, indicates a shift of prominence from pure drift-wave instabilities towards fully developed turbulence. Numerical coefficients characterizing the Pearson system are derived which demonstrates the progressive deviation of the PDF from Gaussian towards gamma from the density gradient region, towards the far SOL. Based on a simple stochastic differential equation, a direct correspondence between the multiplicative noise amplitude, increased intermittency, and hence change in PDF is discussed.

Investigation of Freestream Plasma Flow Produced by Inductively Coupled Plasma Wind Tunnel

The freestream air plasma jet produced by the Plasmatron facility at the von Kármán Institute for Fluid Dynamics is investigated. Intrusive and nonintrusive measurement techniques are combined to characterize the plasma flow at pressures between 1500 and 20,000 Pa and electrical power between 120 and 300 KW, covering a broad range of atmospheric entry conditions relevant for thermal protection systems testing. The high-speed camera imaging technique is applied to investigate the unsteadiness features of the plasma jet, and a novel frequency-spatial-domain elaboration procedure is proposed. The results show that the power supply ripple and the test chamber static pressure are the main driving parameters of the plasma jet unsteadiness. The optical emission spectroscopy measurement allow the conclusion that the freestream flow is in local thermochemical equilibrium in nearly the whole operating envelope investigated. Comparison between spectroscopy measurement and freestream temperature calculations based on intrusive techniques show that the surface catalytic efficiency of the cold-wall copper sensors used to measure heat flux is close to . This catalytic property is found to increase with the freestream temperature for the lowest pressure condition investigated.

Correlations of Cu(In, Ga)Se2 imaging with device performance, defects, and microstructural properties

Camera imaging techniques have been used for the characterization of Cu(In,Ga)Se2 (CIGS) solar cells. Photoluminescence (PL) imaging shows brightness variations after the deposition of the CIGS layer that persist through CdS deposition and subsequent processing steps to finish the devices. PL and electroluminescence imaging on finished cells show a correlation to the devices’ corresponding efficiency and open-circuit voltage (VOC), and dark defect-related spots correspond to bright spots on images from illuminated lock-in thermography (LIT) and forward-bias dark LIT. These image-detected defect areas are weak diodes and shunts. Imaging provides locations of defects detrimental to solar cell performance. Some of these defects are analyzed in more detail by scanning electron microscopy using cross-sectional views.

Experimental study on mixing effect of falling film on coated division tube by thermal tracing technique

Experimental investigations have been carried out for liquid films flowing on the vertical coated division tube. A new thermal tracing technique was developed to measure the mixing effect and liquid film velocity of falling liquid film on the coated division tube. In general, mixing of solution could refresh the interface of bulk liquid, and hence lead to the more efficient heat transfer within the liquid film. By using the high speed video camera and thermal imaging technique, the flow patterns and mixing effect of liquid film on the coated division tube were investigated experimentally. Flow visualization experiments revealed that the liquid film formed a bifurcate flow at the upper edge of the vertical coated regions. The bifurcate flow converged and resulted in stronger mixing that drove the thermal tracing liquid particles from the interface to the internal of liquid film. There was deformation of temperature distribution on the coated division tube. The average mixing intensity on the coated division tube was about 1.2 times larger than that on the bare brass tube.

High-speed imaging investigation of transition phenomena in the pilot arc phase in Hf cathodes for plasma arc cutting

The behaviour of Hf cathodes has been investigated with high-speed camera (HSC) imaging techniques during the low-current pilot arc phase to highlight phenomena that take place during the transition from an insulating, non-emissive, cold phase to a conductive, emissive, hot phase for Hf-based materials used in electrodes for plasma arc cutting (PAC) of mild steel plates. The different behaviours during the start-up phases of new or used electrodes have been considered. Such phenomena have been partially described on physical bases in the past but can now be fully seen and analysed using diagnostics. Conclusions can be drawn concerning the particular conditions under which heat transfer transients in the cathode tip during the PAC pilot arc take place, giving additional useful information for future design-oriented simulation of such phenomena under different geometric and operating conditions, with the final aim of optimizing the cathode's expected service life.

Heat Transfer Characteristics of Falling Film Process on Coated Division Tubes: Effect of the Surface Configurations

In general, mixing of solution could refresh the interface of bulk liquid, and hence lead to the more efficient heat transfer within the liquid film. By using the high speed video camera and thermal imaging technique, the flow patterns and heat transfer characteristics of liquid film on coated division tubes, on which the hydrophobically coated regions and the bare regions presented alternately, were investigated experimentally. Flow visualization revealed that the minimum wetting rate increases with the increase in the effective contact angle of this surface. The cumulative liquid ring was observed at the boundary of bare region and coated region. The fluctuations of liquid film temperature were measured at different liquid film mass flow rates and the initial fluid temperatures. The temperature fluctuation periods on the coated division tube increased with the decrease of flow rate and initial liquid temperature. The liquid film surface temperature on the coated division tubes was higher than that on th...

No Significant Translocation of Inhaled 35-nm Carbon Particles to the Circulation in Humans

Human pulmonary retention of 35 nm 99mTc-labeled carbonaceous particles, produced with a modified Technegas generator, was followed for 24 h using a gamma camera imaging technique. Nine healthy subjects and four asthmatics inhaled the test particles. Particle labeling stability was tested in vitro during 48 h. We also measured in vivo leaching in blood and in urine for 24 h. One additional subject was exposed to particles with unstable labeling. There were no significant differences between healthy and asthmatic subjects in any of the parameters studied. Particle retention after 24 h was 102% (SD ± 4.7). Cumulative in vitro leaching of 99mTc activity from the particles was 1.7% (±1.1) after 24 h. In blood samples, 80 min after exposure, 1.1% (± 0.4) of initially deposited activity was detected and 91% of the activity was not bound to particles. In urine sampled during the first 24 h after exposure, 3.6% (± 0.9) of lung deposited activity was detected. Lung retention was 30% after 1 h in the subject exposed to the leaching aerosol (n = 1). Thirty-one percent of the deposited activity was detected in the blood after 80 min and 80% was not bound to particles. Fifty percent of the activity was excreted with urine within 24 h. On gamma camera images the activity visibly translocated from lungs to thyroid and gastrointestinal tract. In conclusion, over a 24-h period there was no significant translocation of inhaled 35-nm particles to the systemic circulation.