Simple Jet Research Articles

Concepts and characteristics of the ‘COST Reference Microplasma Jet’

Biomedical applications of non-equilibrium atmospheric pressure plasmas have attracted intense interest in the past few years. Many plasma sources of diverse design have been proposed for these applications, but the relationship between source characteristics and application performance is not well-understood, and indeed many sources are poorly characterized. This circumstance is an impediment to progress in application development. A reference source with well-understood and highly reproducible characteristics may be an important tool in this context. Researchers around the world should be able to compare the characteristics of their own sources and also their results with this device. In this paper, we describe such a reference source, developed from the simple and robust micro-scaled atmospheric pressure plasma jet (μ-APPJ) concept. This development occurred under the auspices of COST Action MP1101 ‘Biomedical Applications of Atmospheric Pressure Plasmas’. Gas contamination and power measurement are shown to be major causes of irreproducible results in earlier source designs. These problems are resolved in the reference source by refinement of the mechanical and electrical design and by specifying an operating protocol. These measures are shown to be absolutely necessary for reproducible operation. They include the integration of current and voltage probes into the jet. The usual combination of matching unit and power supply is replaced by an integrated LC power coupling circuit and a 5 W single frequency generator. The design specification and operating protocol for the reference source are being made freely available.

Simulation of Partial and Supercavitating Flows around Axisymmetric and Quasi-3D Bodies by Boundary Element Method Using Simple and Reentrant Jet Models at the Closure Zone of Cavity

A fixed-length Boundary Element Method (BEM) is used to investigate the super- and partial cavitating flows around various axisymmetric bodies using simple and reentrant jet models at the closure zone of cavity. Also, a simple algorithm is proposed to model the quasi-3D cavitating flows over elliptical-head bodies using the axisymmetric method. Cavity and reentrant jet lengths are the inputs of the problem and the cavity shape and cavitation number are some of the outputs of this simulation. A numerical modeling based on Navier-Stokes equations using commercial CFD code (Fluent) is performed to evaluate the BEM results (in 2D and 3D cases). The cavitation properties approximated by the present research study (especially with the reentrant jet model) are very close to the results of other experimental and numerical solutions. The need for a very short time (only a few minutes) to reach the desirable convergence and relatively good accuracy are the main advantages of this method.

Simple Synthetic Jet Actuators for Cooling Applications Using Soft or Rigid Magnets

Consumer electronics are getting both smaller and more powerful. Hence, there is a need for small, scalable, silent, reliable and low-cost cooling systems. In order to meet these requirements, we designed simple synthetic jet (SynJet) actuators using silicone elastomer membranes together with either soft composite or rigid neodymium magnets. The SynJet actuators were electromechanically driven near their mechanical resonance frequency in the low-frequency range between 5Hz and 120Hz. In order to compare both configurations, we characterized the SynJet actuators thoroughly by measuring the air pressure in the SynJet housing, the magnet's deflection and the electric current and voltage at the driving electromagnet. In test configurations, the fabricated SynJet actuators reduced the thermal resistance by about 60% compared to natural convection, which proves their feasibility for active cooling solutions.

THEγ-RAY DETECTED NARROW-LINE SEYFERT 1 GALAXY 1H 0323+342:SWIFTMONITORING ANDSUZAKUSPECTROSCOPY

As a radio-loud narrow-line Seyfert 1 galaxy (NLS1) detected by Fermi/LAT in GeV γ-rays, 1H 0323+342 is a remarkable active galactic nucleus showing properties characteristic of both NLS1s and blazars. Here we present results of simultaneous X-ray and UV/optical monitoring observations on 1H 0323+342 taken with the UV/Optical Telescope and X-ray Telescope onboard the Swift satellite over six years from 2006. Overall, the object showed statistically correlated variations in both the UV and X-ray bands on timescales of years as well as on timescales of days. A deep Suzaku observation reveals X-ray variability on timescales as short as a few tens of thousand seconds, and an X-ray spectrum typical of Seyfert galaxies. The broadband spectral energy distribution, for which the data of UV and X-ray observations taken on 2009 July 26–27 were used, can be well modeled with a simple one-zone leptonic jet model plus accretion disk/corona emission. The latter is predominantly responsible for the UV/optical and X-ray (0.3–10 keV) emission and their observed variations. The correlated UV–X-ray variability on the timescale of days is consistent with reprocessing of the X-ray radiation by the accretion disk. The shortest timescale and large normalized excess variance of the X-ray variability detected with Suzaku suggest a relatively small black hole mass of the order of , consistent with the estimation based on the broad Hβ line in the optical.

Inactivation of <italic>Candida albicans</italic> by Cold Atmospheric Pressure Plasma Jet

Nonthermal atmospheric pressure plasma jets (APPJs) are characterized by very reactive chemistry without the need of elevated temperatures. Also, plasma jets are capable of producing cold plasma plumes that are not spatially confined by electrodes, which makes them very attractive for biomedical applications. In this paper, we investigate the antimicrobial efficiency of a simple plasma jet device operating with pure He as working gas. The device was driven by an ac power supply operated at 31.0 kHz, 13.0 kV amplitude with mean power around 1.8 W. The jet was directed perpendicularly on a standard Petri dish (Ø90 mm × 15 mm) filled with agar. The jet fungicidal efficiency was tested against Candida albicans (reference strains SC 5314 and ATCC 18804) and five clinical isolates from previously obtained denture stomatitis lesions. In this paper, the effects of treatment time and distance to the target were evaluated. In most treatments the samples did not have direct contact with the plasma plume; therefore, the reactive oxygen species produced by interaction between the plasma jet and ambient air were the principal inactivate agent.

Synthesis and characterization of MgO nanocrystals for biosensing applications

MgO nanocrystals were prepared using a simple direct current arc plasma jet chemical vapor deposition method. Magnesium nitrate was used as source material and Mo film was used as a substrate and catalyst. The high-temperature plasma produced ensured rapid synthesis of the MgO nanocrystals. The as-prepared nanocrystals were characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, energy-dispersive spectroscopy, Fourier transform infrared spectrometry, ultraviolet–visible spectrophotometry, and photoluminescence measurements. The as-synthesized samples were found to consist of cubic MgO nanobelts and nanosheets with large surface areas and low coordination oxide ions, and contained numerous contacts, rough edges, vacancies, and doping defects. The nanostructures exhibited excellent electrochemical sensing properties with high-sensing sensitivity toward ascorbic acid. Their high electrocatalytic activity was attributed to the effect of defects and the surface electron transfer ability of the one-dimensional MgO nanobelts.

A novel simple one-step air jet spinning approach for deposition of poly(vinyl acetate)/hydroxyapatite composite nanofibers on Ti implants.

A biocompatible coating consists of a poly(vinyl acetate)/hydroxyapatite (PVAc/HA) composite nanofiber mat was applied to NaOH-treated titanium metal by means of a novel, facile and efficient air jet spinning (AJS) approach. Results showed that HA nanoparticles (NPs) strongly embedded onto the AJS single fiber surface resulting in a strong chemical interfacial bonding between the two phases due to the difference in kinetic energies. It was proven that AJS membrane coatings can provide significant improvement in the corrosion resistance of titanium substrate. Interestingly, the biocompatibility using MC3T3-E1 osteoblast to the PVAc/HA fiber composite layer coated on Ti was significantly higher than pure titanium-substrates.

Multi-photon molecular tagging velocimetry with femtosecond excitation (FemtoMTV)

We present results for first molecular tagging velocimetry (MTV) measurements in water under resonant femtosecond excitation/emission process of a phosphorescent supramolecule. Both two-photon and three-photon absorption processes are examined, and the feasibility of measurements is demonstrated by single component velocimetry in a simple jet flow. The new capabilities enabled by FemtoMTV include elimination of the need for short wavelength UV excitation source and UV optical access in flow facilities, and potential for high rep-rate flow imaging.

Shaping gas jet plasma density profile by laser generated shock waves

The Gaussian plasma density profile from a simple cylindrical nozzle jet was modified using laser generated shock wave. This modification provided great variety of density profiles suitable for different applications. The Gaussian plasma density distribution was modified into fast-rise slow-fall profile with adjustable gradients, almost flat-top profiles, and profiles with variable lengths. Position of the shock wave center and time delay were the major parameters used for shaping the density profiles. Other easily adjustable parameters such as shock wave energy and backing pressure provided linear scaling of the modified plasma densities.

Jet substructures of boosted polarized top quarks

We study jet substructures of a boosted polarized top quark, which undergoes the semileptonic decay $t\ensuremath{\rightarrow}b\ensuremath{\ell}\ensuremath{\nu}$, in the perturbative QCD framework. The jet mass distribution (energy profile) is factorized into the convolution of a hard top-quark decay kernel with the bottom-quark jet function (jet energy function). Computing the hard kernel to the leading order in QCD and inputting the latter functions from the resummation formalism, we observe that the jet mass distribution is not sensitive to the helicity of the top quark, but the energy profile is: energy is accumulated faster within a left-hand top jet than within a right-hand one, a feature related to the $V\ensuremath{-}A$ structure of weak interaction. It is pointed out that the energy profile is a simple and useful jet observable for helicity discrimination of a boosted top quark, which helps identification of physics beyond the standard model at the Large Hadron Collider. The extension of our analysis to other jet substructures, including those associated with a hadronically decaying polarized top quark, is proposed.

Ultra-high throughput synthesis of nanoparticles with homogeneous size distribution using a coaxial turbulent jet mixer.

High-throughput production of nanoparticles (NPs) with controlled quality is critical for their clinical translation into effective nanomedicines for diagnostics and therapeutics. Here we report a simple and versatile coaxial turbulent jet mixer that can synthesize a variety of NPs at high throughput up to 3 kg/d, while maintaining the advantages of homogeneity, reproducibility, and tunability that are normally accessible only in specialized microscale mixing devices. The device fabrication does not require specialized machining and is easy to operate. As one example, we show reproducible, high-throughput formulation of siRNA-polyelectrolyte polyplex NPs that exhibit effective gene knockdown but exhibit significant dependence on batch size when formulated using conventional methods. The coaxial turbulent jet mixer can accelerate the development of nanomedicines by providing a robust and versatile platform for preparation of NPs at throughputs suitable for in vivo studies, clinical trials, and industrial-scale production.

High flow-rate ultrasonic seeder

Application of optical techniques to gaseous flows usually requires seeding the fluid with tracers sufficiently small to follow the flow, added in suitable concentrations. This work describes the design and manufacture of a seeder based on ultrasonic atomization of aqueous solutions or other fluids of similar viscosity, capable of operating in a continuous way with high atomization rates. It includes a dozen piezoceramic disks that oscillate at 1.65MHz, generating droplets with Sauter mean diameter in the range of 4–5μm and rates over 0.6g/s when working with water. To test its performance, the device has been used to seed a simple free air jet issuing from a 3.5cm diameter pipe. Initially the seeding density is very satisfactory, but if only water is nebulized the droplets evaporate in a short time and the concentration becomes too low when moving downstream. The situation can be greatly improved mixing the water with a less volatile liquid. Here, a small percentage of glycerol (5% in volume) has been added to the water to extend the droplet lifetime, although in general, atomization rate strongly decreases when increasing the liquid viscosity. The seeded flow has been visualized, and the 3D velocity field has been successfully measured using stereoscopic particle image velocimetry.

Effect of the coflow stream on a plane wall jet

We propose in this work to study an isothermal and a non-isothermal laminar plane wall jet emerging in a coflow steam. The numerical solution of the governing equations was performed by a finite difference method. In this work, we are interested in the study of the influence of Grashof numbers on the wall jet emerging in a medium at rest. Further, we will examine the effect of the coflow stream on the behavior of the dynamic and thermal properties of the wall jet subjected to a constant temperature. A comparison with a simple wall jet is carried out. The results show that for a buoyant wall jet, two parameters can influence the flow: the inertial and buoyancy forces. The velocity effect indicates that the potential core length increases with the velocity ratio. We are also showed that when using a momentum length scale, the normalized longitudinal maximum velocity can reach an asymptotic curve at different velocity ratios.

Differential Cross Sections for Ionization of Argon by 1 keV Positron and Electron Impact

Differential information was generated by establishing coincidences and imposing conditions on data recorded for target ions, scattered projectiles, and ejected electrons, as a function of projectile energy loss and scattering angles; in order to describe the interaction between a positron (electron) 1 keV beam and a simple Ar jet. Single ionization triply differential cross section (TDCS) results exhibit two distinct regions (lobes) for which binary (events arising from 2-body interaction) and recoil (events which can only be produced by many-body interactions) interactions are associated. Results indicate that binary events are significantly larger for positron impact, in accordance with theoretical predictions. A similar feature is found for different energy losses and scattering angles. Intensity of the recoil lobe for both projectiles, positron and electron, is observed to depend on the energy loss and scattering angle. Also, it can be noticed that for positron impact the recoil interactions intensity is larger than that observed for electron impact.

Adjoint-based control of loud events in a turbulent jet

AbstractEfforts to reduce the noise from turbulent jets at fixed flow conditions, with aircraft noise as the principal technological motivation, have generally involved some degree of parametric empiricism often based upon a series of trial-and-error testing. As a result, it is unclear if the modest reductions found, in rare cases that do not greatly affect the flow field or incur prohibitive losses, are near the limit of what can be accomplished or if there are undiscovered opportunities for more substantive reductions with better designs or active control. We assess this using an adjoint-based optimization procedure in conjunction with an experimentally validated large-eddy simulation of a Mach 1.3 turbulent jet. The adjoint solution provides a definitive direction in which to adjust a model control actuation in order to reduce noise, providing guidance that seems lacking by any other current means. It is found that three conjugate-gradient iterations in the control space provide ∼3.5 dB of reduction, comparable to other reductions found empirically. The control seems to work by disrupting the coherence of acoustically efficient axisymmetric flow structures. The control and noise-reduction mechanisms are informative, but also suggest that any significantly quieter state would not be a simple perturbation from the uncontrolled jet. Additional iterations might reduce noise more significantly, but there might be only modest opportunities to reduce the sound from simple round turbulent jets without radical changes or relatively sophisticated controls. Though it is difficult to prove any behaviour in a global space of actuations, there does not seem to be a direct route based upon a local sensitivity gradient to substantially quieting a jet, even with an unrealistically flexible actuation. More complex jets or other noisy flows may be more amenable to control, in which case the adjoint-based optimization procedure demonstrated here could provide invaluable engineering guidance.

Biased showers: A common conceptual framework for the interpretation of high-PTobservables in heavy-ion collisions

After the start of the LHC, a plethora of novel observables for jet tomography in heavy-ion collisions has appeared. Many of these studies have yielded counter-intuitive null results of apparently unmodified jets, which have sparked (sometimes exotic) theoretical efforts to explain these findings. However, it has to be realized that almost all current high P_T observables measure conditional probabilities of events, not probabilities. Thus, the correct starting point for their theoretical understanding is Bayes' formula, and the biases introduced by the conditioning are crucial to understanding the outcome. Once this is introduced properly into the modelling process, the counter-intuitive results are seen to find a natural explanation in terms of various biases and the puzzles largely disappear. In this work, a conceptual framework to classify the various observables according to the types of bias they are sensitive to is presented and illustrated with a large number of case studies ranging from simple jet finding to 2+1 dihadron triggered correlations.

Factors Affecting Performance of Dual Fuel Compression Ignition Engines

Compression Ignition Diesel Engine use Diesel as conventional fuel. This has proven to be the most economical source of prime mover in medium and heavy duty loads for both stationary and mobile applications. Performance enhancements have been implemented to optimize fuel consumption and increase thermal efficiency as well as lowering exhaust emissions on these engines. Recently dual fueling of Diesel engines has been found one of the means to achieve these goals. Different types of fuels are tried to displace some of the diesel fuel consumption. This study is made to identify the most favorable conditions for dual fuel mode of operation using Diesel as main fuel and Gasoline as a combustion improver. A single cylinder naturally aspirated air cooled 0.4 liter direct injection diesel engine is used. Diesel is injected by the normal fuel injection system, while Gasoline is carbureted with air using a simple single jet carburetor mounted at the air intake. The engine has been operated at constant speed of 3000 rpm and the load was varied. Different Gasoline to air mixture strengths investigated, and diesel injection timing is also varied. The optimum setting of the engine has been defined which increased the thermal efficiency, reduced the NOx % and HC%.

Azimuthal anisotropy in a jet absorption model with fluctuating initial geometry in heavy ion collisions

The azimuthal anisotropy due to path-length-dependent jet energy loss is studied in a simple jet absorption model that includes event-by-event fluctuating Glauber geometry. Significant anisotropy coefficients ${v}_{n}$ are observed for $n=1$, 2, and 3, but they are very small for $n>3$. These coefficients are expected to result in a ridge for correlations between two independently produced jets. The correlations between the orientation of the $n\mathrm{th}$-order anisotropy induced by jet absorption (${\ensuremath{\Phi}}_{n}^{\mathrm{QP}}$) and the $n\mathrm{th}$-order participant plane (${\ensuremath{\Phi}}_{n}^{\mathrm{PP}}$) responsible for harmonic flow are studied. Tight correlations are observed for $n=2$ in mid-central collisions, but they weaken significantly for $n\ensuremath{\ne}2$. The correlations are positive for $n\ensuremath{\leqslant}3$, but become negative in central collisions for $n>3$. The dispersion between ${\ensuremath{\Phi}}_{n}^{\mathrm{QP}}$ and ${\ensuremath{\Phi}}_{n}^{\mathrm{PP}}$ is expected to break the factorization of the Fourier coefficients from two-particle correlation ${v}_{n,n}$ into the single particle ${v}_{n}$, and has important implications for the high-${p}_{\mathrm{T}}$ ridge phenomena.

Removal of heavy metals from aqueous solutions by liquid cation exchanger in a jet loop contactor

The paper focuses on the use of naphthenic acid as a low cost ion exchanger for removing heavy metal ions from aqueous solutions. Extraction of Cu++ from dilute aqueous solutions by naphthenic acid dissolved in kerosene in a simple jet loop reactor was studied. Variables studied were; circulation velocity, initial Cu++ concentration, nozzle diameter and nozzle height (the vertical distance between nozzle and the surface of the liquid in the reactor). An increase in the rate of extraction was observed with increasing nozzle diameter and circulation velocity. Increasing initial metal ion concentration and the nozzle height was found to decrease the rate of extraction. The rate of extraction was expressed in terms of the volumetric mass transfer coefficient (kA), the data were correlated by the dimensionless equation:Shm=0.044Sc0.33Re1.54Ldn−0.36The possibility of using the present reactor for removing heavy metals such as removal of copper from printed circuit etching solution, pickling solutions, electroplating and electroless plating rinse solution and copper mines drainage solutions was highlighted.

Experimental Studies for the characterization of the mixing processes in negative buoyant jets

A negatively buoyant jet (NBJ) corresponds to the physical phenomenon that develops when a fluid is discharged upwards into a lighter environment or downwards into a heavier receptor fluid. In a NBJ the flow is initially driven mostly by the momentum, so it basically behaves as a simple jet released with the same angle, while far from the outlet the buoyancy prevails, bending the jet axis down and making it similar to a plume. The coexistence in the same phenomenon of both the characteristics of simple jets and plumes makes the NBJs a phenomenon still not entirely explained but, considering also the numerous practical applications, very interesting to study. Here some of the experimental results are presented. The laboratory experiment were obtained on a model simulating a typical sea discharge of brine from desalination plants: a pipe laid down on the sea bottom, with orifices on its lateral wall, releasing brine (heavier than the sea water) with a certain angle to the horizontal, in order to increase the jet path before sinking to the seafloor. A non-intrusive image analysis technique, namely Feature Tracking Velocimetry, is applied to measure velocity fields, with the aim at understanding the influence of some non-dimensional parameters driving the phenomenon (e.g. Reynolds number, release angle) on the structure of the NBJ and of the turbulence.